Objective: There is limited research comparing demographic and clinical characteristics between patients who present with atrial fibrillation (AF) and new-onset cardiomyopathy (CM) to patients with new-onset CM without dysrhythmia. We aimed to evaluate clinical characteristics and outcomes in patients with new-onset CM with and without AF and to report their real-world treatment.

Methods and results: The study population was identified using patient records from our healthcare system from January 1, 2012 to September 30, 2016. Patients with a left ventricular ejection fraction ≤40% without a prior history of CM were divided into two groups; those with an antecedent or concomitant diagnosis of AF (AF-CM group) and those with no history of dysrhythmia (CM group). Patients in the AF-CM group (n=196) were older, more likely to be male, had a higher burden of comorbidities but lower levels of cardiac biomarkers, and had lower voltage on surface electrocardiogram than the CM group (n=197). In AF-CM, symptom onset was insidious, leading to a higher likelihood of outpatient diagnosis; 88.3% of AF-CM patients presented with atypical symptoms of AF. The AF-CM group had higher mortality on follow-up. Only 8.7% of patients in this group underwent an ablation procedure. Women, those with a history of coronary artery disease, and older patients were less likely to receive a cardioversion or ablation procedure.

Conclusions: Patients presenting with new-onset CM associated with AF have a markedly different risk factor and demographic profile, clinical presentation, and outcomes. In real-world practice, a minority of patients undergo a rhythm control strategy.