Abstract 4147610: Efficacy and Safety of Selective Cardiac Myosin Inhibitors in Symptomatic Hypertrophic Obstructive Cardiomyopathy: A Meta-Analysis of Randomized Controlled Trials

Background: Hypertrophic Obstructive Cardiomyopathy (HOCM) is an autosomal dominant inherited condition with limited management options, primarily focusing on symptom improvement through beta blockers. A novel selective cardiac myosin inhibitor, Mavacamten has been shown to improve exercise tolerance and NYHA functional class as compared to placebo in multiple randomized controlled trials (RCTs). A recent RCT from 2024 studied another oral cardiac myosin inhibitor, Aficamten which potentially decreases left ventricular outflow tract obstruction (LVOTO) in symptomatic HOCM. One limitation of all these RCTs, for obvious reasons, is the small sample size, which poses a challenge in its actual clinical significance. Aims: To analyze the efficacy and safety of novel selective cardiac myosin inhibitors in symptomatic HOCM patients Methods: We included 4 RCTs, comparing the efficacy and safety of selective cardiac myosin inhibitors and placebo groups. These studies were selected through a detailed search of the MEDLINE, COCHRANE, and PUBMED databases. We compared various common primary and secondary endpoints between both the groups: changes in exercise tolerance, NYHA functional class, and Kansas City Cardiomyopathy Questionnaire-Clinical Summary Score (KCCQ-CSS). The results were reported as Odds Ratios (OR) with 95% confidence intervals (CI), using a random effects model. Results: The outcomes from 704 HOCM patients, which consisted of 361 patients who received a myosin inhibitor and 343 who received a placebo were analyzed. The primary endpoint in all the studies was improvement in exercise tolerance [measured as 1.5 mL/kg per min or greater increase in peak oxygen consumption (pVO2)], which was not statistically significant in our study (OR: 1.75, 95% CI: 0.89-3.43, p:0.1). There was a statistically significant improvement in ≥1 NYHA functional Class (OR: 3.9, 95% CI:2.49-6.12 p<0.05). There was no significant change seen in KCCQ-CSS (OR: 1.26, 95% CI: 0.75-2.12, p:0.3) and1 or more Serious Adverse Events (OR: 0.75, 95% CI: 0.42-1.32, p:0.3). (Figures A-D) Conclusion: Novel cardiac myosin inhibitors have shown statistically significant results in improving NYHA functional class, but not much difference in objective criteria like pVO2 with no significant adverse events. While these results appear promising and 2024 ACC/AHA guidelines have Class 1 Recommendation regarding their use for symptomatic HOCM, further analysis from a large population is needed.