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Usefulness of the ergometric testing in patients with the long Q-T syndrome
Insights
Exercise stress tests reveal a higher prevalence of long Q-T intervals in coronary artery disease patients. This finding impacts antiarrhythmic drug choices, as long Q-T intervals contraindicate certain treatments.
Area of Science:
- Cardiology
- Electrophysiology
Background:
- Coronary artery disease (CAD) diagnosis often involves exercise testing.
- The Q-T interval, corrected for heart rate (Q-Tc), is a marker of ventricular repolarization.
- Abnormal Q-Tc intervals have implications for antiarrhythmic drug therapy.
Purpose of the Study:
- To evaluate the prevalence of long Q-Tc intervals in patients with exercise test-positive coronary artery disease.
- To determine the diagnostic utility of exercise stress testing for identifying prolonged Q-Tc intervals in CAD patients.
Main Methods:
- Analysis of 50 patients with exercise test-positive coronary artery disease.
- Comparison of Q-Tc intervals from resting electrocardiograms (ECG) and exercise tests.
- Assessment of Q-Tc interval duration in relation to CAD diagnosis.
Main Results:
- Only 6% (3/50) of patients had a long Q-Tc at rest.
- Exercise testing increased the detection rate of long Q-Tc intervals to 24% (12/50).
- Patients unable to complete the test were presumed to have CAD with normal Q-Tc intervals.
Conclusions:
- Exercise stress testing significantly increases the detection of prolonged Q-Tc intervals in coronary artery disease patients compared to resting ECG.
- Identifying long Q-Tc intervals during exercise is crucial for guiding appropriate antiarrhythmic drug selection.
- Failure to identify long Q-Tc intervals can lead to the inappropriate use of contraindicated medications.
Abstract:
Fifty patients with an exercise test positive for coronary artery disease (CAD) were analyzed for the presence of a long Q-T interval corrected for heart rate (Q-Tc). While there were only 3 patients with a long Q-Tc (6%) in the resting ECG, with the exercise test their number increased to 12 (24% of the total). If the test could not be done, such subjects were considered to have CAD and normal Q-T intervals. This is of great importance because patients with normal Q-T intervals are treated with group I antiarrhythmic drugs, whereas these drugs are contraindicated in patients with long Q-T intervals.