Transcatheter Myotomy to Reduce Left Ventricular Outflow Obstruction

Left ventricular outflow tract (LVOT) obstruction is a source of morbidity in hypertrophic cardiomyopathy (HCM) and a life-threatening complication of transcatheter mitral (TMVR) and aortic valve replacement (TAVR). Available surgical and transcatheter approaches are limited by high surgical risk, unsuitable septal perforators, and heart block requiring permanent pacemakers. We report the initial experience of a novel transcatheter electrosurgical procedure developed to mimic surgical myotomy. Methods: We used SEptal Scoring Along Midline Endocardium (SESAME) to treat patients, on a compassionate basis, with symptomatic LVOT obstruction or to create space to facilitate TMVR or TAVR. In this single-center retrospective study between 2021-2023, 76 patients underwent SESAME. Eleven (14%) had classic HCM, and the remainder underwent SESAME to facilitate TMVR or TAVR. All had technically successful SESAME myocardial laceration. Measures to predict post-TMVR LVOT significantly improved (neo-LVOT 42(7,117)to 170(95,265)mm2,p<0.001; skirt-neo-LVOT 169(153,193) to 214(180,262)mm2,p<0.001). Among patients with HCM, SESAME significantly decreased invasive LVOT gradients (resting: 54[40,70] to 29[12,36]mmHg,p=0.023; provoked 146[100,180] to 85[40,120]mmHg,p=0.076). Seventy-four (97.4%) survived the procedure. Five suffered 3/76(3.9%) iatrogenic ventricular septal defects that did not require repair, and 3/76(3.9%) ventricular free wall perforations. Neither occurred in patients treated for HCM. Permanent pacemakers were required in 4/76(5.3%), including two after concomitant TAVR. Lacerations were stable and did not propagate after SESAME (remaining septum: 5.9±3.3mm to 6.3±3.4mm,p=0.6). With further experience, SESAME may benefit patients requiring septal reduction therapy for obstructive hypertrophic cardiomyopathy, with LVOT obstruction after heart valve replacement, and/or to prepare for transcatheter valve implantation.