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.
Picture of a cross section of the heart. When one or more coronary arteries narrow, it may make it difficult for adequate blood to reach the heart, especially during exercise. This can cause the heart muscle to ache like any other muscle in the body. Should the arteries continue to narrow, it may take less activity to stress the heart and provoke symptoms. The classic symptoms of chest pain and shortness of breath due to atherosclerotic or coronary artery disease are called angina. Should one of the coronary arteries become completely blocked, usually due to a blood clot that forms, blood supply to part of the heart muscle is completely lost and that piece of muscle dies. This is called a heart attack or myocardial infarction (myo=muscle + cardia=heart + infarction = tissue death).