Septal Scoring Along Midline Endocardium (SESAME)
SESAME is a novel transcatheter electrosurgical technique that uses radiofrequency energy to create controlled lesions in the interventricular septum, reducing left ventricular outflow tract (LVOT) obstruction in hypertrophic obstructive cardiomyopathy (HOCM) patients who are not candidates for traditional septal reduction therapies.
What is SESAME?
SESAME (Septal Scoring Along the Midline Endocardium) is an emerging minimally invasive procedure that represents an alternative to traditional septal reduction therapies 1, 2, 3. The technique involves using electrosurgical energy delivered via a transcatheter approach to create controlled septal lesions along the midline endocardium, resulting in septal thinning and widening of the LVOT 1, 2.
Unlike alcohol septal ablation which relies on coronary anatomy and creates an infarction through septal perforator arteries, SESAME directly targets the septum through an endocardial approach, offering greater precision in lesion placement 3.
Clinical Indications
Primary Indications:
SESAME is indicated for symptomatic HOCM patients with LVOT obstruction who have:
- Failed or inadequate response to prior alcohol septal ablation 1
- Unsuitable coronary anatomy (lack of appropriate septal perforator branches for alcohol ablation) 1
- Extreme septal thickness (≥30 mm), where alcohol septal ablation shows limited benefit 4, 1
- High surgical risk precluding traditional septal myectomy 1, 2
Adjunctive Use:
SESAME can be performed as an adjunct to transcatheter aortic valve replacement (TAVR) or transcatheter mitral valve replacement (TMVR) in patients with concomitant septal hypertrophy to prevent iatrogenic LVOT obstruction 1, 5, 3.
Patient Selection Algorithm
Start with traditional guideline-based criteria for septal reduction therapy:
Severe symptoms (NYHA class III-IV) despite optimal medical therapy with beta-blockers, calcium channel blockers, or disopyramide 4, 6, 4
Documented LVOT gradient ≥50 mm Hg at rest or with physiologic provocation (exercise, Valsalva) 4, 7, 8
Gradient attributable to systolic anterior motion (SAM) of the mitral valve with septal contact 9
Then consider SESAME specifically when:
- Prior alcohol septal ablation has failed to adequately reduce gradients 1
- Coronary angiography reveals no suitable septal perforator artery for alcohol ablation 1
- Septal thickness exceeds 30 mm (where alcohol ablation efficacy is limited) 4, 1
- Patient requires concomitant TAVR or TMVR with risk of LVOT obstruction 1, 5
- Patient is high surgical risk but younger patients who would otherwise benefit from myectomy's superior long-term data should still be referred for surgery 4
Procedural Outcomes and Considerations
Early data from the Asia-Pacific region demonstrates:
- Successful completion in all reported cases with immediate LVOT gradient reduction 1
- Improved functional status at 1-3 month follow-up 1
- Risk of high-grade AV block requiring permanent pacemaker (similar to alcohol septal ablation's 10-20% risk) 4, 1
Critical Caveats:
This technique is in early evolution with limited long-term outcome data 5, 2. Traditional septal myectomy remains the gold standard for most patients, particularly younger, healthy adults, given its superior long-term follow-up data and lower pacemaker requirement (2% vs 10-20% with ablative techniques) 4, 10.
SESAME should only be performed:
- At comprehensive HCM centers with experienced structural heart teams 8
- With advanced pre-procedural imaging (CT, echocardiography) for precise anatomic planning 5, 3
- With intraprocedural echocardiographic or TEE guidance 5, 3
Comparison to Established Therapies
Septal myectomy remains preferred for most severely symptomatic HOCM patients, especially younger individuals, because it offers:
- Direct visualization and tailored resection 4
- Ability to address mitral valve abnormalities simultaneously 4
- Long-term survival equivalent to age-matched general population 4
- Lower pacemaker requirement 4, 10
Alcohol septal ablation is preferred over myectomy when:
- Surgery is contraindicated or high-risk (particularly elderly patients) 4, 6, 10
- Patient autonomy dictates choice after informed discussion 4, 10
SESAME fills a niche for patients who fail or are unsuitable for both traditional approaches, or as an adjunct to transcatheter valve procedures 1, 5, 2.
Monitoring Requirements
Following SESAME, patients require:
- TTE within 3-6 months to evaluate procedural results, septal thinning, gradient reduction, and residual SAM 8
- Continuous monitoring for conduction abnormalities given AV block risk 1
- Ongoing SCD risk assessment as septal reduction does not eliminate need for ICD evaluation 4
The technique represents a promising addition to the armamentarium for HOCM management but requires further multicenter studies to establish long-term safety and efficacy profiles 1, 2.