The rise of evidence based medicine
Traditional medical teaching held that clinical experience, observation, and acumen would lead to optimal care for patients. Although these remain laudable goals, we now know that seemingly logical clinical insights may turn out to be seriously flawed when scientifically scrutinised. Two examples from the cardiovascular literature will illustrate the point.
In the 1950s, several cardiologists and surgeons logically presumed that they could improve the quality of life of patients with angina pectoris by shunting a greater percentage of the cardiac output through the coronary vessels. Surgeons began ligating the internal mammary arteries to force more oxygen rich blood to the myocardium. The belief that this would ameliorate chest pain was supported by early case series, in which patients experienced both symptomatic relief and improvements in exercise tolerance postoperatively. However, when the procedure was tested in a randomised trial comparing arterial ligation and sham surgery (in which the skin on the chest was incised but the arteries left intact), it quickly became evident that the benefits of the procedure were no greater than those obtainable with the surgical equivalent of a placebo.4 5
A second example concerns the proper management of patients with myocardial infarction. Cardiologists, noting that ventricular arrhythmias represented the most common cause of death immediately after myocardial infarction, reasoned that administering drugs to suppress these arrhythmias should improve survival. Testing this sensible theory in a placebo controlled trial yielded a disconcerting lesson: not only were class Ic antiarrhythmic agents ineffective, they were actually associated with an increased risk of death.6 Doctors soon accepted both sets of results; arterial ligation and postinfarction class Ic antiarrhythmic drugs were quickly eliminated from our therapeutic armamentarium.