For the first time, medication that impacts heart muscle thickness and function, rather than addressing symptoms, is found to treat hypertrophic cardiomyopathy.
Hypertrophic cardiomyopathy (HCM) is an inherited disease of the heart muscle. It is specifically characterised by thickening of the myocardium, which makes the heart muscle stiff. In most HCM patients, the septum between the ventricles becomes thicker than normal, and blocks blood flow out of the heart. This is called obstructive HCM. Unfortunately, there are no current therapies for obstructive HCM that can modify disease expression or outcome. There are also no therapies that can affect any of the heart structural abnormalities that define this disease. For example, the thickness of the heart muscle, resultant stiffness and abnormalities in other cardiac structures.
The EXPLORER-HCM randomised controlled trial was a Phase 3, randomised, double-blind, placebo-controlled trial across 13 countries. The results were released in August in The Lancet and demonstrated the benefits of mavacamten in patients with obstructive HCM. Mavacamten is a cardiac myosin inhibitor that reduces actin-myosin cross-bridge formation. Patients were found to have significant improvements in obstruction to blood flow in the heart and also showed improvements in markers like exercise capacity.
In this recent substudy, published in Circulation, researchers explored some of the reasons why individuals were potentially feeling better. The substudy was done using imaging of the study participants’ hearts. Specifically, they used cardiac magnetic resonance (CMR) imaging to examine the effect of mavacamten versus placebo on cardiac structure and function. They found that mavacamten associated with significant reductions in left ventricular (LV) mass index, LV wall thickness and left atrial volume index. All of these are predictors of poor prognosis in obstructive HCM. Also, they found no changes in fibrosis or myocardial contractile fraction observed over 30 weeks and contractile function remained normal.
This substudy is the first to show a favourable impact of a pharmacologic agent on cardiac remodelling in HCM. These findings suggest that even short-term mavacamten treatment can have a favourable effect on cardiac structure in patients with obstructive HCM.
Image credit: By pch.vector – www.freepik.com