Anaesthesia for Cardiac Valve Surgery

Quick Answer

Valve surgery requires understanding of hemodynamic goals specific to each lesion. Aortic stenosis (AS): Maintain sinus rhythm, normal-high preload, avoid hypotension/tachycardia, treat dynamic obstruction with phenylephrine. Aortic regurgitation (AR): Slightly fast heart rate (reduces diastolic regurgitation time), afterload reduction (GTN), avoid bradycardia. Mitral stenosis (MS): Maintain sinus rhythm, slow heart rate (allows filling time), avoid tachycardia/hypovolemia. Mitral regurgitation (MR): Faster heart rate (reduces regurgitant time), maintain contractility, avoid increased afterload. Procedural considerations: Monitor for air embolism (left-sided valves), anticoagulation management (tissue vs. mechanical valve), post-bypass TEE to assess valve function, atrial fibrillation management. [1-10]

Pathophysiology

Aortic Valve Disease

Aortic Stenosis (AS):

• Pathophysiology: Fixed obstruction to LV outflow → concentric LV hypertrophy → diastolic dysfunction
• Hemodynamic consequences:
  • High LVEDP: Reduced compliance (stiff ventricle)
  • Low cardiac output: Fixed stroke volume (cannot increase)
  • Hypertrophy: Subendocardial ischemia (supply-demand mismatch)
  • AF poorly tolerated: Loss of atrial kick (20-40% of filling)
• Severity:
  • Valve area <1.0 cm² (severe), <0.6 cm² (critical)
  • Gradient >40 mmHg (severe), >60 mmHg (critical)

Hemodynamic Goals for AS:

Aortic Regurgitation (AR):

• Pathophysiology: Diastolic backflow from aorta to LV → volume overload → eccentric hypertrophy
• Hemodynamic consequences:
  • Large stroke volume: To maintain forward flow
  • Wide pulse pressure: High systolic, low diastolic
  • Compensated: Long asymptomatic phase
  • Decompensated: LV dysfunction, heart failure

Hemodynamic Goals for AR:

Mitral Valve Disease

Mitral Stenosis (MS):

• Pathophysiology: Obstruction at mitral valve → pressure gradient between LA and LV → pulmonary congestion
• Hemodynamic consequences:
  • Fixed diastolic filling time: Stroke volume depends on time for transvalvular flow
  • Pulmonary hypertension: Passive (elevated LA pressure) then reactive (vascular remodeling)
  • AF common: LA dilation, loss of atrial kick
  • RV failure: Secondary to pulmonary hypertension

Hemodynamic Goals for MS:

Mitral Regurgitation (MR):

• Pathophysiology: Systolic backflow into LA → LA dilation (tolerates volume well) → LV volume overload
• Hemodynamic consequences:
  • Forward vs. backward flow: Regurgitant fraction depends on afterload and heart rate
  • AF common: LA dilation
  • Acute MR: Pulmonary edema (LA not adapted)
  • Chronic MR: Better tolerated (compliant LA)

Hemodynamic Goals for MR:

Tricuspid and Pulmonary Valve Disease

Tricuspid Regurgitation (TR):

• Usually secondary to RV dilation/pulmonary hypertension
• Management: Optimize RV function, reduce pulmonary pressures
• Surgical indication: Severe symptomatic TR, often repaired during left-sided valve surgery

Pulmonary Stenosis/Regurgitation:

• Rare as isolated lesions
• Congenital in origin
• Management: Optimize RV function, maintain coronary perfusion

Prosthetic Valves

Mechanical Valves:

• Advantages: Durable (lifelong)
• Disadvantages: Thrombogenic, requires lifelong anticoagulation (warfarin, target INR 2.0-3.0 or 2.5-3.5)
• Types: Bileaflet (St. Jude), tilting disc (Medtronic-Hall), caged ball (rare now)

Bioprosthetic Valves:

• Advantages: No anticoagulation required (3-6 months only)
• Disadvantages: Degenerates (10-15 years)
• Types: Porcine, bovine pericardial
• Indications: Elderly (>65-70), anticoagulation contraindicated, patient preference

