Congestive Heart Failure (cont.)
Congestive Heart Failure Causes
Congestive heart failure (CHF) is a syndrome that can be brought about by several causes. Congestive heart failure is a weakening of the heart caused by an underlying heart or blood vessel problem, or a combination of several different problems, including the following:
- Weakened heart muscle (cardiomyopathy)
- Damaged heart valves
- Blocked blood vessels supplying the heart muscle (coronary arteries), which may lead to a heart attack (This is known as ischemic cardiomyopathy. If there are other, noncoronary causes, these are collectively termed nonischemic cardiomyopathy.)
- Toxic exposures, such as alcohol or cocaine
- Infections, commonly viruses, which for unknown reasons affect the heart in only certain individuals
- High blood pressure that results in thickening of the heart muscle (left ventricular hypertrophy)
- Congenital heart diseases
- Certain genetic diseases involving the heart
- Prolonged, serious arrhythmias
- A variety of less common disorders in which the heart muscle is infiltrated by a disease process
There are over a hundred other less common causes of heart failure, which include a variety of infections, exposures (such as radiation or chemotherapy), endocrine disorders (including thyroid disorders), complications of other diseases, toxic effects, and genetic predisposition. However, the cause of congestive heart failure is often idiopathic, or unknown. People who have diabetes are at increased risk for both ischemic and nonischemic heart failure.
Congestive heart failure may be exacerbated by the following lifestyle habits:
- Unhealthy habits, such as smoking and excessive use of alcohol
- Obesity and lack of exercise (May contribute to congestive heart failure, either directly or indirectly through accompanying high blood pressure, diabetes, and coronary artery disease.)
- High salt intake, which may cause more fluid retention
- Noncompliance with medications and other therapies
Whether through disease and/or complicating lifestyle choices, the pumping action of the heart can be impaired by several physiologic mechanisms:
- Direct heart muscle damage (cardiomyopathy): The heart muscle can become weak because of damage or disease and thus does not contract or squeeze as forcefully as it should. This damage to the muscle can occur from any of the diseases mentioned above, but sometimes, the cause is unknown.
- Damage to heart muscle due to blockage: When the coronary blood supply is blocked, this results in a heart attack (myocardial infarction). A heart attack commonly causes severe pain in the chest, shortness of breath, nausea, sweating, and/or a feeling of impending doom. A heart attack may rapidly lead to either cardiac arrest (no heartbeat) or permanent damage to the left ventricle. If this damage is bad enough, that part of the heart will not work properly, which leads to heart failure. Prompt (emergency) medical attention is critical for all heart attacks.
- High blood pressure (hypertension): Abnormally high blood pressure increases the amount of work the left ventricle has to do to pump blood out to the circulatory system. Over time, this greater workload can damage and weaken the heart, leading to heart failure. Proper treatment of high blood pressure can prevent left ventricular failure.
- Heart valve problems: The valves of the heart normally keep the blood flowing in the proper direction through the heart. Abnormal heart valves impede this forward flow in one of two ways:
- An incompetent valve is a valve that does not close properly when it should and allows blood to flow backward in the heart, "against the current." When blood flows the wrong way across a valve, the heart has to work harder to keep up its output. Eventually, this backed up blood accumulates in the lungs and the body and the heart muscle weakens.
- A stenotic valve is a valve that does not open properly. Blood flow through the narrowed opening is blocked, creating an increased workload on the heart that can also lead to heart failure.
- Abnormal rhythm or irregular heartbeat: Abnormal heart rhythms can lower the heart's effectiveness as a pump. The rhythm may be too slow or too fast, or irregular. The heart has to pump harder to overcome these rhythm disorders. If this excessively slow or fast heartbeat is sustained over hours, days, or weeks, the heart can weaken, which may lead to heart failure.
Terrence X O'Brien, MD, FACC
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