Atherosclerosis is a distinctive form of arteriosclerosis known from ancient times. The disease atherosclerosis has great relevance today. The terms ‘athere’ (meaning-porridge) and sclerotic (hardening or fibrosis) derived from Greek terminology, do not represent the complete morphology of disease. Despite our familiarity with this disease, some of its fundamental characteristics remain poorly recognised and understood. The cause and pathogenesis of atherosclerosis remain subject of lively speculation and controversy.¹

Atherosclerosis is a pathological entity and a multifactoid disease of large- and medium-sized arteries, characterised by plaque-like intimal deposits, which contain neutral fats, cholesterol, lipophages, blood elements, at times, other evidence of haemorrhage and calcium deposits. Complications of which are disastrous - ischaemic heart disease, cerebral stroke, peripheral gangrene and so on. It is a pandemic, percentage incidence of morbidity varies from country to country. It is a modern epidemic in United States of America, Europe, Canada, New Zealand and Australia.²

Among the diseases in the western world, atherosclerosis is overwhelmingly the prime disorder leading to death and serious morbidity. Despite recent reduction in mortality of coronary heart diseases (CHD) about 50% of all deaths in United States are still attributable to atherosclerosis-related diseases.¹ The developing countries such as India and others are catching up and registering a steady increase in the mortality rates due to atherosclerotic heart diseases.³ In India, CHD accounts for 10–15% of all cardiovascular diseases.⁴

The exact global incidence of atherosclerosis is impossible to calculate because it can exist without producing any symptoms or signs. These asymptomatic cases can be diagnosed only if an autopsy is done, in all cases of death.⁵ The mortality rates due to atherosclerotic heart disease in different countries are lowest in Japan (8%) and highest in Finland (41%). In United Kingdom, United States of America and Canada, the average mortality rate is 36%. The disease is increasing in countries undergoing industrialisation.⁶

Unfortunately, in India, there are no statistics giving the national incidence of this disorder.³ However, Padmavathi et al.⁷ gave the average incidence of atherosclerotic heart disease in seven different states during 1958–1959 as 0.51% per 1,000 population. In another study, conducted at All India Institute of Medical sciences, New Delhi, with the help of autopsy studies and taking atherogenic index as an indicator, the incidence of CHD is given as 35.5% in males and in females as 14%.⁵

Although global incidence, a wide range of variation in the prevalence and severity of atherosclerosis has been shown to exist in different geographic population. Against this background, the present study has been done in order to determine the severity and distribution of coronary atherosclerosis in the selected autopsies of the deaths occurring in general population of Karnataka state, which has good representation of all social classes.

The material for the present study included 50 heart specimens obtained from medico-legal autopsies performed in the Department of Forensic Medicine, Basaveshwara Medical College and Hospital, Chitradurga, and other heart specimens received at the Department of Pathology, Basaveshwara Medical College and Hospital, Chitradurga, sent for histopathological examination to define any suspected cardiovascular pathology. Hearts were obtained by standard procedures from all autopsies.

The age, sex and relevant information including age, sex, socio-economic status, dietary habits of the deceased were obtained from the informant accompanying the deceased. The methods used for the analysis of the material were as per the procedure recommended by White, Edward and Dry⁸ Tejada and Gore⁹, W.H.O. study group (Technical report series).^10,11,12

All autopsies were carried out within 4–24 h after death. All the specimens of right and left coronary arteries blocks were taken at a particular fixed distance at from 1.5 cm and 3 cm from the Ostia, also from the circumflex branch of the left coronary artery, bits were taken at the same distance form the point of branching of the left coronary artery into anterior descending and circumflex branches. Additional bits of tissue were taken from other regions of the vessels which showed stenosis. This stenosis is graded based on the luminal narrowing of the coronaries when examined by hand lens and is graded from grade 0 (no narrowing/normal) to grade IV (complete obliteration).

The bits of the tissue were fixed in 10% formalin and embedded in paraffin. Sections for histological study were taken from the paraffin blocks and stained with haematoxylin and eosin. The following special stains were also done whenever indicated, namely, Verhoeff and Van-Gieson's for demonstration of elastic tissues, smooth muscle and collagen, and Alcain blue for the demonstration of mucopolysaccharide ground substance. All histological sections were studied for microscopic evidence of atherosclerotic lesions.

