What Factors Affect Ejection Fraction Values?

Stroke volume refers to the volume of blood ejected from one ventricle in one stroke, referred to as stroke volume.

Stroke volume

The stroke volume of the left and right ventricles is basically equal. Stroke volume is equal to the difference between end-systolic volume and end-systolic volume. End diastolic volume

The ratio of stroke volume to end-diastolic volume is called

Myocardial contractility

Refers to an intrinsic property that myocardial fibers change their contraction strength (the degree of muscle fiber shortening and the amount of tension generated) and speed (the shortening speed and the rate of tension development) independently of the front and rear loads. In the case of constant heart rate, the greater the myocardial contractility, that is, the stronger the contraction intensity, the faster the contraction speed, the more stroke volume, and vice versa. The size of myocardial contractility is related to its structural characteristics and functional status. Those who have been exercised have more developed myocardium and have stronger contractility. In a certain range, when the venous return volume increases, the ventricular filling degree increases, the initial length of the myocardium increases, the myocardial contractility increases, and the stroke volume increases. The initial length (preload) of myocardial fibers before contraction is appropriately lengthened, and the strength during contraction increases. This law is called Starling's law of the heart. Myocardial contractility is regulated by nerves and body fluids. Cardiac sympathetic nerves, norepinephrine, and epinephrine enhance it; vagal nerves and acetylcholine weaken it.

Stroke volume venous return

Dynamic balance with stroke volume. The more venous return flow per unit time, the more cardiac output. At this time, the main factor for increasing cardiac output is not only the myocardial initial length (preload), but also the first to increase the heart rate by neuromodulation and enhance the myocardial contractility. Increased myocardial contractility can increase cardiac output and accelerate venous blood flow back to the heart, bringing the two to a new balance.

Arterial blood pressure plays the role of ventricular afterload, which is the resistance encountered during ventricular bleeding. Arterial blood pressure increases, and the indoor pressure must be increased accordingly to eject blood. If the myocardial contractility does not change, the energy consumed by the myocardium to generate tension is relatively increased, the energy used to shorten myocardial fibers is relatively reduced, the degree and speed of myocardial fiber shortening during ejection are reduced, the ejection speed is slowed, and the stroke volume is corresponding It is reduced, and subsequently adjusted, the preload increases, and the myocardial contractility increases to match the postload to maintain proper cardiac output.