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Diastole (/ d aɪ ˈ æ s t ə l i / dy-AST-ə-lee) is the relaxed phase of the cardiac cycle when the chambers of the heart are refilling with blood. The contrasting phase is systole when the heart chambers are contracting. Atrial diastole is the relaxing of the atria, and ventricular diastole the relaxing of the ventricles.
The period of relaxation that occurs as the chambers fill with blood is called diastole. Both the atria and ventricles undergo systole and diastole, and it is essential that these components be carefully regulated and coordinated to ensure blood is pumped efficiently to the body. [1] The cardiac cycle as correlated to the ECG
At this point, the atrial systole applies contraction pressure to 'topping-off' the blood volumes sent to both ventricles; this atrial contraction closes the diastole immediately before the heart again begins contracting and ejecting blood from the ventricles (ventricular systole) to the aorta and arteries.
Blood velocities in arteries are higher during systole than during diastole. One parameter to quantify this difference is the pulsatility index (PI), which is equal to the difference between the peak systolic velocity and the minimum diastolic velocity divided by the mean velocity during the cardiac cycle. This value decreases with distance ...
As diastole ends, the ventricles begin depolarizing and, while ventricular pressure starts to rise owing to contraction, the atrioventricular valves close in order to prevent backflow to the atria. At this stage, which corresponds to the R peak or the QRS complex seen on an ECG , the semilunar valves ( aortic and pulmonary valves) are also closed .
It is caused by the closure of the semilunar valves (the aortic valve and pulmonary valve) at the end of ventricular systole and the beginning of ventricular diastole. As the left ventricle empties, its pressure falls below the pressure in the aorta. Aortic blood flow quickly reverses back toward the left ventricle, catching the pocket-like ...
In clinical cardiology the term "diastolic function" is most commonly referred as how the heart fills. [1] Parallel to "diastolic function", the term "systolic function" is usually referenced in terms of the left ventricular ejection fraction (LVEF), which is the ratio of stroke volume and end-diastolic volume. [2]
End-systolic volume (ESV) is the volume of blood in a ventricle at the end of contraction, or systole, and the beginning of filling, or diastole. ESV is the lowest volume of blood in the ventricle at any point in the cardiac cycle. The main factors that affect the end-systolic volume are afterload and the contractility of the heart.