Abstract and Introduction
Abstract
Aims To assess the role of cardiac troponin T (cTnT) levels on admission using a new, highly sensitive assay (hsTnT) in the risk assessment of normotensive patients with acute pulmonary embolism (PE).
Methods and results We prospectively studied 156 consecutive normotensive patients with confirmed PE. The prognostic value of hsTnT at baseline was compared with the conventional cTnT troponin assay and with N-terminal pro-brain natriuretic peptide concentrations. Long-term follow-up was available for 153 patients (98.1%). Highly sensitive troponin T values ranged from 0.001 to 357.2 pg/mL [median 27.2 (25th–75th percentile 9.4–69.4) pg/mL]. Overall, 100 patients (64%) had hsTnT ≥14 pg/mL. Baseline hsTnT was higher in patients with an adverse 30-day outcome (≥1: death, need for catecholamines, endotracheal intubation, or cardiopulmonary resuscitation) compared with an uncomplicated course [71.7 (35.5–117.9) vs. 26.4 (9.2–68.2) pg/mL; P = 0.027]. The cut-off value of 14 pg/mL showed an excellent prognostic sensitivity and negative predictive value (both 100%). In comparison, as many as 50% of the patients with an adverse early outcome would have been misclassified as low risk by cTnT (cut-off 0.03 ng/mL). Logistic regression indicated a two-fold increase in the risk of an adverse outcome for each increase of hsTnT by 1SD of the natural logarithm (P = 0.037). Patients with elevated hsTnT levels had a reduced probability of long-term survival (P = 0.029 by log-rank); by Cox's regression analysis, hsTnT was the only laboratory biomarker predicting an elevated risk of death over the long term.
Conclusion Highly sensitive troponin T assays may be capable of improving risk stratification of non-high-risk PE.
Introduction
Recent guidelines emphasize the importance of early risk stratification of patients with acute pulmonary embolism (PE). Consensus exists that patients presenting with refractory arterial hypotension (systolic blood pressure <90 mmHg or a pressure drop ≥40 mmHg for ≥15 min) or shock indicating overt right ventricular (RV) failure are particularly at high risk of early death and should therefore undergo prompt recanalization treatment. On the other hand, the strategies for prognostic assessment of patients who are haemodynamically stable on admission (non-high-risk PE) remain controversial to date. Laboratory biomarkers and particularly elevated circulating levels of cardiac troponins T and I were associated with an increased risk of death or complications during the acute phase of PE, but most of the studies published thus far failed to exclude haemodynamically unstable patients who are at high risk anyway and do not necessitate further risk stratification. In fact, a recent cohort study as well as a meta-analysis focusing on patients with non-high-risk PE questioned the prognostic value of cardiac troponins in the absence of arterial hypotension. Moreover, cardiac troponin concentrations on admission did not appear to predict the patients' outcome beyond discharge from the hospital.
Conventional troponin assays are characterized by inadequate precision at the lower detection limit. As a consequence of the low prognostic sensitivity and negative predictive value of these assays, repeated troponin measurements may be required for risk assessment both in patients with acute chest pain and in those with confirmed acute PE. In order to overcome these limitations, a new generation of highly sensitive troponin assays were developed which are capable of defining the 99th percentile of a normal (healthy) reference population with a coefficient of variation (CV) of <10%. Recent studies in patients with acute myocardial infarction indicated an excellent diagnostic performance of these assays and the potential to improve early risk stratification.
In the present study, we assessed the prognostic value of baseline cardiac troponin T (cTnT) levels measured by a highly sensitive assay in normotensive patients with acute PE. More specifically, we sought to determine whether the new assay improves the prognostic sensitivity and negative predictive value of troponin testing, whether it increases the additive value of this biomarker to other determinants of early outcome, and whether it may also be capable of predicting long-term prognosis.