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Identification of septal ischemia during exercise by Q-wave analysis: correlation with coronary angiography
Insights
Septal Q-wave amplitude changes during exercise can predict left anterior descending (LAD) coronary artery disease. A decrease in Q-wave amplitude suggests LAD narrowing and potential ischemia.
Area of Science:
- Cardiology
- Diagnostic Imaging
- Exercise Physiology
Background:
- Coronary artery disease (CAD) diagnosis often relies on invasive angiography.
- Non-invasive methods to predict specific coronary artery pathologies are valuable.
- Septal Q-wave changes during exercise may indicate regional myocardial ischemia.
Purpose of the Study:
- To assess the diagnostic utility of septal Q-wave amplitude changes in lead CM5 for predicting segmental coronary artery pathoanatomy.
- To correlate exercise-induced Q-wave variations with specific coronary artery stenoses.
Main Methods:
- Measured septal Q-wave amplitudes in 41 patients with CAD and 12 controls before and after treadmill exercise.
- Categorized patients by coronary artery disease location: left anterior descending (LAD), right coronary, or left circumflex (LC).
- Analyzed Q-wave amplitude changes (increasing, decreasing, no change) in relation to exercise and angiographic findings.
Main Results:
- A decreasing septal Q-wave amplitude with exercise showed 62% sensitivity and 100% specificity for isolated LAD narrowing.
- Patients with LAD narrowing consistently exhibited decreased or unchanged Q-wave amplitudes post-exercise.
- Patients with right or LC CAD, or normal coronaries, displayed varied Q-wave responses.
Conclusions:
- Reduced septal Q-wave voltage and lack of increase post-exercise suggest abnormal septal activation.
- This abnormality likely reflects ischemia due to LAD narrowing.
- Exercise-induced septal Q-wave changes offer a non-invasive marker for LAD artery disease detection.
Abstract:
Septal Q-wave amplitudes were studied in lead CM5 to evaluate its utility in predicting segmental coronary artery pathoanatomy. Q-wave amplitudes were measured in 41 patients with coronary artery disease (CAD) before and immediately after treadmill exercise. All patients studied had either significant single-vessel CAD (greater than 70% diameter reduction) or normal coronary anatomy; 13 had left anterior descending (LAD) CAD, 8 had right coronary occlusions, 8 had left circumflex (LC) CAD, and 12 had angiographically normal coronary arteries. Septal Q-wave amplitude measurements at rest and during peak exercise were recorded in 0.5 mm increments and classified as increasing in 20 patients, decreasing in 8, and no change in 13 with exercise. All 13 patients with isolated LAD narrowing had either no change (5 patients) or a decrease (8 patients) in the septal Q wave with exercise. Statistical analysis revealed 62% sensitivity and 100% specificity for single LAD narrowing if a decreasing Q wave was noted with exercise. Patients with isolated right or LC CAD or normal coronary anatomy had mixed septal Q-wave responses to exercise. Only patients with LAD narrowing had reductions in Q-wave amplitude with treadmill exercise. This finding suggests that low Q-wave voltage and its failure to increase after exercise imply abnormal septal activation, reflecting loss of contraction associated with ischemia from LAD narrowing.