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

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.

The next step in ED-centric decision-instrument development may come from New Zealand and Australia, with the Emergency Department Assessment of Chest Pain Score (EDACS).⁶ This score incorporates many of the same elements seen in the HEART Score but at a more detailed and granular level. Rather than each of the five elements being awarded up to two points, the EDACS breaks age, coronary disease, and signs and symptoms into myriad additive and subtractive elements. The advantage of this is greater specificity. In the original derivation and validation cohort, it was used in conjunction with zero-hour and two-hour troponin measurements to classify nearly 50 percent of the cohort as low risk, with a sensitivity greater than 99 percent. The downside: get out your calculator. While not nearly as bad as the GRACE (Global Registry of Acute Coronary Events) Score, this decision instrument approaches the complexity limit for clinical acceptability. Increasing availability of computerized decision support potentially decreases the resultant cognitive strain, but this remains a limitation. Prospective validation of the EDACS-Accelerated Diagnostic Protocol is under way in Europe and North America.

Most important, however, the development of these ED-centric decision instruments and disposition pathways, along with the North American Chest Pain Rule, indicate emergency medicine has moved beyond the hand-me-downs from our cardiology brethren. Not only is it time for TIMI to be retired, it’s likely time to reconsider the relevance of the other American Heart Association recommendations for the evaluation of acute nonspecific chest pain in the emergency department. Universal recommendations for early provocative or anatomic testing are discordant with the reality of our resource-limited settings, and a recognition of the harms of false positives further informs the need for practice evolution. ACEP should support emergency physicians utilizing these prospectively derived risk-stratification tools for early disposition of patients from the emergency department, specifically to address the medical legal fallout from moving to a rational, but not “zero miss,” strategy. We’ve gone too far down the rabbit hole, but there may yet be light at the end of the tunnel.

Dr. Radecki is assistant professor of emergency medicine at The University of Texas Medical School at Houston. He blogs at Emergency Medicine Literature of Note (emlitofnote.com) and can be found on Twitter @emlitofnote.

References

1. Antman EM, Cohen M, Bernink PJ, et al. The TIMI risk score for unstable angina/non-ST elevation MI: A method for prognostication and therapeutic decision making. JAMA. 2000;284:835-842.
2. Hess EP, Agarwal D, Chandra S, et al. Diagnostic accuracy of the TIMI risk score in patients with chest pain in the emergency department: a meta-analysis. CMAJ. 2010;182:1039-1044.
3. Six AJ, Backus BE, Kelder JC. Chest pain in the emergency room: value of the HEART score. Neth Heart J. 2008;16:191-196.
4. Six AJ, Cullen L, Backus BE, et al. The HEART score for the assessment of patients with chest pain in the emergency department: a multinational validation study. Crit Pathw Cardiol. 2013;12:121-126.
5. Backus BE, Six AJ, Kelder JC, et al. A prospective validation of the HEART score for chest pain patients at the emergency department. Int J Cardiol. 2013;168:2153-2158.
6. Than M, Flaws D, Sanders S, et al. Development and validation of the Emergency Department Assessment of Chest pain Score and 2 h accelerated diagnostic protocol. Emerg Med Australas. 2014;26:34-44.