June 27, 2024
The American College of Cardiology (ACC) and the American Heart Association (AHA) released a new clinical guideline for the diagnosis and treatment of patients with hypertrophic cardiomyopathy (HCM). The new guideline was published in the Journal of the American College of Cardiology and in Circulation in May 2024.
The 2024 ACC and AHA guideline was developed in collaboration with and endorsed by the American Medical Society for Sports Medicine, the Heart Rhythm Society, Pediatric & Congenital Electrophysiology Society, and the Society for the Cardiovascular Magnetic Resonance.
Key changes in the 2024 HCM clinical guideline: A new drug therapy and less restricted exercise. The guideline encourages collaborative decision-making with patients and recommends seeking HCM specialists at an experienced multidisciplinary center.
New drug class
A genetic condition, HCM causes a thickening of the heart muscle and can impair the heart from adequately pumping blood throughout the body. People with HCM may go undiagnosed if they don't experience chest pain, shortness of breath, fainting or an irregular heartbeat.
Cardiac myosin inhibitors are now recommended as therapy for patients with obstructive HCM who have symptoms due to left ventricular outflow tract obstruction despite the use of beta blockers (first-line therapy) or nondihydropyridine calcium channel blockers (used if beta blockers are ineffective). Mavacamten is the only FDA-approved myosin inhibitor, although another one is in development.
"The addition of mavacamten is an option alongside surgical myectomy, percutaneous septal ablation, or disopyramide, for patients with symptomatic obstructive HCM who have not responded to first-line medications. Patients who fit in this category deserve to hear about the risks, benefits and success rates of all options," says Steve R. Ommen, M.D., medical director of the Hypertrophic Cardiomyopathy Clinic at Mayo Clinic in Rochester, Minnesota, and chair of the AHA and ACC guideline writing committee.
"This class of medications can be a big benefit for patients with symptomatic obstructive HCM, but there are limitations," says Dr. Ommen. "There are also mandatory logistics in using mavacamten that may turn off some patients."
Cardiac myosin inhibitors are monitored under the FDA's Risk Evaluation and Mitigation Strategies (REMS) program. Clinicians need special training to prescribe the medications, and patients receive more-frequent screenings.
"Cardiac myosin inhibition requires knowledge of drug-drug interactions and extensive echocardiographic surveillance to monitor for the uncommon finding of left ventricular systolic dysfunction," says Jeffrey B. Geske, M.D., a cardiologist who leads hypertrophic cardiomyopathy research efforts at Mayo Clinic in Minnesota.
"It's great to have a new tool in the tool belt for managing HCM. Myosin inhibition therapy will help patients, but it's not right for everyone. Some patients may still choose septal reduction therapy (myectomy or alcohol septal ablation) instead," says Dr. Geske.
Exercise intensity
Through the years, patients diagnosed with HCM have received unclear messages about exercise. The updated guideline recommends that all patients diagnosed with HCM who don't have symptoms get regular mild to moderate aerobic exercise and that more vigorous aerobic exercise is reasonable for many. Strength or resistance exercise also is suggested.
Light, moderate and vigorous exercise have not been associated with ventricular arrhythmias in short-term studies.
"While low-moderate intensity exercise was introduced in the 2020 guideline, with the 2024 guideline, more vigorous exercise is reasonable for many patients with HCM," says Dr. Ommen. "Disqualification from competitive sports is no longer an automatic in patients with HCM but may be considered for individuals after comprehensive evaluation and discussion about the potential risks of extreme training."
Assessing risks
HCM may lead to complications including sudden cardiac death (SCD). Each patient should be assessed for a risk of SCD. Risk factors can be different for pediatric and adult patients. The new guideline refined the evaluation and management of children and adolescents with HCM. Recommendations include doing exercise testing to assess for physical limitations and using tools to aid in SCD risk assessment.
Use tools to aid in the prediction of atrial fibrillation (AFib) and screen for asymptomatic AFib in patients with a higher risk of developing it.
What's next?
Moving forward, more research is needed. "Myosin inhibitor therapy is a novel treatment," says Dr. Geske. "How will hearts remodel with this therapy? Is the treatment effect durable? Will monitoring requirements evolve? Do these therapies have a role in treatment of nonobstructive disease? It's an exciting time to ask these questions and care for patients with HCM."
For more information
Ommen SR, et al. 2024 AHA/ACC/AMSSM/HRS/PACES/SCMR guideline for the management of hypertrophic cardiomyopathy: A report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines. Journal of the American College of Cardiology. 2024;83:2324.
Ommen SR, et al. 2024 AHA/ACC/AMSSM/HRS/PACES/SCMR guideline for the management of hypertrophic cardiomyopathy: A report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines. Circulation. 2024;149:e1239.
Refer a patient to Mayo Clinic.