Improving Early Risk Stratification in Patients Presenting to Emergency Departments With Undifferentiated Chest Pain

Chest pain is one of the most common complaints in patients presenting to emergency departments (ED) globally, representing 2.5% of all ED presentations in Hong Kong. Acute coronary syndrome (ACS) cannot be immediately excluded in the majority of patients presenting with chest pain, and is confirmed in about 15-25% cases. The current evaluation of patients in most EDs is a lengthy process that involves serial ECGs and troponin tests taken 3-6 hours apart. However, challenges over ED crowding and the need for acceptable risk stratification have prompted the search for safe, cheap, but effective accelerated chest pain pathways.

An ever increasing evidence base is emerging from emergency departments in different geographical settings, using different combinations of clinical assessment tools, more rapid biochemical tests and variable outcomes. While making an accurate diagnosis is clearly important, from the patients' perspective it is more important to minimize the risk of adverse events. Therefore, the identification of tools which allow risk stratification to permit very low risks of MACE is more clinically relevant to ED specialists than the precise diagnostic label applied to the patient.

In the Asia-Pacific region a 2-hour diagnostic protocol involving serial point-of-care biomarkers, such as troponin I, creatine kinase MB, and myoglobin, combined with electrocardiograph (ECG) changes and a Thrombolysis in Myocardial Infarction (TIMI) score has been shown to safely exclude 30-day MACE in low risk patients with chest pain. Highly sensitive troponin T (hs-cTnT) and troponin I (hs-cTnI) perform well in the early diagnosis of acute myocardial infarction (AMI), non-ST elevation myocardial infarction (NSTEMI) and in the prediction of two year mortality. Undetectable levels of hs-cTnT alone at initial blood testing appears to rule-out 60-day NSTEMI with a negative predictive value of 94% and a sensitivity of 90%. A TIMI score incorporating hs-cTnT was no better at predicting 30-day MACE than front-door TIMI alone without measurement of biomarkers, but the value of a TIMI score of zero in ruling-out low risk patients was not demonstrated.

Despite evidence favouring early rule out pathways, there is still a need for further validation and refinement of such tools using different diagnostic pathways, in other clinical settings, and with other clinical tools such as HEART.

In this study we aimed firstly to evaluate the effectiveness of a combined use of an early modified TIMI score with hs-cTnT and a modified HEART score to rule out MACE in 30 days. Applying this protocol in clinical practice has the potential to reduce ED waiting times, ED crowding and hospital admission rates for chest pain patients.