Wolff-Parkinson-White syndrome: mechanocardiographic study on the mechanical consequences of ventricular pre-excitation.

ABSTRACT

To elucidate the mechanical consequences of ventricular pre-excitation in patients with the W,W syndrome, electrical and mechanical events in the ventricles during anomalous pathway conduction and normal atrioventricular conduction were examined mechanocardiographically in 11 cases of Group A and 19 cases of Group B, in whom anomalous pathway conduction was stopped by procaine amide, resulting in normalization of conduction. Eight healthy persons were employed as a control group. In the control group, procaine amide had no significant effect on the mechanocardiographic values. In the WPW syndrome, significant prolongation of the P-X, P-J, P-T, P-C, P-I, P-Ao, and P-II intervals was induced by the drug. From the results of statistical analyses of measured values, it would appear that mechanical events in the ventricles were accelerated by ventricular pre-excitation but the extent of acceleration of the former was less than the extent of prematurity of the latter. The anomalous ventricular pre-excitation occurred earlier in cases of Group B than in those of Group A, while initiation of ventricular contraction, atrioventricular valve closure, and aortic vlave opening were accelerated more in Group A. In one case of Group B, electrical phenomena could not be related to mechanical events.