Pacing rate increase as cause of syncope in a patient with severe cardiomyopathy

Hemodynamic deterioration occurs with ventricular pacing rate increase in the presence of severe chagasic cardiomyopathy. Syncope and orthopnea occurred during ventricular pacemaker evaluation when the pacing rate was temporarily increased by magnet application. Cardiac output decreased by 54%, the arterial blood pressure by 38%, and the pulmonary wedge pressure increased by 54%. Such severe myocardial compromise may limit the use of rate modulated pacemakers.