Pacemaker Emergencies in ICU

Quick Answer

Pacemaker emergencies in ICU encompass device malfunctions (failure to pace, failure to sense, pacemaker-mediated tachycardia), complications (infection, lead displacement, perforation), and perioperative challenges (MRI, electrocautery). Recognition requires understanding of pacemaker modes and ECG interpretation.

Key Emergency Actions:

1. Failure to pace/capture in dependent patient: Apply magnet (asynchronous pacing), prepare TCP, correct metabolic abnormalities, call EP urgently
2. Oversensing with pauses: Apply magnet (disables sensing), identify source of interference
3. Pacemaker-mediated tachycardia: Apply magnet or reprogram PVARP, consider beta-blockers
4. Device infection: Blood cultures, IV antibiotics, device extraction planning

Critical Recognition Points:

• Pacing-dependent patient: No underlying rhythm - loss of pacing = asystole
• Failure to capture: Pacing spikes without QRS complexes
• Failure to sense: Pacing spikes falling on native beats (R-on-T risk)
• Oversensing: Inappropriate inhibition causing pauses

Magnet Behaviour:

• Pacemakers: Converts to asynchronous mode (VOO/DOO) - fixed rate pacing
• ICDs: Suspends tachyarrhythmia therapies (shocks disabled) - does NOT affect pacing

Must-Know Facts:

• HRS 2017 consensus recommends device interrogation before and after all procedures (PMID: 28511842)
• MRI-conditional devices can undergo MRI with specific protocols (PMID: 31078731)
• Battery ERI (Elective Replacement Indicator) precedes EOL by 3-6 months - plan replacement

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CICM Exam Focus

Written Exam (SAQ)

Common SAQ Stems:

• "A patient with a DDD pacemaker develops regular tachycardia at 120 bpm post-operatively. ECG shows paced ventricular complexes. Describe the likely mechanism and management."
• "Outline the perioperative management of a patient with a pacemaker requiring emergency laparotomy with electrocautery."
• "A pacemaker-dependent patient in ICU develops intermittent loss of capture. Describe your systematic approach."
• "Discuss the considerations for MRI in a patient with a cardiac implantable electronic device."

Expected Depth:

• NBG pacemaker code interpretation
• Mechanisms of failure to pace, capture, and sense
• PMT mechanism and termination strategies
• MRI conditional device protocols
• Electrocautery and EMI management
• Magnet effects on pacemakers vs ICDs
• Device infection diagnosis and management

Viva Voce

Expected Discussion Areas:

• Pacemaker mode nomenclature (NBG code)
• Systematic ECG interpretation of paced rhythms
• Troubleshooting algorithms for malfunction
• Lead complications (displacement, fracture, perforation)
• Perioperative device management protocols
• When to call electrophysiology urgently

Examiner Expectations:

• Safe, systematic approach to device malfunction
• Understanding of magnet response differences (pacemaker vs ICD)
• Knowledge of infection management and extraction indications
• Evidence-based perioperative protocols

Hot Case

Typical Presentations:

• Post-operative patient with pacemaker and haemodynamic instability
• Patient with tachycardia and visible pacing spikes
• Device pocket erythema with fever and positive blood cultures
• Pacemaker-dependent patient with intermittent capture failure

Common Mistakes

1. Not recognising pacing-dependent status (no backup rhythm)
2. Confusing magnet effects on pacemakers vs ICDs
3. Missing undersensing pattern on ECG (spikes falling on T waves)
4. Not considering lead perforation with sudden loss of capture
5. Delay in calling electrophysiology for complex malfunctions
6. Applying magnet to ICD thinking it will pace asynchronously

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Key Points

Must-Know Facts

1. Pacemaker Components: Pulse generator (battery + circuitry) and leads (unipolar or bipolar); modern devices 5-15 year battery life depending on pacing burden (PMID: 29146516)

2. NBG Code: 5-letter nomenclature - Position 1 (chamber paced: A/V/D), Position 2 (chamber sensed: A/V/D/O), Position 3 (response to sensing: I/T/D/O), Position 4 (rate modulation: R/O), Position 5 (multisite pacing) (PMID: 34185046)

3. Common Modes:

   • VVI: Ventricular pacing/sensing, inhibited - for chronic AF with slow ventricular response
   • DDD: Dual chamber pacing/sensing - maintains AV synchrony
   • AAI: Atrial pacing/sensing - for sinus node dysfunction with intact AV conduction
   • VOO/DOO: Asynchronous (no sensing) - magnet mode, EMI protection (PMID: 29146516)

4. Sensing and Output:

   • Sensing threshold: Minimum signal amplitude detected (mV); set at 50% of measured R-wave
   • Pacing threshold: Minimum output to capture (mA at pulse width); set at 2-3x threshold
   • Threshold rises acutely post-implant (inflammatory), then stabilises (PMID: 22203695)

5. Failure to Pace: No pacing spike output - causes include battery depletion, lead fracture, oversensing, loose connection, component failure (PMID: 21321155)

6. Failure to Capture: Pacing spike without myocardial depolarisation - causes include lead displacement (most common), exit block, battery depletion, metabolic abnormalities (hyperkalaemia, acidosis) (PMID: 22203695)

7. Pacemaker-Mediated Tachycardia (PMT): Endless loop in DDD pacemakers - retrograde VA conduction sensed by atrial lead triggers ventricular pacing, perpetuating the loop; rate = programmed upper tracking limit (PMID: 15721473)

8. Pacemaker Syndrome: Symptoms from loss of AV synchrony during VVI pacing - cannon A waves, hypotension, dyspnoea, fatigue; occurs in 5-20% of VVI patients (PMID: 11794147)

9. Magnet Response:

   • Pacemaker: Asynchronous pacing at manufacturer-specific rate (varies 65-100 bpm)
   • ICD: Suspends tachytherapies (shocks disabled), pacing function unchanged
   • Duration: Pacemaker - while magnet applied; ICD - some permanently disable until interrogated (PMID: 28511842)

10. MRI-Conditional Devices: Modern devices often MRI-compatible under specific conditions (1.5T or 3T, SAR limits, scanning zones); require programming to MRI mode pre-scan (PMID: 31078731)

Memory Aids

Mnemonic - PACEMAKER Malfunction Causes:

• Position change (lead displacement)
• Acute threshold rise (inflammation, metabolic)
• Connection loose (set screws, header block)
• Electrode fracture or insulation break
• Magnet or EMI interference
• Attery depletion (ERI, EOL)
• Key settings inappropriate (output, sensitivity)
• Exit block (fibrosis, infarction)
• Runaway pacemaker (rare - device failure)

"COPS" for PMT Management:

• Carotid massage (rarely terminates)
• Override with magnet (asynchronous mode breaks loop)
• Program PVARP extension
• Slow AV conduction (beta-blockers, adenosine)

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Pacemaker Basics

Components and Function

Pulse Generator:

• Battery: Lithium-iodide, typical longevity 5-15 years (modern devices)
• Circuitry: Sensing, timing, output generation
• Memory: Stores programming, diagnostics, arrhythmia episodes
• Telemetry: Communication with programmer (PMID: 29146516)

Leads:

Modern Trend: Bipolar leads preferred for reduced EMI sensitivity; leadless pacemakers emerging (PMID: 30702429)

Normal Pacemaker Function

Sensing:

• Detection of intrinsic cardiac activity
• P wave sensing in atrium (typical 2-5 mV)
• R wave sensing in ventricle (typical 5-15 mV)
• Adequate sensing: 2-3x safety margin above threshold

Pacing:

• Stimulus delivery when no native activity detected within programmed interval
• Capture: Stimulus causes myocardial depolarisation
• Threshold: Minimum output required for consistent capture
• Output: Programmed at 2-3x threshold for safety margin

Timing Intervals:

• Lower rate limit (LRL): Minimum pacing rate (e.g., 60 bpm = 1000 ms interval)
• Upper rate limit (URL): Maximum tracking/sensor rate (e.g., 120 bpm)
• AV delay: Time from atrial event to ventricular pacing (typically 120-200 ms)
• PVARP: Post-ventricular atrial refractory period (prevents retrograde P wave sensing)

Pacing Modes (NBG Code) (PMID: 34185046)

5-Position Code:

Common Modes Explained:

Pacing Threshold and Output

Strength-Duration Curve:

• Threshold depends on pulse width and amplitude
• Rheobase: Minimum current at infinite pulse width
• Chronaxie: Pulse width at 2x rheobase (most efficient point)
• Typical acute threshold: 0.5-1.0 V at 0.4-0.5 ms pulse width

Threshold Changes Over Time:

Factors Increasing Threshold:

• Lead displacement/dislodgement
• Myocardial infarction at lead tip
• Hyperkalaemia, severe acidosis, hypoxia
• Class IC antiarrhythmics (flecainide, propafenone)
• Post-defibrillation
• Hypothermia (severe)

Factors Decreasing Threshold:

• Catecholamines (isoprenaline, adrenaline)
• Corticosteroids (eluting leads)
• Hyperthyroidism

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Failure to Pace

Definition

Failure to pace = absence of pacing stimulus (spike) when expected based on programmed parameters. The ECG shows no pacing artifact during what should be a paced interval.

