RIGHT-VENTRICULAR DYSFUNCTION AFTER MAJOR PULMONARY RESECTION

Right ventricular performance was assessed by thermodilution in 20 patients at rest and during exercise before and after lobectomy or pneumonectomy. The right ventricular ejection fraction was significantly decreased on the first postoperative day (0.36 +/- 0.34), the second postoperative day (0.34 +/- 0.04), and the third postoperative week (0.37 +/- 0.06) relative to the preoperative right ventricular ejection fraction value (0.43 +/- 0.07, P<0.05). The right ventricular end-diastolic volume index was significantly increased by the second postoperative day (130 +/- 24 ml/m(2)) compared with the preoperative value (112 +/- 20 ml/m(2)). A significant decrease in the right ventricular stroke volume index was observed after operation, with a significant increase in heart rate considered necessary to maintain cardiac output. Pulmonary arterial pressure, the pulmonary vascular resistance index, and central venous pressure were unaltered over time. Indices of left ventricular function (that is, cardiac index, arterial pressure, and pulmonary arterial wedge pressure) were also preserved throughout the postoperative period. To explain the right ventricular dysfunction, ergometric exercise values were compared and the heart rate, pulmonary arterial pressure, central venous pressure, pulmonary vascular resistance index, and right ventricular end-diastolic volume index were all higher and the right ventricular ejection fraction lower during exercise after the operation. However, indices of left ventricular function remained unchanged. Significant elevations in pulmonary arterial pressure and the pulmonary vascular resistance index only during exercise; occurred. These findings indicate that changes in right ventricular function at rest compensate for the increase in right ventricular volume, but adequate compensation does not occur during exercise, with a resultant increase in pulmonary arterial pressure and the pulmonary vascular resistance index. This suggests that a change in afterload may be the main determinant of the deterioration in right ventricular pump performance during exercise. We speculate that the main cause of right ventricular dysfunction after major pulmonary resection might be the changes in right ventricular afterload. The right ventricle may play an important role serving as a ''reservoir'' for afterload.