What is the treatment for left septal hypertrophy?

Treatment for Left Septal Hypertrophy

For patients with left septal hypertrophy, treatment depends entirely on the presence and severity of left ventricular outflow tract (LVOT) obstruction and symptoms—asymptomatic patients without significant obstruction require only surveillance, while symptomatic patients with gradients ≥50 mmHg despite optimal medical therapy should undergo septal reduction therapy at experienced centers. 1

Initial Assessment and Risk Stratification

Before initiating treatment, you must determine:

• Resting and provoked LVOT gradient using echocardiography with Valsalva maneuver or exercise testing—a gradient ≥50 mmHg is the threshold for considering intervention 1
• Symptom severity using NYHA functional class—Classes III-IV symptoms refractory to medical therapy warrant invasive intervention 1, 2
• Septal thickness measurement—while classic HCM involves thickness ≥15 mm, approximately 7% of obstructive HCM patients have septal thickness ≤15 mm (including some with only 10-12 mm), where obstruction is primarily driven by mitral valve abnormalities 3, 4
• Mitral valve morphology—elongated anterior mitral leaflet, abnormal chordal attachments, and papillary muscle abnormalities can cause obstruction even with mild septal hypertrophy 3, 4

Medical Management (First-Line)

Beta-blockers are the initial therapy of choice for symptomatic patients with LVOT obstruction 1, 2:

• Start with beta-blockers and titrate to maximum tolerated dose to reduce outflow obstruction and improve symptoms 2
• If beta-blockers are ineffective or contraindicated, use verapamil (non-dihydropyridine calcium channel blocker) as second-line therapy 1, 2
• Avoid verapamil in patients with severe obstruction and hypotension due to risk of hemodynamic collapse 5
• Disopyramide can be added to beta-blockers or verapamil for additional gradient reduction, but monitor QTc interval and reduce dose if it exceeds 480 ms 1, 2

Critical caveat: In patients with hypertrophic cardiomyopathy and quinidine, avoid combining with verapamil due to risk of significant hypotension 5. Beta-blockers combined with verapamil require extreme caution due to additive negative effects on heart rate and AV conduction 5.

Low-dose diuretics may be used cautiously to improve exertional dyspnea, but avoid aggressive diuresis which can worsen obstruction 1.

Indications for Septal Reduction Therapy

Proceed to invasive septal reduction when ALL of the following criteria are met 1, 2:

1. Hemodynamic: LVOT gradient ≥50 mmHg at rest or with physiologic provocation 1, 2
2. Clinical: Severe symptoms (NYHA Class III-IV) or recurrent exertional syncope despite maximum tolerated medical therapy 1, 2
3. Anatomic: Sufficient septal thickness to perform the procedure safely in the judgment of the operator 1

Never perform septal reduction therapy in asymptomatic patients or those whose symptoms are controlled on medical therapy 1.

Choice of Septal Reduction Procedure

Surgical Myectomy (Preferred for Most Patients)

Surgical septal myectomy is the preferred treatment for most symptomatic patients, especially younger healthy adults 1, 2:

Advantages 1, 2:

• Direct visualization allows tailored resection of specific anatomic abnormalities 1
• Lower risk of permanent pacemaker requirement (approximately 2% vs 7-20% with ablation) 1
• Effective even in patients with massive septal thickness (≥30 mm) 1
• Can address concomitant mitral valve abnormalities, papillary muscle malposition, and abnormal chordal attachments in the same operation 1, 3, 4
• Long-term data shows 70-80% achieve sustained symptomatic benefit with survival comparable to general population 1

Specific considerations for mild septal hypertrophy: In patients with septal thickness ≤15 mm where obstruction is primarily due to elongated mitral valve leaflets, myectomy combined with mitral valve reconstruction (without valve replacement) effectively relieves obstruction 3, 4.

Complications: Complete heart block (2%), iatrogenic ventricular septal defect (1%), aortic regurgitation 1.

Alcohol Septal Ablation (Alternative Option)

Alcohol septal ablation is preferred when surgery is contraindicated or considered high risk, particularly in elderly patients or those with significant comorbidities 1, 2:

Advantages 1, 2:

• No surgical incision or general anesthesia 1
• Shorter recovery time and less overall discomfort 1
• Similar hemodynamic and functional improvement compared to myectomy over 3-5 years in appropriate candidates 1

Limitations and contraindications 1, 2:

• Should not be performed in patients <21 years of age and is discouraged in adults <40 years if myectomy is viable 1
• Ineffective in patients with marked septal hypertrophy (>30 mm) 1
• Higher risk of permanent pacemaker requirement (7-20%) 1
• Dependent on suitable septal perforator artery anatomy—if myocardial contrast echocardiography shows contrast extending to papillary muscles or free wall, the procedure must be abandoned 1
• Should not be performed if concomitant cardiac surgery is needed (e.g., coronary artery bypass grafting, mitral valve repair for ruptured chordae) 1
• Less effective in patients with extensive septal scarring on CMR 2

Mandatory procedural requirement: Myocardial contrast echocardiography must be performed before alcohol injection to ensure proper localization exclusively to the basal septum 1, 2.

Avoid injecting large volumes of alcohol in multiple septal branches—this approach increases risk of complications and arrhythmic events 1.

Procedural Volume Requirements

Both procedures must be performed at experienced centers 1, 2:

• Individual operators should have performed ≥20 procedures OR work in a dedicated HCM program with ≥50 total procedures 1
• The European Society of Cardiology recommends minimum caseload of 10 septal alcohol ablations and 10 myectomies per operator per year 1, 2
• Septal reduction should not be performed outside of programs dedicated to longitudinal multidisciplinary HCM care 1

Special Considerations for Mild Septal Hypertrophy

In the subset of patients with mild septal hypertrophy (≤15 mm) but significant LVOT obstruction 3, 4:

• Obstruction is primarily driven by mitral valve abnormalities (elongated anterior leaflet, abnormal chordal attachments) and papillary muscle abnormalities (increased bifid papillary muscle mobility) 3, 4
• CMR imaging is essential to characterize mitral valve apparatus, papillary muscle morphology, and distribution of hypertrophy 1, 4
• Surgical approach often requires additional procedures beyond myectomy: 52% of such patients needed mitral valve repair/replacement or papillary muscle reorientation in addition to (or instead of) myectomy 3, 4
• Alcohol septal ablation may be less effective in this subgroup since the primary pathology is not septal hypertrophy 3, 4

Contraindications to Septal Reduction

Do not perform septal reduction therapy in the following scenarios 1:

• Asymptomatic patients with normal exercise tolerance 1
• Symptoms controlled or minimized on optimal medical therapy 1
• Outside of dedicated HCM programs 1

Mitral valve replacement for relief of LVOT obstruction should not be performed when septal reduction therapy is an option 1.

Role of Pacemaker Therapy

Permanent pacemaker implantation should not be used as primary therapy to reduce LVOT gradient 1:

• Not indicated in asymptomatic patients or those medically controlled 1
• Not first-line therapy in medically refractory patients who are candidates for septal reduction 1
• May be considered as a trial in patients who already have a dual-chamber device implanted for non-HCM indications 1

Surveillance Without Intervention

For patients with mild septal hypertrophy who are asymptomatic or have well-controlled symptoms on medical therapy:

• Serial echocardiography to monitor gradient progression 1
• Exercise testing with blood pressure monitoring for risk stratification 1
• Consider CMR imaging to detect progression of high-risk features (apical aneurysm, extensive late gadolinium enhancement ≥15% of LV mass, systolic dysfunction) 1