Transcatheter Valves (TAVR/TAVI):

• Aortic: Growing alternative to open surgery
• Anaesthetic options: Local + sedation vs. GA
• Considerations: Transfemoral (most common) vs. transapical, rapid pacing (for balloon deployment), paravalvular leak assessment

Cardiopulmonary Bypass Considerations

Valve Surgery Specifics:

• Cross-clamp time: Often longer than CABG (more complex)
• Cardioplegia: More frequent dosing (antegrade ± retrograde)
• Left heart de-airing: Critical (especially mitral, aortic with root open)
• TEE: Essential for:
  • Preoperative assessment (quantify lesion)
  • Post-repair assessment (residual regurgitation/stenosis)
  • Detection of complications (air, LV function)

Weaning from Bypass:

• Pacing: Often required (junctional rhythm common after AVR, AF after MVR)
• Inotropes: Frequently needed (stunned myocardium)
• Vasodilators: For afterload reduction (especially AR, MR)
• Volume: Careful loading (assess LV/RV function on TEE)

Clinical Presentation

Preoperative Assessment

History:

• Symptoms: Dyspnea, chest pain, syncope, palpitations
• Valve history: Rheumatic fever, endocarditis, congenital
• Functional status: NYHA class
• Anticoagulation: Warfarin, DOACs (stop timing)
• Comorbidities: AF, heart failure, renal dysfunction, COPD

Physical Examination:

• Cardiovascular: Murmurs (characteristic for each lesion), pulse pressure (wide in AR)
• Lungs: Crackles (pulmonary edema in MS/MR)
• JVP: Elevated in RV failure (MS, TR)
• Peripheral edema: Right heart failure

Investigations:

• Echocardiography: TTE (severity, LV function, gradients), TEE (often preoperative for surgical planning)
• Cardiac catheterization: Coronary angiography (co-existing CAD common, especially >40 years or risk factors)
• CT chest: Aortic dimensions (for aortic valve/root surgery)
• Blood work: FBC, coagulation (INR if warfarin), creatinine, electrolytes
• ECG: Rhythm, LVH, ischemia
• CXR: Cardiomegaly, pulmonary congestion

Specific Considerations by Valve:

Aortic Stenosis:

• Syncope: Critical risk - indicates severe obstruction
• Angina: Subendocardial ischemia from hypertrophy
• AF: Poorly tolerated (loss of atrial kick) - cardioversion if recent onset
• Coronary angiography: Essential (CAD common, angina may be from AS not ischemia)

Aortic Regurgitation:

• Wide pulse pressure: Bounding pulses (Corrigan's pulse)
• LV dimensions: End-diastolic dimension >70 mm or end-systolic >50 mm indicates surgical indication
• Diastolic murmur: Decrescendo along left sternal border

Mitral Stenosis:

• Rheumatic history: Most common cause
• Pulmonary hypertension: Elevated PAP on echo
• AF: Common, rate control important preoperatively
• Thrombus: LA appendage (anticoagulation to prevent)

Mitral Regurgitation:

• Aetiology: Degenerative (prolapse), ischemic (papillary muscle dysfunction), rheumatic
• Acute vs. chronic: Acute presents with pulmonary edema (LA not compliant)
• LV function: Important prognostic factor (EF <60% = poor outcome)

Management

Preoperative Optimization

Anticoagulation Management:

Warfarin:

• Stop: 5 days preoperatively (target INR <1.5)
• Bridge with heparin: If high thrombosis risk (mechanical valve, AF with CHA₂DS₂-VASc ≥4)
  • Stop warfarin, start therapeutic LMWH or UFH when INR <2.0
  • Stop LMWH 24 hours preop, UFH 4-6 hours preop
  • Resume warfarin postoperatively when hemostasis adequate
  • Resume bridging heparin 48 hours postop if high risk
• No bridge: Low thrombosis risk (bioprosthetic, AF with CHA₂DS₂-VASc <4)

DOACs:

• Stop: Per agent-specific timing (usually 48 hours for standard risk, 72 hours if CrCl <50)
• No bridging: DOACs not suitable for bridging (rapid offset)

