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.
Heart valve disease occurs when a valve doesn't work right. A valve may not open all the way. Or, a valve may have problems closing. If this happens, blood doesn't move through the heart's chambers the way it should. If a valve doesn't open all the way, less blood moves through to the next chamber.