Systole is the simultaneous contraction of the ventricles by which blood is forced onward to maintain circulation. Diastole is considered ventricular relaxation where the ventricles dilate and fill with blood.
When the heart contracts and aortic valves open allowing blood to flow into the body the proximal arteries (Left and Right Coronary) are blocked by the aortic valves. In the case of an LVAD patient this becomes irrelevant
Therefore, the only time blood returns to the heart via the coronary arteries is during diastole. This is one of the reasons for tachydysrhythmias in the heart. Supraventricular tachydysrhythmias (not to be confused with Supraventricular Tachycardia; one of the Supraventricular tachydysrhythmias) are often produced by disorders of impulse formation and/or disorders of impulse conduction. If there is not enough blood returning to the heart the heart will speed up in an attempt to compensate for the lack of adequate blood flow.