Of the 50 heart specimens studied, 33 showed coronary atherosclerosis with various histological changes, such as fibroblastic activity, mucopolysaccharide deposition, degeneration of the internal elastic lamina, accumulation of lipid cholesterol crystals, hyalinisation, calcification and haemorrhage. Basaveshwara Medical College and Hospital, Chitradurga, observations made from the study are as follows:

The youngest subject was 19 years and the oldest was a male of 80 year age, forming an age range of 19–80 years. The majority of the cases were from 3^rd to 4^th decades of life forming 58% of total number of cases studied. Males and females were in the ratio of 2.5:1.

Among the 50 cases studied, 33 cases showed evidence of coronary atherosclerosis. Coronary atherosclerosis will increase with age and it also shows that males are more affected, i.e., 24 cases (72.72%) and females are affected in 9 cases (27.27%). The coronary atherosclerosis was much common in males but after 5^th decade it takes the same course in both male and female. Segmental involvement of coronary arteries in relation to age.

Of the 33 cases which showed evidence of coronary atherosclerosis, 21 cases (63.63%) had involvement of a single artery, 7 cases (21.21%) had involvement of two arteries and 5 cases (15.15%) showed involvement of all the three arteries. The left anterior descending was affected most commonly either alone or in combination with other artery.

In all these cases, the atherosclerosis involvement was located within the first 2 cm of the left anterior descending artery and left circumflex artery. In the right coronary artery, lesion was most prevalent between 2 and 3 cm from the ostium.

Of the 50 cases studied, 17 did not show any evidence of luminal narrowing. In the remaining 33 cases, the intraluminal narrowing observed was graded. In 18 out of 33 (54.54%) of cases showed grade I narrowing of lumen; 7 out of 33 (21.21%) showed grade II narrowing; 6 out of 33 (18.18%) showed grade III narrowing and 2 out of 33 (6.06%) showed grade IV narrowing.

Of the 50 heart specimens studied, 33 showed coronary atherosclerosis with various histological changes, such as fibroblastic activity, mucopolysaccharide deposition, degeneration of the internal elastic lamina, accumulation of lipid cholesterol crystals, hyalinisation, calcification and haemorrhage.

The autopsy study provides a means of understanding the basic process, which sets a stage for clinically significant atherosclerotic cardiovascular disease. There is no valid method of sampling the living population through an autopsy series. It was, therefore, considered that deaths suspected due to cardiovascular pathology, probably provide the best sample of the living population for studying atherosclerosis. Many epidemiological studies have brought to light a number of factors that are of indisputable importance in the development of atherosclerosis.

The studies by Abraham et al.¹³ and Bhargava¹⁴ showed that the most commonest pattern was involvement of all three segments, i.e., 69% and 84%, respectively. Whereas the present study showed that the commonest pattern was one segment involvement, which was 63.63% of cases followed by two segment involvement (21.21%) and three segment involvement (15.15%) cases.

But all the studies uniformly showed that the anterior descending branch of the left coronary artery was most commonly affected. The proximal 2–3 cm of this vessel shows a special predilection for the development of atherosclerotic lesions. Glasgov et al.¹⁵ have suggested that this could be attributed to the differences in dynamics of blood flow and the resulting differences in dynamics of blood flow and the resulting differences in arterial wall tension in the right and left coronary arteries.

Autopsy study is the most useful measure of the epidemiology of atherosclerosis. Age has a dominant influence. Males are affected more than females. All the observation in the present study showed that the incidence of atherosclerosis in India is same as developed countries. Autopsy study is the most useful measure of the epidemiology of atherosclerosis. It was observed that all the cases that showed evidence of coronary atherosclerosis also showed aortic atherosclerosis and aortic atherosclerosis is more than coronary atherosclerosis. Present study showed that the commonest pattern was one segment involvement. Anterior descending branch of the left coronary artery was most commonly affected. The proximal 2–3 cm of this vessel shows a special predilection for the development of atherosclerotic lesions. This study will help radiologists, interventional cardiologists and cardiothoracic surgeons to diagnose and treat angina and ischemia of heart.

Abbreviations: LAD: left anterior descending artery, LCX: left circumflex artery, RCA: right coronary artery.

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