Causes

Heart failure often develops after other cardiac conditions have damaged or weakened your heart. Over time, the heart can no longer keep up with even the normal demands placed on it. The heart muscle weakens, and the ventricles stretch to the point that the heart can't pump blood efficiently throughout your body. The failing pump causes blood and fluid to back up throughout your circulatory system — your lungs, legs, feet and ankles — and your kidneys retain excess water and sodium. This buildup of fluid is the congestive part of heart failure. The lung congestion occurs only with left-sided heart failure with fluid backing up into the lungs. The most common cause of right-sided heart failure is left-sided heart failure. The extra pressure in the lungs is eventually passed on to the right side of the heart, which then fails — causing fluid to collect in the abdomen and lower extremities.

Heart failure can develop quickly after damage caused by a heart attack, or it can develop gradually after years of high blood pressure or coronary artery disease. A defective heart valve may cause heart failure. In this case, repair or replacement of the valve can often reverse heart failure.

All of the behaviors that you probably associate with heart attack or heart disease — such as smoking, being overweight or eating foods high in cholesterol and fat — may cause or contribute to heart failure. Sometimes, your heart becomes weakened without explanation, a condition known as idiopathic dilated cardiomyopathy.

If you have heart failure, you may have one or more of the following conditions, which can damage or weaken your heart over time. Some of these can be present without even knowing it:

· Right sided heart failure. The extra pressure in the lungs is eventually passed on to the right side of the heart, which then fails — causing fluid to collect in the abdomen and lower extremities.
Coronary artery disease and heart attack. Coronary artery disease is the most common form of heart disease and the most common cause of heart failure. Over time, arteries that supply blood to your heart muscle narrow from a buildup of fatty deposits, a process called atherosclerosis. The buildup containing fats and other substances is called a plaque. Blood moves slowly through narrowed arteries, leaving some areas of your heart muscle chronically deprived of oxygen-rich blood. These areas of the heart may become weak from the lack of oxygen and pump less vigorously. In many cases, the blood flow to the muscle is just enough to keep the muscle alive but not functioning well. A heart attack occurs if an unstable plaque ruptures, causing a blood clot to completely block blood flow to an area of the heart muscle. A heart attack results in the death of heart muscle, which can quickly weaken the heart's pumping ability. Sometimes the coronary artery disease is limited to the small coronary arteries. If these arteries become blocked, this won't cause a heart attack, but over time, it can gradually weaken the heart.

High blood pressure (hypertension). Blood pressure is the force of blood pumped by your heart through your arteries. If your blood pressure is high, your heart has to work harder than it should to circulate blood throughout your body. Over time, the heart muscle may become thicker to compensate for the extra work it must perform. In some cases, the heart will enlarge. Eventually, your heart muscle may become either too stiff or too weak to effectively pump blood.

Faulty heart valves. The four valves of your heart keep blood flowing in the proper direction through the heart. A damaged valve forces your heart to work harder to keep blood flowing as it should. Over time, this extra work can weaken your heart. Faulty heart valves, however, can be fixed, if detected in time.
Cardiomyopathy. This is another type of heart muscle damage. Some of the many causes of cardiomyopathy include infections, alcohol abuse, and the toxic effect of drugs such as cocaine or some drugs used for chemotherapy. In addition, whole-body diseases, such as lupus, or thyroid problems can also damage heart muscle. If a specific cause can't be found, it is referred to as idiopathic dilated cardiomyopathy.

Myocarditis. Myocarditis is an inflammation of the heart muscle. It's most commonly caused by a virus and can lead to left-sided heart failure.
Heart defects present at birth (congenital heart defects). If your heart and its chambers or valves haven't formed correctly, the healthy parts of your heart have to work harder to compensate. Genetic defects contribute to the risk of certain types of heart disease, which in turn may lead to heart failure.
Abnormal heart rhythms (heart arrhythmias). Abnormal heart rhythms may cause your heart to beat too fast. This creates extra work for your heart. Over time, your heart may weaken leading to heart failure. A slow heartbeat may prevent your heart from getting enough blood out to the body and may also lead to heart failure.

Other diseases — such as diabetes, severe anemia, hyperthyroidism, hypothyroidism, emphysema, hemochromatosis and amyloidosis — also may contribute to heart failure.

Heart failure can involve the left side, right side or both sides of your heart. Typically, heart failure begins with the left side — specifically the left ventricle, your heart's main pumping chamber. Your doctor may refer to your condition as left-sided or left ventricular heart failure. He or she may define it further as systolic heart failure (when the left ventricle loses its ability to contract vigorously) or diastolic heart failure (when the left ventricle loses its ability to relax or fill fully) or a combination of both. The distinction is important because the drug treatments for each type may differ. Right-sided heart failure can occur independently or be a consequence of left ventricular heart failure.