Imaging plays a key role in diagnosing hypertrophic cardiomyopathy (HCM), helping specialists keep an eye on the progress of the disease, track the impact of drug treatments and identify the most effective way forward.
Serial cardiac ultrasound exams are a requirement by the U.S. Food and Drug Administration (FDA) for the use of mavacamten (Camzyos), the only drug approved to treat HCM. The FDA requires echocardiogram assessments of left ventricular ejection fraction (LVEF) prior to and during treatment. The agency also stipulates that if a patient's LVEF is 55% or lower, the use of the drug is not recommended. Treatment should also be interrupted if a patient's LVEF is below 50% at any visit.
HCM expert Sherif F. Nagueh, MD, a professor of cardiology with Methodist DeBakey Heart and Vascular Center, explained the key points of HCM imaging when he spoke with Cardiovascular Business at the American Society of Echocardiography (ASE)-sponsored HCM Forum in June. The meeting included numerous HCM experts from across the country.
"Imaging plays an important role in diagnosing HCM and risk stratification, because many of these patients are at higher risk for sudden cardiac death. Many patients with HCM also may have chest pain, which can be due to epicardial coronary artery disease, so imaging plays a role here as well. And last but not least, it helps guide medical treatments now with myosin inhibitors to see what happens to the left ventricular outflow tract (LVOT) gradient when the drug is administered, the dynamic obstruction and to the ejection fraction. Imaging is used as well for guiding procedures, like surgical myectomy and alcohol septal ablation," Nagueh explained.
While echo is mandated for the use of mavecamten, cardiac MRI and CT also play a role in assessing HCM patients.
"Cardiac MRI is key in the evaluation of these patients. Ten or 20 years ago, it was not as frequently used as it is now. MRI can help establish the diagnosis when echocardiography is sometimes borderline. And before you speak to a patient and give them this diagnosis, you want to be comfortable and the MRI can confirm that," Nagueh explained.
He said MRI can identify pathology in patients with an established diagnosis that echo might not be able to detect. This includes apical aneurysms. MRI also can quantify the scar burden injected HCM, which can help assess the risk of heart failure later on as the patient's disease progresses. The scar burden also can play a roll in determining if the patient should have a defibrillator implanted.
Why are serial echocardiograms needed in mavecamten patients?
Echo is used in serial exams of mavecamten patients to ensure they are getting the correct dose of the drug, Nagueh said. The impact of the drug is assessed through serial measurements of HCM hypertrophy. The dose can be raised or lowered according to imaging findings.
The echo results are also used to assess ejection fraction. If a patient gets too much of the drug, Nagueh said their ejection fraction can drop and they may go into heart failure.
When therapy is initiated, echo exams are performed every month for the first three months. Once a patient is stable on a given dose, echos are performed every three months. If the dose changes, Nagueh said echo exams are scheduled in closer intervals. He said assessing the LVEF with actual measurements is necessary to be more accurate in HCM to catch any changes. He also warns visual assessments of ejection fraction should not be used.
"For physicians who rely on visual assessment, in my experience it is not the best approach because you are looking for trends over time," Nagueh said.
Nagueh said Houston Methodist performs full echo serial exams on HCM patients, which also includes the use of strain imaging. But he noted that the bare minimum assessment needed is for the patient's LVOT gradient and ejection fraction.
Dave Fornell has covered healthcare for more than 17 years, with a focus in cardiology and radiology. Fornell is a 5-time winner of a Jesse H. Neal Award, the most prestigious editorial honors in the field of specialized journalism. The wins included best technical content, best use of social media and best COVID-19 coverage. Fornell was also a three-time Neal finalist for best range of work by a single author. He produces more than 100 editorial videos each year, most of them interviews with key opinion leaders in medicine. He also writes technical articles, covers key trends, conducts video hospital site visits, and is very involved with social media. E-mail: dfornell@innovatehealthcare.com