Adjusting therapy to cardiovascular risk status.

The ultimate goal of improving the assessment of cardiovascular risk is to improve cardiovascular management. In this context, cardiovascular management should be considered to include not only improvement in outcomes once symptomatic coronary disease is present (usually termed “secondary prevention”), but also prevention or delay of the onset of symptomatic coronary heart disease (CHD; or “primary prevention”). To make the transition from assessment of risk to clinical decision making, physicians must consider several critical issues. If interventions were free of both cost and side effects, it would not be necessary to target therapy to the level of risk. Economic and safety considerations, however, focus clinical attention on the delivery of therapy where it is most likely to be worthwhile in terms of both cost and safety. Such a strategy allows physicians to identify highrisk individuals, thereby targeting therapy to those patients, while simultaneously identifying low-risk individuals to avoid unnecessary or low-yield therapy. Risk assessment has traditionally been performed either intuitively or, more recently, by the use of relatively simple cut points. New technology as well as epidemiologic science have made global risk scoring more clinically practical. The use of global risk scores (1) increases awareness of the fact that risk is continuous and related to the overall number of risk factors; (2) allows adjustment for the severity of individual risk factors, such as lowdensity lipoprotein (LDL) cholesterol level and blood pressure; (3) allows the clinician to focus on the relative importance of different sources of risk; (4) emphasizes that the clinician must approach the patient as a whole and not be excessively distracted by individual risk factors when multiple factors coexist; and (5) promotes the development of risk-lowering strategies based on multiple components of an individual’s risk. Unfortunately, the largely successful targeted risk-factor approach directed at controlling hypertension, hyperlipidemia, and obesity has tended to promote a narrower clinical focus that may be appropriate for some individuals but is too restricted for others. Because the goal of any therapy does not end with the decision to institute a specific approach but with efforts to ensure a patient’s adherence to treatment, an assessment of cardiovascular risk status can be used for motivational purposes to enhance patient compliance and even to improve a physician’s enthusiasm as he or she recommends specific therapies. A recently published update of a coronary prediction model, based on the most recent follow-up data from the Framingham Heart Study, provides clinicians with userfriendly score sheets developed to predict CHD in men and women. Average CHD risk over 10 years, expressed as the percentage chance of experiencing an event, is derived through a point scoring system and incorporates measures of age, LDL cholesterol, total cholesterol, and high-density lipoprotein (HDL) cholesterol levels, systolic and diastolic blood pressure, and the presence or absence of diabetes and smoking. The 10-year risk for an assessed individual can then be compared with the average 10-year risk for a similarly aged person. This scoring system updates observations made more than 2 decades ago by the Framingham Heart Study, which recognized that both severity and number of risk factors contribute to total CHD risk. A number of potential difficulties must be considered, however, before the Framingham risk score sheets, or any other scoring system, can be widely used to guide treatment decisions. The term “risk” itself, for example, has different meanings and different statistical expressions that are often confusing to clinicians. Treatment decisions must be based not only on the level of risk before the initiation of treatment, but also on the anticipated reduction of that risk with a specific therapy. Although clinicians may estimate the extent to which risk may be reduced based on the results of contemporary clinical trials, how this risk reduction is expressed can have very different meanings. Absolute risk reduction is the difference (usually expressed as a percentage) between a specified event rate in the placebo and treatment groups of a trial, over a specified period of time. Relative risk reduction is the absolute risk reduction for a specified event, divided by the event rate in the placebo group. This can be expressed either as an odds ratio or as a percentage relative risk reduction. In population studies, either an “average” or a “low” risk rate may be substituted for the placebo rate, so that relative risk reduction can be understood as compared with either average or ideal. Relative risk reduction is often derived from a clinical trial’s primary endpoint and is often the only number that appears in media coverage of important studies. Absolute risk reduction, however, is a more clinically relevant assessment of what patients or their physicians might anticipate as a benefit of an applied therapy. Unfortunately, absolute risk reduction, expressed as a number, has much less impact than relative risk reduction and is intuitively more From the Department of Medicine, Preventive Cardiology, Cardiology Division, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA. Requests for reprints should be addressed to Richard C. Pasternak, MD, Cardiology Division, Bigelow 852, Massachusetts General Hospital, Boston, Massachusetts 02114.