Why is the left ventricle more muscular than the right ventricle?
It is the functions of the various parts of the heart muscle which define their requirements. The ventricles are chambers that pump blood and it depends on where the blood needs to go. The left atrium and left ventricle are the hardest workers, and the left ventricle actually pumps blood to various parts of the body via the aorta. The right ventricle pumps blood through the pulmonary arteries to the lungs where it is oxygenated.
The walls of the left ventricle are accordingly up to five times thicker to accommodate this increased pressure and volume and the ventricle is larger. Should a heart attack occur, more major organs and tissues would be at risk should it be centered on the left side.