Effects of ischemia, bypass surgery and past infarction on myocardial contraction, relaxation and compliance during exercise.
Abnormalities of left ventricular function during ischemia have been described in animal models and in humans. Exercise, while a physiologic means of inducing ischemia, has a complex effect on left ventricular function by itself. In addition, patients with coronary artery disease have a diversity of chronic changes in myocardial structure and function. Therefore, with use of micromanometer left ventricular pressure measurements and ventricular volumes, calculated from biplane cineangiograms, left ventricular function at rest and during exercise was studied in 57 patients. Exercise-induced ischemia produced a decrease in ejection fraction, an increase in end-systolic volume, dramatic increases in diastolic pressures and an upward shift in the diastolic pressure-volume relation. Central to these changes was abnormal myocardial contraction and relaxation, with reduced regional shortening and impaired left ventricular pressure decay. However, nonischemic areas were capable of augmented shortening, and global pressure decay did accelerate slightly. These findings demonstrate that exercise-induced adjustments in contraction and relaxation are intertwined with ischemia-related abnormalities. Exercise studies in patients after bypass surgery and in patients with scars from distant myocardial infarction were useful in clarifying confounding factors. For example, asynchrony of contraction and relaxation, and chronic changes in passive chamber properties, also compromise systolic and diastolic function during exercise. In patients with coronary artery disease without ischemia during exercise, left ventricular end-diastolic pressure, but not early diastolic pressure, increased during exercise. The increase in pressure was appropriate for a slight increase in end-diastolic volume in a ventricle with a steep pressure-volume relation. Furthermore, end-systolic volume, while maintained during exercise, was not reduced, as occurs normally.(ABSTRACT TRUNCATED AT 250 WORDS)
Carroll
J D
JD
Department of Medicine, University of Chicago, Zurich, Switzerland.
Hess
O M
OM
Hirzel
H O
HO
Turina
M
M
Krayenbuehl
H P
HP
D006328:Cardiac Catheterization; D003187:Compliance; D001026:Coronary Artery Bypass; D003327:Coronary Disease / Q000503:physiopathology* / Q000601:surgery; D006439:Hemodynamics; D006801:Humans; D009200:Myocardial Contraction; D009203:Myocardial Infarction / Q000503:physiopathology*; D005082:Physical Exertion