Ischaemic heart disease (I.H.D.) is a syndrome caused by inadequate blood supply to the heart muscles chiefly due to coronary artery disease (spasm or occlusion of the coronary arteries). Occlusion of coronary vessels may be commonly due to atherosclerosis but also may be caused by local thrombosis or embolism, syphilitic narrowing of coronary ostium, collagen disease or arteritis.
The following conditions should be looked for:
Left ventricular hypertrophy
Thyrotoxicosis or myxoedema
Syphilitic aortitis — obliterating coronary ostia
Infective or non-specific arteritis
Anomaly of coronary vessels – by angiogram.
All these pathological changes may insidiously or suddenly cause impaired blood flow of the myocardium. Inadequate vascular supply to the heart results in inadequate oxygen supply to the heart muscles for its metabolic requirement. Acid metabolites may accumulate in the myocardial tissues which stimulate nerve-endings, causing pain in the distribution of segmental nerve supply. This pain may be short-lasting, variable, recurrent or prolonged and is known as angina pectoris.
Recent researches suggest that coronary artery spasm is certainly an important cause of angina pectoris. It may occur at rest. Angiographic as well as radio isotopic imaging studies have shown that ischaemia of myocardium leads to abnormal left ventricular function and nitroglycerine wonderfully relieves spasm.
Role of prostaglandin and thromboxane A2 are to encourage platelet aggregation. Hyperlipidaemia also inhibits the protective effects of prostaglandins. Therefore a complex mechanism seems to operate to keep proper physiological balance. One most important extraneous factor also adversely affects this process, i.e. cigarette smoking, which encourages platelet aggregation.
Heart is supplied by the first two branches of the aorta, i.e. right and left coronary arteries, though a small amount of blood may enter myocardial tissues via veins of the Thebases, from the endocardial surface. The anatomy of the coronary arteries can be studied by coronary angiography, which is now a safe procedure in expert hands.
It is to be realised that heart muscle gets its blood supply during the diastole, because in systole the muscles are contracted, compressing the coronaries. Hence during tachycardia, there is precarious blood supply to the heart, as tachycardia reduces diastolic interval time hence coronary filling is also reduced.
Coronary atherosclerosis occurs with advancing age but why it occurs more extensively in some people, than others, is not yet clearly established. Young healthy soldiers who were killed during combat action also had evidence of atherosclerosis discovered during autopsy.
Similarly young people in their twenties and thirties also may show evidence of atherosclerosis during medicolegal autopsy.
There are many risk factors of I.H.D. and quite a few of these are avoidable.
Risk Factors in the Aetiology of I.H.D.:
1. Genetic Factors- (Family history and blood group)
2. Dietary animal fat — in excess (Specially saturated fat)
3. Essential fatty acid deficiency in diet
4. Too much sugar and too much carbohydrate in diet have also been incriminated.
5. Obesity — especially endomorphic types — more fatty and less muscular.
6. Hypertension (especially diastolic)
7. Diabetes Mellitus
8. High cholesterol and triglycerides (serum lipid profile showing low HDL: High LDL and VLDL)
9. Tobacco smoking (even moderate degree)
10. Excessive alcohol consumption
11. Thyroid disorders hypothyroidism and hyperthyroidism
12. Emotional stress of severe type (due to stress hormones). Ambitious and highly conscientious (personality type I).
13. Old age- Although middle age group and even young are susceptible.
14. Doubtful factors-Magnesium deficiency.
15. Racial and Geographical factors- may be important
16. Occupational factors- Top level business executives, politicians, lawyers, doctors, engineers are more susceptible, GP’s suffer more than consulting physicians. Technical workers suffer more than labourers and farmers.
In this country, people with normal lipid profile as well as poor industrial workers also suffer. More data are required to find out importance of diet and environmental factors.
When ischaemia is extensive or if there is sudden occlusion of a major branch of the coronary artery myocardial infarction (M. I.) may occur associated with severe pain in chest with or without various complications.
Gradual narrowing of the blood vessels supplying the heart muscles, results in deficient supply of oxygen more gradually; therefore, initially it may not cause much symptoms at rest, excepting that chest pain occurs during physical exertion.
Coronary artery spasm or gradual narrowing of coronary vessels may cause anterior chest-wall pain especially on exertion which is known as ‘syndrome of angina pectoris’ or ‘Coronary insufficiency’.
William Heberden published his classic paper on angina pectoris long before the discovery of microscope and ECG machine and when the morbid anatomists did not know much about the pathological changes in the coronary arteries.
Pain of Cardiac Ischaemia (I.H.D.):
Classical chest pain of I.H.D. usually starts as angina pectoris, which may be mild or severe. It may be felt as slightly annoying discomfort over and around the sternal area but in severe form it may be unbearable pain or distressing pressure in front of the chest. It may radiate along the inner side of arms, forearms and little fingers on both sides more commonly on the left. It may also radiate to the neck, jaw and even epigastrium. Sudden death may occur after a few minutes of severe precordial pain due to ventricular fibrillation and cardiac arrest.
Various types of pain as experienced by patients may appear as follows:
(1) Some discomfort in anterior chest wall or upper abdominal discomfort or gas pressing on the heart.
(2) Crushing pain across the chest.
(3) Heavy load over the anterior chest wall.
(4) Sensation of heart is being squeezed in vice.
(5) Some annoying feeling over the precordium.
(6) Uncomfortable heart burn related to food.
Localised pricking or stabbing pain over a small coin-sized area near apex of the heart is usually typical of anxiety state (pseudo-angina).
Clinical Syndromes of I.H.D.:
Three clinical types are generally recognised:
(i) Syndrome of angina pectoris.
(ii) Acute coronary insufficiency or unstable angina (pre-infarction syndrome).
(iii) Myocardial infarction.