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| Tuesday, 6 July 2004 |
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Support for the failing heart by Dr. D.P. A. Atukorale The heart may begin to fail due to a number of reasons such as (a) diseases of the myocardium (heart muscle) (b) diseases of the coronary arteries (c) diseases of the heart valves and (d) abnormalities of the heart rhythm. In all these conditions of heart failure, the heart is unable to circulate blood effectively enough to meet the demands of the body. When the underlying cause of heart failure is a valve defect as in rheumatic heart disease, the valve can be repaired or replaced using an artificial (prosthetic) valve. When the underlying problem is one of arrhythmia (disturbance of heart rhythm) the electrical abnormality can be controlled using drugs or an artificial pacemaker (pacesetter). In certain people with hypertension (high blood pressure), the demands of the hart are increased and the heart failure can occur if the blood pressure is not controlled and in these patients with hypertension, heart failure (which is mainly left heart failure or LVF) can be controlled using hypotensive drugs. There are many cases of heart failure in which it is difficult to remedy the real problem and most often the problem lies in the deterioration of the heart muscle caused by coronary heart disease (C.H.D.) and so lack of oxygen supply to myocardium (heart muscle). Infections of the heart muscle (myocarditis) can rarely lead to heart failure due to damage to the myocardium. Myocarditis is very often due to virus infection of the heart. Mild heart failure following myocardial infarction (heart attack) is not uncommon and this usually responds to medical treatment. Where mild heart failure persists, the heart may itself be able to adapt and the persons lifestyle is only slightly affected though the condition may slowly deteriorate over many years. In certain patients which certain forms of severe heart failure which persists in spite of medical treatment as in case of dilated cardiomyopathy when cardiac transplantation has to be considered. At present cardiac transplantation is not performed in Sri Lanka. In majority of patients with heart failure, doctors can offer relief of symptoms such as breathlessness and oedema using cardiac drugs such as diuretics digoxin, nitrates and ace-inhibitors such as enelepril which have been proved to prolong life of heart failure patients. Pumping Problems The right and left sides of the heart each act as pumps, the right ventricle pumping blood to the lungs and the left ventricle (the main pumping chamber of the heart) serving the rest of the body. In majority of patients heart failure affects both pumps left ventricle and right ventricle. However two pumps may be separately affected. Left Ventricular Failure (LVF) When the left side of the heart fails, the patient gets dysproea (breathlessness). In this condition, the weakened left ventricle cannot pump sufficient blood out of the left ventricle and this leads to accumulation of blood in the left atrium (left receiving chamber) which in turn restricts flow of blood out of the lungs. Pressure in the pulmonary veins increases and the liquid element of the blood is forced through the blood vessel walls into the tissues of the lungs itself. The lungs clogged with water in this way become stiff and it is difficult for these patients to expand and deflate their lungs and the exchange of oxygen for carbon-dioxide is reduced. The chest feels tight and the person affected is breathless and may get chest pain and cough. Right Heart Failure When the right ventricle (the right pumping chamber) cannot pump effectively, blood is damped back in the right atrium (the right receiving chamber) and then in the body's veins as the blood seeks to return to the heart. Leakage of fluid out of the veins build up in the body tissues giving them a puffy appearance and causing swelling (oedema) of the ankles. The liver and abdomen also swell and the gut feels congested leading to anorexia (loss of appetite). In heart failure the kidneys are unable to excrete enough water and sodium and this leads to retention of sodium in the body contributing to the build up of fluid in the blood and so leakage into the lungs and body tissues which in turn leads to fatigue, feeling of ill-health, breathlessness and even greater strain in the heart. If the condition cannot be reversed, there is a downward spiral leading to complete collapse of circulation. Management Of Heart Failure In someone who is very elderly and unlikely to make major demands on the heart as in case of mild heart failure, there may be little need for treatment. Rest and a low salt diet play a part in controlling the symptoms at least for a short-term. For someone with left heart failure (LVF), sitting up may be more comfortable than lying down especially during sleep or the patient with LVF can use 2 or 3 pillows or may be propped up using a 'bed rest' to sleep. This is because gravity causes blood to pool in the veins of the lower body and less blood returns to the heart and less blood accumulates in the lungs, and leakage of liquid to the lung tissues is reduced. In majority of patients the problem of heart failure is usually short term requiring support for a brief period while the underlying cause is remedied, or the heart itself is allowed to recover. In case of heart failure following surgery, the heart needs support for a few days after surgery - and thereafter the heart may be able to work on its own. In majority of patients with heart attacks complicated by LVF, the heart failure is of short duration and treatment in these cases is usually by drugs and rarely devices and mechanical assist are necessary to maintain heart function. Since these patients are in hospital drugs such as frusemide are frequently given by injection or slow infusion into a vein. When the underlying heart problem cannot be resolved patient may need long term heart failure therapy with drugs. This is common in some patients after major heart attacks or where the whole heart is damaged by a series of myocardial infarcts (heart attacks). Drugs for heart failure In heart failure the ventricles (pumping chambers of the heart) have difficulty in circulating blood around the body and lungs. There are 3 types of drugs which will help the heart failure patient. (i) Drugs which help the heart to pump with greater force (a) Digitalis preparations In 1785, Birmingham doctor called William Withering described how the heart could be made to pump with greater force using preparation of foxglove leaves first shown by an old woman of Schropshire Extract of foxglove called digitalis (digoxin) is one of the commonest drugs used by doctors for management of heart failure. Digoxin is also commonly used for treatment of cardiac rhythm disturbance called atrial fibrillation. Diuretics Diuretics (also called water tablets) such as frusemide, spironolactone and bumetanide are used in the management of heart failure. These water tablets lower the amount of blood in circulation by making the patient pass extra amounts of urine and getting rid of extra sodium in the body and this is done by increasing the excretion of sodium (salt) by the kidneys. Heart failure patients are advised to reduce the amount of salt in their diet. Vasodilators Vasodilators work by expanding the blood vessels and this lowers the resistance to the pumping action of the heart. Vasodilators also redistribute the blood away from the heart. The body's natural response to heart failure is to constrict the arteries and thus increasing the resistance to the flow of blood. Vasodilators reduce the resistance against which heart has to pump blood. By expanding the blood vessels especially the veins, more blood is kept pooled in the body and less blood returns to the heart. Long acting nitrates such as isosorbide denitrate (ISDN) and isosorbide 5 mononitrate which are commonly used to treat angina are very useful in the treatment of heart failure. Other vasodilators which are very useful include prazosin and hydralazine which are also used to reduce blood pressure (BP). Other very useful drugs used in the treatment of heart failure are (a) ACE inhibitors such as captopril and enelepril and (b) angiotensin 2 receptor antagonists such as losaten potassium. Often patients with heart failure are given a diuretic such as frusemide with or without digoxin and very often physicians add an ACE inhibitor or an angiotensin 2 receptor antagonist such as losarten to above drug regime. In very ill patients admitted with severe heart failure, in addition to intravenous diuretics, doctors use dopamine and dobutamine which are given as infusions. Very ill patients with acute left ventricular failure (LVF) sedatives such as morphine, oxygen and glyceryl trinitrate infusion are used sometimes to provide temporary support to the failing heart especially in cases of heart failure following open heart surgery. Heart transplantation is increasingly used in more developed countries such as Singapore, UK and USA for patients with resistant heart failure which cannot be controlled using drug therapy. Reference: Heart disease by Wallwork and Stapney. |
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