(CCSP074) OUTCOMES OF SEPTAL REDUCTION THERAPY IN A NEWLY ESTABLISHED MULTIDISCIPLINARY HYPERTROPHIC CARDIOMYOPATHY PROGRAM: THE BRITISH COLUMBIA EXPERIENCE

Background: Septal reduction therapy (SRT), in the form of surgical septal myectomy (SSM) or alcohol septal ablation (ASA), is an effective treatment for individuals with symptomatic obstructive hypertrophic cardiomyopathy (HCM) despite optimal medical therapy. SRT reduces left ventricular outflow tract (LVOT) gradients, improves heart failure symptoms, and increases exercise capacity. Current practice guidelines recommend SRT to be performed at experienced HCM centres for optimal safety and benefit. SRT performed in low volume centres is associated with worse outcomes including higher mortality. To address the need for HCM care in British Columbia (BC), a comprehensive HCM program was established at St Pauls’ Hospital in 2015.

METHODS AND RESULTS: We retrospectively reviewed our experience with SRT performed for symptomatic obstructive HCM in Vancouver between January 2015 and December 2021. 1193, consecutive patients were evaluated in the HCM clinic, of whom 151 patients proceeded to SRT during that time frame. ASA was performed in 45 (30%) patients and SSM was performed in 106 (70%) patients. As our myectomy program was only established in September 2019, 40 of these patients underwent surgery outside BC. Thereafter, 66 patients underwent SSM in Vancouver and formed the basis for comparison with ASA. Compared to SSM, patients undergoing ASA were significantly older (69.8 ± 9.1 years vs 61.0 ± 9.9 years, P < 0.001), more likely to be hypertensive (66.7% vs 40.9%, P = 0.008) and had a higher rate of bundle branch block at baseline (20.0% vs 6.1%, P= 0.035). There was no 30-day mortality in the septal myectomy group and only 1 early death in the septal ablation group. The 30-day adverse complications rate (a composite of tamponade, left anterior descending artery dissection, infection, stroke, major bleeding, new dialysis) was low (7.6% with SSM vs 2.1% with ASA, P = 0.40). There were more patients with high grade atrioventricular block requiring PPM at 30 days in the ASA group than the SSM group (22.2% vs 3.0%, P = 0.006). The postprocedural resting and Valsalva provoked LVOT gradients were 8 mmHg (IQR: 5, 11 mmHg) and 11 mmHg (IQR: 7, 16 mmHg) in the SSM group and 13 mmHg (IQR: 9, 36 mmHg) and 20 mmHg (IQR: 14, 54 mmHg) in the ASA group.

Conclusion: It is feasible for a new HCM program to achieve safe and desired SRT outcomes comparable with those of experienced high-volume centres and that meet targets for invasive SRT outcomes recommended by the ACC/AHA 2020 HCM guidelines