New and recurrent atrial fibrillation in patients with obstructive hypertrophic cardiomyopathy receiving mavacamten.

BACKGROUND

Patients with obstructive hypertrophic cardiomyopathy (oHCM) are at an increased risk of the development of atrial fibrillation (AF) and subsequent AF-related morbidity. The impact of treatment with the novel cardiac myosin inhibitor mavacamten on AF is unknown.

OBJECTIVE

This study aimed to evaluate incident and recurrent AF rates in patients with oHCM receiving mavacamten.

METHODS

This was a retrospective observational study of patients with oHCM undergoing mavacamten treatment at the Johns Hopkins Hypertrophic Cardiomyopathy (HCM) Center. Predicted AF risk was calculated using the HCM-AF score at the time of mavacamten initiation. Patients were followed longitudinally for the development of new or recurrent clinically significant AF.

RESULTS

160 patients with oHCM (mean age 62 years; 58% female) were enrolled, including 30 (18.8%) with a diagnosis of AF before mavacamten treatment. Median HCM-AF score at the time of mavacamten initiation was 23. During a median of 1.4 years of mavacamten treatment (interquartile range 0.6-2.3), new AF occurred at a rate of 6.4%/y in those without a previous AF diagnosis. Although the HCM-AF score had reliable discrimination in this population (concordance statistic 0.78), the observed 2-year risk of symptomatic AF modestly exceeded HCM-AF risk predictions (8.2% vs 6.9%). On time-dependent multivariable Cox regression, mavacamten was associated with an increased risk of the development of new, clinically significant AF (hazard ratio 3.0; P = .01). In patients with a previous AF diagnosis, AF recurred during mavacamten treatment at a rate of 19.3%/y.

CONCLUSION

Although patients with oHCM had a high baseline risk of AF, mavacamten treatment was associated with an increased risk of AF development beyond that predicted by the HCM-AF score.