Prognostic significance of atrial fibrillation in dilated cardiomyopathy.

We evaluated the relation of atrial rhythm to a clinical course of treatment in 147 patients diagnosed with dilated cardiomyopathy (DCM). Thirty-six of the patients (24%) had either transient (9 patients) or persistent (27 patients) atrial fibrillation (AF). Compared with DCM patients with sinus rhythm (SR), the AF patients did not differ in age, left ventricular (LV) dimension, fractional shortening, or hemodynamic parameters, but the AF patients had slightly larger left atria. After a mean follow-up of 3.8 +/- 2.9 years, the NYHA functional classifications in the AF patients improved in 20 of the 36 (56%), whereas those of the SR patients improved in only 30 (27%) (p < 0.01). The actuarial 5-year survival rate was significantly better for AF patients than for SR patients (93% versus 68%, p < 0.05). LV function remained unchanged in SR patients but improved significantly in AF patients, particularly in patients with transient AF and with "rate-controlled" AF (those with a mean heart rate of less than 90 beats/min). This study suggests that atrial fibrillation may result in significant LV dysfunction, which is reversible in some cases once the arrhythmia is controlled. Aggressive antiarrhythmic therapy should be considered for patients initially diagnosed with dilated cardiomyopathy and atrial fibrillation.