Peak-A wave pulmonary vein flow as an indicator of PCWP during CABG surgery

Several studies have reported that systolic fraction (SF) of pulmonary vein flow (PVF) predicts left ventricular filling pressure. These hypotheses have not been fully examined during cardiac surgery. This investigation was undertaken to examine in detail, the relationship between PCWP and left and right PVF before and after cardiopulmonary bypass (CPB) during CABG surgery. 50 patients, in sinus rhythm, without significant valvular disease, scheduled for CABG were enrolled in this study. PVF profiles were measured with the Doppler sample volume in either the right or left pulmonary vein where the peak reversed atrial flow velocity (peak-A) was highest at end-expiration. Angle correction was performed when the angle between PVF and the Doppler cursor was >30°. Data were collected during mammary artery harvesting (before CPB) and after weaning from CPB. Doppler flow velocity signals recorded on videotape were analyzed by an investigator blinded to the value of the PCWP for the mean of 3 to 5 measurements. The relationship between SF, or (peak-A) and PCWP was tested by linear regression analysis (P<0.05 was considered significant). Strong, significant associations were found between PCWP and peak-A of left (r=0.89, p= 0.001) and right (r=0.80, p= 0.001) PVF. Less strong, but also significant associations were found between SF and PCWP for left (r=0.75, p= 0.001) and right (r=0.76, p= 0.001) PVF before CPB. Similar results were obtained after CPB. Intra- and inter-observer measurements differed by 2.3%- 4.3%. This investigation suggests that PVF peak-A wave is an excellent predictor of PCWP.