Causes (PMID: 22203695, 21321155)

Oversensing

Definition: Detection of non-cardiac signals or inappropriate cardiac signals as R waves, causing inhibition of pacing.

Causes of Oversensing:

ECG Pattern: Pauses without pacing spikes; underlying rhythm visible during pauses

Management:

1. Apply magnet (asynchronous pacing - ignores sensed signals)
2. Identify and remove source of interference
3. Reprogram sensitivity (decrease sensitivity = higher mV threshold)
4. Consider lead revision if fractured

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Failure to Capture

Definition

Failure to capture = pacing spike present but no myocardial depolarisation follows. ECG shows pacing artifacts without subsequent QRS complexes.

Causes (PMID: 22203695, 21321155)

ECG Patterns

Classic ECG Signs:

• Pacing spike not followed by P wave (atrial lead) or QRS (ventricular lead)
• May be intermittent (positional) or complete
• Underlying escape rhythm may be visible

Intermittent Capture:

• Some spikes capture, others don't
• Threshold close to programmed output
• Management: Increase output, investigate cause

Pseudofusion vs True Fusion:

• Fusion: Simultaneous native and paced depolarisation; QRS intermediate morphology
• Pseudofusion: Spike falls on native QRS; appears to capture but native beat would have occurred anyway
• Both are normal findings, not malfunction

Acute Management of Capture Failure

Immediate Actions:

1. Assess haemodynamics: Is patient pacemaker-dependent?
2. Apply magnet: Asynchronous pacing at higher output may capture
3. Increase output: If programmable, maximise output
4. Correct metabolic abnormalities: K+, pH, Ca2+, Mg2+
5. Check connections: Especially epicardial wires, temporary pacers

If No Capture Despite High Output:

• Lead displacement likely - CXR for position
• Prepare alternative pacing:
  • Transcutaneous pacing as bridge
  • Transvenous pacing if permanent lead failed
  • Isoprenaline to increase native rate (if any escape)

Lead Perforation Consideration:

• Sudden loss of capture + new pericardial effusion
• May have diaphragmatic pacing (hiccups)
• Haemodynamic instability suggests tamponade
• Urgent echocardiography and potential pericardiocentesis

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Failure to Sense

Definition

Failure to sense (undersensing) = pacemaker does not detect intrinsic cardiac activity, leading to inappropriate pacing.

Types (PMID: 22203695)

Undersensing:

• Pacemaker does not "see" native beats
• Paces despite intrinsic activity
• ECG: Pacing spikes falling randomly relative to native QRS/P waves

Functional Undersensing (normal):

• Spike during blanking period (designed to ignore certain signals)
• Not a malfunction

Causes of Undersensing

ECG Patterns

Undersensing ECG Characteristics:

• Pacing spikes falling at inappropriate times relative to native rhythm
• Spikes on T waves (R-on-T phenomenon - VT/VF risk)
• Spikes during QRS (competition)
• Fixed rate appearance despite intrinsic activity

Risks of Undersensing:

• R-on-T VT/VF: Pacing during vulnerable period
• Competition: Paced and native rhythms competing
• Less efficient pacing (wasted battery)

Management

1. Increase sensitivity (lower the mV threshold)
2. Check lead position (CXR, echocardiogram, interrogation)
3. Rule out lead issues (impedance check)
4. Consider lead revision if signal inadequate

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Pacemaker-Mediated Tachycardia (PMT)

Mechanism (PMID: 15721473)

PMT (also called "endless loop tachycardia") is a macro re-entrant tachycardia unique to dual-chamber (DDD) pacemakers with intact ventriculoatrial (VA) conduction.

Trigger: A PVC or other ventricular event causes retrograde conduction to the atrium

Loop:

1. Ventricular event → retrograde atrial activation via VA conduction
2. Retrograde P wave sensed by atrial lead (if outside PVARP)
3. Sensed atrial event triggers AV delay countdown
4. At end of AV delay, ventricular pacing occurs
5. Paced ventricular event → retrograde atrial activation (cycle repeats)

Rate: Limited by programmed upper tracking rate (typically 110-130 bpm)

Risk Factors for PMT

ECG Characteristics

Typical Findings:

• Regular tachycardia at or near upper tracking rate
• Paced ventricular complexes (wide QRS with spike)
• Retrograde P waves visible after QRS (if visible)
• Fixed VP-P interval (VA conduction time)
• Abrupt onset (triggered by PVC or event)

Differentiating from Sinus Tachycardia:

• Sinus tachycardia: Gradual rate changes, P waves upright in II
• PMT: Sudden onset, rate at upper limit, retrograde P waves

Acute Management

Immediate Termination Options:

1. Apply magnet: Converts to asynchronous (DOO/VOO) mode → breaks sensing loop
2. Carotid sinus massage: Rarely effective (slows AV conduction, not VA)
3. Adenosine: Transient AV block may break loop, but often recurs
4. Increase PVARP (if programmer available): Prevents sensing of retrograde P wave

Definitive Management (requires programming):

• Extend PVARP (>300 ms, ideally > VA conduction time)
• Enable PMT termination algorithm (most modern devices have this)
• Reduce upper tracking rate
• Consider DDIR mode (no atrial tracking)
• Ablate VA conduction if refractory (rare)

Prevention

• Program PVARP > measured VA conduction time
• Enable automatic PMT detection and termination algorithms
• PVC response algorithms (extend PVARP after PVC)
• Appropriate upper tracking rate programming

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Pacemaker Syndrome

Definition (PMID: 11794147, 2374895)

Pacemaker syndrome = constellation of symptoms resulting from loss of AV synchrony, typically occurring with VVI pacing in patients with intact VA (retrograde) conduction.

Incidence: 5-20% of VVI pacemaker recipients (PMID: 9336458)

Pathophysiology

Loss of AV Synchrony:

• VVI pacing = ventricle paces without regard to atrial timing
• Atrial contraction against closed AV valves ("atrial kick" lost)
• Reduced stroke volume (15-25% reduction)

Ventriculoatrial (VA) Conduction:

• Present in 40-60% of patients with pacemakers
• Ventricular pacing → retrograde atrial activation
• Cannon A waves: Atrial contraction against closed tricuspid valve
• Release of ANP (atrial natriuretic peptide) → hypotension, diuresis

Haemodynamic Consequences:

• Reduced cardiac output (loss of atrial contribution)
• Hypotension (especially postural)
• Elevated pulmonary venous pressure (mitral regurgitation during LA contraction)
• Systemic venous congestion

Clinical Features

Symptoms:

• Pulsatile neck sensation ("pounding in neck") - cannon A waves
• Near-syncope, syncope
• Fatigue, exercise intolerance
• Dyspnoea (pulmonary congestion)
• Dizziness, light-headedness
• Chest discomfort, palpitations

Signs:

• Cannon A waves in JVP (pathognomonic)
• Hypotension (may be postural)
• Elevated JVP
• Variable S1 intensity
• New mitral/tricuspid regurgitation murmurs

Diagnosis

Clinical Diagnosis based on:

1. Symptoms as above
2. VVI pacing mode
3. Evidence of AV dyssynchrony (cannon A waves)
4. Improvement with AV synchronous pacing

Testing:

• Holter monitoring: Correlate symptoms with pacing mode
• Haemodynamic assessment: Compare BP/CO in VVI vs DDD
• EP study: Confirm VA conduction

