Evaluation of Hemodynamic Changes of the Left Ventricle Following the Use of Extracorporeal Circulation

The interpretation of perioperative measures of cardiac function during cardiac surgery is complicated. In particular, the evaluation of the diastolic compliance of the left ventricle. In addition, they are subject to variations induced by post-charge changes caused by the anesthesia, extracorporeal circulation (ECC) and the surgical procedure itself.

Left ventricular failure is frequently measured by alteration of LV contractile properties, and very rarely by alteration of LV compliance. However, both contractility (systolic) and relaxation (diastolic) parameters are important for the left ventricle to perform its function adequately. Left ventricular failure after cardiac surgery with extracorporeal circulation and cardiac arrest under cardioplegia protection is an important and frequently reported complication. The investigator's objectives are to characterize the diastolic hemodynamic mechanisms of this left ventricular failure and to identify predictors of this failure in the postoperative period.

The quantification of the systolic and diastolic functions of the left ventricle by ventricular pressure-volume curves is the technique of reference today, because it allows to determine parameters that are independent of the pre- and post-load conditions. Previous studies using the conductance catheter for the purpose of estimating left ventricular function perioperatively are rare and report conflicting results. In addition, they were mainly intended to measure the systolic function of the left ventricle. Only one reported the diastolic relaxation parameters evaluated by a conductance catheter. This study showed immediately after withdrawal of the extracorporeal circulation a significant alteration of the diastolic relaxation of the left ventricle, but was not interested in its early (kinetic) evolution peroperatively.

The investigator's experience shows that, in the quarter-hour following the weaning of the extracorporeal circulation, a decrease in filling pressures of the left ventricle concomitant with an increase in cardiac output is objectified. These observations are consistent with a significant improvement in left ventricle compliance, but have never been reported.

The objectives of this study are:

• To characterize the left ventricular diastolic failure after withdrawal of the extracorporeal circulation in coronary surgery.
• To identify the kinetics of this early diastolic failure after withdrawal of the extracorporeal circulation.