Coronary Artery Disease Prevention: As Easy As 1, 2, 3?

to the editor: When reading the cover article on coronary artery disease (CAD) in the February 1, 2010, issue of American Family Physician, I first felt appreciation, then frustration. Throughout the article, the authors wrongly characterize CAD prevention following myocardial infarction (MI) or revascularization as secondary prevention, whereas it should be tertiary prevention. Imprecision in terminology may be contributed by the article's cited literature^1,2 that likewise gets it wrong. The error is worth correcting.

Prevention can and should be divided into three stages: primary, secondary, and tertiary.³ Primary prevention represents the earliest possible interventions to foil disease before it begins. For CAD, this includes measures that prevent atherosclerotic plaques from ever developing. Secondary prevention includes early detection and halting the progression of established but asymptomatic disease. For CAD, this includes taking measures to prevent cardiovascular symptoms (e.g., dyspnea), damage (e.g., ventricular dysfunction), and events (e.g., acute coronary syndromes). However, once such symptoms, damage, or events occur, it is too late for secondary prevention. At this point, the only option is to try to rein in further disease progression with tertiary prevention. Tertiary prevention involves slowing, arresting, or reversing disease to prevent recurrent symptoms, further deterioration, and subsequent events. It is this type of prevention that the authors discuss primarily in their article.

Examples of tertiary prevention include percutaneous coronary intervention and coronary artery bypass grafting. These interventions are only for patients with established symptoms, objective dysfunction, or a history of events. Percutaneous coronary intervention and coronary artery bypass grafting are not examples of secondary prevention. Other interventions described by the authors could represent prevention that is either tertiary or secondary— or even primary (e.g., physical activity, weight and dietary management, tobacco cessation). Overlap in the appropriateness of different interventions at different stages of disease contributes to the muddled distinctions among the stages of prevention. Indeed, the authors, like the statements from the American Heart Association they cite,^1,2 seem to combine secondary and tertiary stages of prevention under the imprecise umbrella term, “secondary prevention.” Such imprecision is dangerous.

To illustrate the danger, consider the case of beta blockers. The authors duly note that, “Multiple clinical trials have shown that beta-blocker therapy can reduce recurrent MI, sudden cardiac death, and mortality in patients after MI,” (i.e., beta blockers for tertiary prevention). However, at least two meta-analyses of clinical trials have suggested that beta blockers may lead to an increased risk of cardiovascular events and death in patients with hypertension who have not already had an MI (i.e., beta blockers for secondary prevention).^4,5 Thus, recommending beta blockers for “secondary prevention” might do harm if it is unclear whether secondary or tertiary prevention is actually meant. For family physicians, distinguishing between secondary and tertiary prevention should be a primary concern.

EDITOR’S NOTE: Although Dr. Lucan’s definitions of secondary and tertiary prevention are consistent with primary care usage, including that of the U.S. Preventive Services Task Force,¹ other physicians often use “secondary prevention” to refer to reducing the risk of recurrences of disease-related events, such as myocardial infarction,² stroke,³ and osteoporotic fracture.⁴ Dr. Lucan’s observation that failing to precisely define what is meant by secondary prevention may occasionally lead to unnecessary, and potentially harmful, confusion is well taken. Toward this end, we will aim in future articles of this type to be clearer about what is being prevented and the population to whom the interventions apply.