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Association between R-wave amplitude of the electrocardiogram and myocardial function during coronary artery bypass
J V Aittomäki1, M T Salmenperä
1Department of Anaesthesia, Helsinki University Central Hospital, Finland.
Insights
Changes in electrocardiogram (ECG) R-wave amplitude during coronary artery bypass grafting (CABG) surgery have limited utility for assessing left ventricular function. Only 10-27% of R-wave amplitude variations are explained by measured cardiac function parameters.
Area of Science:
- Cardiology
- Cardiac Surgery
- Echocardiography
Background:
- Electrocardiogram (ECG) R-wave amplitude changes post-coronary artery bypass grafting (CABG) may indicate patient outcomes.
- Increased R-wave amplitude has been linked to myocardial dysfunction in exercise testing.
Purpose of the Study:
- To investigate the association between changes in R-wave amplitude and myocardial function during CABG surgery.
Main Methods:
- Prospective clinical study involving ten patients undergoing CABG.
- R-wave amplitude measured at eight time points.
- Left ventricular function parameters (wall tension, stress, contractility, stroke work) calculated via echocardiography and arterial pressure.
Main Results:
- Weak positive associations found between R-wave amplitude and cardiac function parameters, excluding preload.
- R-squared values ranged from 0.101 to 0.266 for most parameters.
- R-squared for preload was only 0.017.
Conclusions:
- Echocardiography-derived left ventricular function indices explain only 10-27% of R-wave amplitude variation in CABG patients.
- R-wave amplitude changes during CABG have limited value as a noninvasive indicator of left ventricular function.
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.