Natural History of Asymptomatic Phenotypically Mild HCM: Insights from the SHaRe Registry (JACC October 2026-2)-Article: Natural History of Asymptomatic Phenotypically Mild HCM: Insights from the SHaRe Registry

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Researchers used the international SHaRe registry to study the natural history of phenotypically mild hypertrophic cardiomyopathy (HCM), defined by no symptoms or prior major cardiovascular events, relatively recent diagnosis or young age, and maximal left-ventricular wall thickness no greater than 25 mm. The analysis included 2,500 people, followed for an average of 7.2 years.<br /><br />During follow-up, 21% experienced a major adverse cardiovascular event (MACE), most often atrial fibrillation (12%); 8% developed heart failure and 3% had a malignant ventricular arrhythmia. Nearly one-quarter developed symptoms. At 10 years, the estimated probability of MACE was 29%. Developing mild symptoms was associated with nearly three times the rate of MACE.<br /><br />Higher baseline age, body mass index, left atrial diameter, ventricular wall thickness, and left-ventricular outflow gradient were independently associated with MACE. Importantly, serial imaging showed that risk was also related to disease trajectory: larger or more rapidly increasing left atrial size, wall thickness, and outflow gradients predicted more events. Participants with relatively stable cardiac measurements had lower event rates. A pathogenic sarcomere variant was associated with higher risk in unadjusted analyses, but not after accounting for other factors.<br /><br />The findings suggest that surveillance should consider changes over time—not just measurements at a single visit—to identify patients who may need closer follow-up or could be candidates for future disease-modifying treatment trials. Because this was a registry study, with potential referral, measurement, and surveillance biases, the results do not establish that treating asymptomatic patients improves outcomes.

Meta Tag

Concept Hypertrophic Cardiomyopathy

Concept Major Adverse Cardiovascular Events

Concept Atrial Fibrillation

Concept Ventricular Arrhythmia

Concept Heart Failure

Keywords

hypertrophic cardiomyopathy

SHaRe registry

major adverse cardiovascular event

atrial fibrillation

heart failure

ventricular arrhythmia

left atrial diameter

left ventricular wall thickness

serial imaging

disease trajectory

Hypertrophic Cardiomyopathy

Major Adverse Cardiovascular Events

Atrial Fibrillation

Ventricular Arrhythmia

Heart Failure