All the organs and tissues of the body require a constant supply of blood to provide oxygen, glucose and other nutrients to keep them working properly. The heart is a remarkable pump in this respect providing for such needs non-stop for 70 to 80 years or more.
In addition the heart has to vary its pumping according to the immediate needs of the body. In physical exercise the oxygen and glucose requirement of muscles increases enormously and the heart has to beat much faster to cope with this. Anger, excitement or fear will also increase the need for more blood flow through the heart.
Sometimes heart failure is confused with heart attack. A heart attack is normally caused by a myocardial infarction. This occurs when one or more of the arteries supplying the heart muscle itself becomes narrowed or blocked. This results in part of the heart muscle dying and bringing about chest pain and collapse.
Causes of Heart Failure
The heart may fail either because of damage to the heart itself or because too great a demand is being placed up on it.
- Heart muscle damage: myocardial infarction, heart muscle disease (sometimes inherited), and inflammation of the heart muscle (myocarditis)
- Overloading the heart: thyroid disease, diabetes, anaemia and obesity can all place excessive demands on the heart.
- Back pressure: high blood pressure and narrowing of the aorta (the main artery exiting the heart) can cause sufficient back pressure to limit efficiency.
- Valve disease: effective pumping relies on the integrity of non-return valves in the heart chambers. Typically the mitral and aortic valves may be damaged.
- Deranged heart rhythm: disturbance to heart rhythm, usually due to myocardial infarction or other heart disease will lower heart efficiency.
- Mechanical pressure on heart: this may be due to constriction of the pericardium (the heart’s surrounding jacket) or pericardial tamponade where bleeding occurs between the pericardium and the heart itself.
Clinical Features of Heart Failure
Not surprisingly, anything that interferes with the heart’s efficiency will soon have secondary effects on various parts of the body.
- Pulmonary congestion: because blood circulation through the lungs becomes inefficient, difficulty in breathing occurs particularly when lying down and on exertion.
- Oedema: fluid builds up in various parts of the body leading to swollen ankles and, if the heart failure is severe, abdominal distension.
- Lack of oxygen: fatigue, lethargy, dizziness, cold hands and feet.
Treatment
Initially management of heart failure entails removal of the cause: repairing faulty valves for example or dealing with thyroid dysfunction.
General measures include stopping smoking, avoiding alcohol and gradually increasing the amount exercise taken.
Drug treatment centres on the use of diuretics which increase urine production and vasodilators which increase the capacity of the arteries.
This article is for information only. If you have any health concerns you should consult your doctor.
Resource: Medicine. Eds. Souhami and Moxham 2002. Pub. Churchill Livingstone
