The beneficial effects of physiologic dual-chamber (DDD) pacing in the treatment of end-stage idiopathic dilated cardiomyopathy were evaluated in 16 patients in whom conventional drug therapy had failed. Candidates for cardiac transplantation as well as patients not accepted for transplantation participated. During DDD pacing at an atrioventricular delay of 100 ms, left ventricular ejection fraction increased from 16.0 +/- 8.4 to 25.6 +/- 8.6% (p less than 0.001) accompanied by a striking improvement in clinical symptoms, such as severe dyspnea at rest and pulmonary edema. The New York Heart Association class decreased from 3.6 +/- 0.4 to 2.1 +/- 0.5 (p less than 0.001). The decrease in cardiothoracic ratio from 0.60 +/- 0.06 to 0.56 +/- 0.05 (p less than 0.001) coincided with a decrease in left atrial and right ventricular echocardiographic dimensions, indicating a decrease in preload. Systolic blood pressure increased from 108 +/- 29 to 126 +/- 21 mm Hg (p less than 0.01) and diastolic blood pressure from 67 +/- 15 to 80 +/- 11 mm Hg (p less than 0.01). Normalization of heart rate was achieved. No major complications developed as a consequence of DDD pacing. All patients could be discharged from the hospital within 3 weeks after pacemaker implantation and return to a relatively normal life. Within 1 year after onset of DDD pacing only 4 of the patients died (from either sudden death or stroke). DDD pacing could represent an alternative approach to the management of chronic heart failure due to dilated cardiomyopathy, especially for heart transplant candidates and patients who are not accepted for cardiac transplantation, but no longer respond to drug therapy.