When is the Right Ventricle at its smallest dimension in the cardiac cycle?

The right ventricle is at its smallest dimension at the end of systole. This phase marks the completion of the ventricular contraction, where the right ventricle has ejected blood into the pulmonary artery. During this stage, the muscle fibers of the ventricle have contracted fully, resulting in a reduction in chamber volume. At this point, the ventricle is emptied, and therefore, its dimensions are minimized.

At end diastole, the ventricle is actually at its maximum volume as it fills with blood returning from the atria. During early diastole, while the ventricle begins to fill again, it is still larger than at end systole. Similarly, mid-systole occurs after the ventricle has started to contract, but not enough time has passed for the ventricle to reach its smallest size. Thus, it is clear that the most contracted state, which corresponds to the smallest dimension of the right ventricle, occurs at the end of systole.