Buckley BJR, Harrison SL, Gupta D, et al. - A likely high prevalence of atrial fibrillation in patients with cardiomyopathy is indicated by the findings. Worsened prognosis was reported in relation to atrial fibrillation in these cases.

• In this large retrospective cohort study utilizing the TriNetX network, the prevalence and associated clinical results of concomitant atrial fibrillation and cardiomyopathy subtypes were inquired among 634,885 participants.

• In patients with hypertrophic, restrictive, and dilated cardiomyopathies, the prevalence of atrial fibrillation was 23.6%, 42.5%, and 44.4%, respectively.

• Elevated odds of mortality in all but restrictive cardiomyopathy cohorts were observed in relation to concomitant atrial fibrillation (odds ratio were 1.26, 1.36, and 0.98 for hypertrophic, dilated, and restrictive cardiomyopathy).

• In all cardiomyopathy subtypes with concomittant atrial fibrillation, there were significantly higher odds of hospitalization, incident heart failure, and incident stroke.

• In atrial fibrillation cases, significantly lower odds of all‐cause mortality in relation to catheter ablation were observed at 12 months across all cardiomyopathy subtypes.