Target population for a selective cardiac myosin inhibitor in hypertrophic obstructive cardiomyopathy: Real-life estimation from the French REgister of hypertrophic cardioMYopathy (REMY)

Background: The efficacy of current pharmacological therapies in hypertrophic cardiomyopathy is limited. A cardiac myosin inhibitor, mavacamten, has recently been approved as a first-in-class treatment for symptomatic hypertrophic obstructive cardiomyopathy.Aims: To assess the profile and burden of cardiac myosin inhibitor candidates in the hypertrophic cardiomyopathy prospective REgister of hypertrophic cardioMYopathy (REMY) held by the French Society of Cardiology.Methods: Data were collected at baseline and during follow-up from patients with hypertrophic cardiomyopathy enrolled in REMY by the three largest participating centres.Results: Among 1059 adults with hypertrophic cardiomyopathy, 461 (43.5%) had obstruction; 325 (30.7%) of these were also symptomatic, forming the “cardiac myosin inhibitor candidates‿ group. Baseline features of this group were: age 58 ± 15 years; male sex (n = 196; 60.3%); diagnosis-to-inclusion delay 5 (1–12) years; maximum wall thickness 20 ± 6 mm; left ventricular ejection fraction 69 ± 6%; family history of hypertrophic cardiomyopathy or sudden cardiac death (n = 133; 40.9%); presence of a pathogenic sarcomere gene mutation (n = 101; 31.1%); beta-blocker or verapamil treatment (n = 304; 93.8%), combined with disopyramide (n = 28; 8.7%); and eligibility for septal reduction therapy (n = 96; 29%). At the end of a median follow-up of 66 (34–106) months, 319 (98.2%) were treated for obstruction (n = 43 [13.2%] received disopyramide), 46 (14.2%) underwent septal reduction therapy and the all-cause mortality rate was 1.9/100 person-years (95% confidence interval 1.4–2.6) (46 deaths). Moreover, 41 (8.9%) patients from the initial hypertrophic obstructive cardiomyopathy group became eligible for a cardiac myosin inhibitor.Conclusions: In this cohort of patients with hypertrophic cardiomyopathy selected from the REMY registry, one third were eligible for a cardiac myosin inhibitor.