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 atrial fibrillation or flutter cause the heart to beat too rapidly, the ventricles do not have enough time to fill completely with blood. Because they do not fill completely, the amount of blood pumped by the heart decreases. This decrease may cause the blood pressure to fall, and heart failure may occur.