Background: Hypertrophic cardiomyopathy (HCM) is defined by left ventricular wall thickening not attributable to other causes, with an estimated prevalence of 1 in 200–500 individuals. HCM is classified as obstructive (HOCM) when the left ventricular outflow tract (LVOT) gradient exceeds 30 mmHg. First-line treatment includes beta-blockers, non-dihydropyridine calcium channel blockers, and disopyramide to reduce LVOT obstruction. Despite medical therapy, up to 50% of patients need septal reduction therapies such as surgical myectomy or alcohol septal ablation, procedures carrying risks even in experienced centres.
Certain patients remain symptomatic and/or exhibit significant LVOT obstruction after surgical myectomy. There is no evidence to support correct medical treatment in this scenario.
Methods: We describe a HOCM case with persistent symptoms and LVOT obstruction despite surgical myectomy in which myosin inhibitors were useful to improve outcomes in this patient. Clinical and demographic data were collected at baseline and during follow-up, including peak LVOT gradient, NT-proBNP and NYHA functional class. Adherence and tolerance to therapy were assessed. Follow-up occurred at 4, 8, and 12 weeks.
Results: A 56-year-old female patient presented to a National Referral Center with exertion dyspnoea. She was diagnosed many years ago with HOCM. Genetic test showed a pathogenic variant in TNNC1. Treatment with beta-blocker and disopyramide was initiated. Symptoms persisted and 5 years before the presentation a surgical myectomy was performed. During last years, her functional class was acceptable without any limitation in daily life but some months ago exertion dyspnoea began, so that was referred to our centre for evaluation and treatment. Transthoracic echocardiography showed a 33mmHg rest LVOT gradient, and 84mmHg during Valsalva manoeuvre despite treatment with non-dihydropyridine calcium channel blockers. NTproBNP was 1,320 in this point.
In this scenario, no treatment has demonstrated benefit and guidelines do not show what to do. Mavacamten was initiated at 5 mg per day.
From this moment functional class began to improve. LVOT gradient and NTproBNP values continued improving during the follow-up. 12 weeks after the treatment was started transthoracic echocardiography did not show any significant gradient and proBNP value was 682.
Conclusion: This case report shows that mavacamten is a safe and effective option for symptomatic HOCM patients after surgical myectomy. Mavacamten may improve functional class in these patients in which, previously, did not have further therapeutic options.