Deterioration of congestive heart failure after converting to VOO mode from DDD mode in a dilated cardiomyopathy patient; importance of atrial contribution.

We describe a 62-year-old dilated cardiomyopathy patient in whom congestive heart failure progressed shortly after DDD mode was changed to VOO mode because of battery exhaustion. Emergency battery exchange with restoration of DDD mode improved his functional status to the previous level; pulmonary capillary wedge pressure decreased from 28 to 24 mmHg and cardiac output increased from 1.5 to 2.0 L/min associated with widening of the aortic pulse pressure. Maintenance of atrial contraction is therefore important even if left ventricular systolic function is markedly impaired and left ventricular end-diastolic pressure is increased.