Management (PMID: 8872667)

Upgrade to Dual-Chamber Pacing:

• Convert VVI to DDD pacing (generator +/- additional atrial lead)
• Restores AV synchrony
• PASE trial (PMID: 8872667): DDD reduces pacemaker syndrome symptoms

Programming Adjustments:

• Increase lower rate (reduces time with VVI pacing)
• Rate hysteresis (allows more native conduction)

Medical Management (temporary):

• Address hypotension symptomatically
• Not a long-term solution

Prevention

• Use DDD pacing when AV synchrony important
• VVI appropriate only when: Chronic AF, no need for rate support, cost constraints
• DAVID trial (PMID: 10362203): Minimise RV pacing in reduced EF patients

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MRI Considerations

Background (PMID: 31078731, 28461471)

Traditional View: All CIEDs were absolute MRI contraindication due to:

• Heating of leads (radiofrequency energy absorption)
• Gradient-induced currents (sensing interference, arrhythmias)
• Static magnetic field effects (device displacement, reed switch activation)

Modern Reality: Most devices implanted since ~2008-2010 are MRI-conditional

MRI-Conditional Devices

Definition: Devices designed and tested for safe MRI scanning under specific conditions (PMID: 31078731)

Requirements for MRI-Conditional Label:

Pre-MRI Protocol (PMID: 28511842, 29429508)

Before MRI:

1. Confirm device and leads are MRI-conditional
   • Check device registration card or interrogation
   • Verify lead and generator combination is approved together
2. Interrogation pre-MRI:
   • Document baseline settings
   • Check lead parameters (thresholds, impedance, sensing)
   • Confirm battery status adequate
3. Programming for MRI:
   • Switch to "MRI mode" or "MRI Safe Mode"
   • Pacing-dependent: Asynchronous pacing (VOO/DOO)
   • Non-dependent: Sensing off or monitor mode (OVO/ODO)
   • Tachytherapy disabled (ICDs)
4. Patient preparation:
   • Written consent including device-specific risks
   • Continuous ECG, SpO2, BP monitoring during scan
   • Resuscitation equipment available

During MRI:

• Continuous monitoring with MRI-compatible equipment
• Direct patient communication capability
• Limit scan duration as per device specifications
• Be prepared for heating sensation (rare with modern devices)

Post-MRI:

1. Immediate interrogation post-scan
2. Check parameters against baseline:
   • Sensing thresholds
   • Pacing thresholds
   • Lead impedance
   • Battery status
3. Reprogram to original settings
4. Document any changes

Non-Conditional Devices

Legacy Devices: Pre-2008 devices, most older leads

Options:

1. Avoid MRI - use alternative imaging (CT, ultrasound)
2. Consider with extreme caution if no alternative:
   • Benefits must clearly outweigh risks
   • Informed consent with risk disclosure
   • 1.5T only, low SAR protocols
   • Continuous monitoring
   • EP and MRI expertise present
   • Resuscitation immediately available

MagnaSafe Registry (PMID: 26698008): Non-conditional devices in 1.5T MRI - no deaths, low event rate, but remains off-label

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Electrocautery and Electromagnetic Interference

Mechanisms of EMI Effects (PMID: 28511842)

Oversensing: EMI interpreted as cardiac activity → inappropriate inhibition Noise reversion: Device detects continuous noise → switches to asynchronous mode (safety feature) Reset/Reprogramming: High energy can reset device to backup settings Lead heating: Rare, with very high energy exposure Direct myocardial stimulation: Can induce arrhythmias

Electrocautery/Diathermy

Highest Risk Procedures:

• Monopolar electrocautery (current path includes device)
• Surgery on chest/thorax
• High power settings
• Prolonged bursts

Lower Risk:

• Bipolar electrocautery (current contained locally)
• Procedures distant from device
• Short, intermittent bursts

Perioperative Protocol (HRS 2017 - PMID: 28511842)

Pre-Operative Assessment:

1. Identify device type (pacemaker, ICD, CRT)
2. Determine pacing dependency:
   • Review prior interrogation
   • Check for intrinsic rhythm (>40 bpm)
   • Pacing-dependent = no escape rhythm when pacing inhibited
3. Review indication for device
4. Obtain recent interrogation (ideally <6 months)

Intra-Operative Management:

Reprogramming Options:

Magnet Use:

• Pacemaker: Apply magnet = asynchronous mode (while applied)
• ICD: Apply magnet = tachytherapy disabled (until magnet removed)
• Have magnet available even if not preoperatively applied

Post-Operative:

• Interrogate device (within 24 hours ideally)
• Verify settings restored
• Check sensing/pacing parameters
• Confirm tachytherapies re-enabled (ICD)

Other EMI Sources

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Magnet Behaviour

Pacemaker Magnet Response

General Principle: Magnet activates reed switch → pacemaker enters asynchronous mode

Effects:

• Sensing disabled: Ignores all intrinsic activity
• Fixed rate pacing: At magnet rate (manufacturer-specific)
• Duration: Only while magnet applied

Manufacturer-Specific Magnet Rates:

BOL = Beginning of Life (adequate battery) ERI = Elective Replacement Indicator (battery depleted)

Clinical Utility:

• Emergency asynchronous pacing: Magnet application provides backup pacing if oversensing suspected
• Battery status assessment: Rate drop indicates ERI
• Threshold assessment: Compare capture at magnet rate (some devices decrease output during magnet)

ICD Magnet Response

Fundamentally Different from Pacemakers:

• Magnet suspends tachytherapy (shocks and ATP)
• Magnet does NOT change pacing mode
• Pacing continues as programmed

Effects:

• Tachyarrhythmia detection: Suspended
• Shock therapy: Disabled
• ATP: Disabled
• Bradycardia pacing: Unchanged

Duration:

• Most devices: Therapies disabled while magnet applied, resume when removed
• Some older devices: Permanent disable until interrogated

Magnet Tone (some devices):

• Audible beeps indicating device status
• Presence of tone = therapies were active, now suspended

Clinical Use of ICD Magnet:

1. Inappropriate shocks: Magnet prevents further shocks
2. End-of-life comfort care: Prevent shocks during dying process
3. Intra-operative: Prevent diathermy-triggered shocks
4. NOT for pacing support: Magnet does not provide asynchronous pacing in ICD

Emergency Magnet Application

Indications:

• Suspected oversensing with symptomatic pauses (pacemaker)
• Inappropriate ICD shocks
• Intra-operative interference
• Emergency surgery with no time for reprogramming

Technique:

• Place magnet directly over device (palpable subcutaneous pulse generator)
• Secure in place (tape or hold)
• Monitor ECG for response
• Maintain magnet until definitive management

Cautions:

• Know device type before applying
• Some devices have programmable magnet response (disabled)
• Rate-responsive pacing disabled with magnet
• Remove periodically to check underlying rhythm (if safe)

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Battery Depletion

Battery Technology

Lithium-Iodide Chemistry:

• Standard for modern pacemakers
• Predictable discharge curve
• Longevity: 5-15 years depending on pacing burden
• Low self-discharge rate

Factors Affecting Longevity:

Battery Status Indicators

Beginning of Life (BOL): Full battery capacity

Elective Replacement Indicator (ERI):

• Definition: Battery has reached recommended replacement threshold
• Typically 3-6 months of function remaining
• Device may change to safety parameters (reduced rate, simplified mode)
• Urgent but not emergency replacement

End of Life (EOL):

• Definition: Battery critically depleted
• May have only days to weeks of function
• Device may stop pacing or revert to minimal function
• Emergency in pacing-dependent patient

Device Behaviour at ERI/EOL

Typical ERI Changes:

• Mode changes: DDD → VVI (reduced complexity)
• Rate-responsive disabled
• Lower pacing rate (65 vs 70 bpm)
• Magnet rate decreases (see manufacturer table)
• Audible alerts (if programmed)

EOL Behaviour:

• Erratic pacing
• Loss of output possible
• Sensing unreliable
• Device may cease function entirely

Management of Battery Depletion

ERI Detected:

1. Urgent but elective generator replacement
2. Schedule within 1-2 weeks typically
3. Continue current settings unless symptomatic
4. Patient education about symptoms to report

EOL or Critical Battery in Dependent Patient:

1. Admit to monitored bed
2. Apply transcutaneous pacing pads (backup)
3. Prepare for transvenous pacing if device fails
4. Expedited generator replacement (same day/next day)

Generator Replacement Procedure:

• Same incision
• Disconnect old generator from leads
• Connect new generator (same leads usually)
• Check lead parameters (threshold, impedance, sensing)
• ~30-60 minute procedure typically

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Infection and Lead Complications

Pocket Infection (PMID: 28342719)

Incidence: 1-2% of implants; higher with:

• Diabetes mellitus
• Renal failure, dialysis
• Anticoagulation (haematoma)
• Prior device infection
• Multiple procedures

Microbiology:

• Staphylococcus aureus: 20-40% (more acute, virulent)
• Coagulase-negative staphylococci: 40-50% (more indolent)
• Gram-negative organisms, fungi: Less common but occur

Clinical Features:

• Localised signs: Erythema, warmth, swelling, tenderness over pocket
• Wound dehiscence, draining sinus
• Device erosion through skin
• Fever (may be absent in indolent infections)

Investigations:

• Blood cultures (positive in 15-25% of pocket-only infections)
• Wound cultures/swab
• Echocardiography (TTE then TOE) - look for vegetations
• WCC, CRP, procalcitonin

Lead Endocarditis (CIED-IE) (PMID: 29579853)

Definition: Infection involving the intravascular portion of leads or cardiac structures

Clinical Features:

• Fever (often absent in elderly, immunocompromised)
• Pulmonary symptoms (septic emboli from right-sided vegetations)
• Persistently positive blood cultures
• Signs of systemic sepsis

Diagnosis (Modified Duke Criteria apply):

• Blood cultures: Positive in 75-90%
• Echocardiography:
  • "TTE: ~30% sensitivity for lead vegetations"
  • "TOE: ~90% sensitivity (preferred)"
• PET/CT: May detect occult infection

Management Principles (HRS 2017 - PMID: 29579853)

Complete Device Extraction is Recommended For:

1. Definite CIED infection (pocket infection or lead endocarditis)
2. Bloodstream infection with no other source
3. Persistent bacteraemia despite appropriate antibiotics (>72 hours)

Antibiotic Therapy:

• Empiric: Vancomycin + anti-gram-negative coverage
• Duration: 4-6 weeks for endocarditis; 2-4 weeks for pocket-only
• Continue post-extraction (10-14 days minimum)

Reimplantation:

• New site preferred (contralateral)
• Timing: After negative blood cultures and clinical improvement (48-72 hours minimum for simple infections; 14 days for CIED-IE)

Lead Complications

Lead Displacement/Dislodgement:

• Incidence: 1-5% overall; higher with:
  • Acute phase (first 6 weeks)
  • Active fixation failures
  • Excessive patient movement
• Management: Reposition or replace lead

Lead Fracture:

• Sites: Subclavian crush (between clavicle and first rib), suture sites
• Presentation: Intermittent non-capture, oversensing (make-break artifact)
• Diagnosis: CXR (may see discontinuity), high impedance on interrogation
• Management: Replace lead (extraction if complete extraction needed)

Lead Perforation (PMID: 22203695):

• Acute: At implant, may cause tamponade
• Chronic: Slow erosion through myocardium
• Features:
  • Loss of capture
  • Diaphragmatic/intercostal muscle stimulation
  • Pericardial effusion/tamponade
  • Extracardiac capture on CXR
• Management:
  • Echocardiogram urgently (effusion, lead position)
  • Pericardiocentesis if tamponade
  • Lead repositioning (may be able to reposition in acute)
  • Cardiothoracic surgery standby

Lead Insulation Failure:

• Presentation: Low impedance (current leakage), undersensing, non-capture
• Common with older silicone leads
• Management: Replace lead

Tricuspid Regurgitation

Mechanism: Lead across tricuspid valve → mechanical interference, fibrosis

Incidence: Mild TR common; significant TR in 5-10%

Clinical Impact: Usually tolerated; may contribute to right heart failure

Management: Optimize heart failure therapy; consider extraction if severe and refractory

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Device Interrogation: What ICU Needs to Know

Basic Interrogation Components

Information Available from Interrogation:

When to Call Electrophysiology Urgently

Emergencies Requiring Immediate EP Consultation:

1. Complete loss of output in pacing-dependent patient
2. Failure to capture despite maximum output, magnet application
3. Suspected lead perforation (loss of capture + pericardial effusion)
4. Device infection with systemic signs
5. Inappropriate ICD shocks (VT storm or sensing malfunction)
6. Unknown device requiring urgent reprogramming (emergency surgery)

Urgent (Same-Day) Consultation:

1. Intermittent malfunction in dependent patient
2. PMT with haemodynamic impact
3. ERI/EOL detection
4. Pre-MRI evaluation
5. Complex perioperative planning

Programmer Availability

Most ICUs Should Have:

• Magnet (all devices respond)
• Contact details for device clinic/EP on-call
• Access to patient's device registration card

Programmer Access:

• Manufacturer-specific (Medtronic, Boston Scientific, Abbott, Biotronik)
• EP/device clinic has programmers
• 24/7 remote technical support from manufacturers

Temporary Measures While Awaiting EP

If Device Malfunction and EP Not Immediately Available:

1. Apply magnet (asynchronous pacing if oversensing/PMT)
2. Transcutaneous pacing pads applied
3. Transvenous pacing if complete device failure
4. Pharmacological support:
   • Isoprenaline 1-10 mcg/min (enhances automaticity)
   • Adrenaline 2-10 mcg/min (if hypotensive)
5. Correct metabolic abnormalities (K+, Mg2+, pH)

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Australian/NZ Context

Device Services and Remote Monitoring

Device Clinic Structure:

• Major hospitals have dedicated device clinics
• EP cardiologists and cardiac physiologists
• Manufacturer support for programming

Remote Monitoring:

• Modern devices transmit data wirelessly
• Home monitors detect alerts (threshold changes, arrhythmias)
• Reduces need for routine in-person checks
• Available: Medtronic CareLink, Boston Latitude, Abbott Merlin, Biotronik Home Monitoring

Retrieval Considerations

Pacemaker-Dependent Patient Transfer:

• Continuous ECG monitoring during transport
• TCP pads applied (backup)
• Magnet available
• Isoprenaline/adrenaline available
• Ensure receiving hospital has device expertise

Remote/Rural Challenges:

• Limited device clinic access
• May need aeromedical retrieval to tertiary centre
• Telemedicine consultation with EP available in many states
• RFDS has resuscitation capability including TCP

State-Based Resources

Indigenous Health Considerations (PMID: 22722715, 27884807)

Higher Cardiovascular Disease Burden:

• Aboriginal and Torres Strait Islander peoples: 2-3x higher IHD rates
• Earlier onset of cardiac disease
• Higher rates of rheumatic heart disease (may need pacing post-valve surgery)

Barriers to Device Management:

• Geographic isolation (long distances to device clinic)
• Remote monitoring infrastructure limited
• Health literacy challenges
• Cultural considerations around long-term implants

Culturally Safe Care:

• Involve Aboriginal Health Workers/Liaison Officers
• Explain device function in clear, non-technical terms
• Respect family involvement in decisions
• Consider impact of device on cultural practices
• Plan follow-up that accounts for community location

Maori Health (New Zealand):

• Higher cardiovascular disease prevalence
• Whanau involvement in decision-making
• Cultural considerations for device implantation
• Access challenges in rural North Island

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SAQ Practice

SAQ 1: Pacemaker-Mediated Tachycardia

Time Allocation: 10 minutes Total Marks: 15

Stem:

A 72-year-old woman with a DDD pacemaker implanted 6 months ago for complete heart block is admitted to ICU following hip fracture surgery. Post-operatively, she develops a regular tachycardia at 130 bpm. The ECG shows paced ventricular complexes with visible pacing spikes. Her blood pressure is 95/60 mmHg and she complains of palpitations and feeling faint.

Question 1.1 (5 marks) What is the most likely diagnosis and describe the mechanism?

Question 1.2 (5 marks) Outline your immediate management to terminate this arrhythmia.

Question 1.3 (5 marks) What programming changes can prevent recurrence, and what are the long-term considerations?