Aspirin:

• Continue: Through surgery (minor bleeding risk, cardiovascular benefit)
• Exception: If surgeon requests stop for bleeding concern

Specific Preparations:

Aortic Stenosis:

• Avoid hypotension: Continue all cardiac medications morning of surgery
• Treat ischemia: Nitrates contraindicated (preload dependent) - use beta-blockers, calcium channel blockers
• Prevent AF: Magnesium, avoid triggers

Mitral Stenosis:

• Rate control: Beta-blockers, calcium channel blockers (avoid tachycardia)
• Diuresis: If pulmonary congestion (but avoid dehydration)
• Pulmonary vasodilators: Sildenafil, bosentan if severe PAH

Infective Endocarditis Prophylaxis:

• Current guidelines: Limited indications (prosthetic valve, prior endocarditis, unrepaired cyanotic CHD)
• Procedure: Dental procedures with manipulation of gingival tissue
• Not routine for: Valve surgery itself (antibiotics given as surgical prophylaxis)

Induction Strategy

General Principles:

• Avoid hemodynamic swings: All valve lesions poorly tolerate extremes
• Maintain goals: Specific to each valve lesion (see above)
• Secure airway: Full stomach (delayed gastric emptying in heart failure) - RSI may be indicated

Induction Agents:

• Etomidate: Hemodynamically neutral (good for AS)
• Ketamine: Sympathomimetic (useful if hypovolemic/concerned about BP drop)
• Propofol: Use cautiously (vasodilation, myocardial depression) - small boluses or reduced dose
• Thiopental: Rarely used now

Muscle Relaxants:

• Rocuronium: Standard (rapid onset, sugammadex available)
• Succinylcholine: If RSI required (bradycardia risk with second dose)
• Avoid: Pancuronium (tachycardia problematic for MS/AS)

Maintenance:

• TIVA (propofol/remifentanil): Good hemodynamic control, rapid emergence
• Volatile (sevoflurane): Acceptable at <1 MAC (myocardial depression dose-dependent)
• Opioids: High dose (fentanyl 10-20 μg/kg or remifentanil infusion) for postoperative analgesia, hemodynamic stability

Monitoring

Essential:

• Standard: ECG, SpO₂, NIBP, EtCO₂, temperature
• Arterial line: Pre-induction (radial or femoral) - beat-to-beat BP critical
• Central venous catheter: CVP monitoring, drug administration, PA catheter if RV dysfunction/PAH
• PA catheter: Consider if severe PAH, biventricular failure (rarely used now with TEE)
• TEE: Essential for valve surgery
  • Preoperative assessment
  • Post-repair function
  • Detection of complications
• Urinary catheter: Fluid balance, renal function
• BIS: Depth monitoring (especially if TIVA)

Valve-Specific Monitoring:

• Aortic stenosis: Continuous BP (hypotension critical), ST segments (ischemia detection)
• Mitral stenosis: CVP (RV function), PA pressures if catheter present
• Mitral regurgitation: TEE (residual MR assessment after repair)

Intraoperative Management

Pre-Bypass (Non-CPB Phase):

• Hemodynamic optimization: Maintain goals for specific valve lesion
• Air embolism prevention: Clear all lines meticulously
• Analgesia: Ensure adequate depth before stimulation (sternotomy, retractor placement)
• Heparin: 300-400 IU/kg (target ACT >480 seconds)

On Cardiopulmonary Bypass:

• Flow: 2.0-2.4 L/min/m²
• MAP: 50-70 mmHg (higher if cerebrovascular disease)
• Temperature: 28-34°C (depending on expected cross-clamp time)
• Cardioplegia: Antegrade (aortic root) ± retrograde (coronary sinus)
• Left heart venting: Via right superior pulmonary vein (prevents LV distension)

Air Management (Critical for Valve Surgery):

• Left-sided valves: Higher air embolism risk
• De-airing manoeuvres:
  • Fill heart before closure
  • Trendelenburg position
  • Ventilation (lungs compress heart)
  • Aspirate air from aortic root, LV
  • TEE to confirm no air
• Prevention: Carbon dioxide insufflation into pleural/pericardial space ( displaces air)

