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[Hyperventilation test in coronary disease: a comparison with a bicycle ergometer exercise test. Report of 100 cases]
Insights
Hyperventilation during exercise tests can reveal cardiac issues. Minor T-wave changes occurred in healthy individuals, while coronary patients showed ST depression or elevation, challenging false positive test assumptions.
Area of Science:
- Cardiology
- Exercise Physiology
- Autonomic Nervous System Function
Background:
- The exercise test is a standard diagnostic tool for coronary artery disease.
- Hyperventilation's effects on cardiac repolarization during exercise are not fully understood.
- Nervous control of circulation plays a role in cardiovascular responses.
Purpose of the Study:
- To investigate the impact of hyperventilation during exercise on ventricular repolarization.
- To differentiate responses in normal subjects, coronary patients, and individuals with circulatory nervous control defects.
- To evaluate the diagnostic significance of hyperventilation-induced ECG changes.
Main Methods:
- Studied 100 subjects: 60 normal, 30 coronary (positive exercise test), 10 with defective nervous control.
- Utilized an exercise test combined with hyperventilation.
- Monitored electrocardiogram (ECG) for ST segment and T wave changes.
Main Results:
- Normal subjects: No ST depression; 73% showed minor T-wave repolarization changes.
- Coronary subjects: 6.7% exhibited ST depression or elevation, challenging the 'false positive' hypothesis.
- Defective nervous control group: 90% showed ischemic ST depression, potentially due to increased sympathetic activity.
Conclusions:
- Hyperventilation during exercise elicits varied repolarization responses.
- ST elevation during hyperventilation in coronary patients does not necessarily indicate a false positive test.
- Defective circulatory nervous control may predispose to hyperventilation-induced ischemic ST depression, possibly via sympathetic activation.
Abstract:
A hundred cases have been studied and divided into three categories:--60 normal subjects;--30 coronary subjects with a positive exercise test;--10 subjects with defective nervous control of the circulation; using the exercise test, we studied the effects of hyperventilation on repolarisation of the ventricle. In the normal subjects there was no ischaemic depression of the ST segment, but there were minor changes in repolarisation which affected the T wave in 73% of subjects and were essentially posterior in distribution. In the coronary subjects, we found three with ischaemic depression of the ST segment and one with ST elevation of 2.5 mm (6.7% of the coronary subjects). This last finding is evidence against the commonly held hypothesis that reproduction of ST depression by hyperventilation during the exercise test indicates a false positive test. In the patients with defective nervous control of the circulation, 9 had an ischaemic type of ST depression, either as a new feature or as a more severe one compared with that found at rest. The mechanism by which these depressions are produced has not been totally explained:--in the cases with defective nervous control of the circulation, it appears that latent increased sympathetic activity is increased by the hyperventilation;--in the coronary subjects, it may be caused by true ischaemia or by an associated defect in nervous control of the circulation.