A NEWLY ESTABLISHED SURGICAL SEPTAL MYECTOMY PROGRAM FOR OBSTRUCTIVE HYPERTROPHIC CARDIOMYOPATHY IN BRITISH COLUMBIA: EARLY CLINICAL AND ECHOCARDIOGRAPHIC RESULTS

Surgical septal myectomy is an effective treatment for drug-refractory heart failure symptoms in patients with obstructive hypertrophic cardiomyopathy (HCM). Given the low case volume, current practice guidelines recommend HCM surgery to be performed at experienced HCM centres for optimal outcomes. To meet the growing need for septal reduction therapy in British Columbia, a dedicated septal myectomy program was established in September 2019 as part of the provincial HCM referral centre at St. Paul's Hospital in Vancouver. Concerted efforts were made to centralize the case volume and develop standardized perioperative protocols. In this study, we report the early clinical and echocardiographic results of our initial case series.

We retrospectively reviewed our initial experience with septal myectomy performed for symptomatic obstructive HCM at our institution between September 2019 and December 2020. Patients whose primary surgical indication was unrelated to obstructive HCM were excluded. Among 45 patients (62±10 years of age; 49% male) reviewed, 69% had isolated septal myectomy while 31% had planned concomitant procedures (CABG, AVR, and/or MV repair/replacement). Intraoperative provocation with inducible PVCs and isoproterenol infusion, with simultaneous direct needle measurement of LVOT gradient, was performed before and after cardiopulmonary bypass. All operations were performed by one surgeon (JMK) with support of another senior surgeon (JA). All patients underwent comprehensive preoperative assessment by a dedicated HCM cardiologist (KO). Preoperatively, 85% of patients were in NYHA class III or IV while 15% were in NYHA class II. Preoperative echocardiography demonstrated resting LVOT gradient of 65±39 mmHg and Valsalva-provoked gradient of 94±38 mmHg. Five patients had SAM-related 3 or 4+ mitral regurgitation (MR). First postoperative echocardiography at 1-3 months showed significant reduction of resting LVOT gradient to 8±6 mmHg and Valsalva-provoked gradient to 11±8 mmHg. None of the patients had significant SAM or residual 3 or 4+ MR. At time of postoperative follow-up at 3-4 months, 98% of patients had improvement in NYHA functional class, with 76% in class I and 24% in class II. There was no mortality. There was no iatrogenic ventricular septal defect, and none of the patients required unplanned mitral valve repair/replacement. There was no postoperative CVA, AKI requiring dialysis, or complete heart block requiring permanent pacemaker. One patient required mediastinal re-exploration for bleeding in immediate postoperative period.

Our experience demonstrates that, with appropriate planning and support, it is feasible for new HCM surgical programs to achieve safe and desired operative results comparable with those of experienced high-volume centres.