The number of people In the United States who were been diagnosed with hypertrophic cardiomyopathy (HCM) increased by 60%between 2013 and 2019, according to findings reported in the American Journal of Cardiology.

Extrapolating from the prevalence they found in large claims database, the researchers calculated that 164,403 people in the U.S. had a clinical diagnosis of HCM in 2013. Six years later, their calculations indicate that 262,591 people had an HCM diagnosis. They speculate that cardiac magnetic resonance imaging techniques that are more likely to identify the thickening of cardiac muscle than echocardiograms are responsible the increasing number of diagnoses.

The study was funded by Cytokinetics, a Bay Area biotech company that has a HCM treatment drug, aficamten, in clinical trials. It was posted online in September, but the full-length version was published in the Nov. 15, 2021, issue of the American Journal of Cardiology.

Lead author Michael Butzner, consultant, health economics and outcomes research, Cytokinetics, and his colleagues noted that their research shows the prevalence of obstructive HCM decreasing even as the HCM overall and nonobstructive form of the disease increased. They also cautioned that extrapolating from the claims database they used to conduct their research could be problematic because the HCM results in that population of people with commercial insurance and in Medicare Advantage plans may not be generalizable to people with other kinds of insurance.

Butzner and his colleagues say their data suggest that the gap between previous estimates of 600,000 undiagnosed persons affected by HCM and those who have been “clinically identified” may not be as large as previously thought.

They conducted their study using claims data from the HealthCore Integrated Research Database. They searched the database for HCM claims and found that 8,526 among the 16,243,109 patients in 2013 could be identified as having an HCM diagnostic code, which works out to a prevalence 0.052%, or 1 in 1,905.

Over the next six years. the prevalence climbed steadily and in 2019, it reached 0.08%, according to Butzner and his co-investigators. They said the decrease in the diagnosis of obstructive HCM might be explained by “subtle morphologic change in HC (HCM) disease expression compared with previous decades” and called for more research to tease out and better characterize the reasons.