Predictive value of a 4-hour accelerated diagnostic protocol in patients with suspected ischemic chest pain presenting to an emergency department.

OBJECTIVES: Currently recommended risk stratification protocols for suspected ischemic chest pain in the emergency department (ED) includes point-of-care availability of exercise treadmill/nuclear tests or CT coronary angiograms. These tests are not widely available for most of the ED's. This study aims to prospectively validate the safety of a predefined 4-hour accelerated diagnostic protocol (ADP) using chest pain, ECG, and troponin T among suspected ischemic chest pain patients presenting to an ED of a tertiary care hospital in Oman.
METHODS: One hundred and thirty-two patients aged over 18 years with suspected ischemic chest pain presenting within 12 hours of onset along with normal or non-diagnostic first ECG and negative first troponin T (<0.010 μg/l) were recruited from September 2008 to February 2009. Low-probability acute coronary syndrome (ACS) patients at 4-hours defined as absent chest pain and negative ECG or troponin tests were discharged home and observed for 30-days for major adverse cardiac events (MACE) (Group I: negative ADP). High-probability ACS patients at 4-hours were defined by recurrent or persistent chest pain, positive ECG or troponin tests and were admitted and observed for in-hospital MACE (Group II: positive ADP).
RESULTS: One hundred and thirty-two patients were recruited and 110 patients completed the study. The overall 30-day MACE in this cohort was 15% with a mortality of less than 1%. 30-days MACE occurred in 8/95 of group I patients (8.4%) and 9/15 of the in-hospital MACE patients in group II. The ADP had a sensitivity of 52% (95% CI: 0.28-0.76), specificity of 93% (0.85-0.97), a negative predictive value of 91% (0.83-0.96), a positive predictive value of 60% (0.32-0.82), negative likelihood ratio of 0.5 (0.30-0.83) and a positive likelihood ratio of 8.2 (3.3-20) in predicting MACE.
CONCLUSION: A 4-hour ADP using chest pain, ECG, and troponin T had high specificity and negative predictive value in predicting 30-day MACE among low probability ACS patients discharged from ED. However, 30-day MACE in ADP negative patients was relatively high in contrast to guideline recommendations. Hence, there is a need to establish ED chest pain unit and adopt new protocols especially adding a point-of-care exercise treadmill test in the ED.