Coronary artery disease in Asian Indians.ME Yeolekar
Department of Internal Medicine, Lokmanya Tilak Municipal Medical College & General Hospital, Mumbai.
Correspondence Address: Source of Support: None, Conflict of Interest: None PMID: 0010703565
Source of Support: None, Conflict of Interest: None
Coronary Heart Disease should new be considered an important public health problem in India. It is a part of the epidemiological transition characterized by changing lifestyles and a probable genetic predisposition. The interplay of factors with regards to their existence, causality and attributable weight-age needs to be understood in the context of management of an individual patient as well as strategic planning for control and prevention.
Keywords: Age Factors, Body Weight, Coronary Disease, blood,epidemiology,prevention &control,Human, India, epidemiology,Lipids, blood,Risk Factors,
World Health Organization has predicted that by A.D. 2020 up to three quarters of deaths in developing countries would result from non-communicable diseases and that coronary heart disease (CHD) will top the list of killers. CHD is considered an important public health problem not only in the developed countries but also in developing countries like India. With changing lifestyle in developing countries like India, particularly in urban areas, chronic and degenerative disease (e.g. CHD) are making an increasingly important contribution to mortality statistics of such countries. Data also indicate that epidemiological transition, which is characterized by ageing and changing lifestyles, which culminate in an epidemic of hypertension and coronary heart disease, is rapidly occurring in the developing countries. Reports of well planned community-based studies and clinical investigations have emphasized the magnitude of the problem. Epidemiological studies over a period of the last 30 years have identified risk factors, which predispose an individual to coronary atherosclerosis. These studies have also shown that bulk of coronary heart disease is preventable or at least its occurrence can be delayed. Public health planning in most developing countries has focused mainly on problems related to communicable diseases, which in the past have been responsible for high morbidity and mortality. During the past three decades, some epidemiological studies have been conducted in India for evaluating the prevalence of CHD. A majority of these studies have been confined to hospitals, select groups of population, or the sample size was too small, making it rather difficult to draw any valid conclusions about the prevalence of CHD and its risk factors. It is believed that while community-based data are relevant for prevalence, for definitive diagnosis sources such as from either proven myocardial infarction or selective coronary arteriography are essential to obtain data on persons with confirmed diagnosis of CAD.
Religion, culture, language, climate and geography all confer particular ethnic characteristics to people in the Indian subcontinent. In most countries, in the rest of the world, these factors influence dietary habits to a great extent, and will do so in Indians too. The difficulties in seeking a unifying hypothesis that embraces and explains the increased prevalence of CHD originating from the Indian subcontinent are obvious. Lack of standardization of laboratory assays and epidemiological methods is one important reason. The high rates of CAD in Asian Indians appears to be a global phenomenon, shared by the inhabitants of the four countries of the Indian subcontinent (India, Pakistan, Bangladesh and Sri Lanka) as well as immigrants from these countries to various regions of the world. Those living in the urban areas of the Indian subcontinent have CAD rates similar to Indians living overseas. The CAD rates in rural India are one-half that of urban India, though smoking is more common in Indian villages.
Asian Indians appears to have a unique pattern of dyslipidaemia, a 'deadly lipid tetrad’. This lipid tetrad consists of elevated Lp(a) in combination with the lipid triad. This lipid tetrad is rarely seen in other populations in epidemiological studies. However, this combination is frequently seen in patients with severe CAD and in those who have had poor outcomes from repeated PTCA, CABG or heart transplants Atherosclerosis in young Asian Indians and their high morbidity and mortality from CAD can be attributed to the tetrad.
A comprehensive Lipid Tetrad Index has been described as the single best predictor of CAD risks in diverse populations, especially Asian Indian. This index reflects the total burden of dyslipidaemia and is derived by multiplying the three lipids directly associated with CAD and dividing the product by HDL, which is inversely associated [total cholesterol x triglycerides x Lp(a)/HDL]
The aetiology of CHD is multifactorial and certainly there is no shortage of risk factors that are associated with CHD. They range from mystifying ear lobe creases and residence in hard water areas to established risk factors such as smoking and hypercholesterolaemia. The large numbers of studies carried out in the areas of causation of CHD have improved the ability to stratify risk in a clinical setting.
Homocysteine is recognized as a risk factor for CHD and its levels are of prognostic value in patients with established CHD. There is indirect evidence to suggest that chronic infections such as Helicobacter pylori, cytomegalovirus, herpes viruses, chronic dental or gingival sepsis, and Chlamydia pneumonias, may predispose to CHD. The epidemiological evidence for Chlamydia pneumonias and vascular disease is strong and the organism is able to infect human smooth muscle cells, endothelial cells and macrophages.
The metabolic syndrome does not occur uniquely in people of Indo-origin. So is the metabolic syndrome a result of Neel's thrifty genotype. Whatever the 'genes' for diseases of civilization, they are bound to have been part of a normal genotype once upon a time. What specific type of malnutrition is responsible is not entirely clear but animal studies suggest that poor maternal protein intake or the ratio of protein to energy intake may be to blame.
Before all people of Indo-origin are labelled 'prone to CHD' there is a need to collect more information. Urbanisation and cross-country migration seem to produce similar changes in lifestyle. Both cause an increase in body mass index, increases in serum cholesterol, a lower HDL cholesterol, a higher blood glucose, and increases in blood pressure. Conventional risk factors are as important in people of Indo-origin as in any other population. As Indians live longer with improved conditions and greater economic prosperity, the pattern of disease will change to that of diseases of developed countries. There will always be a movement of people from rural to urban areas and it is very likely that at some risk factors for CHD will also increase in the semi-rural areas: What matters most is that the clinician takes into account the entire profile of the patient in front of him rather than considering the status of the coronary vasculature aid a few fairly well known risk factors for the comprehensive management and adequate steps for the secondary/tertiary prevention. Further the policy maker and the public health strategist will have to well understand the complexity and intricacy of the host of factors that may operate in the Indian context. A flow chart should be of adequate help to understand the inter relationships of the various factors in the socio-economic and time frame [Figure - 1].
Suffice to say that much can be achieved in terms of reduction of early deaths and morbidity associated with coronary artery disease in the Indians with a sound understanding of clinical epidemiology and concerted action towards known factors.
[Figure - 1]