Intra-operative left ventricular functions were measured by epicardial echocardiography, which was obtained by small ultrasound transducer (5 megaheltz) on the epicardium of the right ventricular outflow.
Canine left cardiac functions after cardiopulmonary bypass were compared in 2 groups, one being 60-minute cardiac arrest with cardioplegia (group A) and the other 45-minute ischemic arrest (group B).
The results obtained were as follows:
1. It was simple and reliable to determine the state of left ventricular function with epicardial echocardiography during operation.
2. There was good correlation between the values for cardiac output as measured by thermodilution and calculated by epicardial echocardiography.
3. Contractility after cardiopulmonary bypass was well maintained in both groups. Some indices of systolic cardiac function in group B after cardiopulmonary bypass were compromised, but those of group A remained normal.
4. The posterior left ventricular wall motion in diastole in group B was slower than that in group A after cardiopulmonary bypass. Ischemic arrest (group B) was shown particularly to impair myocardial relaxation and to raise left ventricular wall stress in diastole.
It was concluded in the present study that impairment in cardiac function appeared first in diastole following cardiac surgery and that epicardial echocardiography would be a convenient and simple tool for determining cardiac function during surgical intervention. It was also found that cardioplegia preserved cardiac function near normal level even in diastole.
