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Serial changes in left ventricular relaxation and chamber stiffness after large myocardial infarction in rats
T E Raya1, R G Gay, L Lancaster
1Department of Internal Medicine, Tucson Veterans Administration Medical Center, AZ 85723.
Insights
This study reveals dynamic changes in left ventricular diastolic properties following myocardial infarction in rats. Key findings show altered relaxation and stiffness over time, impacting cardiac function recovery.
Area of Science:
- Cardiovascular Physiology
- Cardiac Remodeling
- Myocardial Infarction Research
Background:
- Left ventricular diastolic dysfunction is a critical complication of myocardial infarction.
- Understanding the temporal changes in diastolic properties is crucial for managing heart failure post-infarction.
Purpose of the Study:
- To investigate the serial changes in left ventricular relaxation, chamber stiffness, and cavity-to-wall volume ratio after induced myocardial infarction in a rat model.
- To elucidate the time course of these diastolic property alterations over an extended period.
Main Methods:
- Myocardial infarction was induced by coronary artery ligation in rats.
- Left ventricular pressures and dP/dt were measured using micromanometer-tipped catheters.
- Left ventricular relaxation was assessed via pressure tracing digitization; chamber stiffness was calculated from ex vivo pressure-volume curves at various time points (3 hr to >22 days).
Main Results:
- Ventricular relaxation was initially prolonged, peaking at 10-15 min post-occlusion, returning to normal by 1 hr, but prolonged again by 5 days.
- Left ventricular stiffness increased at 3 and 24 hr, shifting the pressure-volume relation leftward; normalization occurred by 3 days.
- At >22 days, the pressure-volume relation shifted rightward with decreased stiffness at low filling pressures. The cavity-to-wall volume ratio (V/VW) decreased significantly at 3 and 24 hr and increased substantially at >22 days.
Conclusions:
- Left ventricular diastolic properties undergo significant and dynamic alterations after myocardial infarction, with distinct phases of impaired relaxation and altered stiffness.
- These changes, including significant modifications in V/VW, suggest complex remodeling processes that influence diastolic function recovery and long-term cardiac health.
Abstract:
To determine the time course of changes in left ventricular diastolic properties after a large myocardial infarction, we serially measured left ventricular relaxation, chamber stiffness, and the ratio of left ventricular cavity to wall volume (V/VW) after coronary artery ligation in rats. Left ventricular relaxation was measured during the occlusion and then both relaxation and chamber stiffness were measured at 3 hr, 24 hr, and 3, 5, and more than 22 days after infarction. Left ventricular pressures and left ventricular dP/dt were recorded with micromanometer-tipped catheters. Left ventricular relaxation was measured by computer digitization of the left ventricular pressure tracings and averaged over 100 to 150 cardiac cycles. Five chamber stiffness constants were calculated from pressure-volume curves that were obtained ex vivo. We found ventricular relaxation prolonged for the first hour after coronary occlusion; relaxation was maximally prolonged at 10 to 15 min after onset of occlusion. After 1 hr relaxation returned to normal. However, by 5 days ventricular relaxation was again prolonged. Left ventricular stiffness constants were increased at 3 and 24 hr, resulting in a shift of the left ventricular pressure-volume relation to the left. At 3 days after coronary artery ligation, all stiffness constants and the pressure-volume relation returned to normal. At more than 22 days the pressure-volume relation was shifted to the right and the stiffness constant for low filling pressures was decreased. V/VW was significantly decreased from 0.603 +/- 0.021 at 3 and 24 hr to 0.379 +/- 0.024 and 0.362 +/- 0.032, respectively. V/VW was significantly increased at more than 22 days (0.921 +/- 0.094).(ABSTRACT TRUNCATED AT 250 WORDS)