The combination of TIMI score of zero at presentation, no new ischemic changes on initial electrocardiogram, and negative troponin results at zero and 2 hours had a sensitivity of 99.7%.

In a prospective observational study of 1975 patients who presented to two hospitals in Australia and New Zealand with chest pain suggestive of acute coronary syndrome, researchers assessed whether or not an accelerated diagnostic protocol could identify patients at low risk for major adverse cardiac events within 30 days. Patients with ST segment elevation on initial electrocardiogram (ECG) were excluded. Patients received usual care, including serial troponin testing, in accordance with international guidelines; each hospital used its standard troponin test.

The protocol consisted of a Thrombolysis in Myocardial Infarction (TIMI) score at presentation, initial ECG results, and troponin I concentrations at zero and 2 hours; patients with a TIMI score of zero, no new ischemic changes on initial ECG, and negative troponin results at zero and 2 hours were deemed low risk.

Major adverse cardiac events (acute myocardial infarction, death, cardiac arrest, cardiogenic shock, emergency revascularization, and ventricular dysrhythmia requiring intervention) occurred in 302 patients (15%), usually within 10 days. The protocol identified 392 patients (20%) as being low risk; one of these patients (0.25%) had a major cardiac event (myocardial infarction diagnosed on the basis of an elevated troponin result at 12 hours). The sensitivity and negative predictive value of the protocol for identifying patients with major adverse cardiac events were both 99.7%, and the specificity was 23.4%.

Comment: This study begs for a randomized trial in which low-risk patients are actually sent home, but such a study is unlikely to ever be conducted. The study’s strength is its use of current (i.e., not highly sensitive) troponin assays from two different manufacturers. These findings support institutions developing internal protocols to efficiently evaluate patients with low-risk chest pain. Developers of such protocols should recognize that most patients will require further testing, such as exercise tolerance testing, to exclude ischemia.

Source: Journal Watch Emergency Medicine