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Exercise-induced S-wave prolongation in left anterior descending coronary artery stenosis
A P Michaelides1, H Boudoulas, G P Vyssoulis
1Department of Cardiology, Athens Medical School, Greece.
Insights
Exercise-induced S-wave prolongation on ECGs occurs significantly in patients with left anterior hemiblock or right bundle branch block and left anterior descending (LAD) coronary artery stenosis, indicating myocardial ischemia. This finding aids in diagnosing coronary artery disease.
Area of Science:
- Cardiology
- Exercise Electrocardiography
- Coronary Artery Disease
Background:
- Myocardial ischemia can affect cardiac conduction, leading to ECG changes like QRS prolongation.
- The S wave's myocardial territory is supplied by different coronary arteries depending on intraventricular conduction status.
Purpose of the Study:
- To investigate whether S-wave prolongation during exercise is specific to patients with left anterior descending (LAD) coronary artery stenosis and either left anterior hemiblock or right bundle branch block.
Main Methods:
- Studied 88 patients with normal conduction, 66 with left anterior hemiblock, and 36 with right bundle branch block.
- Assessed S-wave duration changes during exercise in relation to LAD, right, and left circumflex coronary artery stenoses.
Main Results:
- In patients with normal coronary arteries, S-wave duration decreased with exercise.
- S-wave prolongation occurred slightly in coronary artery disease patients with normal conduction.
- Significant S-wave prolongation (12.5 ms and 10.4 ms) was observed only in patients with LAD stenosis and left anterior hemiblock or right bundle branch block during exercise.
Conclusions:
- Exercise-induced S-wave prolongation is a significant indicator of myocardial ischemia in patients with LAD coronary artery stenosis and specific conduction abnormalities (left anterior hemiblock or right bundle branch block).
- This ECG finding may help identify ischemia in specific patient groups with coronary artery disease.
Abstract:
Myocardial ischemia may decrease conduction velocity and produce QRS prolongation in the surface electrocardiogram. In cases with normal intraventricular conduction, areas of the myocardium contributing to the development of the S wave receive blood from all 3 major coronary arteries, whereas in left anterior hemiblock or right bundle branch block, most of the blood supply to the areas of the myocardium contributing to the development of the S wave is from the left anterior descending (LAD) coronary artery. To test the hypothesis that the S wave will be prolonged with exercise only in patients with LAD coronary artery stenosis and left anterior hemiblock or right bundle branch block, 88 patients with normal intraventricular conduction, 66 with left anterior hemiblock and 36 with right bundle branch block were studied. Sixty-four, 32 and 21 patients had LAD, right and left circumflex coronary artery stenoses, respectively. In patients with normal coronary arteries, S-wave duration decreased with exercise regardless of the status of ventricular conduction. In patients with coronary artery disease and normal intraventricular conduction, the S wave was prolonged slightly with exercise, but in those with left anterior hemiblock and right bundle branch block, it was prolonged significantly (12.5 +/- 6 and 10.4 ms, respectively) only in those with LAD, but not in those with circumflex or right coronary artery stenosis. S-wave prolongation in patients with LAD coronary artery stenosis and left anterior hemiblock or right bundle branch block most likely is related to exercise-induced ischemia in the areas of the myocardium contributing to the development of the S wave.