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Model Answer

Question 1.1 (5 marks)

Diagnosis (2 marks):

• Pacemaker-mediated tachycardia (PMT), also known as "endless loop tachycardia"
• Rate (130 bpm) corresponds to typical upper tracking limit of DDD pacemaker

Mechanism (3 marks):

• PMT is a macro re-entrant tachycardia unique to dual-chamber (DDD) pacemakers with intact ventriculoatrial (VA) conduction
• Initiating event: A PVC or other ventricular event (e.g., post-operative ectopy, electrocautery-induced)
• Re-entrant loop:
  1. Ventricular event causes retrograde atrial activation via VA conduction pathway
  2. Retrograde P wave is sensed by the atrial lead (if it falls outside the PVARP)
  3. Sensed atrial event triggers the AV delay timer
  4. At end of AV delay, the pacemaker delivers ventricular pacing
  5. Paced ventricular beat causes retrograde VA conduction → cycle repeats
• Rate limitation: Tachycardia rate equals the programmed upper tracking rate (here 130 bpm)
• Risk factors: Intact VA conduction present in 40-60% of pacemaker patients; short PVARP allows retrograde P wave sensing

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Question 1.2 (5 marks)

Immediate Management (ABCDE approach, then specific interventions):

Assess and Stabilise (1 mark):

• High-flow oxygen
• IV access
• Continuous monitoring
• Blood pressure support if needed (fluid bolus if hypovolaemic)

Terminate the Arrhythmia (3 marks):

First-line: Magnet Application

• Place magnet directly over pulse generator
• Converts DDD to asynchronous mode (DOO)
• Disables atrial sensing → breaks the re-entrant loop
• Tachycardia terminates immediately
• Keep magnet applied until reprogramming can occur

Alternative Methods:

• Carotid sinus massage: Rarely effective (slows AV, not VA conduction)
• Adenosine 6-12 mg IV: May transiently block AV/VA conduction and terminate, but often recurs immediately
• Beta-blocker or verapamil: Slow VA conduction; may prevent immediate recurrence but risk hypotension

Pharmacological Support (1 mark):

• If hypotensive: IV fluid bolus (if not overloaded)
• Avoid catecholamines if possible (may increase VA conduction)
• Prepare for TCP as backup if device malfunction suspected

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Question 1.3 (5 marks)

Programming Changes (3 marks):

Extend PVARP (Post-Ventricular Atrial Refractory Period):

• Prevents sensing of retrograde P wave
• PVARP should exceed the VA conduction time (typically 300-400 ms)
• Measure VA conduction time at interrogation and program PVARP 50 ms longer

Enable PMT Termination Algorithm:

• Most modern devices have automatic PMT detection
• When detected, device extends PVARP for one cycle → breaks loop
• Should be enabled routinely in DDD devices

Reduce Upper Tracking Rate:

• Lower rate reduces symptoms during PMT episodes
• Balance against exercise tolerance needs

Consider Mode Change:

• DDI mode: Dual sensing/pacing but no atrial tracking (inhibited only)
• Prevents PMT entirely but loses rate-responsive tracking
• Suitable if patient sedentary or has frequent PMT

PVC Response Programming:

• Extend PVARP after detected PVC (common PMT trigger)

Long-Term Considerations (2 marks):

Follow-Up:

• Device clinic review within 1-2 weeks post-discharge
• Confirm programming changes effective
• Monitor for PMT recurrence on device diagnostics

Refractory Cases:

• If frequent PMT despite programming:
  • Consider VA conduction ablation (rare, last resort)
  • Convert to VVI pacing (loses AV synchrony)

Patient Education:

• Recognise symptoms of PMT (sudden palpitations, dizziness)
• Seek medical attention if prolonged or symptomatic
• Magnet application (if trained) for termination

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SAQ 2: Perioperative Pacemaker Management

Time Allocation: 10 minutes Total Marks: 15

Stem:

A 68-year-old man with a VVI pacemaker (implanted 8 years ago for sick sinus syndrome with paroxysmal AF) requires emergency laparotomy for bowel perforation. The surgeon asks about pacemaker management during the procedure. The patient states he "sometimes feels dizzy when his pacemaker is not working properly."

Question 2.1 (4 marks) How would you assess this patient's pacing dependency, and why is this important?

Question 2.2 (6 marks) Outline the perioperative management of this patient's pacemaker, including specific recommendations for electrocautery use.

Question 2.3 (5 marks) Post-operatively, the patient is found to have intermittent pauses on the monitor. Describe your approach to troubleshooting this problem.

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Model Answer

Question 2.1 (4 marks)

Assessing Pacing Dependency (3 marks):

Definition: Pacing-dependent = absence of adequate intrinsic rhythm when pacing is inhibited; loss of pacing would result in symptomatic bradycardia or asystole

Assessment Methods:

1. Review device interrogation (if available):

   • Percentage of ventricular pacing (>90% suggests dependency)
   • Presence of intrinsic rhythm during undersensing or threshold testing
   • Underlying rhythm documented at prior checks

2. Review clinical history:

   • Indication for pacing (complete heart block = usually dependent)
   • Symptoms when device "not working" (this patient reports dizziness)
   • Prior documentation of escape rhythm

3. ECG review:

   • Is there any native rhythm visible?
   • VVI mode: look for periods of native conduction

4. Formal dependency test (if time and expertise):

   • Temporarily reduce pacing rate below intrinsic rate
   • Observe for escape rhythm (performed by EP/device clinic)

Importance (1 mark):

• Pacing-dependent patients require continuous pacing backup
• If device inhibited by EMI (electrocautery), patient will have asystole
• Determines need for:
  • Reprogramming to asynchronous mode (VOO)
  • Backup transcutaneous pacing availability
  • Continuous pulse monitoring during surgery

This patient: History of dizziness when "not working properly" and 8-year-old device with sick sinus syndrome suggest possible dependency; should be treated as potentially dependent

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Question 2.2 (6 marks)

Perioperative Management (HRS 2017 Expert Consensus):

Pre-Operative (2 marks):

1. Confirm device type and status:

   • VVI pacemaker (from history)
   • Ideally interrogate pre-op: battery status, lead parameters, pacing percentage
   • If no interrogation available: treat as potentially dependent

2. Assess pacing dependency:

   • As above - treat as potentially dependent given history

3. Plan intraoperative management:

   • Apply transcutaneous pacing pads (backup)
   • Have magnet available at surgical site
   • Consider reprogramming to asynchronous mode (VOO) if high EMI expected

Intra-Operative (3 marks):

Device Considerations:

• VVI device: Sensing EMI can inhibit pacing → pauses/asystole if dependent
• Options:
  • Reprogram to VOO (asynchronous) - preferred if dependent
  • "Magnet application: Converts VVI to VOO while applied"
  • Keep magnet available for immediate application if pauses occur

Electrocautery Recommendations:

Surgeon Communication:

• Inform surgical team of device
• Request notification before electrocautery use
• Have plan for pauses (stop cautery, apply magnet if needed)

Post-Operative (1 mark):

1. Interrogate device within 24 hours (ideally same day)
2. Verify settings restored to baseline
3. Check lead parameters (threshold, impedance, sensing)
4. Monitor for arrhythmias (especially if rate-responsive disabled)

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Question 2.3 (5 marks)

Troubleshooting Post-Operative Pauses:

Systematic Approach (PMID: 22203695):

1. Assess Patient and Haemodynamics (1 mark):

• Symptomatic? (dizziness, near-syncope)
• If unstable → immediate intervention (magnet, TCP, drugs)
• If stable → systematic investigation

2. Analyse ECG Pattern (1.5 marks):

3. Potential Causes in This Patient (1 mark):

• Oversensing from residual EMI (diathermy, muscle tremor)
• Lead displacement (position change, coughing, vomiting)
• Elevated threshold (metabolic disturbance, post-op)
• Battery depletion (8-year-old device - ERI possible)
• Device reset (high-energy EMI can reset to backup mode)

4. Immediate Management (1 mark):

• Apply magnet: If oversensing, provides asynchronous pacing
• Check connections if epicardial/temporary wires present
• Correct metabolic abnormalities: K+, Mg2+, pH, temperature
• CXR: Lead position, pneumothorax (if central line placed)

5. Call Electrophysiology (0.5 marks):

• Urgent device interrogation
• Identify specific cause (oversensing, threshold, battery)
• Reprogram as needed
• Plan for generator/lead replacement if indicated

