A substantial proportion of patients classified as asymptomatic demonstrate impaired exercise capacity on formal testing. This analysis, presented at the American Heart Association (AHA) 2025 Scientific Sessions, evaluated the diagnostic and prognostic value of TSE in patients with HCM deemed to be New York Heart Association (NYHA) Class I after comprehensive evaluation at a tertiary referral center.

Between January 2002 and December 2018, 1,126 asymptomatic patients underwent symptom-limited TSE from a total cohort of 7,954 patients with HCM. Patients were classified as oHCM or nHCM based on a left ventricular outflow tract (LVOT) gradient ≥30 mm Hg. Peak-exercise LVOT gradient, metabolic equivalents (METs), and %AGP-METs were recorded. The primary outcome was a composite of mortality, appropriate internal cardioverter defibrillator (ICD) discharge, or cardiac transplantation. The need for myectomy was also documented.

Despite being asymptomatic, 413 patients (37%) failed to achieve ≥85% AGP-METs. During a mean follow-up of 12.9 ± 5 years, 200 composite events occurred, including 173 deaths, 23 appropriate ICD discharges, and 7 cardiac transplants. After a mean of 988 ± 1271 days, 190 patients underwent myectomy. Patients achieving ≥85% AGP-METs had better long-term survival than those who did not. Patients with nHCM and those with oHCM who underwent myectomy had greater long-term freedom from composite events than patients with oHCM who did not undergo myectomy.

TSE identified functional limitation and obstructive physiology despite absence of symptoms. These findings support its role in risk stratification and in guiding timing of therapeutic intervention in asymptomatic HCM.