How big is a significantly enlarged right ventricle?

Doctors consider the heart's lower right pumping chamber (the right ventricle) to be significantly enlarged if it appears in imaging tests to be more than twice the size of the pumping chamber next to it (the left ventricle). Enlargement typically is the result of poor blood control by the two valves that allow blood flow into and out of the right ventricle (the tricuspid and pulmonary valves). If valves leak from disease, infection or birth defect, too much blood enters the right ventricle instead of passing normally through the lungs, causing the muscular chamber to work harder and get bigger. Enlargement leads to inefficient pumping that can result in heart failure.