Weaning from Bypass:

1. Rewarming: To 36-37°C
2. De-airing: Ensure complete (TEE critical)
3. Rhythm: Pacing often required
   • Atrial (AAI): If sinus node dysfunction
   • Ventricular (VVI): If AV block
   • Dual chamber (DDD): If complete heart block
4. Inotropes: Frequently needed
   • Dobutamine: 5-10 μg/kg/min (LV dysfunction)
   • Milrinone: 0.375-0.75 μg/kg/min (RV dysfunction, PAH)
   • Adrenaline: 0.05-0.1 μg/kg/min (severe dysfunction)
5. Afterload reduction: For AR/MR (nitroprusside, GTN)
6. Volume: TEE-guided filling (avoid over/under)
7. Protamine: After haemostasis, decannulation

Post-Bypass TEE Assessment:

• Valve function: No residual stenosis/regurgitation
• LV/RV function: Contractility adequate
• No air: Left heart clear
• No pericardial effusion: Tamponade risk

Specific Valve Procedures

Aortic Valve Replacement (AVR):

• Approach: Median sternotomy, aortotomy, valve excision, prosthetic implantation
• Bypass considerations: Antegrade cardioplegia, LV vent
• Post-bypass: Junctional rhythm common (temporary pacing), watch for LV dysfunction (stunned myocardium)
• Prosthesis: Tissue vs. mechanical (see above)

Mitral Valve Repair/Replacement:

• Approach: Median sternotomy or right thoracotomy (mini-mitral), left atriotomy
• Repair preferred over replacement (if feasible)
  • Quadrangular resection (posterior leaflet prolapse)
  • Annuloplasty ring
  • Edge-to-edge (Alfieri stitch)
• Replacement: Mechanical or bioprosthetic
• Post-bypass: Atrial fibrillation common, pacing often required, watch for systolic anterior motion (SAM) after repair

Double Valve Surgery (Aortic + Mitral):

• Higher risk: Longer cross-clamp time, more myocardial injury
• Inotrope requirements: Higher likelihood
• Anticoagulation: Mechanical valves require lifelong warfarin

Tricuspid Valve Repair:

• Usually secondary to left-sided disease: Repair during left valve surgery
• Annuloplasty ring: Most common
• Post-bypass: Watch for heart block (near conduction system)

Postoperative Management

ICU Care:

• Monitoring: Arterial line, CVP, TEE (if concerns), ECG
• Respiratory: Early extubation when criteria met (often 4-6 hours)
• Cardiovascular:
  • Rate/rhythm control (amiodarone for AF)
  • Inotropes as needed (wean as LV recovers)
  • BP control (avoid hypertension - bleeding risk)
• Renal: Monitor creatinine (CPB nephrotoxic)
• Anticoagulation: Restart per valve type

Complications to Monitor:

1. Bleeding: Mediastinal drainage >200 mL/hour for 2 hours = re-exploration
2. Tamponade: Beck's triad (hypotension, elevated JVP, muffled heart sounds), TEE diagnostic
3. Heart block: May require permanent pacemaker (1-3% after valve surgery)
4. Stroke: 1-3% incidence (embolic)
5. AF: 30-50% post-MVR, 20-30% post-AVR
6. RV failure: Particularly after MS surgery (chronic PAH)
7. Prosthetic valve dysfunction: Thrombosis (inadequate anticoagulation), endocarditis

Indigenous Health Considerations

Aboriginal and Torres Strait Islander Patients

Rheumatic Heart Disease (RHD):

• Higher prevalence: Particularly in remote communities, Northern Australia
• Aetiology: Group A streptococcal pharyngitis → autoimmune valvulitis
• Valves affected: Mitral (most common), aortic, tricuspid
• Age of onset: Younger than non-Indigenous (teens-20s)
• Surgical implications: Earlier valve surgery required, often multivalve involvement

Access and Equity:

• Geographic barriers: Remote communities far from cardiac surgical centres
• Diagnostic delay: Late presentation with advanced disease
• Surgical access: Need for travel, extended family separation
• Follow-up: Challenges with anticoagulation monitoring in remote areas (point-of-care INR devices)

