A measurable rise in ischemic stroke risk emerges when AF occurs in the presence of HCM. The analysis, published in Circulation, examined real-world outcomes using a large TriNetX dataset and compared event rates after careful propensity-score matching (PSM).

The database included 34,169 individuals with AF and HCM and more than 1.86 million individuals with AF but no HCM. After PSM, two balanced cohorts of 33,867 individuals were followed for an average of 2.6 to 2.7 years. Ischemic stroke occurred in 12% of the AF–HCM group compared with 10.4% of the AF-only group.

Risk estimates showed a consistent pattern. The hazard ratio (HR) of 1.113 with a 95% confidence interval (CI) of 1.064 to 1.165 and a p value less than .001 indicated an 11.3% higher ischemic stroke risk in the AF–HCM cohort. Survival probability at the end of follow-up was 66.14% in the AF–HCM group and 70.46% in the AF-only group.

These findings position HCM as a clinically important modifier of stroke risk in AF. Recognizing HCM in risk assessment may support more precise prevention strategies in this high-risk population.