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  • Title: Association between R-wave amplitude of the electrocardiogram and myocardial function during coronary artery bypass grafting.
    Author: Aittomäki JV, Salmenperä MT.
    Journal: J Cardiothorac Vasc Anesth; 1997 Dec; 11(7):856-60. PubMed ID: 9412884.
    Abstract:
    OBJECTIVE: The recovery of R-wave amplitude in the V5 lead of the electrocardiogram (ECG) was recently found to be worse in nonsurvivors than in survivors after coronary artery bypass grafting (CABG). On the contrary, an increase in R-wave amplitude has been found to reflect myocardial dysfunction in exercise testing. The purpose of this study was to examine whether the changes in R-wave amplitude are associated with changes of myocardial function during CABG. DESIGN: A prospective clinical study. SETTING: Cardiothoracic division of surgery in a university hospital. PARTICIPANTS: Ten consecutive patients undergoing CABG. MEASUREMENTS: R-wave amplitude was measured at eight different time points. Left ventricular end-systolic wall tension, wall stress at isovolumic contraction (afterload), end-diastolic wall stress (preload), end-systolic wall stress per end-systolic area (contractility), and stroke work were calculated using transesophageal echocardiography and arterial pressure. MAIN RESULTS: Linear regression was calculated between changes in R-wave amplitude and echo parameters. A weak positive association within subjects was noted among R amplitude and all measured cardiac function parameters except preload. R2 value varied from 0.101 to 0.266, and R2 for preload was 0.017. CONCLUSIONS: These results suggest that only 10% to 27% of variation in R-wave amplitude can be explained by left ventricular function indices measured by echocardiography in patients with CABG. Thus, R-wave amplitude changes in an individual patient undergoing CABg have very limited utility as a noninvasive measure of left ventricular function.
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