Effect of coronary artery bypass surgery on myocardial function as assessed by tissue Doppler echocardiography

Coronary artery bypass graft (CABG) surgery may induce myocardial stunning and thereby affect cardiac function. We aimed to assess whether myocardial function is affected by CABG in patients with preserved preoperative systolic function.

Myocardial tissue peak velocities were recorded at the lateral and septal angle of the mitral annulus as well as at the lateral tricuspid annulus by pulsed wave tissue Doppler echocardiography before cardiac surgery, and then at 5 days, 6 weeks and 18 months after surgery.

Thirty-two consecutive patients with preserved systolic left ventricular function (31 male, 63+/-10 years) undergoing CABG (9 with cardiopulmonary bypass on-pump, 23 beating heart off-pump) were included. Peak systolic velocity on tissue Doppler echocardiography was unchanged after surgery. In contrast, peak early diastolic velocities (E') improved significantly 5 days and 6 weeks after surgery in the septal area (6.2+/-2.3 to 7.4+/-2.6 and 7.6+/-2.6 cm/s, respectively; p<0.05) and at the left ventricular lateral wall (9.1+/-3.0 to 10.1+/-3.0 and 11.3+/-2.9 cm/s, respectively; p<0.05), and then declined slowly to preoperative values after 18 months. In contrast, right ventricular E' decreased significantly immediately after surgery (9.8+/-2.7 preoperatively to 7.7+/-1.7 cm/s at 5 days, p=0.005) with only incomplete recovery over time. This was similar in both the conventional and the off-pump CABG cohort.

Left ventricular function did not deteriorate after CABG in patients with preserved preoperative systolic function. On the contrary, diastolic function improved immediately after CABG. Right ventricular function, in contrast, appeared to be damaged by surgery, to similar degrees regardless of whether patients underwent off-pump or on-pump surgery. Hypothermia and immune-inflammatory activation are, therefore, not plausible explanations for this decline in right ventricular function.