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Relation of diastolic function and exercise capacity in ischemic left ventricular dysfunction. Role of beta-agonists
H Pouleur1, C Hanet, M F Rousseau
1Department of Physiology, University of Louvain, Brussels, Belgium.
Insights
Resting ejection fraction poorly predicts exercise capacity in myocardial infarction patients. Xamoterol improved exercise duration and reduced heart rate, suggesting benefits for cardiac function after myocardial infarction.
Area of Science:
- Cardiology
- Cardiovascular Physiology
Background:
- Assessing exercise capacity post-myocardial infarction is crucial for patient management.
- Global left ventricular function at rest may not fully predict exercise tolerance.
Purpose of the Study:
- To examine the relationship between resting left ventricular function and exercise capacity in patients with previous anterior myocardial infarction.
- To evaluate the effect of xamoterol on exercise capacity and left ventricular diastolic function.
Main Methods:
- Cardiac catheterization to assess resting left ventricular function (ejection fraction, volumes, diastolic pressure-volume relation).
- Exercise testing to measure exercise duration and heart rate response.
- Treatment with xamoterol (a beta 1-adrenoceptor partial agonist) in a subset of patients.
Main Results:
- Resting ejection fraction showed a poor correlation with exercise duration (r = 0.47).
- Patients with depressed exercise capacity had an upward-shifted diastolic pressure-volume relation and higher mean left ventricular filling pressure.
- Xamoterol treatment significantly increased exercise duration (20 +/- 14%) and decreased maximal exercise heart rate.
Conclusions:
- Resting ejection fraction is an insufficient predictor of exercise capacity in anterior myocardial infarction survivors.
- Abnormal diastolic function, indicated by an elevated left ventricular pressure-volume relation, is associated with reduced exercise capacity.
- Xamoterol effectively improves exercise capacity and favorably alters diastolic function in these patients.
Abstract:
The relation between global left ventricular function at rest (evaluated during cardiac catheterization) and exercise capacity was examined in a group of 33 untreated patients with a previous anterior myocardial infarction. The resting ejection fraction (range, 24-68%) correlated poorly with exercise duration (r = 0.47) and did not separate patients with a depressed exercise capacity (exercise duration less than 500 seconds: group A, n = 18) from patients with preserved exercise tolerance (group B, n = 15). The resting left ventricular end-diastolic and end-systolic volume indexes were comparable in groups A and B, but the diastolic pressure-volume relation was shifted upward, and the mean left ventricular pressure during diastolic filling was higher in group A than in group B (19 +/- 8 versus 14 +/- 4 mm Hg; p less than 0.02). The heart rate at maximal exercise was similar in both groups (160 +/- 16 versus 160 +/- 17 beats/min; NS), but heart rate was higher at any given level of exercise in group A than in group B. When 12 patients of group A were treated with xamoterol, a beta 1-adrenoceptor partial agonist, their exercise duration increased by 20 +/- 14% (p less than 0.001), and their maximal exercise heart rate decreased from 158 +/- 16 to 143 +/- 11 beats/min (p less than 0.001). This improved exercise capacity was accompanied by a downward shift of the resting diastolic left ventricular pressure-volume relation and by a decrease in mean left ventricular pressure during diastolic filling.(ABSTRACT TRUNCATED AT 250 WORDS)