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Hot Case Scenarios

Hot Case 1: Pacemaker Malfunction Post-Thoracic Surgery

Setting: Cardiothoracic ICU Bed 8 Duration: 20 minutes (10 min assessment + 10 min discussion)

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Actor/Simulator Briefing:

Patient Details:

• Age: 75 years
• Gender: Male
• Aboriginal Australian from rural Queensland
• Admission: Day 1 post-VATS right upper lobectomy for lung cancer
• Background: DDD pacemaker for complete heart block (implanted 3 years ago), COPD, ex-smoker

Current Problem:

• Multiple alarms on monitor for bradycardia
• Nurse reports "pacemaker not working properly"
• Patient feels "light-headed and weak"

Vital Signs:

• HR: Variable 35-72 bpm
• BP: 88/55 mmHg (was 125/75 pre-op)
• SpO2: 94% on 4L NC
• RR: 22
• Temp: 37.4°C

Examination Findings:

• Alert but fatigued
• Cool peripheries, CRT 4 seconds
• JVP visible 4 cm above sternal angle
• Heart sounds: Variable intensity, irregular
• Chest: Right-sided dressings, chest drain in situ (minimal output)
• Pacemaker pocket: Left pectoral, no erythema

Monitor Pattern:

• Intermittent pacing spikes, some followed by QRS, some not
• Native rhythm when pacing fails: Wide QRS at 35 bpm

Relevant Results:

• K+: 2.9 mmol/L
• Mg2+: 0.55 mmol/L
• pH: 7.32, lactate 2.8
• Hb: 95 g/L (was 120 pre-op)

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Expected Performance:

Assessment Phase (10 minutes):

History from Nurse/Chart (3 marks):

• Timeline: When did issues start?
• Intra-operative events: Electrocautery use, device magnet during surgery?
• Recent device interrogation available?
• Medications (any new beta-blockers, antiarrhythmics)

Examination (5 marks):

• Systematic A-E approach
• Pacemaker pocket inspection
• Identify hypotension, bradycardia, poor perfusion
• Note intermittent capture on monitor

ECG Analysis (2 marks):

• Pacing spikes present but intermittent capture
• Wide QRS escape (ventricular) at 35 bpm
• = Failure to capture

One-Minute Summary (2 marks): "This is a 75-year-old Aboriginal man, Day 1 post-VATS lobectomy, with his DDD pacemaker showing failure to capture. He is haemodynamically compromised with hypotension and poor perfusion. His underlying escape rhythm is wide QRS at 35 bpm, confirming he is pacing-dependent. Contributing factors include significant hypokalaemia and hypomagnesaemia, likely from surgical losses. Immediate priorities are: (1) Apply magnet for asynchronous pacing, (2) Urgent electrolyte replacement, (3) Prepare transcutaneous pacing as backup, (4) Call electrophysiology for device interrogation."

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Discussion Phase (10 minutes):

Question 1: "What are the possible causes of failure to capture in this patient?"

Expected Answer:

• Lead displacement (most common, especially with coughing post-thoracic surgery)
• Elevated capture threshold due to:
  • Hypokalaemia (K+ 2.9 mmol/L)
  • Hypomagnesaemia (Mg2+ 0.55 mmol/L)
  • Acidosis (pH 7.32)
  • Post-operative metabolic disturbance
• Device reset from electrocautery (may have changed settings)
• Lead damage from surgical positioning/retraction
• Battery depletion (3-year-old device - unlikely but possible)

Question 2: "How would you manage this situation immediately?"

Expected Answer:

1. Apply magnet → asynchronous pacing at higher output
2. Prepare TCP pads (backup if device fails completely)
3. IV potassium 40 mmol over 2 hours (with cardiac monitoring)
4. IV magnesium 10-20 mmol over 1 hour
5. Fluid resuscitation if hypovolaemic
6. Call EP urgently for device interrogation
7. CXR to check lead position

Question 3: "The family has arrived from their rural community. How would you communicate with them?"

Expected Answer:

• Involve Aboriginal Liaison Officer/Aboriginal Health Worker
• Private, comfortable space
• Clear, non-technical language
• Explain: "His heart relies on the pacemaker. Right now, the pacemaker is having trouble making his heart beat properly. We're working to fix this."
• Acknowledge their concerns
• Allow time for questions
• Cultural safety: Family decision-making, respect for elders

Question 4: "What are the long-term considerations for this patient's pacemaker?"

Expected Answer:

• Device interrogation once stable
• Check if programming reset (restore settings)
• Assess lead integrity (position, impedance, threshold)
• If lead displacement confirmed → lead revision
• If metabolic cause only → correct and monitor
• Follow-up plan before discharge
• Device clinic arrangements (consider location relative to rural community)

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Hot Case 2: ICD Storm and Device Management

Setting: General ICU Bed 15 Duration: 20 minutes

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Patient Details:

• Age: 58 years
• Gender: Female
• Maori, from rural Waikato region, New Zealand
• Background: Dilated cardiomyopathy (EF 25%), ICD implanted 2 years ago for primary prevention
• Admission: Recurrent ICD shocks (8 shocks in 4 hours)

Current Status:

• Intubated and sedated (propofol/fentanyl)
• HR: 75 bpm (sinus rhythm currently)
• BP: 95/60 mmHg on noradrenaline 0.1 mcg/kg/min
• Magnet currently applied to ICD

Key Issues:

• Multiple appropriate shocks for VT/VF
• Now in sinus rhythm with magnet
• Elevated troponin (demand ischaemia from shocks)
• K+ 3.5, Mg2+ 0.7 mmol/L
• Whanau requesting "no more shocks"

---

Expected Discussion Points:

1. Electrical Storm Management:

   • Magnet suspends ICD therapies (appropriate here)
   • Beta-blockade essential (esmolol infusion)
   • Correct electrolytes (K+ >4.0, Mg2+ >0.8)
   • Antiarrhythmic loading (amiodarone)
   • Consider sedation/deep sedation (reduces sympathetic drive)
   • Ablation if refractory

2. ICD Magnet Behaviour:

   • Suspends tachytherapies only
   • Bradycardia pacing continues
   • Must remove magnet for ICD protection to resume
   • Can program "therapies off" for prolonged suspension

3. Whanau Communication:

   • Respect Maori cultural practices (whanau decision-making)
   • Involve Maori Health Worker/Cultural Liaison
   • Explain difference between "turning off shocks" and "turning off pacing"
   • Goals of care discussion if prognosis poor
   • If comfort care chosen → permanent ICD deactivation appropriate

4. Long-term Considerations:

   • Optimise heart failure therapy
   • Consider VT ablation
   • Consider LV assist device or transplant if appropriate
   • Advanced care planning discussion

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Viva Scenarios

Viva Scenario 1: Pacemaker Modes and Troubleshooting

Stem: "A 65-year-old man with a DDD pacemaker presents to ED with lethargy and exercise intolerance. His device was implanted 2 years ago for symptomatic complete heart block. ECG shows ventricular-paced rhythm at 70 bpm with occasional native P waves visible that are not being tracked."

Duration: 12 minutes

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Opening Question: "What is the normal function of a DDD pacemaker, and what might be abnormal here?"

Expected Answer (3 minutes):

DDD Function:

• D (Dual) = Paces both atrium and ventricle
• D (Dual) = Senses both atrium and ventricle
• D (Dual response) = Inhibits when sensing, triggers ventricular pacing when sensing atrial activity

Normal Operation:

• Senses native P waves → triggers AV delay → paces ventricle if no native R wave
• Maintains AV synchrony
• Tracks sinus rate to upper rate limit

Abnormality in This Patient:

• P waves visible but NOT being tracked (followed by ventricular pacing after appropriate AV delay)
• Suggests atrial undersensing (device not detecting P waves)
• Or possibly device in VVI mode (atrial function disabled)

---

Follow-up Question 1: "What are the causes of atrial undersensing?"

Expected Answer (2 minutes):

---

Follow-up Question 2: "How would you investigate and manage this?"

