Causes of Heart Failure

The main causes for congestive heart failure can vary in different parts of the world. For example, in the United States, the main causes for heart failure are:

1. Coronary artery disease 62%. The accumulation of plaque (atherosclerosis) within the coronary arteries reduces the blood flow within the heart muscle which eventually leads to its weakness and can result in heart failure.
2. Smoking 16%. Smoking is a major risk factor for atherosclerosis. It is believed that nicotine promotes atherosclerosis due to its damaging effect on the inner lining of the arteries.
3. Hypertension 10%. Increased blood pressure creates resistance which the heart must overcome to provide sufficient blood flow in systemic circulation. This leads to hypertrophy (enlargement) of the left ventricle in order to increase the force with which the heart can pump the blood. As the blood pressure continues to rise, the heart is no longer able to compensate and which leads to the dilation of the heart’s chambers. This leads to overstretching and weakness of the heart muscle and results in left-sided heart failure. Moreover, the increased blood pressure damages the inner lining of the arteries which promotes atherosclerosis.
4. Obesity 8%. Obesity is a major risk factor for atherosclerosis (due to metabolic syndrome which often accompanies obesity), high blood pressure and resistance of the tissues to insulin (type II diabetes). 
5. Type I and II diabetes 3%. Glycosylation of cells, which happens due to abnormally high blood sugar, is a major contributing factor for atherosclerosis.
6. Heart valve disease 2% (in the older population, this percentage is much higher). Both the stenosis and insufficiency of the heart valves leads to an increased strain on the heart. In the case of stenosis, the heart has difficulty pushing the blood through a narrow valve. In the case of insufficiency, the backward flow of the blood increases the pressure within the heart chamber that is located before the valve, making the heart work extra hard. At first, this leads to hypertrophy of the heart’s muscle and later to the dilation of the heart’s chambers which then leads to heart failure.

Rare causes of congestive heart failure include:

• Myocarditis caused by viral infection. The inflammation caused by a viral agent can impair the heart’s ability to contract resulting in heart failure.
• Amyloidosis of the heart muscle (saturation of the heart muscle cells with a special type of protein called Amyloid). Amyloidosis is a result of chronic inflammation within the body. Amyloidosis of the myocardium leads to its weakness.
• Cardiomyopathy caused by HIV. HIV causes dilated cardiomyopathy during which the chambers of the heart become enlarged and this reduces the ability of the myocardium to contract.
• Systemic lupus erythematosus. The autoimmune reaction caused by this disease may cause endocarditis, myocarditis and pericarditis. Moreover, systemic lupus erythematosus promotes atherosclerosis which can lead to heart failure.
• Abuse of various drugs including cocaine and alcohol. Various toxic substances have a direct damaging effect on the heart which can cause its weakness. For example, people suffering from alcoholism often have alcoholic myocardial dystrophy which results in substitution of the myocardial cells with fatty tissues.
• Drugs used in chemotherapy. These drugs can sometimes result in myocarditis eventually leading to heart failure.
• Arrhythmias. Even though arrhythmias do not decrease the force with which the heart can contract, they can impair its function sufficiently that the person may have symptoms similar to heart failure. For example, a third-degree atrioventricular block may result in the inability of the heart to beat faster than 40 times per minute which can produce symptoms similar to heart failure.

Next chapter: Symptoms of Heart failure