What is the recommended evaluation and treatment for septal hypertrophy?

Evaluation and Management of Septal Hypertrophy

Initial Diagnostic Evaluation

All patients with suspected septal hypertrophy require comprehensive transthoracic echocardiography (TTE) as the cornerstone diagnostic test to establish the diagnosis, quantify septal thickness, assess for left ventricular outflow tract (LVOT) obstruction, and evaluate systolic anterior motion (SAM) of the mitral valve. 1, 2

Essential Echocardiographic Assessment

• Measure septal thickness at multiple levels: A septal thickness ≥15 mm is the standard diagnostic threshold for hypertrophic cardiomyopathy (HCM), though affected family members may have thicknesses below this cutoff 1
• Quantify LVOT gradients both at rest and with provocation (Valsalva maneuver or exercise), as dynamic obstruction may only manifest with physiologic stress 1, 2
• Document left atrial volume index: Values ≥34 mL/m² indicate chronically elevated filling pressures and predict worse outcomes 2
• Assess for SAM of the mitral valve and degree of mitral regurgitation, which are key contributors to obstruction 1

Additional Diagnostic Studies

• Obtain 12-lead ECG immediately to identify left ventricular hypertrophy patterns, deep T-wave inversions, pathological Q-waves, and conduction abnormalities 2
• Perform 24-hour Holter monitoring for risk stratification and detection of ventricular tachycardia 2
• Consider cardiac MRI when TTE is suboptimal, to evaluate apical variants, detect apical aneurysms, or assess for late gadolinium enhancement indicating fibrosis 2
• Exercise treadmill testing is reasonable for sudden cardiac death risk stratification and to assess functional capacity 2

Critical Differential Diagnosis Considerations

• Distinguish from secondary hypertrophy due to aortic stenosis, systemic hypertension, amyloidosis, or Fabry disease 1
• Hypertensive cardiac hypertrophy shows dominant basal septal thickening, whereas HCM shows dominant mid-septal hypertrophy 3
• Infiltrative diseases (amyloidosis, Fabry) may show concentric hypertrophy, sparkling myocardial texture, thickened interatrial septum, and small pericardial effusion 1

Treatment Algorithm

Step 1: Determine Presence of Obstruction

The critical first decision point is whether LVOT obstruction exists, defined as a dynamic gradient ≥50 mm Hg at rest or with provocation. 1

Step 2: Assess Symptom Severity

For patients with obstruction, determine if symptoms are severe and refractory to medical therapy (typically NYHA functional class III-IV, syncope, or near-syncope interfering with quality of life). 1

Step 3: Medical Management First-Line

• Initiate beta-blockers as first-line therapy to reduce outflow obstruction and improve symptoms 4
• Calcium channel blockers (verapamil or diltiazem) are alternatives if beta-blockers are contraindicated or ineffective 4
• Disopyramide can be added for refractory symptoms, but monitor QTc interval and reduce dose if it exceeds 480 ms 4
• Medical therapy must be optimized before considering invasive interventions 4

Step 4: Septal Reduction Therapy for Refractory Cases

Septal reduction therapy should ONLY be performed for patients with all three criteria: (1) LVOT gradient ≥50 mm Hg, (2) severe symptoms (NYHA III-IV or recurrent syncope) despite optimal medical therapy, and (3) sufficient septal thickness to perform the procedure safely. 1

Surgical Myectomy (Preferred Option)

Surgical septal myectomy is the first consideration and preferred treatment for the majority of eligible patients, particularly younger patients, those with concomitant cardiac disease requiring surgery, and those with marked septal hypertrophy >30 mm. 1

• Mortality rate is approximately 1% at experienced centers 1
• Complete heart block occurs in ~2% and iatrogenic ventricular septal defect in ~1% 4
• Survival free from recurrent symptoms is superior to ablation (89% vs 71% at long-term follow-up) 1
• Can address concomitant mitral valve abnormalities and papillary muscle malposition 1

Alcohol Septal Ablation (Alternative Option)

Alcohol septal ablation is recommended when surgery is contraindicated or considered unacceptable risk due to advanced age, significant comorbidities, or strong patient preference after thorough discussion of both options. 1

• Mortality ranges from 0-4% at experienced centers 1
• High-grade atrioventricular block requiring permanent pacemaker occurs in 10-20% of patients, an inherent consequence of septal infarction 1
• Success depends on variable septal artery anatomy, which may not supply the targeted area in 20-25% of patients 1
• Generally discouraged in patients with marked septal hypertrophy >30 mm 1
• Requires intracoronary contrast echocardiography to ensure correct localization before alcohol injection 1, 4

Critical Contraindications to Septal Reduction

Septal reduction therapy should NOT be performed in asymptomatic patients or those whose symptoms are controlled on optimal medical therapy. 1

Septal reduction should NOT be performed unless part of a dedicated multidisciplinary HCM program. 1

Operator and Institutional Requirements

Procedures should only be performed at experienced centers with operator volume of at least 20 procedures OR within an HCM program with cumulative volume of at least 50 procedures. 1

Target benchmarks are mortality rates ≤1% and major complication rates ≤3%. 1

Special Populations

Pediatric Patients

Surgical myectomy can be beneficial in symptomatic children with severe resting obstruction >50 mm Hg who have failed standard medical therapy. 1

Nonobstructive HCM with Systolic Dysfunction

Patients who develop systolic dysfunction with ejection fraction ≤50% should be treated with evidence-based heart failure therapy including ACE inhibitors, angiotensin receptor blockers, and beta-blockers. 1

Common Pitfalls to Avoid

• Do not perform TTE more frequently than every 12 months in stable patients when changes are unlikely to impact clinical decisions 1, 2
• Do not proceed with alcohol septal ablation in patients with concomitant disease requiring surgical correction (e.g., coronary artery bypass grafting, mitral valve repair for ruptured chordae) 1
• Do not use mitral valve replacement for relief of LVOT obstruction when septal reduction therapy is an option 1
• Do not implant permanent pacemakers as first-line therapy to relieve symptoms in medically refractory patients who are candidates for septal reduction 1

Prognostic Considerations

Greater extent of septal hypertrophy is an independent predictor of progression to atrial fibrillation (odds ratio 5.44), which significantly increases morbidity and mortality. 5

Maximal wall thickness ≥30 mm has a relatively linear association with sudden death risk, representing the highest risk category. 1