Assessment of right ventricular function by pressure-volume loops in off-pump coronary artery bypass surgery

摘要

Background Right ventricular function plays an important role in the hemodynamic derangement during off-pump coronary artery bypass (OPCAB) surgery. Pressure-volume loops have been shown to provide load-independent information of cardiac function. Therefore, the aim of this study was to investigate the feasibility of construction of right ventricular pressure-volume loops with pressure and volume data measured by a volumetric pulmonary artery catheter (PAC) and to evaluate right ventricular systolic and diastolic function by end-systolic elastance (EEs) and end-diastolic stiffness (EED) in OPCAB surgery.Methods Twenty-eight patients who underwent OPCAB surgery were included. After anesthesia induction, a volumetric PAC was placed via the right internal jugular vein. Data were recorded at: anesthesia steady-state before skin incision (T1); 5 minutes after the stabilizer device was placed for anastomosis on the heart's anterior wall (T2), lateral wall (T3),posterior wall (T4), respectively; after sternal closure (T5). Three sets of data were collected at each time point: first,hemodynamic variables were measured; second, right ventricular EES and EED were calculated; third, right ventricular pressure-volume loops were constructed with pressure and volume data measured from end-diastole point,end-isovolumic systole point, peak-ejection point, end-systole point and end-isovolumic diastole point.Results Right ventricular pressure-volume loops generally shifted to the left during OPCAB surgery. Especially, the end-diastolic point shifted upward and to the left at T2-T5 compared with that at T1. Decrease in right ventricular ejection fraction, stroke volume index and end-diastolic volume index occurred (P＜0.05) at T4 compared with values at T1. Pulmonary vascular resistance index at T4 increased relatively compared with that at T2 and T3. The change of EES was not statistically significant during operation. Right atrial pressure increased only during coronary anastomoses (T2-T4, P＜0.05), whereas EED increased throughout OPCAB surgery (P＜0.05).Conclusions Right ventricular pressure-volume loops can be constructed using a volumetric PAC. Right ventricular systolic dysfunction occurred during anastomoses on the heart's posterior wall not due to impaired myocardial contractility but as a result of reduced preload and a relative increase in afterload. Right ventricular diastolic function was impaired throughout OPCAB surgery.