Background: A small percentage of patients who present to the emergency department are discharged despite meeting criteria for acute myocardial infarction (MI), which can result in increased morbidity and mortality.

In the ambulatory care setting, the diagnosis of acute MI provides more of a challenge because of the lack of diagnostic testing. In primary care, the missed diagnosis of acute MI is one of the leading reasons for malpractice litigation. Currently, there are no studies that evaluate how often patients with acute MI were examined in the ambulatory setting before hospitalization. Sequist and associates assessed the number of patients with acute MI and no history of CHD who were evaluated by primary care professionals before the event. They also assessed prediction tools for the ability to identify patients at risk.

The Study: The study was a case-control evaluation of patients from 14 ambulatory health centers. The patients had no previous CHD and were admitted to acute care facilities with the diagnosis of acute MI. Those who met the study criteria were divided into three groups: (1) missed opportunity (i.e., outpatient visit within 30 days of the event and not sent to emergency department); (2) qualified outpatient visit and sent to emergency department; and (3) no outpatient visit within 30 days of the event. Missed opportunities were defined as those patients who presented with nontraumatic chest pain, dyspnea, shoulder pain, jaw pain, epigastric pain, upper back pain, or dizziness. A control population was identified for comparison to the study group.

Three prediction models were used to calculate risk of MI: (1) the Framingham risk scoring system, which uses age, sex, blood pressure, cholesterol levels, smoking status, and diabetic status; (2) the Diamond and Forrester model, which uses chest pain characteristics; and (3) the Goldman prediction tool, which uses age, electrocardiographic (ECG) changes, and symptoms.

Results: Of the 966 patients in the study population, 261 were evaluated by a primary care professional for chest pain or anginal equivalent within 30 days of an acute MI. Of this group, 155 were sent directly to the emergency department, and 106 (11 percent of the total population) were classified as missed opportunities. The most common presenting symptoms included chest pain (50 percent), shoulder pain (31 percent), and dyspnea (26 percent). If patients had a risk score of 10 percent or greater using the Framingham system, they were more likely to fall into the missed opportunity category (odds ratio = 19.5; 95% confidence interval, 9.3 to 40.6). Patients with increased scores on the Diamond and Forrester model and the Goldman prediction tool were also more likely to be in the missed opportunity group.

Patients in the missed opportunity group who also had a Framingham risk score of 10 percent or greater were given the diagnosis of possible angina 33 percent of the time, and ECG was performed 51 percent of the time. Two common alternative diagnoses given were musculoskeletal pain (25 percent of cases) and gastro-esophageal reflux (18 percent of cases).

Conclusion: The authors conclude that primary care physicians have an important role in the diagnosis of acute MI and can reduce the number of missed opportunities. They add that the Framingham risk scoring system can be used to identify patients at high risk of CHD as well as those who need further cardiac evaluation.