Direct comparison of cardiac troponin I and cardiac troponin T in the detection of exercise-induced myocardial ischemia

Background: It is unknown, whether cardiac troponin (cTn) I or cTnT is the preferred biomarker in the detection of exercise-induced myocardial ischemia.

Methods: We investigated patients with suspected myocardial ischemia referred for exercise or pharmacological rest/stress myocardial perfusion single-photon emission computed tomography (SPECT) to directly compare the diagnostic accuracy of high-sensitivity cTnI (hs-cTnI) and hs-cTnT. Diagnostic performance was analyzed separately according to stress modality. Hs-cTnI and hs-cTnT were measured before, immediately after, as well as 2h and 4h after maximal exercise in a blinded fashion. Further, all clinical information available to the treating cardiologist was used to quantify the clinical judgment regarding the presence of myocardial ischemia using a visual analog scale twice: once prior and once after stress-testing. The presence of stress-induced myocardial ischemia was adjudicated using SPECT combined with coronary angiography findings.

Result: A total of 403 consecutive patients were enrolled in our study, of which 229 underwent exercise stress and 174 patients pharmacological stress. Exercise-stress-induced myocardial ischemia was detected in 90 patients (39.3% of 229). Levels of hs-cTnI and hs-cTnT were both significantly higher at all time-points examined in patients with exercise-induced myocardial ischemia as compared to patients without myocardial ischemia (all p<0.001). Correlation of hs-cTnI and hs-cTnT was high in direct comparison of time-points (Spearman's rho all ≥0.7). The AUCs for baseline/peak/2h/4h for hs-cTnI and hs-cTnT were 0.71/0.71/0.72/0.69 vs. 0.74/0.73/0.71/0.72, respectively (all p=ns for hs-cTnI versus hs-cTnT). In patients undergoing pharmacological stress, the AUCs for baseline/peak/2h/4h for hs-cTnI and hs-cTnT were 0.66/0.66/0.68/0.67 and 0.61/0.62/0.64/0.59, respectively (all p=ns for hs-cTnI versus hs-cTnT). Also the combinations including clinical judgment or changes during serial sampling were similar for hs-cTnI and hs-cTnT (all p=ns).

Conclusions: Hs-cTnI and hs-cTnT provide comparable diagnostic information regarding exercise-induced myocardial ischemia. Overall, their diagnostic accuracy seems moderate.

Unique identifier: NCT01838148.