ED Protocol Pegs Low-Risk Cardiac Patients Quickly

An accelerated diagnostic protocol in the emergency department identified a sizable group of symptomatic patients who were at low risk of having a short-term major cardiac event and who could be safely discharged, according to an observational study.

Assessment with a combination of Thrombolysis In Myocardial Infarction (TIMI) score, electrocardiogram, and baseline plus 2-hour troponin levels had a sensitivity of 99.7% (95% CI 98.1 to 99.9) and a specificity of 23.4% (95% CI 21.4 to 25.4) for identifying patients at low risk, according to Martin Than, MBBS, of the University of Otago in Christchurch, New Zealand, and colleagues.

In addition, the negative predictive value of the diagnostic protocol was 99.7% (95% CI 98.6 to 100) and the positive predictive value was 19% (95% CI 17.2 to 21), Than and colleagues reported in the June 5 Journal of the American College of Cardiology.

Chest pain represents the second most frequent complaint in the emergency department, and patients typically have an extensive work-up. This contributes to department overcrowding and possible adverse outcomes. Yet only 15% ultimately receive a diagnosis of acute coronary syndrome.

Because there is a need for a way of identifying patients at lowest risk who could be released quickly and followed closely on an outpatient basis, the researchers considered the suitability of a predefined rapid assessment protocol that required a TIMI risk score of zero, no new ischemic findings on ECG, and cardiac troponin (cTn) levels below the hospital's established cutoff.

They enrolled 1,975 patients, most of whom were older white men. Many had risk factors such as a history of coronary artery disease, hypertension, and dyslipidemia.

During the 30 days after initial presentation, 15.3% of the cohort experienced an event such as acute myocardial infarction, cardiac arrest, serious ventricular arrhythmias, or death.

The risk stratification protocol used determined that 20% of patients were at low risk for an event, and only one of these patients actually experienced a major cardiac event during the month after evaluation, according to Than's group.

This man had presented with chest pain, a normal ECG, and troponin levels below 0.01 µg/L at baseline, 0.03 µg/L 2 hours later, and 16.8 µg/L at 12 hours.

Angiography revealed stenosis of the right coronary and circumflex arteries; a stent was placed and the patient remained cardiac disease-free for the subsequent year.

The investigators also looked at the efficacy of the individual components for predicting an event, and found that TIMI score plus ECG findings alone missed five cases, while inclusion of baseline and 2-hour troponin concentrations identified four of these successfully.

A majority of the patients who were considered low risk did undergo further diagnostic evaluation - most commonly stress tests - during the subsequent month, with interventions in slightly more than 20%.