High-sensitivity Troponin-T levels in reperfused STEMI patients: A comparison with CMR

Background

In reperfused ST-segment elevation myocardial infarction (STEMI), CMR late gadolinium enhancement (LGE) is the gold-standard for quantifying myocardial infarct (MI) size. Serum cardiac biomarker area-under-the-curve (AUC) is also used (CK-MB, Troponin T and I) and is more widely available than CMR. However, whether acute MI size measured by the 5^th generation high-sensitivity Troponin T assays (hs-Trop T) correlates with that by LGE-CMR is not known.

Methods

Forty-eight patients presenting with an acute STEMI treated by primary angioplasty (PPCI) had CMR and hs-Trop T levels were measured prior to PPCI and at 6, 12 and 24 hours post-PPCI. These 4 time-points were used for the AUC calculation. The assay was a one-step enzyme immunoassay (electro-chemiluminescence based, Elecsys 2010, Roche, Switzerland). Of note, it cannot further quantify elevations >10,000 ng/L. CMR was performed on a 1.5-T scanner 3-6 days after PPCI. Acute MI size was quantified by LGE 10 minutes after gadolinium injection (Otsu method) using ImageJ (National Institutes of Health, Bethesda, Maryland), which was also used for volume and mass. Microvascular obstruction (+/- haemorrhage) was included in the infarct area. Infarction was expressed in gram mass. Pearson's correlation coefficient and Independent Student's t-test were used.

Results

Hs-Trop T AUC showed good correlation (r = 0.64, p < 0.0001) with LGE infarct size, as did 12-hour hs-Trop T (r = 0.63, p < 0.0001). There was an inverse correlation between hs-TropT AUC and LV ejection fraction (r = -0.633, p < 0.0001). Hs-TropT AUC levels were also significantly higher (p < 0.0001) in patients with microvascular obstruction (MVO).

Conclusions

The widely available 5^th generation hs-TropT can quantify acute MI size. A single measurement at 12 hours was as good as 24-hour AUC. Elevations in hs-TropT were associated with a lower LV ejection fraction and the presence of MVO.

Figure 1

Scatter-plot of hs-TropT AUC (x10,000 ng/L × hour) measurements against MI size (g).

Figure 2

Scatter-plot of hs-TropT AUC (x10,000 ng/L × hour) measurements against Ejection Fraction (%).