For patients with suspected acute myocardial infarction (AMI), adding clinical judgment and electrocardiogram (EKG) findings to high-sensitivity cardiac troponin (hs-cTn) measurement improved identification of unstable angina but reduced rule-out of AMI.
The multicenter study included 3,123 patients presenting to an ED with suspected AMI. Its goal was to test the hypothesis that adding clinical judgment and EKG findings to the European Society of Cardiology hs-cTn measurement at presentation and after one hour (ESC hs-cTn 0/1 h algorithm) would improve prediction of major adverse cardiovascular events (MACE) within 30 days. MACE was defined as all-cause death, cardiac arrest, AMI, cardiogenic shock, sustained ventricular arrhythmia, and high-grade atrioventricular block. Results were published by JACC on Aug. 12.
AMI was ruled out in significantly more patients when the algorithm, using a troponin T measurement, was applied alone compared with the algorithm plus judgment and EKG (60% [95% CI, 59% to 62%] vs. 45% [95% CI, 43% to 46%]; P<0.001). Rates of MACE within 30 days were similar in these ruled-out groups (0.6% [95% CI, 0.3% to 1.1%] vs. 0.4% [95% CI, 0.1% to 0.9%]; P=0.429), resulting in a similar negative predictive value (99.4% vs. 99.6%; P=0.097). The ESC hs-cTn 0/1 h algorithm ruled in fewer patients (16% [95% CI, 14.9% to 17.5%] vs. 26% [95% CI, 24.2% to 27.2%]; P<0.001), and it had a higher positive predictive value (76.6% vs. 59%; P<0.001). When unstable angina with revascularization within 24 hours was added to MACE as an outcome, the hs-cTn 0/1 h algorithm had a higher positive predictive value for rule-in, whereas the algorithm plus judgment and EKG had a higher negative predictive value for rule-out. Results were similar when troponin I was used.
There is controversy about how to manage patients whose ESC hs-cTn 0/1 h results indicate that AMI should be ruled out, but either their EKGs or the visual analog scale for acute coronary syndrome suggests otherwise, and this is particularly tricky if their troponin results are negative at three hours, the study authors noted. “The low but not very low risk of MACE observed in these patients in this large study should provide for joined informed decision-making by the physician and the patient,” they wrote.
Although overall the algorithm alone “better balanced efficacy and safety in the prediction of MACE,” detecting unstable angina is also “of considerable importance,” and the study shows that adding clinician judgment and EKG can be valuable for this, the authors said. The study was limited by its inclusion of only ED patients with symptoms suggestive of AMI, all of whom could provide informed consent and none of whom were on chronic dialysis, the authors noted.
An accompanying editorial comment noted that the patients were also younger than those in other studies of suspected acute coronary syndrome and that accuracy of the algorithm alone might have been lower if the patient population were broader. The study's results do reinforce the accuracy of the algorithm, but thorough assessment of a patient's history and EKG is also still essential, the editorialists said.