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Effects of coronary artery stenosis on left ventricular end-ejection pressure-ejected volume relationships in
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Assessing left ventricular function during coronary stenosis revealed that the pressure-volume loop slope is not a reliable indicator. However, a significant decrease in the ejected volume axis intercept suggests regional ischemia.
Area of Science:
- Cardiovascular Physiology
- Cardiac Mechanics
- Ischemic Heart Disease
Background:
- Left ventricular (LV) function is crucial for cardiac output.
- Coronary artery stenosis can impair LV performance.
- Understanding the pressure-volume relationship is key to assessing cardiac function.
Purpose of the Study:
- To investigate the left ventricular end-ejection pressure-ejected volume relation in the presence and absence of left circumflex coronary stenosis.
- To determine if the slope or intercept of this relation can indicate depressed ventricular function due to ischemia.
Main Methods:
- Isolated perfused canine hearts were used.
- Ventricular afterload was manipulated by altering peripheral resistance in a hydraulic model.
- The end-ejection pressure-ejected volume relation was analyzed under pre-ischemic and ischemic conditions.
Main Results:
- The end-ejection pressure-ejected volume relationship remained nearly linear in both states.
- The slope of the relation showed no significant average change between pre-ischemic and ischemic states (-7.4 vs. -8.4 mmHg/ml).
- The ejected volume axis intercept significantly decreased from 16.5 ml to 13.6 ml (p < 0.05) with regional ischemia.
Conclusions:
- The slope of the end-ejection pressure-ejected volume relation is not a reliable indicator of depressed ventricular function caused by coronary stenosis.
- A decrease in the ejected volume axis intercept is a significant indicator of regional ischemia and impaired ventricular function.
Abstract:
We investigated the behavior of the left ventricular end-ejection pressure-ejected volume relation with and without left circumflex coronary stenosis in isolated perfused canine hearts. To change ventricular afterload pressure, the peripheral resistance of the hydraulic model attached to the aortic root of the excised hearts was changed in a stepwise fashion to five different levels. The end-ejection pressure-ejected volume relationship was nearly linear in both pre-ischemic and ischemic states. The slope changes following left circumflex coronary stenosis differed among the hearts used in the present study, and there was no significant difference in average slope (n = 10) between the pre-ischemic and ischemic states (i.e., -7.4 +/- 1.0 and -8.4 +/- 1.2 mmHg/ml, respectively). Therefore, the, slope of the relation was not useful in judging the presence of depressed ventricular function induced by coronary stenosis. In contrast, the ejected volume axis intercept decreased significantly from 16.5 +/- 1.1 ml to 13.6 +/- 1.1 ml (p less than 0.05) with regional ischemia.