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

Right mid left ventricular pressure curves and electrocardiogram were recorded in the dog during sinus rhythm and during mechanically induced right and left ventricular premature systoles. The normal range during sinus rhythm for the relationship between onset of right and left ventricular contraction was determined. At one extreme, right ventricular contraction commenced 0.02 second before the left; at the other extreme, left ventricular contraction started 0.03 second before the right. In most instances, the onsets of ventricular contraction were either temporally identical or one ventricle contracted 0.01 second prior to the other.