Prognostic value of troponin I levels for predicting adverse cardiovascular outcomes in postmenopausal women undergoing cardiac surgery

Abstract

Background: Adverse cardiac events that follow cardiac surgery are an important source of perioperative morbidity and mortality for women. Troponin I provides a sensitive measure of cardiac injury, but the levels after cardiac surgery may vary between sexes. Our purpose in this study was to evaluate the prognostic value of troponin I levels for predicting cardiovascular complications in postmenopausal women undergoing cardiac surgery.

Methods: The cohort of this study were women enrolled in a previously reported clinical trial evaluating the neuroprotective potential of 17beta-estradiol in elderly women. In that study, 175 postmenopausal women not receiving estrogen replacement therapy and scheduled to undergo coronary artery bypass graft (with or without valve surgery) were prospectively randomized to receive 17beta-estradiol or placebo in a double-blind manner beginning the day before surgery and continuing for 5 days postoperatively. Serial 12-lead electrocardiograms were performed and serum troponin I concentrations were measured before surgery, after surgery on arrival in the intensive care unit, and for the first four postoperative days. The primary end-point of the present study was major adverse cardiovascular events (MACE) defined as a Q-wave myocardial infarction, low cardiac output state or death within 30 days of surgery. The diagnosis of Q-wave myocardial infarction was made independently by two physicians blinded to treatment and patient outcomes with the final diagnosis requiring consensus. Low cardiac output state was defined as cardiac index <2.0 L x min(-1) x m(-2) for >8 h regardless of treatment.

Results: Troponin I levels on postoperative day 1 were predictive of MACE (area under the receiver operator curve = 0.862). A cutoff point for troponin I of >7.6 ng/mL (95% confidence interval, 6.4-10.8) provided the optimal sensitivity and specificity for identifying patients at risk for MACE. The negative predictive value of a troponin I level for identifying a patient with a composite cardiovascular outcome was high (96%) and the positive predictive value moderate (40%). Postoperative troponin I levels were not different between women receiving perioperative 17beta-estradiol treatment compared with placebo and the frequency of MACE was not influenced by 17beta-estradiol treatment.

Conclusions: In postmenopausal women, elevated troponin I levels on postoperative day 1 are predictive of MACE. Monitoring of perioperative troponin I levels might provide a means for stratifying patients at risk for adverse cardiovascular events.

Trial registration: ClinicalTrials.gov NCT00123539.

Figures

Figure 1

Estimated sensitivities and specificities for various cut-points for troponin I levels obtained on postoperative day 1. The optimal cutoff with the highest sensitivity and specificity was 7.6 ng/mL.

Figure 2

Receiver operating characteristic (ROC) curve for the detection of the primary outcome of a major adverse cardiovascular events (MACE) (consisting of postoperative Q-wave myocardial infarction, low cardiac output state, or operative death) versus troponin I levels determined on postoperative day 1. The area under the ROC curve for a troponin cutoff value of 7.6 ng/mL on postoperative day 1 was 0.8623, provided the optimal sensitivity and specificity for detection of the composite outcome.

Figure 3

Distribution of troponin values obtained on postoperative day 1 (POD 1) for women with (open bars) and without (solid bars) a major adverse cardiovascular event (MACE). The best cut-point is specified by the arrow at 7.6 ng/mL. The open bars to the left of the arrow represent the false negatives, while the solid bars to the right of the arrow represent the false positives. Four troponin POD 1 values between 108 and 294 ng/mL, all of each were for patients with a MACE are not shown in the Figure.