6.3 Interventional Electrocautery: Open SESAME

These proceedings summarize the educational activity of the 17th Biennial Meeting of the International Andreas Gruentzig Society held January 30 to February 2, 2024 in Chiang Rai, Thailand.

Faculty Disclosures     Vendor Acknowledgments

2024 IAGS Summary Document

Statement of the problem or issue

The opposite end of the spectrum from dilated cardiomyopathy, which is typically accompanied by thinning of the left ventricular (LV) walls, is hypertrophic cardiomyopathy, where the left ventricular wall is too thick and often misshapen. With hypertrophy, we want to reduce this thickness with ventricular septal reduction therapies. The overall goal is to enlarge the LV outflow tract (LVOT): (1) because there is obstruction to flow from a distorted septum (HOCM), causing symptoms; or (2) we want to create additional space needed to safely implant a transcatheter mitral valve. The treatment approach can be focal, for example using surgical myomectomy, or it can be nonsurgical and zonal, using alcohol septal ablation or radiofrequency (RF) ablation.

Gaps in current knowledge

Surgical myomectomy can be very effective in relieving symptoms from LVOT obstruction, but experience is critical, and so this approach is not widely applicable generally as outcomes are not as good at low volume centers, in the elderly, and in patients with significant comorbidities. The advantage of a non-surgical, zonal approach is that it is less invasive. There are several disadvantages — they can be incomplete and leave residual obstruction, or there may be heart block with a need for a pacemaker. Also, later, scarring and fibrosis may produce late arrhythmias.^1,2

Possible solutions and future directions

A new percutaneous procedure has been developed, SEptal Scoring Along the Midline Endocardium (SESAME). It is an electrosurgical procedure that mimicks surgical myotomy, and first entails maneuvering a wire along a trajectory through the midline endocardium of the septum at a prespecified depth and length (Figure). Applying an electric current to the wire creates a myocardial laceration that splays apart over the subsequent days and weeks, ultimately enlarging the area to what is achieved with surgical myomectomy. This procedure has been used in over 100 patients in the US, with results from the first 76 patients treated at Emory University in Atlanta now published.³ In these selected patients, SESAME successfully reduced the median LVOT gradient at rest from 54 to 29 mmHg (p=0.023), and the median LVOT gradient under provocation from 149 to 85 mmHg (p=0.076). Assessment using computed tomography showed that septal thickness was reduced by one-half (16.4 mm to 8.5 mm) with most patients reporting improvement in symptoms. Clearly, clinical trials are needed to compare this promising new percutaneous procedure to other forms of therapy.

Figure. The SESAME percutaneous myotomy procedure.

References

1. Elhadi M, Guerrero ME, Collins JD, Rihal CS, Eleid MF. Safety and outcomes of alcohol septal ablation prior to transcatheter mitral valve replacement. J Soc Cardiovasc Angio & Interv. 2022; doi: 10.1016/j.jscai.2022.100396.
2. Hoskins MH, Lisko JC, Greenbaum AB, et al. Septal bipolar ablation to prevent left ventricular outflow tract obstruction after transcatheter mitral valve implantation. Circ Cardiovasc Interv. 2023;16:e013333. doi: 10.1161/CIRCINTERVENTIONS.123.013333. PMID: 37712286.
3. Greenbaum AB, Ueyama HA, Gleason PT, et al. Transcatheter myotomy to reduce left ventricular outflow obstruction. J Am Coll Cardiol. 2024;83(14):1257-1272. doi: 10.1016/j.jacc.2024.02.007.