Electrical activation and mechanical asynchronism in the cardiac cycle of the dog

¹ Cardio-Pulmonary Laboratory, Mt. Sinai Hospital, Miami Beach, Section of Cardiology, Department of Medicine and Department of Surgery, University of Miami School of Medicine, Coral Gables, and Jackson Memorial Hospital, Miami, Florida

Dissociation of electrical and mechanical asynchronism in the right and left ventricle of the dog has been studied by simultaneous registration of the precordial electrocardiogram and right and left ventricular pressure curves. Observations were made during sinus rhythm and during digitalis-induced ventricular premature beats with widened aberrant QRS complexes. Measurements were made of the time of onset of isometric contraction in the ventricles, relative to each other, and to the onset of the QRS complex. The results indicate that mechanical asynchronism in onset of isometric contraction is not a necessary consequence of the asynchronous electrical depolarization of ventricular premature systoles.