Atrial fibrillation (AF) is a multivariable disease. Young patients with paroxysmal AF without structural cardiac abnormality ("lone AF") likely have a primary electropathy with excellent results from radiofrequency ablation. However, with persistent AF with cardiac abnormalities, including left atrial enlargement and systolic ventricular dysfunction (ejection fraction percent), the electropathy is considered secondary and ablation results poor. We describe a case with persistent AF, depressed systolic function, and marked left atrial enlargement but without echo Doppler evidence of diastolic dysfunction. At electrophysiology study, findings were consistent with a primary electropathy, and the patient did well following ablation.