Managing Hypertrophic Cardiomyopathy
January 04, 2016
Success requires interplay of genetics, cardiology, electrophysiology and cardiac surgery
Increased understanding of the specific genetic mutations responsible for hypertrophic cardiomyopathy (HCM) has led to increased requests for evaluation among those at risk.
“Most of the people with a diagnosis or suspicion of HCM are seen because they have a family history of the condition,” says Guilherme Oliveira, MD, Director, Advanced Heart Failure & Transplant Center, and Director, Onco-Cardiology Program, UH Harrington Heart & Vascular Institute; Associate Professor of Medicine, Case Western Reserve University School of Medicine. “However, with HCM, there’s often a dissociation between genotype and phenotype. There are patients who have the same genotype but have different manifestations of the disease. Disease may not manifest at all, or it may manifest in a completely different way.”
For patients with a positive genetic test, the next step is noninvasive evaluation with an echocardiogram to determine whether there is a phenotype of hypertrophy. Supplemental cardiac MRI with gadolinium is also particularly useful, Dr. Oliveira says.
“Even if the echo does not show hypertrophy, there is value in proceeding with a cardiac MRI to evaluate the amount of fibrosis in the myocardium,” he says.
For patients without a positive genetic test and unexplained hypertrophy, the diagnostic focus shifts to ruling out other possibilities. Endomyocardial biopsy is useful, for example, to rule out amyloid or storage diseases.
“Without a positive family history of HCM, it’s particularly important to look for amyloidosis and to identify the specific type,” Dr. Oliveira says. “Storage diseases, such as glyocogen storage disease and lysosomal storage diseases, the most common which is Fabry’s disease, can also masquerade as HCM.”
As complex as the diagnosis may be, medical treatment for HCM is equally fraught with challenges.
“In terms of medical therapy for this disease, it really has been very disappointing,” Dr. Oliveira says. “We use beta blockers, calcium channel blockers, some ACE inhibitors, and that’s about it.
What is being increasingly realized, however, is that atrial fibrillation (AF) is very common in patients with HCM, occurring in about 30 percent, and that it significantly exacerbates their symptoms.
“These patients have very poor tolerance to AF,” Dr. Oliveira says. “When they go into AF, they become very symptomatic and go into heart failure. In these patients, it’s very important to try to maintain sinus rhythm. AF ablation is particularly attractive in this group of patients.”
Treatment for HCM also sometimes includes an implantable defibrillator, due to the high risk of sudden cardiac death associated with the condition. However, this risk is not uniform throughout the HCM patient population.
“Patients with known disease are evaluated to see whether they fall into a high-risk category,” says Judith Mackall, MD, Chief Community Officer, Eastern Region, and Director, Center for Cardiovascular Genetics, UH Harrington Heart & Vascular Institute, Irving B. and Virginia Spitz Master Clinician in Cardiology, University Hospitals; Associate Professor of Medicine, Case Western Reserve University School of Medicine. “We consider imaging, exercise stress test, monitoring results, personal history of syncope and family history of sudden cardiac death. We put all of the clinical factors together with the structural factors, such as wall thickness and obstruction, to see whether they’re at high risk of sudden death. Those that are at high risk are offered an implantable defibrillator.”
For many patients with HCM, however, the best solution is often a surgical one.
“The most efficacious and long-lasting therapy we have is septal myectomy,” says Soon Park, MD, Director of Cardiac Surgery at UH Harrington Heart & Vascular Institute. “What we call extended septal myectomy is really ideal. We do more than take out the thickened septum that is obstructing bloodflow out of the heart. We excavate further to create more space. It mostly involves the septum, but may involve papillary attachment. In doing that, you create a larger opening. With the resulting decrease in velocity of bloodflow, the mitral valve does not get pulled in. When this surgery is thorough and effective, mitral valve regurgitation either goes away entirely or is very mild.”
“It’s imperative to do a thorough job of removing all the obstructive muscles and creating an opening deep into the left ventricle, excavating obstructive muscles that do not need to be there,” Dr. Park adds. “Symptoms sometimes recur after surgery, but the most common reason for repeat surgery is that the extensive excavation has not been done.”
Dr. Park gained extensive experience with septal myectomy during his time at Mayo Clinic. In the two years since his arrival at UH, he has completed about 15 procedures. Dr. Park is also a national leader in performing concomitant septal myectomy in patients undergoing aortic valve replacement.
“Patients with severe aortic stenosis are often found to have asymmetric septal hypertrophy,” Dr. Park says. “Echo often misses it. In fact, in about one-third of patients, the septal thickening is only diagnosed intraoperatively via visual and digital inspection.”
For more information or to refer a patient, call 216-868-8918 or (855) 977-5725 (1-877-703-7936).