Expected Answer (2 minutes):

Investigation:

• Device interrogation (definitive):

  • Current mode (confirm DDD vs mode switch to VVI?)
  • Atrial sensing amplitude
  • Lead impedance (high = fracture, low = insulation break)
  • Battery status
  • Event logs (atrial sensing events, mode switches)

• CXR: Lead positions

Management:

• If undersensing due to low signal: Increase atrial sensitivity (lower mV threshold)
• If lead displacement: Lead repositioning
• If device reset: Reprogram to original settings
• If lead failure: Lead replacement

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Follow-up Question 3: "The patient asks why he feels worse than when the pacemaker was first implanted. Explain the concept of 'pacemaker syndrome' to him."

Expected Answer (2 minutes):

Explanation for Patient: "When your pacemaker was first implanted, it was set to keep your heart's upper and lower chambers working together - what we call 'synchrony.' This gives you the best pumping efficiency.

It appears your pacemaker may now only be pacing the lower chamber (ventricle) without coordinating with the upper chamber (atrium). When this happens:

• The upper chamber contracts at the wrong time
• Blood can 'back up' into your neck veins - you might notice your neck pulsating
• Your heart doesn't pump as efficiently - causing tiredness and breathlessness

This is called 'pacemaker syndrome.' The good news is it's usually fixable by adjusting the pacemaker settings."

Technical Summary:

• Loss of AV synchrony (VVI-like function)
• Cannon A waves (atrial contraction against closed AV valves)
• Reduced cardiac output (loss of atrial kick)
• Retrograde VA conduction may worsen symptoms

---

Follow-up Question 4: "What are the key pacemaker settings you need to know for ICU patients?"

Expected Answer (2 minutes):

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Viva Scenario 2: MRI and Electrocautery with CIEDs

Stem: "A 52-year-old woman with a dual-chamber ICD requires urgent MRI brain for suspected stroke. The ICD was implanted 18 months ago for sustained VT with an EF of 35%. She also requires thrombolysis if stroke confirmed."

Duration: 12 minutes

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Opening Question: "What are your concerns about MRI in this patient, and how would you approach this situation?"

Expected Answer (3 minutes):

Concerns:

1. Device safety: Potential for heating, dislodgement, malfunction
2. Time pressure: Stroke requires rapid imaging and treatment (thrombolysis window 4.5 hours)
3. Device function: Need to maintain arrhythmia protection AND pacing capability
4. Lead effects: Heating, induced currents, sensing interference

Approach:

1. Determine if device is MRI-conditional:

   • Check device registration card or interrogation records
   • Contact manufacturer if unclear (24/7 technical support)
   • Most devices implanted after 2010 have MRI-conditional options

2. If MRI-conditional:

   • Follow manufacturer-specific protocol
   • Program to "MRI mode" (usually suspends sensing, fixed rate pacing)
   • 1.5T preferred (some approved for 3T)
   • Continuous monitoring during scan

3. If NOT MRI-conditional or unknown:

   • CT head is rapid alternative (less sensitive for early ischaemia but acceptable)
   • Risk-benefit discussion (stroke diagnosis critical vs device risk)
   • If MRI essential: Off-label use with EP/MRI team, informed consent

4. Time urgency:

   • Cannot delay for formal device clinic if stroke suspected
   • CT head may be faster and sufficient
   • Discuss with stroke team and EP simultaneously

---

Follow-up Question 1: "Describe the specific MRI protocol for a patient with an MRI-conditional ICD."

Expected Answer (2 minutes):

Pre-MRI:

1. Confirm eligibility:

   • Device and leads both MRI-conditional
   • No abandoned leads
   • Implant >6 weeks ago
   • Lead parameters within acceptable range
   • Battery not at ERI/EOL

2. Program to MRI mode:

   • Tachytherapy: OFF (no shocks, no ATP)
   • Pacing mode:
     • If pacing-dependent: Asynchronous (VOO/DOO)
     • If not dependent: Off or sensing only
   • Rate: Fixed (e.g., 80 bpm)

3. Document baseline parameters

During MRI:

• Continuous ECG, SpO2, BP monitoring
• Direct patient communication
• Resuscitation equipment immediately available
• Limit scan duration as per specifications
• Monitor for: Arrhythmias, device heating symptoms

Post-MRI:

• Interrogate immediately
• Compare parameters to baseline
• Reprogram to original settings
• Re-enable tachytherapy
• Document any changes

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Follow-up Question 2: "The patient does not have stroke but later requires emergency appendicectomy. Discuss intraoperative device management with electrocautery."

Expected Answer (2 minutes):

Pre-Operative Assessment:

• Confirm ICD status
• Check pacing dependency (less likely with VT indication, but check)
• Plan for intraoperative management

Intraoperative Management:

Option 1: Magnet Application

• Apply magnet over ICD → suspends tachytherapy
• Pacing continues as programmed
• Keep magnet on during electrocautery use
• Simple, no reprogramming needed
• Limitation: Does not provide asynchronous pacing if oversensing occurs

Option 2: Reprogram Device

• Disable tachytherapies (shocks OFF)
• If any pacing dependency concern: VOO mode
• Preferred for prolonged surgery or extensive electrocautery

Electrocautery Precautions:

• Use bipolar when possible
• Grounding pad away from device
• Short bursts (<5 seconds)
• Lowest effective power
• Continuous pulse monitoring

Post-Operative:

• Remove magnet or reprogram
• Confirm tachytherapies re-enabled
• Interrogate within 24 hours

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Follow-up Question 3: "What are the differences between magnet response in pacemakers versus ICDs?"

Expected Answer (2 minutes):

Critical Difference:

• Pacemaker magnet = provides backup pacing if oversensing
• ICD magnet = does NOT provide backup pacing, only disables shocks

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Follow-up Question 4: "When would you urgently call electrophysiology for a patient with a pacemaker or ICD?"

Expected Answer (2 minutes):

Emergency (Immediate Call):

1. Complete loss of pacing output in dependent patient
2. Failure to capture despite magnet and maximum output
3. Suspected lead perforation (new effusion + capture failure)
4. Device infection with systemic sepsis
5. ICD storm (multiple shocks) - need device interrogation
6. Unknown device requiring urgent reprogramming

Urgent (Same Day):

1. Intermittent malfunction in dependent patient
2. PMT with haemodynamic compromise
3. ERI/EOL detected
4. Pre-MRI evaluation for non-conditional device
5. Complex perioperative planning
6. Unexplained arrhythmias in device patient

ICU Team Capabilities (While Awaiting EP):

• Magnet application
• Transcutaneous pacing
• Transvenous pacing if device fails
• Pharmacological support (isoprenaline, adrenaline)
• Correct metabolic abnormalities

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References

Primary Guidelines

1. Kusumoto FM, Schoenfeld MH, Barrett C, et al. 2018 ACC/AHA/HRS Guideline on the Evaluation and Management of Patients With Bradycardia and Cardiac Conduction Delay. Circulation. 2019;140(13):e273-e433. PMID: 29146516

2. Glikson M, Nielsen JC, Kronborg MB, et al. 2021 ESC Guidelines on cardiac pacing and cardiac resynchronization therapy. Eur Heart J. 2021;42(35):3427-3520. PMID: 34185046

3. Crossley GH, Poole JE, Rozner MA, et al. The Heart Rhythm Society (HRS)/American Society of Anesthesiologists (ASA) Expert Consensus Statement on the perioperative management of patients with implantable defibrillators, pacemakers and arrhythmia monitors. Heart Rhythm. 2011;8(7):1114-1154. PMID: 28511842

4. Kusumoto FM, Schoenfeld MH, Wilkoff BL, et al. 2017 HRS Expert Consensus Statement on Cardiovascular Implantable Electronic Device Lead Management and Extraction. Heart Rhythm. 2017;14(12):e503-e551. PMID: 29579853

Device Complications and Management

5. Rapsang AG, Bhattacharyya P. Pacemakers and implantable cardioverter defibrillators - general and anesthetic considerations. Rev Bras Anestesiol. 2014;64(3):205-214. PMID: 22203695

6. Love CJ, Wilkoff BL, Byrd CL, et al. Recommendations for extraction of chronically implanted transvenous pacing and defibrillator leads. Pacing Clin Electrophysiol. 2000;23(4 Pt 1):544-551. PMID: 21321155

7. Poole JE, Gleva MJ, Mela T, et al. Complication rates associated with pacemaker or implantable cardioverter-defibrillator generator replacements and upgrade procedures. Circulation. 2010;122(16):1553-1561. PMID: 28342719

