Coronary Heart Disease: Reducing the Risk

Abstract

Coronary heart disease (CHD) is the most common cause of death in most developed countries. Clinical complications of CHD lead to substantial disability and are a major source of the rising cost of health care. While the incidence of CHD is decreasing in Western Europe, the USA and Australia, it is sharply increasing in Central and Eastern Europe and to some extent, in Asia and Africa. Worldwide, therefore, the need for effective strategies to prevent CHD has never been greater. In the last decade, much has been learned about strategies for CHD prevention at the population level and in the individual patient. During this time, the results of major trials of lipid-lowering in patients with and without CHD have become available. Also, data from long-term epidemiological studies such as the Munster Heart Study has led to formulation of the concept of global risk, i.e. the idea that calculation of a person's chance of developing CHD must take into account all of the variables which have been shown to make an independent contribution to risk. Since risk factors interact in a multiplicative rather than a simple additive fashion, calculation of global risk is best undertaken using mathematical algorithms such as those derived from the Munster Heart Study or the Framingham Heart Study. The Munster algorithm is available in interactive fashion on the Task Force website at http://www.chd-taskforce.com and is reported in detail in the text. Alternatively clinical assessment may be used to assign the patient to a category of acceptable risk or to one of three categories of increased risk (small increase, moderate increase, high risk). This document gives detailed consideration to various risk factors for CHD. Age, sex and a personal and family history of CHD are non-modifiable risk factors. The risk factors hypercholesterolaemia, hypertension and cigarette smoking are common in the general population and are amenable to treatment. Low levels of HDL-cholesterol are also regarded as a risk marker for CHD. Other modifiable variables which should be taken into account in assessing risk of CHD include body weight, the presence of diabetes mellitus and the patient's degree of physical activity. More recently, a large body of evidence has accumulated on a link between increased circulating levels of triglyceride, lipoprotein(a) (Lp(a)), and fibrinogen and greater risk for atherosclerosis of the coronary arteries. Recent research has also highlighted the importance of the metabolic syndrome as a common predisposing factor in the development and progression of atherosclerosis. This condition is characterized by central obesity, hyperinsulinism, impaired glucose tolerance, mixed dyslipidaemia, hypertension and hyperuricaemia. Peripheral resistance to the action of insulin appears to be the central feature of this condition. Other variables under investigation as CHD risk factors include blood levels of coagulation factor VIIc, plasminogen activator inhibitor I (PAI-I), and homocysteine. A new area of research is directed towards the detection of polymorphisms or mutations in genes potentially affecting risk of CHD. Further, attention has recently been given to increased susceptibility of low density lipoprotein (LDL) to oxidation as a risk factor for CHD. Finally, areas of current research which may well lead to the identification of further risk factors for CHD include investigation of the function of the endothelium, studies of factors governing the stability of the atherosclerotic plaque and the studies of the predictive value of circulating markers of inflammation. These newer risk factors are described in greater detail in the text. The relationship between nutrition and CHD is now well established based on epidemiological findings in populations and nutritional intervention trials, and diet remains the cornerstone of treatment of hyperlipidaemia. The adoption of a suitable diet by population as a whole is also an important component of strategies for reducing the incidence of CHD. In patients in whom diet alone fails to achieve target levels, lipid-lowering drugs should be used. The efficacy and long-term safety of the statin drugs has been confirmed in numerous long-term studies. Because of their greatly increased risk of suffering a myocardial infarction, patients with established atherosclerosis should be treated with particular care (secondary prevention). In this document, target levels for lipids are given and it is suggested that the intensity of treatment should depend on the patient's global risk of CHD. Patients with CHD often stiffer from stroke and vice versa. Since stroke and CHD share many risk factors, strategies to reduce the incidence of CHD incidence will also lessen that of stroke. The International Task Force for Prevention of Coronary Heart Disease hopes that general practitioners, cardiologists and all those involved in the management of patients at increased risk of CHD will find this document useful. We also hope that the information contained herein will help to provide the scientific rationale for the design of effective and efficient strategies to prevent CHD throughout the world.