Weakness of the left side of the heart is called systolic heart failure and causes a decrease in the amount of blood that is pumped to the body from the heart, explains WebMD. Causes include coronary artery disease, cardiomyopathy, hypertension, aortic stenosis, mitral regurgitation, viral myocarditis and arrhythmia.
Coronary artery disease leads to systolic heart failure by causing a gradual decrease of blood flow to the heart muscle, according to WebMD. The decreased blood flow may occur for short periods of time or may be chronic. During these episodes, the heart tissue does not receive enough oxygen, and eventually, some of it becomes damaged. The heart slowly becomes weak and loses its ability to pump blood.
Mitral valve regurgitation causes back flow of blood into the left atrium each time the left ventricle contracts, explains WebMD. With each contraction the left ventricle receives extra blood from the left atrium from the backflow and has to contract harder. The left ventricle dilates over time to accommodate the extra blood, which causes the stretching and weakening of the heart muscle.
Another common cause of systolic heart failure is from a heart attack, during which blood supply to the heart is cut off and causes tissue damage or death, explains WebMD. When a large area of the heart is damaged from a heart attack it can lose its ability to normally pump blood to the body.