Missed myocardial infarctions in ED patients prospectively categorized as low risk by established risk scores

Few studies have prospectively compared multiple cardiac risk prediction scores. We compared the rate of missed acute myocardial infarction (AMI) in chest pain patients prospectively categorized as low risk by unstructured clinical impression, and by HEART, TIMI, GRACE, and EDACS scores, in combination with two negative contemporary cardiac troponins (cTn) available in the U.S.

We enrolled 434 patients with chest pain presenting to one of seven emergency departments (ED). Risk scores were prospectively calculated and included the first two cTn. Low risk was defined for each score as HEART≤3, TIMI≤0, GRACE≤50, and EDACS≤15. AMI incidence was calculated for low risk patients and compared across scores using Χ² tests and C statistics.

The patients' median age was 57, 58% were male, 60% white, and 80 (18%) had AMI. The missed AMI rate in low risk patients for each of the scores when combined with 2 cTn were HEART 3.6%, TIMI 0%, GRACE 6.3%, EDACS 0.9%, and unstructured clinical impression 0%. The C-statistic was greatest for the EDACS score, 0.94 (95% CI, 0.92-0.97).

Using their recommended cutpoints and non high sensitivity cTn, TIMI and unstructured clinical impression were the only scores with no missed cases of AMI. Using lower cutpoints (GRACE≤48, TIMI=0, EDACS≤11, HEART≤2) missed no case of AMI, but classified less patients as low-risk.