Myocardial contractility evaluated from cross-oriented segments during beta-adrenergic blockade or sympathetic nerve stimulation
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Published on: September 17, 2015
1Department of Surgery, University of Bergen, Haukeland Hospital, Norway.
Insights
Assessing regional myocardial contractility in ischemic hearts is crucial. The pressure-length loop area versus end-diastolic length relationship effectively measures left ventricular inotropic state, making it the best index for ischemic regions.
Area of Science:
- Cardiovascular Physiology
- Myocardial Mechanics
- Ischemic Heart Disease Research
Background:
- Characterizing the inotropic state of remaining myocardium is vital in models of left ventricular ischemia.
- Dysfunctional regions require accurate assessment of myocardial contractility for effective treatment strategies.
Purpose of the Study:
- To evaluate different indices of regional myocardial contractility in ischemic conditions.
- To identify the most reliable index for assessing left ventricular inotropic state in regional ischemia.
Main Methods:
- Studied 18 pentobarbitone-anesthetized open-chest cats with acute circumflex coronary artery occlusion.
- Investigated effects of sympathetic nerve stimulation and beta-adrenergic blockade on myocardial contractility.
- Evaluated contractility using pressure-length relationships of longitudinal and circumferential segments.
Main Results:
- End-systolic pressure-length relationship was insensitive to interventions in longitudinal segments.
- Circumferential end-systolic pressure-length relationship indicated low contractility; peak systolic shortening velocity indicated high contractility.
- The pressure-length loop area versus end-diastolic length relationship reflected both increased and decreased left ventricular inotropic states.
Conclusions:
- The pressure-length loop area versus end-diastolic length relationship is the optimal index for regional myocardial contractility in ischemic hearts.
- This index provides a comprehensive measure of contractility changes in dysfunctional myocardial regions.
Abstract:
In patient and experimental models of regions of the left ventricle subjected to ischaemia and thus made dysfunctional it is important to characterize the inotropic state of the remaining myocardium. Eighteen pentobarbitone-anaesthetized open-chest cats with an acute circumflex coronary artery occlusion were therefore studied during either sympathetic nerve stimulation (n = 9), or after beta-adrenergic blockade (n = 9). Myocardial contractility was evaluated from cross-oriented segments in the left ventricular anterior wall during stable haemodynamics and during 5 s inferior caval occlusion. The end-systolic pressure-length relationship of longitudinal segments was rather insensitive to beta-adrenergic blockade and sympathetic nerve stimulation. The end-systolic pressure-length relationship of circumferential segments was suitable as a marker of contractility in the low contractility range, whereas the peak systolic shortening velocity parameter was more suitable in the upper contractility range. The pressure-length loop area versus end-diastolic length relationship of both circumferential and longitudinal segments reflected both increased and decreased left ventricular inotropic state. We therefore conclude that the pressure-length loop area versus end-diastolic length relationship is the best index of regional myocardial contractility in regional ischaemic hearts.
