Background: Right ventricular (RV) long-axis function is known to be depressed after cardiac surgery, but the mechanism is not known. We hypothesized that intraoperative transesophageal echocardiography could pinpoint the time at which this happens to help narrow the range of plausible mechanisms.
Method: Transthoracic echocardiography was conducted in 33 patients before and after elective coronary artery bypass graft. In an intensively monitored cohort of 9 patients, we also monitored RV function intraoperatively using serial pulsed wave tissue Doppler (PW TD) transesophageal echocardiography.
Results: There was no significant difference in myocardial velocities from the onset of the operation up to the beginning of pericardial incision, change in RV PW TD S' velocities 3% +/- 2% (P = not significant). Within the first 3 minutes of opening the pericardium, RV PW TD S' velocities had reduced by 43% +/- 17% (P < .001). At 5 minutes postpericardial incision, 2 minutes later, the velocities had more than halved, by 54% +/- 11% (P < .0001). Velocities thereafter remained depressed throughout the operation, with final intraoperative S' reduction being 61% +/- 11% (P < .0001). One month after surgery, in the full 33-patient cohort, transthoracic echocardiogram data showed a 55% +/- 12% (P < .0001) reduction in RV S' velocities compared with preoperative values.
Conclusions: Minute-by-minute monitoring during cardiac surgery reveals that, virtually, all the losses in RV systolic velocity occurs within the first 3 minutes after pericardial incision. Right ventricular long-axis reduction during coronary bypass surgery results not from cardiopulmonary bypass but rather from pericardial incision.
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