Septal reduction therapies are used to mitigate the symptoms caused by dynamic left ventricular outflow tract (LVOT) obstruction and the associated mitral regurgitation (MR) that can surge in hypertrophic cardiomyopathy (HCM).
Alternative therapies to treat LVOT obstruction include surgical procedures, i.e. surgical myotomy or myomectomy, or alcohol and radiofrequency septal ablation (intracardiac, transthoracic and endocardial, uni or bipolar).
Even though alcohol ablation is most commonly used, it can present septal mismatch in some cases, residual gradients, fibrosis potentially leading to arrhythmia and iatrogenic AV block requiring pacemaker implantation.
The team lead by Greenbaum et al. has developed a technique to carry out an electrochemical transcatheter myomectomy called SESAME (SEptal Scoring Along Midline Endocardium). Selected patients were symptomatic poor TMVR candidates with LVOT gradient ≥ 30 mmHg, hypertrophic cardiomyopathy or severe mitral valve disease.
Patients were divided in three groups: those with hypertrophic cardiomyopathy and dynamic and symptomatic LVTO obstruction (n=11), and the rest of patients who needed reduction therapy to facilitate TAVR/TMVR, divided into those with gradient (n=31) if they had intracranial gradient (> 30 mm Hg) and those without intracranial gradient (n=34).
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The SESAME technique simulates a surgical myotomy by marking the myocardium septal mid-wall and making an incision to initially reach 2/3 myocardial thickness, and afterwards 50%. It’s carried out by advancing a stiff CTO guidewire, with microcatheter support, with intracardiac trajectory and left ventricular re-entry into a snare, to generate thermal laceration between 30-70W.
The study included 76 patients, mostly women (82%) with high morbidity and prohibitive surgical risk. 14% presented classic dynamic LVTO and the rest received SESAME to facilitate another transcatheter procedure (8 TAVR and 57 TMVR).
Technical success was observed in 100%, in anchoring and laceration. All procedures, except for one, were done via the retrograde approach through the aortic valve. Mean procedural duration was 174 minutes (Q1-Q3: 137-231 min) and it mean required 73-minute fluoroscopy time (Q1-Q3: 54-102 min). Mean hospital stay was 4.5 days, with one day in intensive care.
There were major complications such as bleeding, new ventricular septum defect, access site vascular complications or potentially mortal induced arrhythmias. Six patients presented myocardial perforation and three presented restrictive iatrogenic ventricular septal defects.
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4% of patients presented stroke within 30 days. Mean MACE incidence was 24% (death, stroke, major vascular complications and emergency structural intervention).
Following CT analysis showed a reduction of septal thickness in almost all groups, 16.4 to 8.5 mm (p≤ 0.001). Also, there was new LVTO, approximately 100 mm2, in patients with HCM, and 150 mm2 in those requiring another transcatheter intervention. From the hemodynamic point of view, 82% of patients with HCM experienced immediate 50% reduction, while 67% of those with intracranial gradient showed hemodynamic relief.
Conclusiones
The SESAME technique might benefit patients with obstructive, symptomatic HCM and those requiring transcatheter intervention. According to data, it is feasible, but requires high technical expertise and raises questions at followup of some phenotypes.
Dr. Omar Tupayachi.
Member of the Editorial Board of SOLACI.org.
Original Title: Transcatheter Myotomy to Reduce Left Ventricular Outflow Obstruction.
Reference: Greenbaum AB, Ueyama HA, Gleason PT, Khan JM, Bruce CG, Halaby RN, Rogers T, Hanzel GS, Xie JX, Byku I, Guyton RA, Grubb KJ, Lisko JC, Shekiladze N, Inci EK, Grier EA, Paone G, McCabe JM, Lederman RJ, Babaliaros VC. Transcatheter Myotomy to Reduce Left Ventricular Outflow Obstruction. J Am Coll Cardiol. 2024 Mar 11:S0735-1097(24)00280-8. doi: 10.1016/j.jacc.2024.02.007. Epub ahead of print. PMID: 38471643.
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