Haemodynamics in the first seconds after coronary artery occlusion
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Sudden blockage of the left coronary artery in dogs caused rapid drops in cardiac function and blood pressure. Recovery was slow, with temporary overshoots before stabilization.
Area of Science:
- Cardiovascular Physiology
- Hemodynamics
- Myocardial Ischemia
Background:
- Coronary artery occlusion and subsequent reperfusion significantly impact cardiac function and overall hemodynamics.
- Understanding the immediate and delayed effects of coronary artery events is crucial for managing cardiovascular emergencies.
Purpose of the Study:
- To investigate the acute hemodynamic and cardiac changes during and after coronary artery occlusion and desocclusion in a canine model.
- To quantify the severity and time course of functional alterations following left coronary artery occlusion.
Main Methods:
- Studied hemodynamic parameters in 28 dogs subjected to temporary occlusion of major coronary arteries (left, right, anterior interventricularis, circumflexus).
- Monitored changes in cardiac contractility, left ventricular systolic and end-diastolic pressures, coronary sinus outflow, and blood flow.
- Analyzed responses during occlusion, immediate desocclusion, and a subsequent compensatory phase.
Main Results:
- Left coronary artery trunk occlusion caused rapid decreases in myocardial blood inflow, contractility, left ventricular systolic pressure, and coronary sinus outflow.
- Systolic pressure dropped significantly within seconds, while end-diastolic pressure increased.
- Following desocclusion, a delayed recovery of blood flow, contractility, and pressure was observed, with a transient overshoot and a compensatory phase.
Conclusions:
- The left coronary artery is critical, with its occlusion leading to severe, rapid hemodynamic deterioration.
- Recovery from coronary occlusion is a complex process involving delayed reperfusion and a distinct compensatory phase.
- Occlusion of smaller branches or the right coronary artery had less pronounced effects, though right coronary occlusion induced arrhythmias.
Abstract:
The changes in cardiac and in total haemodynamics, occurring during the first seconds of occlusion and the subsequent desocclusion of coronary arteries were studied on 28 dogs. The most intensive changes were observed after the trunk occlusion of the left coronary artery. Simultaneously with decreasing blood inflow into the myocardium its contractility and the systolic pressure in the left ventricle and the outflow from the coronary sinus began to fall rapidly. The systolic pressure in the left ventricle decreased within the first 10 s from 24 to 13-15 kPa (180 to 100-110 mm Hg), which means that the systolic pressure fell about 1 kPa (7-8 mm Hg) per second, or 0.5-0.6 kPa (4-5 mm Hg) per systole. At the same time the end-diastolic pressure in the left ventricle also increased from zero to 3-4 kPa (25-30 mm Hg). After the trunk desocclusion of the left coronary artery the systolic pressure in the left ventricle proceeded to fall by about 2-3 kPa (15-22 mm Hg). Only then, 20-25 s after the desocclusion, blood flow in the left coronary artery began to rise intensively and 4-6 s later the myocardial contractility and the systolic pressure in the left ventricle also increased. After unclamping (50-60 s), there was an overshoot of haemodynamic values above preocclusive values and then followed the compensatory phase. This phase lasted 80-90 s and on its peak the pressure and flow parameters increased by about 50-60% above preocclusive values. During the occlusion of ramus interventricularis anterior or ramus circumflexus for 30-60 s the haemodynamic parameters changed only slightly. The same was observed during trunk occlusion of the right coronary artery (30-60 s), but in that case many extrasystoles occurred.