Single resting hsTnT level predicts abnormal myocardial stress test in acute chest pain patients with normal initial standard troponin

Abstract

Objectives: The goal of this study was to determine the ability of a single, resting high-sensitivity troponin T (hsTnT) measurement to predict abnormal myocardial perfusion imaging (MPI) in patients presenting with acute chest pain to the emergency department (ED).

Background: HsTnT assays precisely detect very low levels of troponin T, which may be a surrogate for the presence and extent of myocardial ischemia.

Methods: We included all patients from the ROMICAT I (Rule Out Myocardial Infarction Using Computer Assisted Tomography) trial, an observational cohort study, who underwent both single-photon emission computed tomography (SPECT)-MPI stress testing and 64-slice computed tomography angiography (CTA) and in whom hsTnT measurements were available. We assessed the discriminatory value of hsTnT for abnormal SPECT-MPI and the association of reversible myocardial ischemia by SPECT-MPI and the extent of coronary atherosclerosis by CTA to hsTnT levels.

Results: Of the 138 patients (mean age 54 ± 11 years, 46% male), 19 (13.7%) had abnormal SPECT-MPI. Median hsTnT levels were significantly different between patients with normal and abnormal SPECT-MPI (9.41 pg/ml [interquartile range (IQR): 5.73 to 19.20 pg/ml] vs. 4.89 pg/ml [IQR: 2.34 to 7.68 pg/ml], p = 0.001). Sensitivity of 80% and 90% to detect abnormal SPECT-MPI was reached at hsTnT levels as low as 5.73 and 4.26 pg/ml, respectively. Corresponding specificity was 62% and 46%, and negative predictive value was 96% and 96%, respectively. HsTnT levels had good discriminatory ability for prediction of abnormal SPECT-MPI (area under the curve: 0.739, 95% confidence interval: 0.609 to 0.868). Both reversible myocardial ischemia and the extent of coronary atherosclerosis (combined model r(2) = 0.19 with partial of r(2) = 0.12 and r(2) = 0.05, respectively) independently and incrementally predicted the measured hsTnT levels.

Conclusions: In patients with acute chest pain, myocardial perfusion abnormalities and coronary artery disease are predicted by resting hsTnT levels. Prospective evaluations are warranted to confirm whether resting hsTnT could serve as a powerful triage tool in chest pain patients in the ED before diagnostic testing and improve the effectiveness of patient management.

Figure 1. HsTnT Levels Between Patients With Normal and Abnormal SPECT-MPI

Median high-sensitivity troponin T (hsTnT) levels were significantly higher in patients with abnormal single-photon emission computed tomography–myocardial perfusion imaging (SPECT-MPI) compared with those with normal SPECT-MPI (9.41 pg/ml [interquartile range (IQR): 5.73 to 19.20 pg/ml] vs. 4.89 pg/ml [IQR: 2.34 to 7.68 pg/ml], p = 0.001).

Figure 2. ROC Curve for hsTnT Values for Prediction of Abnormal SPECT-MPI Results

HsTnT had good discriminatory value for abnormal SPECT-MPI (area under the curve [AUC]: 0.739, 95% confidence interval [CI]: 0.609 to 0.868). The hsTnT cutoffs for sensitivities of 60%, 70%, 80%, and 90% are marked on the receiver-operating characteristic (ROC) curve. Other abbreviations as in Figure 1.

Figure 3. Correlation of HsTnT With Extent of Reversible Myocardial Ischemia as Well as With Coronary Atherosclerotic Plaque

The levels of log-transformed high-sensitivity troponin T (hsTnT) were correlated separately to summed difference score (SDS) (red circles), a measure of reversible myocardial ischemia, and to coronary segments containing any plaque (blue squares), a measure of atherosclerotic plaque burden. The correlation coefficients were r² = 0.15 (p < 0.0001) and r² = 0.08 (p = 0.0004), respectively.

Figure 4. Association of Estimated HsTnT Levels With Reversible Myocardial Ischemia and Coronary Plaque Extent

The levels of log-transformed high-sensitivity troponin T (hsTnT) were estimated with a linear regression model using the extent of reversible myocardial ischemia (summed difference score [SDS]) and the number of coronary artery segments containing any atherosclerotic plaque as predictors. For better clinical interpretation, the labeling of the y-axis was back-transformed from log-hsTnT levels into hsTnT levels with a unit of picograms/milliliter. Combined information on myocardial ischemia and coronary atherosclerosis explained nearly 20% of the variability in hsTnT (r² = 0.19), and the 2 variables were independent of each other. The estimated levels of hsTnT are illustrated by different colors as shown in the color key.

Figure 5. Various Pathophysiological Mechanisms for the Release of HsTnT in the Circulation

CAD = coronary artery disease; HsTnT = high-sensitivity troponin T.