Comparison of single and paired electrical heart stimulation on cardiac hemodynamics at rest and during exercise in dogs with atrioventricular heart block.

Abstract

1. On transition from a single electrical heart stimulation to a paired stimulation at a same fixed heart rate, no major differences arc noted in cardiac output, left ventricular systolic pressure, mean systemic blood pressure and calculated peripheral resistance in dogs with a chronic total atrioventricular heart block both at rest and during muscular exercise.2. However, paired stimulation was characterised by a significant increase in the peak rate of rise dP/dT of the ventricular pressure curve, which in the presence of an unchanged peak systolic pressure, suggests an augmentation of the contraction velocity.3. The administration of a beta adrenergic blocking agent propranolol does not abolish this « electroaugmentation » induced by paired stimulation in such dogs.