Relationship of QRS amplitude changes during exercise to left ventricular function and volumes and the diagnosis of coronary artery disease.

Abstract

Preliminary studies have suggested that QRS-amplitude changes due to exercise-induced alterations in ventricular volume and function can improve the diagnostic value of the exercise test. To evaluate this, electrocardiographic data and equilibrium radionuclide angiographic images were recorded simultaneously in 18 normal subjects and 60 coronary artery disease patients at rest and during supine bicycle exercise. In 24 of the 60 coronary artery disease patients, left ventricular volumes were also calculated. The measured QRS amplitudes were the R waves in V, X, Y and Z, the Q wave in Z and the sum of amplitudes of R waves in X and Y and the Q wave in Z (2iR). The mean left ventricular ejection fraction increased significantly from rest to peak exercise in the normal subjects; however, the mean left ventricular ejection fraction and mean volumes did not change significantly in the coronary patients. There was no significant difference in the mean QRS-amplitude changes during exercise between the coronary artery disease patients and the normal subjects in any of the measured leads. The sensitivity and specificity of exercise-induced QRS-amplitude changes for coronary disease were lower than ST-segment changes. For ST-segment changes, the sensitivity was 57% and specificity was 100%; the best sensitivity and specificity for QRS amplitude occurred in RZ, 48% and 67%, respectively. When ejection fraction was related to 2R at rest and peak exercise for both normal subjects and coronary patients the correlations were fair (0.50, 0.51 respectively); however, the correlation between the magnitude of 2R and ejection fraction change from rest to peak exercise was poor and did not improve with any other measured QRS amplitudes or by separating normal subjects from coronary patients with and without previous myocardial infarction. There were also poor correlations between end-diastolic and endsystolic volumes to QRS amplitudes at rest, peak exercise and their magnitude of change from rest to peak exercise. Thus, R-wave amplitude changes during exercise testing have little diagnostic value and are not related to exercise-induced changes in left ventricular function or volumes.

Dissociation between regional myocardial dysfunction and ECG changes during ischemia in the conscious dog.

“…However, STsegment displacement on the body surface ECG is not specific for ischemia,' and both false-negative and false-positive ECG findings during exercise testing for detecting coronary artery disease have been reported.2 In the experimental setting, regional wall function dynamics are highly sensitive to local ischemia both at rest5 and during exercise in the conscious dog;6 in clinical studies, simultaneous recordings of ventricular function using radionuclide angiographic techniques and ECG recordings during exercise have suggested superiority of mechanical over electrical events for the detection of temporary myocardial ischemia. [7][8][9] Nevertheless, the exercise test with ECG recordings is still the most popular and economical screening test for coronary artery disease in man, 4 1' and further understanding of the relations between electrical and mechanical events during ischemia is needed. Smith et al, 1' using openchest dogs, reported that endocardial ST-segment elevation may be a more sensitive index of ischemia than depression of myocardial contractile function, but the surface ECG was not recorded.…”

Pacing echocardiography regional wall motion, left ventricular dimension and R wave amplitude in patients with angina pectoris.

“…Positive changes in ST segment were noted in 11 of 12 angina cases while positive changes in R wave were found in only 6 angina cases. Low sensitivity of R wave criteria was also noted by other investigators.18), 57) Bonoris et al16),17) related R wave change to the left ventricular volume changes according to Brody.58) Left ventricular volume in normal subjects has been reported to decrease,4) increase,12),24),59),60) or be unchanged12),25), 61),62) during exercise . Thus, because of this considerable variability, a decrease in R wave during exercise can not be simply taken as a normal response if R wave change is related to volume change alone.…”

An Introduction to the Appücations, Methodology and Interpretation of Exercise Electrocardiography

“…The data on QRS changes during exercise are equivocal and further work is needed to deter mine their importance in evaluating the severity of coronary artery disease and ventricular dysfunction. Though R wave amplitude should drop during exercise (29,30), it is not specific or sensitive for left ventricular dysfunction and is affected by the factors listed in table XI. The patient's symptoms and appearance during an exercise test provide valuable ancillary information.…”