Risk-stratification tools such as the HEART Score, EDACS score, and North American Chest Pain Rule may replace TIMI to evaluate patients with chest pain
Explore This IssueACEP Now: Vol 33 – No 04 – April 2014
Can you recite the elements of the TIMI Score—the Thrombolysis in Myocardial Infarction Risk Score for Unstable Angina/Non-ST Elevation Myocardial Infarction—from memory?1 If you still can, it’s not surprising. Over the last decade, this score has been drilled, dogmatically, into many specialties, including emergency medicine. Numerous studies have utilized it, attempting to define a low-risk cohort from unselected chest pain patients presenting to the emergency department. Fortunately for EM, but unfortunately for the brain cells sacrificially dedicated to its memory, the next wave of decision instruments promises to eliminate it from use.
The original TIMI Score is not derived from an emergency department cohort. These were patients admitted and anticoagulated for concerning chest pain in the setting of ECG changes, known coronary artery disease, or positive biomarkers. The original predictive value of the TIMI Score was intended to prognosticate 14-day mortality or new cardiac ischemia for cardiac inpatients, not emergency department presentations. The generalizability of this cohort to our setting is simply lacking, and the logistic regression identifies elements—aspirin use within seven days—that may add specificity for poor outcomes in an intermediate- to high-risk cohort but fails in providing utility for describing a minimal-risk cohort. As expected, the largest meta-analysis of prospective studies using TIMI in the emergency department demonstrated even requiring a TIMI of 0 for discharge is only 97.2 percent (95 percent CI, 96.4–97.8) sensitive for cardiac events.2 This strategy would result in 78 percent of patients being admitted for cardiac evaluation and still result in adverse outcomes for one in 50 discharged patients. Pursuing this strategy is clearly foolish.
The development of these ED-centric decision instruments and disposition pathways indicate EM has moved beyond the hand-me-downs from cardiology.
Fortunately, science marches on. From the Netherlands, the HEART (History, ECG, Age, Risk Factors, Troponin) Score was derived and designed for use in the emergency department.3 Reflecting several elements common to clinician gestalt, HEART demonstrates substantially improved performance over TIMI. When used as recommended by the authors, a HEART Score of 0 to 3 reflects a six-week event-free prognosis with a miss rate ranging between 0.6 percent and 1.8 percent in validation studies.4,5 At the same time, the number of patients classified as low risk increases to up to a third of the presenting cohort—an improvement that, by itself, ought to retire TIMI to its intended place on the inpatient side.