External validation of atrial fibrillation risk prediction tools in a racially diverse cohort of patients with hypertrophic cardiomyopathy.

Background: Atrial fibrillation (AF) is the most common sustained arrhythmia in patients with hypertrophic cardiomyopathy (HCM). The 2024 American Heart Association/American College of Cardiology guidelines recommend validated clinical tools such as the HCM-AF score for individualized assessment of AF risk. To date, these tools have been validated only in predominantly white HCM patient populations.

Objective: This study aimed to compare the performances of published AF risk prediction tools in a racially diverse cohort of patients with HCM.

Methods: This was a retrospective study of patients with HCM without previous AF evaluated at the Johns Hopkins HCM Center. Assessments of AF risk were generated using the HCM-AF score and other non-HCM-specific risk scores (C2HEST, HARMS2-AF, CHADS-VASc, and CHARGE-AF). Patients were followed longitudinally for the development of new-onset, clinically significant AF. Discrimination was assessed using concordance-based c-statistics.

Results: A total of 631 patients with HCM were included, with a mean age of 55.9 ± 15.3 years; 49.7% were women, 64.7% were white, 24.1% were black, and 11.2% identified with other nonwhite race. During a median follow-up of 3.1 years, new AF was diagnosed in 18.9% of patients. The HCM-AF score demonstrated better risk discrimination (c-statistic 0.72) than other non-HCM-specific risk scores (c-statistics 0.56-0.67) and effectively stratified patients into low-risk (0.9% AF/year), medium-risk (3.4% AF/year), and high-risk groups (7.4% AF/year). Discrimination of AF risk by the HCM-AF score was similar for white (c-statistic 0.71) and nonwhite patients (c-statistic 0.74).

Conclusion: The HCM-AF score demonstrated good AF risk discrimination in a diverse cohort of patients with HCM, outperforming alternative non-HCM-specific AF risk scores and validating its use in nonwhite HCM populations.