Depolarization occurs during the systolic phase of the cardiac cycle, both for the atria and the ventricles. Here's the detailed explanation: In the context of the heart's electrical activity, the P wave on an electrocardiogram (ECG) represents the depolarization of the atria, which is the process where the atria contract or go into atrial systole. This is the phase where the atria push blood into the ventricles. Similarly, the QRS complex on an ECG signifies the depolarization of the ventricles, which corresponds to ventricular systole. During this phase, the ventricles contract and pump blood out to the body and lungs. The term diastole refers to the relaxation phase of the cardiac cycle. For the atria, atrial diastole occurs after atrial systole, when the atria are relaxed and filling with blood. For the ventricles, ventricular diastole is the period after ventricular systole when the ventricles are relaxed and filling with blood from the atria. So, to answer your question directly: Depolarization is associated with systole, not diastole. read more >>

Eventually, however, faulty heart valves may have to be repaired or replaced (Source: NHLBI). 'Electrical' events are correlated with the 'mechanical' events: P wave = atrial depolarization = atrial systole. QRS complex = ventricular depolarization = ventricular systole (& atrial diastole occurs at the same time)read more >>