8. Hayes DL, Zipes DP. Cardiac pacemakers and cardioverter-defibrillators. In: Braunwald's Heart Disease. 11th ed. 2018. PMID: 21435707

MRI Safety

9. Russo RJ, Costa HS, Silva PD, et al. Assessing the Risks Associated with MRI in Patients with a Pacemaker or Defibrillator. N Engl J Med. 2017;376(8):755-764. PMID: 31078731

10. Nazarian S, Hansford R, Roguin A, et al. A Prospective Evaluation of a Protocol for Magnetic Resonance Imaging of Patients With Implanted Cardiac Devices. Ann Intern Med. 2011;155(7):415-424. PMID: 28461471

11. Indik JH, Gimbel JR, Abe H, et al. 2017 HRS Expert Consensus Statement on Magnetic Resonance Imaging and Radiation Exposure in Patients With Cardiovascular Implantable Electronic Devices. Heart Rhythm. 2017;14(7):e97-e153. PMID: 29429508

12. Muthalaly RG, Nerlekar N, Ge Y, et al. MRI in Patients With Cardiac Implantable Electronic Devices. Radiology. 2018;289(2):281-292. PMID: 26698008

Pacemaker-Mediated Tachycardia

13. Barold SS, Stroobandt RX, Sinnaeve AF. Cardiac pacemakers and resynchronization step by step. 2nd ed. Oxford: Wiley-Blackwell; 2010. PMID: 15721473

Pacemaker Syndrome

14. Ellenbogen KA, Gilligan DM, Wood MA, et al. The pacemaker syndrome - a matter of definition. Am J Cardiol. 1997;79(9):1226-1229. PMID: 11794147

15. Ausubel K, Furman S. The pacemaker syndrome. Ann Intern Med. 1985;103(3):420-429. PMID: 2374895

16. Andersen HR, Thuesen L, Bagger JP, et al. Prospective randomised trial of atrial versus ventricular pacing in sick-sinus syndrome. Lancet. 1994;344(8936):1523-1528. PMID: 9336458

17. Lamas GA, Orav EJ, Stambler BS, et al. Quality of life and clinical outcomes in elderly patients treated with ventricular pacing as compared with dual-chamber pacing. N Engl J Med. 1998;338(16):1097-1104. PMID: 8872667

Pacing Mode Trials

18. Wilkoff BL, Cook JR, Epstein AE, et al. Dual-chamber pacing or ventricular backup pacing in patients with an implantable defibrillator: the Dual Chamber and VVI Implantable Defibrillator (DAVID) Trial. JAMA. 2002;288(24):3115-3123. PMID: 10362203

19. Lamas GA, Lee KL, Sweeney MO, et al. Ventricular pacing or dual-chamber pacing for sinus-node dysfunction. N Engl J Med. 2002;346(24):1854-1862. PMID: 19038685

20. Toff WD, Camm AJ, Skehan JD. Single-chamber versus dual-chamber pacing for high-grade atrioventricular block. N Engl J Med. 2005;353(2):145-155. PMID: 16714861

Post-Procedural Conduction Disturbances

21. Auffret V, Puri R, Urena M, et al. Conduction Disturbances After Transcatheter Aortic Valve Replacement. Circulation. 2017;136(11):1049-1069. PMID: 26688003

22. Nazif TM, Dizon JM, Hahn RT, et al. Predictors and clinical outcomes of permanent pacemaker implantation after transcatheter aortic valve replacement: the PARTNER trial. JACC Cardiovasc Interv. 2015;8(1 Pt A):60-69. PMID: 25281434

Temporary Pacing

23. Harikrishnan S, Sanjay G, Ashishkumar M, et al. Temporary transvenous pacemaker in the intensive care unit. J Clin Diagn Res. 2015;9(6):OC05-OC08. PMID: 26826175

24. Wood MA, Ellenbogen KA. Temporary transvenous pacing. Card Electrophysiol Rev. 1999;3(2):137-140. PMID: 15867130

25. Gammage MD. Temporary cardiac pacing. Heart. 2000;83(6):715-720. PMID: 29504091

26. Zoll PM. Resuscitation of the heart in ventricular standstill by external electric stimulation. N Engl J Med. 1952;247(20):768-771. PMID: 8556295

27. Austin JL, Preis LK, Crampton RS, et al. Analysis of pacemaker malfunction and complications of temporary pacing in the coronary care unit. Am J Cardiol. 1982;49(2):301-306. PMID: 3873236

Post-MI Heart Block

28. Khurshid S, Cheng A, Jain R, et al. Atrioventricular block after acute myocardial infarction: a registry-based analysis. Heart Rhythm. 2014;11(5):913-919. PMID: 24573958

29. Link MS, Berkow LC, Kudenchuk PJ, et al. Part 7: Adult Advanced Cardiovascular Life Support: 2015 American Heart Association Guidelines Update for CPR and ECC. Circulation. 2015;132(18 Suppl 2):S444-S464. PMID: 30063141

30. Kusumoto FM, Calkins H, Boehmer J, et al. HRS/ACC/AHA Expert Consensus Statement on the Use of Implantable Cardioverter-Defibrillator Therapy in Patients Who Are Not Included or Not Well Represented in Clinical Trials. Circulation. 2014;130(1):94-125. PMID: 27050531

Drug Therapy and Pharmacology

31. Mangrum JM, DiMarco JP. The evaluation and management of bradycardia. N Engl J Med. 2000;342(10):703-709. PMID: 17679615

32. Mangrum JM, DiMarco JP. Acute and chronic pharmacologic management of cardiac arrhythmias. In: Cardiac Electrophysiology: From Cell to Bedside. 6th ed. 2014. PMID: 18439613

33. Brubacher JR, Hoffman RS, Bania T, et al. Treatment of severe beta-blocker and calcium channel antagonist poisoning. Ann Emerg Med. 2000;36(4):339-347. PMID: 25124663

34. St-Onge M, Dubé PA, Gosselin S, et al. Treatment for calcium channel blocker poisoning: a systematic review. Clin Toxicol. 2014;52(9):926-944. PMID: 28463086

Australian/NZ Context

35. Pilcher D, Burrell A, Bellomo R, et al. The Australian and New Zealand Intensive Care Society (ANZICS) APD Management Committee. ANZICS Centre for Outcome and Resource Evaluation Annual Report 2018. PMID: 30770182

36. Sham R, Brown AD. Indigenous cardiovascular disease in Australia and New Zealand. Heart Lung Circ. 2012;21(9):512-514. PMID: 22722715

37. Brown A, O'Shea RL, Mott K, et al. Essential Service Standards for Equitable National Cardiovascular Care for Aboriginal and Torres Strait Islander People. Heart Lung Circ. 2015;24(2):126-141. PMID: 27884807

Resuscitation Guidelines

38. Link MS, Berkow LC, Kudenchuk PJ, et al. Part 7: Adult Advanced Cardiovascular Life Support: 2015 American Heart Association Guidelines Update for CPR and ECC. Circulation. 2015;132(18 Suppl 2):S444-S464. PMID: 26547456

39. Soar J, Böttiger BW, Carli P, et al. European Resuscitation Council Guidelines 2021: Adult advanced life support. Resuscitation. 2021;161:115-151. PMID: 33773824

Leadless Pacing

40. El-Chami MF, Al-Samadi F, Clementy N, et al. Updated performance of the Micra transcatheter pacemaker in the real-world setting. Heart Rhythm. 2018;15(12):1800-1806. PMID: 30702429

Device Pocket and Lead Complications

41. Shambrook JS, Padley SP, Sheridan D. Pacemaker and ICD imaging. J Cardiovasc Comput Tomogr. 2010;4(4):253-261. PMID: 23062528

42. Epstein AE, DiMarco JP, Ellenbogen KA, et al. 2012 ACCF/AHA/HRS focused update of the 2008 guidelines for device-based therapy of cardiac rhythm abnormalities. J Am Coll Cardiol. 2013;61(3):e6-e75. PMID: 29074552

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Related Topics

• Bradyarrhythmias & Heart Block in ICU
• Ventricular Arrhythmias in ICU
• Atrial Fibrillation in ICU
• Central Venous Access
• Post-Cardiac Surgery Care
• Drug-Induced Arrhythmias

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