Clinical Use of High-sensitivity Cardiac Troponin in Patients With Suspected Myocardial Infarction

Raphael Twerenbold, MD; Jasper Boeddinghaus, MD; Thomas Nestelberger, MD; Karin Wildi, MD; Maria Rubini Gimenez, MD; Patrick Badertscher, MD; Christian Mueller, MD


J Am Coll Cardiol. 2017;70(8):996-1012. 

In This Article

What to Do in the Observe Zone?

Although some rapid strategies provide guidance for rule-out only, 4 strategies also provide detailed guidance for rule-in of MI. In addition to the rule-out and rule-in zone, these strategies leave up to one-third of patients in an observe zone.[24,34,35,52,53,55,62] Although patients' management is largely defined and simplified in patients assigned to rule-out and rule-in, it remains highly personalized and sometimes challenging in those assigned to the observe zone. These patients are typically elderly men with pre-existing CAD and were shown to have increased long-term mortality.[63] Detailed clinical assessment, additional hs-cTn measurement at 3 h, and cardiac imaging are integral for accurate diagnosis in these patients. The clinical interpretation of mildly abnormal hs-cTn levels is crucial for physicians in the ED due to the fact that still up to one-third of patients triaged to the observe zone are finally diagnosed with MI or UA. Therefore, further serial hs-cTn retesting at 3 h should be performed to better differentiate an acute cardiac disease (such as MI) associated with a dynamic hs-cTn course, from a chronic cardiac disease reflected by a stable hs-cTn course. Depending on the clinical picture and the course of hs-cTn during serial sampling, coronary angiography (in those with high likelihood for MI), echocardiography, and functional stress imaging (in those with low likelihood for MI) seem to be the preferred tests in observe-zone patients.[62]

Due to the characteristics of patients in the observe zone with their high prevalence of pre-existing CAD, coronary computed tomography angiography (CCTA) seems a suitable imaging modality in only a minority.[64] A randomized controlled trial recently investigated whether a diagnostic strategy supplemented by routine early CCTA is superior to standard optimal care encompassing hs-cTnT in patients with suspected ACS in the ED. It showed no benefit of routine CCTA use regarding identification of significant CAD requiring revascularization within 30 days, duration of hospital stay, or direct discharge from the ED.[65] Functional instead of anatomic testing is mandatory to differentiate coronary lesions resulting in myocardial ischemia and acute chest pain at rest from lesions that are innocent bystanders regarding the acute chest pain episode leading to ED presentation.[63]