Dallas, TX and Washington, DC - "It still has the reputation of something that's hard to treat, and what we've done here, not only in the guidelines, but in the research leading up to the guidelines, is to try to change that perception," said Dr Barry J Maron (Minneapolis Heart Institute, MN), referring to a landmark set of society-sponsored recommendations for the diagnosis and management of patients with hypertrophic cardiomyopathy (HCM) [1].
Medicine's perception of the disorder, "the most common cause of sudden death in young people," Maron told heartwire, has evolved from something a bit mysterious with a generally poor outcome to "a complex but highly treatable genetic heart disease. The guidelines are an accurate recognition of not only the change in our perception of the disease and its treatment, but also of what hypertrophic cardiomyopathy is today."
Treatment follows several, sometimes overlapping, pathways that address the heightened sudden-death risk and development and progression of heart failure; atrial fibrillation is another possible manifestation that can be directly addressed.
In particular, "the defibrillator, translated to patients with hypertrophic cardiomyopathy, has altered the clinical course of the disease for many patients and is in fact the only treatment available in HCM that is proven to prolong life," Maron said.
"The idea that you can effectively prevent sudden death in this disease is a major innovation for the patient population. These are young, otherwise-healthy people, generally, who—if they are high risk—can now have the expectation that it's possible to prevent sudden cardiac death and achieve normal longevity."
The new recommendations are published online today in Circulation and copublished in the Journal of the American College of Cardiology and the Journal of Thoracic and Cardiovascular Surgery, with Maron and Dr Bernard Gersh (Mayo Clinic, Rochester, MN) as the first two authors and noted as cochairs of the writing committee.
With the American College of Cardiology Foundation (ACCF) and the American Heart Association (AHA) as its marquis sponsoring organizations, the document, it says, was developed in collaboration with the American Association for Thoracic Surgery, American Society of Echocardiography, American Society of Nuclear Cardiology, Heart Failure Society of America, Heart Rhythm Society, Society for Cardiovascular Angiography and Interventions, and Society of Thoracic Surgeons.
The writing committee acknowledged that their recommendations (aimed mainly at cardiologists, Maron noted) are rooted primarily in expert consensus (level of evidence C) given a "lack of high levels of evidence regarding HCM provided by clinical trials." But that in itself may represent something of an achievement, given the broad subspecialty spectrum of the organizations that signed off on the recommendations and their sometimes-contrasting takes on diagnostic and therapeutic approaches.
Septal reduction therapy: Two strategies
For example, the document's class I position on invasive correction of left ventricular outflow tract (LVOT) obstruction, a hallmark of HCM, says "septal-reduction therapy should be performed only by experienced operators in the context of a comprehensive HCM clinical program and only for the treatment of eligible patients with severe drug-refractory symptoms and LVOT obstruction."
But how septal reduction is carried out has sometimes been a touchy issue, one on which different subspecialties—and their representing organizations, to some extent—have historically had different takes. Although the guidelines favor a long tried-and-true surgical approach as first line and define a catheter-based technique as second tier, in clinical practice the latter is performed more broadly than that.
"The guidelines say that for patients with progressive heart failure refractory to drug treatment who are severely symptomatic, the preferred and gold-standard treatment for most of those patients is surgical septal myectomy," Maron said, adding that the percutaneous strategy, alcohol septal ablation, is an effective alternative in selected patients.
"When surgery is contraindicated or the risk is considered unacceptable because of serious comorbidities or advanced age," the guidelines state, "alcohol septal ablation, when performed in experienced centers, can be beneficial in eligible adult patients with HCM."
Gene testing most powerful for relatives
Genetic testing, another issue that has evolved over the years and been crystallized in the new guidelines, should be reserved for HCM patients and their families and only in some circumstances; it isn't specific enough for broad population screening.
The guidelines, Maron said, point out that tests for known HCM-related gene variants can't usefully predict outcomes "but have proved to be most powerful in family screening and early detection of relatives without left ventricular hypertrophy."
In class I recommendations, the guidelines state that "screening (clinical, with or without genetic testing) is recommended in first-degree relatives of patients with HCM" and that "genetic testing for HCM and other genetic causes of unexplained cardiac hypertrophy is recommended in patients with an atypical clinical presentation of HCM or when another genetic condition is suspected to be the cause" (level of evidence B for both).
Otherwise, a class IIa recommendation states, genetic testing of the HCM patient is "reasonable . . . to facilitate the identification of first-degree family members at risk for developing HCM" (level of evidence B).
Exercising caution
The guidelines document is much further reaching, however, covering risk-stratification techniques; the roles and relative value of different imaging modalities, including transthoracic echocardiography (TTE), angiography, and cardiac magnetic resonance (CMR); drug therapy, with beta blockade a cornerstone and positive inotropic agents generally persona non grata; and recommendations on engaging in sports and other physical activities.
Almost any sport at an advanced competitive level should be off-limits for patients with HCM, according to the document, but it makes room for engagement in light competitive sports such as golf and in a range of recreational sports, including cycling, "modest hiking," lap swimming, doubles tennis, and bowling.
But "patients with HCM should avoid recreational sports in which participation is intense and simulates competitive organized athletics." Sports that entail "burst exertion" are less suitable than those with more consistent exertion, such as lap swimming or cycling.
"General recommendations for recreational exercise in patients with HCM should be tailored to the individual's desires and abilities," the document states.
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