Australian Guidelines for Myomectomy in Hypertrophic Cardiomyopathy
Surgical septal myectomy is the gold standard treatment for patients with hypertrophic cardiomyopathy (HCM) who have severe drug-refractory symptoms and significant left ventricular outflow tract obstruction (LVOTO ≥50 mm Hg). 1
Patient Selection Criteria
Indications for Surgical Myectomy
- Primary candidates:
- Patients with drug-refractory NYHA class III-IV symptoms
- Resting or provocable LVOT gradient ≥50 mm Hg
- Septal thickness sufficient for effective and safe myectomy
- Failure of maximal medical therapy (beta-blockers, calcium channel blockers, disopyramide)
Preoperative Assessment
Comprehensive echocardiography to assess:
- Degree and location of septal hypertrophy
- LVOT gradient at rest and with provocation
- Mitral valve abnormalities (elongated leaflets, direct papillary muscle insertion)
- Presence and severity of mitral regurgitation
- Left atrial size (predictor of outcomes) 1
Cardiac catheterization with coronary angiography for:
- Patients with angina or risk factors for coronary artery disease
- Confirmation of LVOT gradient when noninvasive imaging is inconclusive 1
Procedural Considerations
Surgical Approach
- Transaortic approach is the primary method of exposure
- Extended myectomy (7 cm) may be preferred over traditional Morrow procedure (3 cm) for more complete relief of obstruction 1
- Intraoperative transesophageal echocardiography (TEE) is mandatory to:
- Guide the extent of myectomy
- Assess mitral valve anatomy and function
- Evaluate adequacy of resection
- Detect complications (ventricular septal defect, aortic regurgitation) 1
Concomitant Procedures
- Consider mitral valve repair when:
- Intrinsic mitral valve abnormalities are present
- Elongated anterior leaflet contributes to obstruction
- Papillary muscle abnormalities may require:
- Shaving of hypertrophied papillary muscles
- Mobilization from ventricular free wall
- Repositioning via suture approximation 1
Outcomes and Complications
Expected Benefits
- Near-complete elimination of LVOT gradient (reduced from mean 66±32 mmHg to 1-10 mmHg) 1, 2
- Significant improvement in symptoms (83-94% of patients improve to NYHA class I-II) 2, 3
- Reduction in mitral regurgitation without need for valve replacement in most cases
- Normalization of LV pressures and wall stress
- Potential reduction in long-term mortality compared to non-operated patients 1
Complications
- Operative mortality: 1-3% at experienced centers (as low as 0.8% in recent series) 1, 3
- Complete heart block requiring permanent pacemaker: approximately 2%
- Higher risk (50-85%) in patients with pre-existing right bundle branch block or prior alcohol septal ablation 1
- Iatrogenic ventricular septal defect: approximately 1% 1
Special Considerations
Surgical Volume and Expertise
- Operator experience is crucial for optimal outcomes
- Recommended minimum operator volume: 20 procedures
- Institutional volume: at least 50 procedures
- Target mortality rate of ≤1% and major complication rate of ≤3% 1
Myectomy vs. Alcohol Septal Ablation
Myectomy is preferred for:
Alcohol septal ablation may be considered for:
Long-term Follow-up
- Echocardiography at 3-6 months post-procedure to evaluate results 1
- Regular clinical assessment and echocardiography every 1-2 years 1
- Continued assessment for risk of sudden cardiac death as myectomy does not eliminate this risk 1
Prognostic Factors
Predictors of mortality after myectomy include:
- Age ≥50 years at surgery
- Female gender
- History of preoperative atrial fibrillation
- Concomitant CABG
- Preoperative left atrial diameter ≥46 mm 2
Surgical myectomy remains the gold standard treatment for symptomatic obstructive HCM with excellent long-term outcomes when performed at experienced centers.