ERA. 1  baseball, baseball game - a ball game played with a bat and ball between two teams of nine players; teams take turns at bat trying to score runs; he played baseball in high school; there was a baseball game on every empty lot; there was a desire for National League ball in the area; play ball!.
The contraction of the heart muscle starts in the two atria, which push the blood into the ventricles. Then the walls of the ventricles squeeze together and force the blood out into the arteries: the aorta to the body and the pulmonary artery to the lungs.
When a coronary artery is partially blocked, it cannot supply enough blood to the heart muscle. The muscle needs this blood to meet its needs during exertion. If someone with coronary artery disease exerts himself, it causes chest pain. This is from lack of blood and oxygen to part of the heart muscle.