Sinus arrest occurred in a patient with acute diaphragmatic myocardial infarction associated with right ventricular infarction. Cardiac output fell dramatically despite maintenance of a junctional rate of 72. Ventricular pacing at rate 82 and dopamine administration resulted in only slight hemodynamic improvement. Atrial pacing at rate 84 restored normal cardiac output until resumption of sinus node activity. These results suggest that atrial contraction is important for the maintenance of ventricular function in some patients with acute infarction, and may be of particular importance in the presence of right ventricular infarction. Temporary atrial or atrioventricular sequential pacing may be of great hemodynamic benefit in selected patients with conduction defects complicating myocardial infarction.