Critical Alerts

• Unstable tachycardia (hypotension, altered consciousness, ischemia, acute heart failure) requires immediate cardioversion
• Wide complex tachycardia should be treated as VT until proven otherwise
• Avoid AV nodal blockers in atrial fibrillation with WPW (can cause VF)
• Polymorphic VT (Torsades de Pointes) requires IV magnesium, not amiodarone
• Regular narrow complex tachycardia often responds to vagal maneuvers or adenosine

Key Diagnostics

• 12-lead ECG (essential for classification)
• Continuous cardiac monitoring
• Electrolytes (K+, Mg2+, Ca2+)
• Troponin if ischemia suspected
• TSH for new-onset atrial fibrillation
• Medication/toxicology screen if indicated

Emergency Treatments

• Unstable: Synchronized cardioversion (50-200J biphasic)
• Stable narrow regular: Vagal maneuvers → Adenosine 6mg → 12mg → 12mg
• Stable narrow irregular (AF): Rate control (diltiazem, metoprolol)
• Stable wide regular (VT): Amiodarone 150mg IV over 10 min
• Torsades de Pointes: Magnesium 2g IV bolus, defibrillation if unstable

Tachycardia is defined as a heart rate greater than 100 beats per minute in adults. While sinus tachycardia is a physiologic response to various stimuli, pathological tachycardias arise from abnormal impulse generation or conduction and may be life-threatening.

Classification by Mechanism

Automaticity

• Enhanced normal automaticity (sinus tachycardia)
• Abnormal automaticity (ectopic atrial tachycardia)

Triggered Activity

• Early afterdepolarizations (Torsades de Pointes)
• Delayed afterdepolarizations (digitalis toxicity)

Re-entry

• Macro-re-entry (atrial flutter, AVRT)
• Micro-re-entry (AVNRT, VT)

Classification by QRS Width and Regularity

Signs of Hemodynamic Instability

High-Risk Arrhythmias

Approach to Narrow Complex Tachycardia

Step 1: Regular or Irregular?

Regular NCT

• Sinus tachycardia
• AVNRT
• AVRT (orthodromic)
• Atrial flutter with fixed block
• Ectopic atrial tachycardia

Irregular NCT

• Atrial fibrillation
• Atrial flutter with variable block
• Multifocal atrial tachycardia
• Sinus tachycardia with ectopy

Approach to Wide Complex Tachycardia

Assume VT until proven otherwise (75-80% of WCT is VT)

Differential

1. Ventricular tachycardia (most common)
2. SVT with aberrant conduction (LBBB, RBBB)
3. SVT with pre-excitation (antidromic AVRT)
4. Pacemaker-mediated tachycardia
5. Hyperkalemia with sinus tachycardia

Secondary Causes of Sinus Tachycardia

Initial Assessment

ABCDE Approach

1. Airway: Patent
2. Breathing: Assess for pulmonary edema
3. Circulation: Pulse quality, BP, perfusion
4. Disability: Mental status
5. Exposure: Signs of underlying cause

Key Questions

• Stable or unstable?
• Narrow or wide QRS?
• Regular or irregular?

ECG Interpretation Algorithm

Tachycardia (>100 bpm)
         ↓
QRS <120ms (Narrow) or ≥120ms (Wide)?
         ↓
    [NARROW]                      [WIDE]
         ↓                              ↓
  Regular or Irregular?         Treat as VT until proven
         ↓                              ↓
[Regular]    [Irregular]        Cardiovert if unstable
    ↓              ↓               OR
Vagal → AF        MAT          Antiarrhythmics if stable
Adenosine  Flutter w/
           variable block

Laboratory Studies

Imaging

• Chest X-ray: Cardiomegaly, pulmonary edema
• Echocardiography: Structural heart disease, EF, wall motion abnormalities
• CT-PA: If PE suspected

Admission Criteria

ICU/Telemetry

• Hemodynamic instability
• Cardioversion performed
• VT or high-risk arrhythmia
• Significant structural heart disease
• Ongoing ischemia
• New heart failure

Observation/Telemetry

• First episode requiring treatment
• Symptomatic recurrence after treatment
• Need for medication adjustment
• Electrolyte abnormalities

Discharge Criteria

• Stable rhythm (sinus or controlled AF)
• Hemodynamically stable
• No concerning symptoms
• Electrolytes normal
• Clear diagnosis with management plan
• Follow-up arranged

Outpatient Referrals

Understanding Tachycardia

• Tachycardia means fast heart rate
• Many causes exist, from benign to serious
• Treatment depends on the type and cause
• Some conditions can be cured with ablation procedures

Vagal Maneuvers at Home

For patients with documented SVT:

• Valsalva maneuver (bearing down)
• Cold water on face
• Only attempt if trained and safe to do so

Warning Signs to Return

• Palpitations lasting >15-20 minutes
• Associated chest pain
• Shortness of breath
• Dizziness or near-fainting
• Fainting
• Palpitations with exercise

Medication Adherence

• Take rate control medications as prescribed
• Do not miss anticoagulation doses if prescribed
• Avoid excessive caffeine and alcohol
• Report side effects promptly

Pediatric Considerations

Normal Heart Rates by Age

SVT in Children

• Most common arrhythmia in pediatrics
• Often AVRT (accessory pathway)
• Vagal maneuvers: Ice to face very effective
• Adenosine dosing: 0.1mg/kg (max 6mg) then 0.2mg/kg (max 12mg)

Elderly Patients

• Higher risk of falls with hypotension
• More likely to have structural heart disease
• More sensitive to medications
• Caution with rate control agents

Pregnancy

Safe Medications

• Adenosine: Safe
• Beta-blockers: Generally safe (prefer metoprolol, labetalol)
• Cardioversion: Safe at any gestational age

Avoid if Possible

• Amiodarone (thyroid, neurological effects on fetus)
• ACE inhibitors (if treating underlying cause)

Heart Failure

• Avoid negative inotropes when possible
• Amiodarone preferred for rate control
• Digoxin remains option
• Cardioversion may improve hemodynamics rapidly

Performance Indicators

Documentation Requirements

• 12-lead ECG findings
• Classification of tachycardia
• Hemodynamic status
• Treatments given and response
• Post-treatment rhythm
• Anticoagulation plan (if AF)
• Disposition rationale
• Follow-up instructions

Diagnostic Pearls

1. Wide complex = VT until proven otherwise (80% are VT)
2. Look for AV dissociation - cannon A waves, variable S1
3. Regular at 150 bpm - think atrial flutter with 2:1 block
4. Irregularly irregular without P waves = Atrial fibrillation
5. Adenosine can be diagnostic even if it doesn't convert

Treatment Pearls

1. Unstable = cardiovert - don't waste time with drugs
2. Modified Valsalva has higher success than standard
3. Adenosine needs fast push - arm with tourniquet, stopcock setup
4. Avoid AV blockers in WPW with AF - can cause VF
5. Magnesium is first-line for Torsades - not amiodarone

Disposition Pearls

1. First VT = admission even if terminated
2. Recurrent SVT may benefit from ablation - refer to EP
3. New AF needs stroke risk assessment (CHA2DS2-VASc)
4. Ensure electrolytes normalized before discharge
5. Follow-up with cardiology for all arrhythmias requiring treatment