What if feeling perfectly healthy could actually hide a silent heart risk? That’s the unsettling truth emerging from new research on hypertrophic cardiomyopathy (HCM)—a genetic heart disease that can appear harmless at first glance. Many people diagnosed early seem completely fine, but stress echocardiography is beginning to reveal what routine checkups miss: hidden exercise limitations and long-term health risks. And here’s where it gets controversial—how can someone be symptom-free if their heart is already under strain?
A long-term observational study spanning nearly 13 years followed over 1,100 adults with HCM who were classified as asymptomatic (New York Heart Association class I). Every participant underwent treadmill stress echocardiography (TSE), a test that measures heart performance during exercise. Researchers assessed metabolic equivalents (METs), the percentage of age- and gender-predicted METs (%AGP-METs), and peak left ventricular outflow tract (LVOT) gradients to evaluate how well the heart handled physical exertion. The study’s main outcome combined all-cause mortality, internal cardioverter-defibrillator (ICD) activation, and cardiac transplantation. The results—presented at the 2025 American Heart Association (AHA) Scientific Sessions and published in the Journal of the American College of Cardiology—offered an unexpected picture of risk hiding in plain sight.
Exercise Tolerance Is Lower Than Expected
Even though all participants were considered symptom-free, 37% failed to reach 85% of their expected exercise capacity. That means over a third of these so-called healthy individuals already had reduced physical performance—a red flag for hidden dysfunction. Patients with obstructive HCM (oHCM), where the LVOT gradient reached or exceeded 30 mm Hg, often had thicker heart walls and more severe mitral valve issues from the start. Unsurprisingly, they scored lower on MET and %AGP-MET tests compared to those with nonobstructive HCM (nHCM).
The follow-up period told an even more striking story. Over almost 13 years, 18% of participants experienced major adverse outcomes—173 deaths, 23 ICD shocks, and 7 heart transplants. Reduced exercise performance turned out to be a powerful predictor: patients who achieved 85% or more of their targeted METs lived longer than those who didn’t (event rates 16% vs 20%, P = .004). Importantly, those who underwent surgical myectomy—a procedure that relieves obstruction—fared significantly better, whether they had obstructive or nonobstructive HCM. Without the operation, the risk of poor outcomes jumped to 23%.
Stress Testing May Expose the 'Silent' Disease
The findings challenge a common assumption: that being asymptomatic always means being safe. Researchers concluded that even patients who feel fine may have underlying problems affecting heart function, particularly if obstruction is present. Stress echocardiography helps uncover these subtle issues by showing how the heart behaves under pressure. According to the study’s authors, HCM can remain clinically silent for years while structural and functional problems quietly progress. TSE helps doctors see those early warnings—long before dangerous symptoms like shortness of breath or fainting occur.
As the authors noted, TSE provides valuable diagnostic and prognostic insights. It reveals who is truly asymptomatic and helps determine the right timing for interventions, such as surgery or medical therapy, before irreversible damage occurs. Still, the authors caution that because the study was retrospective and from a single center, more research is needed to confirm these results across diverse populations.
The Bigger Question
If one-third of “healthy” patients already show hidden impairment, should the definition of “asymptomatic” in HCM be reexamined? Some experts suggest it might be dangerous to wait until symptoms appear. Others argue that intervening too early poses its own risks. What do you think—should cardiologists proactively treat those who appear symptom-free, or stay cautious until more evidence emerges? Share your thoughts in the comments—this debate could reshape how we define wellness in heart disease.
