Normal coronary blood flow

2021-05-17 05:25 PM

Left coronary flow decreases during systole, unlike other vessels in the body. Because during systole, the coronary artery is strongly compressed by contraction of the left ventricular myocardium

Normal coronary blood accounts for about 5% of cardiac output; coronary blood flow at rest averages 70 ml/min/100 g of cardiac weight, or 225 ml/min, about 4-5 percent of the total. pumped blood from the heart.

During exercise, cardiac output is increased four-fold to seven-fold, and one higher than that of a normal artery. Thus, the work of the heart in severe conditions can increase sixfold to ninefold. At the same time, the coronary blood flow is tripled four times to provide the necessary nutrients to the heart. This increase is not as much as the increase in workload, meaning the rate at which the heart expends energy to increase coronary blood flow. Thus, the "efficiency" of the heart increases its use of energy to compensate for the lack of coronary blood supply.

Changes in coronary blood flow during systole and during systole affect the myocardium. The figure shows the change in blood flow supplied by the left coronary artery in ml/min during systole and diastole. From the figure it is shown that the left coronary flow decreases during systole, which is different from other vessels in the body. Because during systole, the coronary artery is strongly compressed by contraction of the left ventricular myocardium.

Figure. Phased blood flow through the coronary capillaries of the human left ventricle during systole and diastole (as extrapolated from flow measured in dogs).

During diastole, the ventricles are dilated and there is no obstruction to the blood circulation in the left coronary artery, so the blood flow is quickly circulated, the blood flow through the right coronary artery also changes according to the cycle of the heart but due to the force of contraction. The right ventricle is weaker than the ventricle, so the phase change is only partial.

Coronary pericardium and subendocardial artery plexus- affect myocardial contractility. The figure shows a special arrangement of coronary vessels at different depths in the myocardium, on the outer surface of the pericardial coronary artery that supplies most of the myocardium. Smaller, artery-derived pericardial arteries penetrate the muscle, providing needed nutrients. Located just below the endocardium is the subendocardial artery. During systole, left ventricular contraction reduces coronary blood flow, but the subendocardial arteries compensate for this decrease. The difference between pericardial and subendocardial blood flow plays an important role in coronary ischemia.

Figure. Diagram of the pericardium, myocardium, and sub myocardium.