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 an arrhythmia causes the heart to beat too fast, the heart doesn't pump effectively. Specifically, there may not be enough time between heartbeats for the heart to fill with blood, causing blood to back up into the lungs. The increased pressure and fluid in the lungs results in the feeling of shortness of breath.