Ischaemic Heart Disease, otherwise known as Coronary Artery Disease, is a condition that affects the supply of blood to the heart. The blood vessels are narrowed or blocked due to the deposition of cholesterol plaques on their walls. This reduces the supply of oxygen and nutrients to the heart musculature, which is essential for proper functioning of the heart. This may eventually result in a portion of the heart being suddenly deprived of its blood supply leading to the death of that area of heart tissue, resulting in a heart attack.
As the heart is the pump that supplies oxygenated blood to the various vital organs, any defect in the heart immediately affects the supply of oxygen to the vital organs like the brain, kidneys etc. This leads to the death of tissue within these organs and their eventual failure or death. Ischaemic Heart Disease is the most common cause of death in several countries around the world.
Cause and Pathogenesis
A multitude of factors are responsible for the development of Ischaemic Heart Disease. The major risk factors are smoking, diabetes mellitus and cholesterol levels. Those with Hypercholesterolaemia (elevated blood levels of cholesterol) have a much higher tendency to develop the disease. There is also the theory that Hypertension is a risk factor in the development of Ischaemic Heart Disease, Genetic and hereditary factors may also be responsible for the disease. Males are more prone to Ischaemic Heart Disease. However, in post-menopausal women, the risk is almost similar to that of men. Stress is also thought to be a risk factor, though there has been a great deal of debate on this factor of late. The disease process occurs when an atheromatous plaque forms in the coronary vessels, leading to narrowing of the vessel walls and obstructing blood flow to the musculature of the heart. Complete blockage results in deficient oxygenation and nutrient supply to the heart tissues, leading to damage, death and necrosis of the tissue, which is known as Myocardial Infarction (heart attack).
Symptoms and Signs
Quite often, the first sign of Ischaemic Heart Disease may be the severe chest pain of Myocardial Infarction, which may be fatal. However, the warning symptoms occur in a large number of patients in the form of Angina Pectoris. The main symptom of Angina is pain over the central chest that may sometimes radiate down the left arm, to the jaw or to the back. The characteristic feature of the pain is that it is usually aggravated by exercise and relieved by rest, though variant forms may occur. The pain is also relieved by the use of nitrates kept under the tongue. The pain is usually described as a sense of compression or tightness in the middle of the chest, and may last for five to twenty minutes. The pain may be accompanied by sweating. The presence of anginal episodes is virtually diagnostic of Ischaemic Heart Disease.
Other signs that can be observed on clinical examination is the presence of Tendon Xanthomas, thickening of the Achilles Tendon and Arcus Lipidus in young patients, all of which may indicate a hereditary Hyperlipdaemia. The patient should also be examined for anaemia, obesity, diabetes, thyroid and peripheral vascular disease.
Investigations and Diagnosis
Electrocardiography (ECG) may be normal in several patients at rest between attacks of Angina. However, during the episodes of pain there may be depression of the ST segment and a T wave inversion in several leads, indicating Ischaemia. In cases of Infarction (heart attack), there will be ST segment elevation in the ECG, which may gradually evolve. An Echocardiogram may help in showing any functional abnormalities in the various cardiac chambers and in assessing the pumping efficiency of the heart. An exercise testing (Treadmill Test-TMT) is often indicated in patients who have symptoms but have normal ECG patterns. Nowadays, TMT is being indicated in all high-risk categories beyond the age of 35 irrespective of symptoms. Myocardial perfusion scanning with radioactive thallium may also be helpful in the diagnosis. Coronary Angiogram provides accurate information about the actual site and extent of the stenosis (narrowing) and helps in deciding the method of therapy required.
Treatment and Prognosis
Drug therapy with Nitrates, which dilate the diseased coronary arteries, administered sub-lingually are very effective in relieving the pain in a few minutes. Drugs such as Isosorbide Dinitrate and Isosorbide Mononitrate belong to the category of Nitrates. These drugs are also used as a prophylactic to prevent the pain from occurring. Beta-blockers like Propranolol are also highly effective in relieving pain by reducing myocardial oxygen demand, mainly by decreasing the heart rate. Calcium channel antagonists produce vasodilatation and relieve the symptoms by reducing the excitability and conductivity of cardiac muscle and by reducing blood pressure. For patients with hypercholesterolaemia, drugs may be used to lower cholesterol levels.
Surgical therapy is indicated when medical treatment has failed to relieve symptoms or when the Angiogram shows significant disease in the blood vessels. Coronary Angioplasty – dilating the blocked vessel by inflating a balloon inside the vessel and Coronary Artery Bypass Grafting (CABG) – replacing the blocked area of the vessel using a graft from the patient, may be done to relieve the blockage.
The indications for bypass surgery are increasingly becoming limited. This is due to the growing realization that except in selected cases, bypass surgery only helps to improve the quality of life and relieve symptoms. It does not significantly increase life expectancy. The current trends are to focus on medical treatment and techniques like angioplasty. With proper treatment, most patients will be able to lead normal and healthy lives. Treatment also involves advice regarding regular exercise, avoiding smoking, diet control and life style modification. Good control of diabetesand hypertension significantly improves the outlook.
Risk factors like a fatty diet, smoking, sedentary lifestyle and stress should be avoided, as they are the main areas of focus in prevention. Avoiding foods rich in saturated fats is vital to reduce lipid levels in the blood and to prevent arteriosclerosis. Adequate regular exercise is also essential. Diabetes Mellitus and hypertension should be kept under good control with proper treatment.