Selective right ventricular impairment following coronary artery bypass graft surgery

The right ventricle (RV) may be selectively impaired following coronary artery bypass graft (CABG) surgery. We tested this hypothesis in two study parts: a prospective cohort undergoing CABG, and a retrospective cross-sectional cohort of heart-failure patients with and without a history of CABG.

In the prospective study, 20 patients undergoing CABG had echocardiography prior to surgery and 3 months postoperatively. In the retrospective study, 101 patients with established heart failure underwent echocardiography, 40 of whom had undergone previous CABG and 61 of whom had not. Myocardial tissue Doppler velocities were used as a measure of left and right ventricular function. To adjust for varying degrees of overall cardiac impairment, we calculated the ratio between the velocities of the RV and left ventricle (LV).

In the prospective study, there was a significant fall in RV:LV ratio following CABG surgery. For S', the ratio fell from 2.27 to 1.13 (50%, p<0.0001), for E' from 1.49 to 0.94 (37%, p<0.0001) and for A' from 1.66 to 1.05 (37%, p<0.0001). In the retrospective study, the RV:LV ratio was lower in the CABG group compared with the non-CABG group for S' (by 32%, p<0.001), E' (by 39%, p<0.001) and A' (by 37%, p<0.001). In the retrospective study, even when the CABG patients were compared with the ischaemic aetiology heart-failure patients without CABG, a similar relative impairment was seen: 25% in S' (p<0.001), 34% in E' (p<0.001) and by 38% in A' (p<0.002).

Both prospectively and cross-sectionally, there is evidence of substantial, selective right ventricular impairment following CABG. These features cannot be explained simply by some general feature of ischaemia and, therefore, must be a consequence of surgery.