A severe case of myopotential interference in a patient with a respiratory-dependent rate modulated pacemaker.

Symptomatic myopotential interference was observed in a patient with a respiratory-dependent rate modulated pacemaker (RDP3). During treadmill exercise, prolonged interference suspended the rate responsive function and resulted in reversion to the interference mode with the pacing rate falling back to the basic frequency during the interference. This loss of rate response resulted in severe impairment of exercise tolerance and reduction in cardiac output during exercise. The unit was replaced with a bipolar activity sensing rate modulated pacemaker.