ASSOCIATION BETWEEN R-WAVE AMPLITUDE OF THE ELECTROCARDIOGRAM AND MYOCARDIAL-FUNCTION DURING CORONARY-ARTERY BYPASS-GRAFTING

Objective: The recovery of R-wave amplitude in the V-5 lead of the ele ctrocardiogram (EGG) was recently found to be worse in nonsurvivors th an in survivors after coronary artery bypass grafting (CABG). On the c ontrary, an increase in R-wave amplitude has been found to reflect myo cardial dysfunction in exercise testing. The purpose of this study was to examine whether the changes in R-wave amplitude are associated wit h changes of myocardial function during CABG. Design: A prospective cl inical study, Setting: Cardiothoracic division of surgery in a univers ity hospital, Participants: Ten consecutive patients undergoing CABG. Measurements: R-wave amplitude was measured at eight different time po ints, Left ventricular end-systolic wall tension, wall stress at isovo lumic contraction (afterload), end-diastolic wall stress (preload), en d-systolic wall stress per end-systolic area (contractility), and stro ke work were calculated using transesophageal echocardiography and art erial pressure, Main Results: Linear regression was calculated between changes in R-wave amplitude and echo parameters, A weak positive asso ciation within subjects was noted among R amplitude and all measured c ardiac function parameters except preload. R-2 value varied from 0.101 to 0.266, and R-2 for preload was 0.017, Conclusions: These results s uggest that only 10% to 27% of variation in R-wave amplitude can be ex plained by left ventricular function indices measured by echocardiogra phy in patients with CABG. Thus, R-wave amplitude changes in an indivi dual patient undergoing CABG have very limited utility as a noninvasiv e measure of left ventricular function. Copyright (C) 1997 by W.B. Sau nders Company.