What is it like to have HCM?

The cardiac muscle thickening seen in HCM causes a reduced ability of the heart to pump efficiently and reduced output of blood to essential body organs.. These can all contribute to fatigue and symptoms that include shortness of breath and chest pain. Additionally, other structural changes such as left atrial enlargement occur, leading to the development of arrhythmias and heart failure. 

HCM is a chronic disease, and for the majority of patients the disease progresses slowly with the development of severe symptoms despite existing medical therapies. Mild physical effort  can quickly result in fatigue or shortness of breath, and a patient’s ability to participate in normal work, family or recreational activities can be substantially diminished. People with HCM have significantly higher rates of death compared to that of the general U.S. population. Further, patients with genetic HCM exhibited disease at younger ages and were more likely to experience HCM-related complications and early death. In approximately 15% to 20% of patients, disease progression results in disabling heart failure that can prevent the patients from holding a job or performing everyday activities. HCM can also cause stroke or sudden cardiac death due to abnormal rhythmic beating of the heart. HCM is the most common cause of sudden cardiac death in young people, with a five-year incidence among children of 3%. Some populations are more prone to sudden cardiac death- in fact, 50% of all sudden cardiac deaths in HCM occur in young African American males during sports or athletics.

The current treatment options for HCM patients are only designed to treat symptoms and are not curative.  The beta-blocker propranolol is recommended for the treatment of symptomatic HCM and is used to manage abnormal heart rhythms. However, beta blockers are frequently ineffective and have side effects that often limit their usefulness. Patients are often also prescribed additional drugs for the treatment of high blood pressure, heart failure or other drugs such as calcium channel blockers (e.g. verapamil and diltiazem) and the antiarrhythmic drug disopyramide.  These drugs do not address the underlying cause of HCM, and do not appear to affect the progression of the disease to late stage heart failure. For a subset of HCM patients with more advanced disease or more severe symptoms, surgical or other invasive interventions may be appropriate, including heart transplantation, use of an implantable defibrillator, cardiac myectomy, or alcohol septal ablation.

In addition to patients with symptoms, there are many who carry one of the gene mutations associated with HCM, but do not yet have symptoms.  These patients are known as the “genotype +/phenotype -” population. These patients may go on to develop symptoms or evidence of heart wall thickening or other heart damage depending on their genetic mutation and other lifestyle factors. The hope is that through new medical research, treatments can be identified that may prevent cardiac cell damage in these patients at the earliest stages before it leads to scarring (fibrosis), heart wall thickening (cardiac hypertrophy) and all the resultant symptoms described for patients with clinical HCM noted above.