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Chapter: Biology of Disease: Disorders of the Cardiovascular System

Cardic Failure: Investigation, Treatment, Chronic and Acute Heart Failure

Investigation, Treatment, Chronic Heart Failure, Acute Heart Failure.

CARDIAC FAILURE

Cardiac failure is the inability of the heart to maintain an adequate cardiac output, that is pump a volume of blood per minute sufficient to meet the demands of the body. The heart does not stop beating as is often thought, but its diminished ability imposes severe demands. It is a serious condition but commoner in older people. The incidence is about one in a hundred for individuals over 65 years, and irrespective of the cause, the prognosis is poor. Approximately 50% of patients will die within two years, although new drug treatments are improving mortality and morbidity.

There are many possible causes of heart failure and, indeed, any disease that affects the heart and circulatory system can lead to heart failure. The commonest of these is coronary artery disease that limits the flow of blood, and hence oxygen and nutrients to the heart muscle and can lead to heart attack. Bacterial and viral infections can also damage the heart muscle, as can diabetes, an overactive thyroid and obesity. Obstruction of the heart valves or heart valves that leak increases itsworkload and this eventually weakens the contractions. Similarly, a narrowed aortic valve means that the heart has to work harder because it has to force blood through a smaller exit, again imposing an extra metabolic burden. High blood pressure also means that the heart has to work too hard. Diseases that affect electrical conduction in the heart can result in an abnormal heartbeat that reduces the pumping efficiency. Other causes are also known. Although the increased workload initially results in enlargement, or hypertrophy, of the heart muscle so that it can contract with greater force, eventually the heart malfunctions making the heart failure worse.

 

Heart failure results in tiredness and weakness during physical activities because the skeletal muscles are starved of blood. The disease may be on one side of the heart or the other, but the condition usually affects the whole heart. Nevertheless, there are characteristic symptoms depending on which side is affected. Thus right-sided disease tends to cause a build-up of blood flowing into the right side of the heart, which leads to swelling of the feet, ankles, legs and liver. In contrast, left-sided disease increases fluid in the lungs (pulmonary edema) causing, in turn, shortness of breath. At first this is only experienced during exertion but it gradually increases in severity so that the breathlessness occurs even at rest. If this happens at night, the patient may wake up gasping for breath and may find it better to sleep in a sitting position. Cardiac failure gradually worsens with time if the underlying disease is not treated, although patients may continue to live for many years.


INVESTIGATION

The symptoms described above are usually sufficient for an initial diagnosis of heart failure, which would be confirmed by a weak and rapid pulse, lowered blood pressure and abnormal heart sounds. However, its underlying cause must also be identified. In many cases taking a clinical history and examining the patients will be sufficient. General diagnostic tests include chest X-ray to demonstrate an enlarged heart and fluid accumulation in the lungs, ECG, echocardiography, blood tests, for example full blood count, liver function, urea and electrolytes, and analysis of cardiac enzymes in acute heart failure to diagnose myocardial infarction will then usually be carried out. Functional tests may also be performed, including exercise testing, ECG monitoring and angiography at rest and under stress.


TREATMENT

The treatment for heart failure is focused on relieving the symptoms, retarding the progression of the disease and aiming to improve the chances  of survival. This means that any factor aggravating the failure should be identified and treated. The precise cause of failure should be identified and if possible corrected. Patients should be nursed in a comfortable, upright position.


CHRONIC HEART FAILURE

In chronic heart failure, the circulation at rest is adequate but there is an inadequate reserve to pursue daily activities. Its treatment depends upon the underlying disease to be dealt with. For example, heart surgery can correct narrowed or leaking heart valves, and bypass surgery can correct blocked coronary arteries. If the disease is caused by an infection the condition may be improved by antibiotics without surgery. Additionally, there are many things a patient can be advised to do to help the condition, including giving up smoking, eating less salt, reducing excessive weight and controlling alcohol consumption.

The best treatment for heart failure is to prevent it happening in the first place or by reversing its underlying cause as soon as possible. Nevertheless, there is still much that can be done. For example, if reducing the salt intake does not lower fluid retention then diuretics may be prescribed. A reduction in the amount of body fluid reduces the volume of blood to be pumped and so alleviates the strain on the heart. Digoxin may be given to increase the power of each heart contraction and will slow a rate that is too rapid. Vasodilatory drugs may be prescribed to expand blood vessels, lowering the blood pressure. Some of the older drugs dilate arteries more than veins or vice versa. However, the ACE inhibitors (angiotensin converting enzymeinhibitors ) dilate both arteries and veins are, perhaps, the most commonly used. These improve the symptoms and prolong life. A heart transplant is perhaps the ultimate possibility but there are never enough good hearts to go round!


ACUTE HEART FAILURE

In acute heart failure, the hemodynamic derangement is so severe that it results in symptoms even at rest. If fluid suddenly accumulates in the lungs the condition is known as acute pulmonary edema and the person has to gasp for breath and emergency treatment is required. Oxygen is given by a facemask and together with intravenous diuretics may result in a rapid and dramatic improvement. Glyceryltrinitrate may be given intravenously or placed under the tongue and this leads to dilation of the veins, reducing the amount of blood flowing through the lungs. It may be necessary to insert a tube into the patient’s airway to help breathing. The treatment for acute heart failure is essentially as for the chronic condition described above.

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