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Effects of nitrates on R-wave variations after exercise in coronary heart disease: differences in patients with and
Insights
Exercise-induced R-wave changes in coronary heart disease patients indicate ischemic ventricular dysfunction. Nitrates reduce R-wave changes, suggesting improved ventricular function during exercise.
Area of Science:
- Cardiology
- Exercise Physiology
- Medical Diagnostics
Background:
- Coronary heart disease (CHD) affects left ventricular function.
- Exercise can reveal underlying cardiac dysfunction.
- R-wave changes during exercise may reflect myocardial ischemia.
Purpose of the Study:
- To investigate R-wave voltage changes after exercise in CHD patients.
- To explore the relationship between R-wave changes and left ventricular function.
- To assess the effect of nitrate therapy on exercise-induced R-wave alterations.
Main Methods:
- Studied 44 patients with CHD, categorized into three groups based on angina and prior myocardial infarction.
- Patients underwent two exercise tests: a control test and one after sublingual isosorbide dinitrate administration.
- Measured R-wave voltage variations during exercise in both conditions.
Main Results:
- Patients with angina (Groups A & B) showed increased R-wave voltage in the control test, which decreased after nitrates (p<0.05 and p<0.002).
- Patients without angina (Group C) exhibited reduced R-wave voltage in both control and nitrate tests (not significant).
- Angina groups demonstrated exercise-induced R-wave increase, reversed by nitrates, unlike the non-angina group.
Conclusions:
- Exercise-induced R-wave increase suggests ischemic ventricular dysfunction.
- Nitrate administration mitigates R-wave changes, indicating reduced ventricular dysfunction.
- R-wave monitoring during exercise, with and without nitrates, can assess ischemic ventricular dysfunction in CHD.
Abstract:
With the purpose of investigating the pathophysiology of changes in the R wave after exercise and its relationship with left ventricular function, we studied 44 patients with coronary heart disease. They were classified into the following three groups: group A, 11 patients with angina pectoris and no prior myocardial infarction; group B, 18 patients with angina pectoris and prior myocardial infarction; and group C, 15 patients with prior myocardial infarction but no angina. All patients performed two exercise tests; one was a control test, and the other was performed after the sublingual administration of 5 mg of isosorbide dinitrate. In group A, variations in the R-wave voltage in control test and in the test after isosorbide dinitrate were 1.5 +/- 0.8 mm and -1.2 +/- 0.9 mm (P less than 0.05), respectively. In group B, results were 1.2 +/- 0.7 mm on the control test and -0.7 +/- 0.6 mm after isosorbide dinitrate (P less than 0.002), and in group C were -1.6 +/- 1.2 mm on the control test and -0.7 +/- 0.7 mm after isosorbide dinitrate (not significant). Thus, the two groups of patients with angina showed an increase of the R-wave after exercise in the control test but a decrease after the administration of nitrates, whereas the patients without angina showed a reduced R-wave after exercise both before and after the administration of nitrates (like normal subjects). This study suggests that ischemic ventricular dysfunction with exercise results in an increase in the R-wave, while exercise after nitrates results in a decrease in the R-wave consistent with less or no ventricular dysfunction due to nitrate therapy.