A variety of agents have been shown to reduce mortality after an acute myocardial infarction (AMI), primarily beta blockers, aspirin and angiotensin-converting enzyme (ACE) inhibitors. Despite strong evidence of their effectiveness in preventing reinfarction, beta blockers are prescribed in fewer than 40 percent of patients following an AMI. Sarasin and colleagues evaluated the effectiveness of locally produced treatment guidelines in influencing the prescription of medications, particularly beta blockers, for secondary prevention of coronary artery disease following an AMI.

All patients over 20 years of age with a diagnosis of AMI on discharge were eligible for the study. The study was structured in two phases: a 12-month control period in which prescription patterns were monitored, followed by a six-month intervention period in which guidelines were presented and distributed to physicians. During the control period, physicians were unaware that their prescription patterns were being monitored. A local expert panel, including cardiologists and internists, developed the treatment guidelines based on published meta-analyses and randomized trials. These guidelines included information about relative and absolute risk reductions and number-needed-to-treat to prevent reinfarction, cardiac death or sudden death. The guidelines also specified that use of nitrates and calcium channel blockers did not reduce the risk of adverse events. Not only were the guidelines presented in lecture and grand rounds formats, they were also distributed to physicians and placed in the charts of all patients with a diagnosis of AMI. At the end of the study period, physicians completed a survey to assess their opinions about the clarity and effectiveness of the guidelines in influencing their prescription patterns. Demographic information was collected on all patients in the study, as well as information about comorbidities, including AMI.

After guideline implementation, prescription rates for nitrates decreased from 45 to 31 percent, whereas the rates for aspirin, ACE inhibitors and calcium channel blockers were not significantly changed. However, beta blocker use increased from 38 to 63 percent, and the combination of ACE inhibitors and beta blockers increased from 11 to 21 percent. Guideline implementation was judged to be an independent factor in the prescription of beta blockers. Sixty-three percent of the physicians felt that the presence of the guidelines in the patient's chart was important in influencing their medication choices, and 90 percent of the physicians were interested in similar guidelines on other topics.

The authors conclude that implementing guidelines developed by local experts and educating physicians about them increased beta blocker use in patients with AMI. Placing a copy of the guidelines in the patient‘s chart was highly successful in modifying prescription patterns.