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Myocardial structure in patients with exercise-induced ischemia
O M Hess1, J Schneider, H Nonogi
1Department of Internal Medicine, University Hospital, Zürich, Switzerland.
Circulation
|May 1, 1988
Summary
Structural changes in the heart muscle, including larger muscle fibers and increased interstitial tissue, occur in areas of the left ventricle experiencing recurrent ischemia during exercise. These alterations are particularly prominent in the endocardial layers, even when the heart functions normally at rest.
Area of Science:
- Cardiology
- Pathology
- Biomedical Engineering
Background:
- Exercise-induced myocardial ischemia can lead to structural changes in the left ventricle.
- Understanding these structural alterations is crucial for diagnosing and managing ischemic heart disease.
Purpose of the Study:
- To evaluate and compare the myocardial structure of left ventricular segments with recurrent ischemia versus those with normal blood supply.
- To investigate the impact of exercise and bypass grafting on left ventricular function and myocardial structure.
Main Methods:
- Morphometric analysis of left ventricular transmural biopsy samples.
- High-fidelity left ventricular pressure measurements and biplane angiocardiography during rest and exercise.
- Comparison of myocardial structure in normally contracting regions versus regions with exercise-induced wall motion abnormalities.
Main Results:
- Significantly larger transmural muscle fiber diameter (29.3 microns) in ischemic regions compared to normal regions (27.3 microns).
- Significantly increased interstitial nonmuscular tissue (19.8%) in ischemic regions versus normal regions (15.5%).
- Interstitial tissue was notably higher in the endocardial half (23.7%) compared to the epicardial half (17.5%) of ischemic segments.
Conclusions:
- Structural alterations, including muscle fiber hypertrophy and increased interstitial tissue, develop in transiently ischemic myocardium, especially in endocardial layers.
- These changes occur even in myocardial segments that exhibit normal function at rest.
- Successful bypass grafting improved left ventricular pressure and ejection fraction during exercise, indicating functional recovery alongside structural considerations.