BOSTON – A simple, validated rule based on age and presenting symptoms was highly sensitive at identifying which emergency department patients need an immediate triage 12-lead ECG to identify ST-segment elevation myocardial infarction in a study population of more than 3 million patients.
According to current guidelines from the American College of Cardiology and the American Heart Association, "ECG should be performed within 10 minutes of ED arrival for all patients with chest discomfort or other symptoms suggestive of STEMI" (Circulation 2004;110:588-636). "These are common-sense guidelines, but we often get caught up in the latter part," said Dr. Seth Glickman of the University of North Carolina at Chapel Hill, noting that about one-third of patients with STEMI do not have a complaint of chest pain.
The study data came from a statewide public health surveillance system in North Carolina comprising about 8.1 million ED visits from 2007-2008. The patients were divided into a derivation cohort in 2007 and a validation cohort in 2008. After the exclusion of those aged 18 years or younger, those with missing data, and all injury, bleeding, or pregnancy-related visits, the final data set included 1,685,633 visits in 2007 and 1,889,545 in 2008.
Of the 6,464 STEMI patients, 78% presented with chest pain. However, this varied dramatically by age. Although more than 90% of the 18- to 49-year-old group diagnosed with STEMI had chest pain, only 53% of those aged 80 years and older did. In contrast, the frequency of other chief complaints increased steadily with age, including dyspnea, syncope, weakness, abdominal pain, and altered mental status, Dr. Glickman said.
Using those factors, the investigators derived the following simplified rule: Immediate ECG is required for patients aged 30 years and older with chest pain; those aged 50 years and older with shortness of breath, altered mental status, upper extremity pain, weakness, or syncope; and patients aged 80 years and older. The rule is meant to identify those who should be prioritized for immediate ECG, not the total group of patients who may ultimately receive one, Dr. Glickman noted.
In the validation cohort, this rule was 92.7% sensitive (95% confidence interval, 91.8-93.5), was 74% specific (CI, 74.0-74.1), had a positive predictive value of 0.62% (CI, 0.60-0.64), and had a negative predictive value of 99.98% (CI, 99.98-99.98).
Regarding the 80-plus population, "clearly, there’s an opportunity to use clinical judgment in the rule. But on the flip side, I can say that the chief complaints of the advanced elderly who are diagnosed with STEMI are so across the map that it is challenging to develop a more specific rule," he said, adding that he and his associates are working on incorporating other elements into the model such as abdominal pain and nausea, which are also common complaints in very elderly patients.
In response to an audience member’s question about gender, Dr. Glickman said that they tried the rule with and without gender and it performed similarly, despite the fact that women are less likely to present with chest pain. "The real dominant factor in the model was age, which trumps gender across the entire spectrum. We thought it would be a lot easier to implement a rule that wasn’t gender-specific in the ambulance or the triage setting."
This study was funded by the American Heart Association Pharmaceutical Roundtable, the Robert Wood Johnson Foundation, the North Carolina Bio-Preparedness Collaborative, and Department of Homeland Security Office of Health Affairs. Dr. Glickman stated that he had no other personal disclosures.