systóla

Systóla, or systole, is the phase of the heartbeat in which the heart muscle contracts, pumping blood from the atria to the ventricles and from the ventricles into the arteries. In the ventricles, contraction raises pressure, causing the semilunar valves to open and blood to be ejected into the aorta and pulmonary artery. This contrasts with diastola (diastole), the relaxation phase when the heart chambers fill with blood.

The cardiac cycle begins with atrial systole contributing to ventricular filling, followed by ventricular systole. Systole includes isovolumetric contraction, rapid ejection, and reduced ejection as pressures change. The timing of systole is coordinated by electrical activity of the heart, notably the QRS complex on an electrocardiogram.

Systolic blood pressure refers to the pressure in arteries during systole, typically reported as the upper value in a reading, such as 120/80 mmHg. Systolic function is a key determinant of cardiac performance; reduced ejection fraction during systole characterizes systolic heart failure, while some conditions cause systolic murmurs. In medical contexts, careful assessment of systolic function and blood pressure informs diagnosis and treatment of cardiovascular disease. Terminology varies by language, but systole generally denotes the contraction phase of the cardiac cycle.