Spontaneous reversal of a cardiomyostimulator to asynchronous mode

A patient who underwent dynamic cardiomyoplasty at our institute 10 months earlier was recently found to have asynchronous function of his cardiomyostimulator (model SP1005A, Medtronic, Inc.). This patient had been exposed to metal detection equipment 3 months earlier at an airport security gate, and this equipment was deemed responsible for this change in device programming. Despite the asynchronous function of the device, the patient did not suffer any functional impairment during this 3-month period. Moderate electromagnetic interference is capable of resetting the SP1005A cardiomyostimulator to the asynchronous mode of operation. Muscle stimulation, therefore, will not precisely occur during the systolic phase of the cardiac cycle and systolic augmentation may be lost. Despite asynchronous muscle stimulation, no impairment of this patient's functional Class was observed. This stability may be credited purely to the effect of the muscular wrap around the ventricles in which ventricular wall stress is decreased.