What Is Ventricular Systole?

The term "ventricular systole" pertains to the period of the cardiac cycle when the ventricles of the heart contract. As the left and right ventricles fill with blood, the heart contracts, forcing out the blood. Blood from the right ventricle pumps into the pulmonary artery, and blood from the left ventricle pumps into the aorta.

The heart is a muscle made up of four chambers. The right and left atria are the upper chambers. The left and right ventricles are the lower chambers. The right atrium receives deoxygenated blood, and the left atrium receives oxygenated blood. The blood flows from the atria into the ventricles.

Blood pumping into the pulmonary artery moves into the lungs, picking up oxygen. Oxygenated blood goes into the left heart chambers via pulmonary veins. The aorta pumps blood into systemic circulation, flowing out to the entire body.

Pressure exerted against arterial walls is referred to as blood pressure and is measured in millimeters of mercury (mmHg). Ventricular systole of the cardiac cycle represents the maximum force of blood during ventricular contraction. It is called systolic pressure. A normal measurement for systolic pressure is 120 mmHg.

Between ventricular contractions, the ventricles fill with blood. During this time, arterial blood pressure is at its lowest. This pressure represents ventricular relaxation and is called diastolic pressure. Ventricular diastole is quickly followed by ventricular systole again. Normal diastolic pressure is about 80 mmHg.


Another way ventricular systole is measured is by palpating the radial artery. This measurement translates into heart rate. The heart rate represents the contraction rate of the left ventricle. The radial artery is located easily on the wrist.

The first part of the heartbeat marks the beginning of ventricular systole. It is the "lub" heard when listening with a stethoscope. This sound is produced by the closing of atrioventricular valves and is referred to as S1. When the aortic and pulmonary valves close, the "dub" sound is produced. It is called the S2 and marks the end of ventricular systole.

Some people develop abnormal heart rhythms. Ventricular fibrillation (VF) is the most common type of heart arrhythmia, during which the ventricles deliver uncoordinated and ineffective contractions. The ventricles quiver, and as a result, blood is not pumped. Without an immediate response, this condition quickly results in death.

Of all cardiac arrest deaths, ventricular fibrillation is the cause in about 80 percent of cases. Out of the total deaths attributed to VF, in 40 percent of cases, nobody was present to respond. VF is more common in men than women. The likelihood of developing the condition increases with age, regardless of race.


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