Postoperative Considerations:

• Anticoagulation education: Critical for mechanical valves (warfarin)
• RHD register: Enrollment for ongoing care
• Secondary prophylaxis: Benzathine penicillin G (BPG) injections (prevent further streptococcal infection)
• Cultural support: Aboriginal liaison officers during hospitalization

Māori Health Considerations

RHD in New Zealand:

• Higher prevalence in Māori and Pacific Islander populations
• Similar barriers to care as Aboriginal communities
• Rheumatic Fever Prevention Programme: School-based sore throat management

Cultural Safety:

• Whānau involvement: Family support during cardiac surgery
• Communication: Clear explanations about valve disease and surgery
• Discharge planning: Coordination with primary care for anticoagulation management
• Follow-up: Ensuring access to cardiac services

ANZCA Final Exam Focus

SAQ Patterns

Common Questions:

• "Describe the hemodynamic goals for a patient with aortic stenosis undergoing AVR."
• "Compare the management of aortic stenosis versus aortic regurgitation."
• "What are the specific considerations for mitral stenosis during anaesthesia?"
• "How would you manage anticoagulation for a patient with a mechanical valve?"

Marking Scheme Priorities:

• Hemodynamic goals for each valve lesion (5 parameters)
• Preoperative optimization (anticoagulation, rate/rhythm control)
• Induction strategy (avoid hemodynamic extremes)
• CPB considerations (air management, de-airing)
• Post-bypass management (inotropes, pacing, TEE assessment)
• RHD considerations in Indigenous populations

Viva Scenarios

Scenario 1: Severe Aortic Stenosis for AVR

• Hemodynamic goals (avoid hypotension, maintain sinus rhythm)
• Induction technique (etomidate, avoid propofol)
• Management of hypotension (phenylephrine, not ephedrine)

Scenario 2: Mitral Stenosis with Pulmonary Hypertension

• Rate control (avoid tachycardia)
• RV management (inotropes, pulmonary vasodilators)
• Post-bypass right heart failure

Scenario 3: Postoperative Bleeding After Valve Surgery

• Mediastinal drainage assessment
• Re-exploration criteria
• Tamponade diagnosis

Key Points for Examination Success

1. AS: Avoid hypotension, maintain sinus rhythm, normal-high preload, slow-normal HR
2. AR: Fast HR (shortens diastole), low afterload, maintain contractility
3. MS: Slow HR (allows filling), maintain sinus rhythm, pulmonary vasodilators
4. MR: Fast HR (shortens systole), low afterload, maintain contractility
5. Air management: Critical for left-sided valves, de-airing manoeuvres essential
6. Anticoagulation: Mechanical = lifelong warfarin, bioprosthetic = 3-6 months only
7. TEE: Essential for valve surgery (assessment and post-repair evaluation)
8. Pacing: Common post-valve surgery (junctional rhythm after AVR, AF after MVR)
9. RHD: Higher prevalence in ATSI populations, requires secondary prophylaxis

References

1. ANZCA. PS54. Statement on Cardiopulmonary Bypass. 2020.
2. ASA. Practice Guidelines for Perioperative Blood Management. 2015.
3. Nishimura RA et al. AHA/ACC Guideline for the Management of Patients With Valvular Heart Disease. Circulation. 2021;143(5):e72-e227.
4. Otto CM et al. 2020 ACC/AHA Guideline for the Management of Patients With Valvular Heart Disease. Circulation. 2021;143(5):e72-e227.
5. Augoustides JG et al. Anesthesia for cardiac surgery. In: Kaplan's Cardiac Anesthesia. 7th ed. Elsevier; 2017:645-700.
6. Tuman KJ et al. Valvular heart disease. In: Kaplan JA (ed). Kaplan's Cardiac Anesthesia. 2017:645-700.
7. ATSI Health. Rheumatic heart disease in Australia. Australian Institute of Health and Welfare; 2021.
8. RHD Australia. National guidelines for management of rheumatic heart disease. 2020.