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Regional myocardial function during contiguous ischaemia in an anaesthetized canine model: comparison of six methods
J A Reitan1, N D Kien, P G Moore
1Department of Anesthesiology, University of California School of Medicine, Davis 95616.
Insights
Assessing cardiac function after myocardial ischemia, this study found that regional end-systolic elastance (Ees) was the most reliable indicator of the non-ischaemic segment
Area of Science:
- Cardiovascular Physiology
- Myocardial Ischemia Research
- Anesthesiology
Background:
- Acute myocardial ischemia significantly impacts overall cardiac performance.
- The function of the non-ischaemic myocardium is critical for maintaining residual cardiac function.
- Understanding how to accurately measure regional myocardial function is essential for clinical management.
Purpose of the Study:
- To compare six different methods for measuring regional function in the non-ischaemic segment of the myocardium.
- To evaluate the sensitivity of these indices to anesthetic agents (halothane, isoflurane) and ischemia.
- To identify the most reliable index for assessing regional myocardial function under these conditions.
Main Methods:
- Sixteen dogs underwent acute ligation of the left anterior descending (LAD) coronary artery.
- Measurements included left ventricular micromanometers, sonomicrometer transducers for segment length and wall thickness, and radioactive microspheres for blood flow.
- Regional myocardial function indices (e.g., %WT, vs, %SS, RSW, RPRSW, Ees) were assessed under varying anesthetic concentrations and after LAD occlusion.
Main Results:
- No assessed index showed enhanced function in the non-ischaemic segment post-LAD ligation.
- Most indices, except Ees, were sensitive to anesthetic-induced depression of cardiac function.
- Regional end-systolic elastance (Ees) increased with isoflurane and remained stable with halothane, indicating preserved contractility.
Conclusions:
- Regional end-systolic elastance (Ees) is a robust index for assessing the function of the non-ischaemic myocardium.
- Standard indices like percent systolic wall thickening (%WT) and velocity of shortening (vs) are less reliable under anesthetic and ischemic conditions.
- This highlights the importance of selecting appropriate functional indices for accurate myocardial assessment during ischemia and anesthesia.
Abstract:
During acute myocardial ischaemia, the function of the unaffected muscle is the primary determinant of residual cardiac performance. We compared six methods of measuring regional function in the remaining non-ischaemic segment after acute ligation of the left anterior descending (LAD) coronary artery in 16 dogs. Preparation included left ventricular micromanometers, regional sonomicrometer transducers to measure segment length and wall thickness, caval occluders and left atrial catheters for injection of radioactive microspheres to measure regional blood flow. Pulmonary artery, central venous and systemic arterial pressures were measured and regional coronary venous blood was collected for direct myocardial oxygen consumption (VO2) calculations. Under basal high-dose fentanyl-neuromuscular blocker anaesthesia, the LAD was occluded after addition of halothane or isoflurane at 0.5 or 1.5 MAC concentrations. Regional myocardial function of the non-ischaemic segment was assessed by the following computer-derived indices: percent systolic wall thickening (% WT), velocity of shortening (vs), percent systolic shortening (%SS), regional stroke work (RSW), regional preload recruitable stroke work (RPRSW) and regional end-systolic elastance (Ees). No index demonstrated enhanced function in the non-ischaemic segment after LAD ligation and all monitors, except Ees, were sensitive to depression of function represented by a decrease in values after administration of halothane and isoflurane (P < 0.05). Ees values increased with the addition of isoflurane and remained constant with halothane. Circulating concentrations of catecholamines were unchanged after ischaemia, while inhalation agents caused a decrease in the concentrations of adrenaline and dopamine (P < 0.05), but not noradrenaline.(ABSTRACT TRUNCATED AT 250 WORDS)