Early diagnosis and risk stratification in patients with symptoms suggestive of acute coronary syndrome

Background: Chest pain is one of the most common symptoms in patients presenting to the emergency department (ED). Identifying the minority of patients with an acute coronary syndrome (ACS) is a challenge. The introduction of high-sensitivity cardiac troponin (hs-cTn T and I) assays has radically improved the assessment. The aim of this thesis was to evaluate four methods of assessing patients presenting with suspected ACS in the era of hs-cTn.

Methods and results: In Study I, we retrospectively evaluated the value of predischarge exercise ECG testing in 951 chest pain patients in whom myocardial infarction (MI) had been ruled out by means of hs-cTnT. We found no significant differences regarding death or MI between patients with a positive or a negative test, neither at 90 (n=1 [1.1%] vs. n=1 [0.2%]), nor at 365 days (n=2 [2.1%] vs. n=4 [0.7%]) of follow-up. In total, there were 9 (0.9%) deaths and 10 (1.1%) MIs within 365 days. The one-year rates of death (1.3%) and MI (0.5%) in a matched Swedish population were comparable.

Study II was a retrospective evaluation of the diagnostic sensitivity of an undetectable level of hs-cTnT at presentation, with and without information from the electrocardiogram (ECG), to rule out MI in a non-ST-segment elevation MI (NSTEMI) population presenting early. Twenty-four (2.6%) of the 911 early presenting NSTEMI patients initially had an undetectable level of hs-cTnT. In patients presenting >1–≤2 hours from symptom onset, the sensitivity for MI when combining hs-cTnT and ECG was 99.4% (95% confidence interval [CI] 98.4%–99.8%). In patients presenting ≤1 hour from symptom onset and in patients aged ≤65 years without prior MI, the sensitivity was insufficient. NSTEMI patients presenting with an undetectable level of hs-cTnT were younger but had a similar 30-day outcome to NSTEMI patients presenting with a detectable level of hs-cTnT.

In Study III, we retrospectively evaluated a one-hour hs-cTnT algorithm in 1,091 chest pain patients with a non-elevated hs-cTnT when presenting to the ED and examined early dynamic changes in hs-cTnT. Dynamic one-hour changes (Δ ≥3 ng/L) occurred in 23 patients (2.1%). Fifteen patients (65.2%) in the dynamic group were admitted, compared to 148 patients (13.9%) in the non-dynamic group (p<0.001). Four of the patients admitted (26.7%) in the dynamic and one (0.7%) in the non-dynamic group were diagnosed with an MI (p<0.001). No death or MI occurred within 30 days among those discharged from the ED.

In Study IV, we evaluated the clinical effects of implementing a one-hour hs-cTnT or I algorithm combined with the HEART score in a prospective observational before-after study including 1,233 patients at six centres. The new strategy was associated with a reduction in admission rate (59% to 33%, p<0.001, adjusted odds ratio [95% CI]: 0.33 [0.25–0.42]), median time to discharge (23.2 to 4.7 hours, p<0.001) and median health care-related costs (€1,651 to €1,019, p<0.001). The rates of death and MI were very low.

Conclusions: Rapid hs-cTn algorithms improve the prognostic assessment in patients with suspected ACS, making routine admission and predischarge exercise ECG testing redundant.

List of scientific papers

I. Ljung L, Sundqvist M, Jernberg T, Eggers KM, Ljunggren G, Frick M. The value of predischarge exercise ECG testing in chest pain patients in the era of high-sensitivity troponins. European Heart Journal Acute Cardiovascular Care. 2018;7(3):278–84.
https://doi.org/10.1177/2048872617690886

II. Ljung L, Reichard C, Hagerman P, Eggers KM, Frick M, Lindahl B, Linder R, Martinsson A, Melki D, Svensson P, Jernberg T. Sensitivity of undetectable level of high-sensitivity troponin T at presentation in a large non-ST-segment elevation myocardial infarction cohort of early presenters. [Submitted]

III. Pettersson A, Ljung L, Johansson C, Heilborn U, Jernberg T, Frick M, Eggers KM, Lindahl B, Linder R, Martinsson A, Svensson P. Experiences of a one-hour algorithm in chest pain patients with a non-elevated troponin T at presentation. Critical Pathways in Cardiology. 2018;17(1):6–12.
https://doi.org/10.1097/HPC.0000000000000138

IV. Ljung L, Lindahl B, Eggers KM, Frick M, Linder R, Löfmark HB, Martinsson A, Melki D, Sarkar N, Svensson P, Jernberg T. A rule-out strategy based on high-sensitivity troponin and HEART score reduces hospital admissions. [Submitted]