Troponin-T Levels After Noncardiac Surgery May Predict 30-Day Mortality

Deborah Brauser

March 24, 2017

WASHINGTON, DC — Perioperative measures of troponin T with high-sensitivity (hs-TnT) assays may help identify myocardial injury after noncardiac surgery (MINS) and increased mortality risk, according to results from the Vascular Events in Noncardiac Surgery Patients Cohort Evaluation (VISION) trial[1].

In the observational study of more than 21,000 patients, peak postsurgery hs-TnT levels of >20 ng/L or a change >5 ng/L were significantly associated with 30-day mortality. The risk also progressed dramatically for higher levels, with a 30-day mortality rate of almost 30% for those who had hs-TnT levels >1000 ng/L.

In addition, "up to 93% in our study would have likely gone undetected without troponin monitoring" since they didn't have any symptoms of ischemia, lead author Dr PJ Devereaux (McMaster University, Hamilton, ON) told attendees here at the American College of Cardiology (ACC) 2017 Scientific Sessions.

Dr PJ Devereaux

"The takeaway is that if physicians do not measure perioperatively in at-risk patients, those 65 or older or under 65 with known vascular disease, they will likely miss a very important prognosis," added Devereaux to heartwire from Medscape.

"Because we're not routinely screening, we're missing a lot of people suffering cardiac events, and, as a result, we're not able to intervene to try to improve outcomes," he said.

"I think this study helps to define the cutoff for high-sensitivity troponin, which will be useful to change practice," noted session panelist Dr Athena Poppas (Rhode Island Hospital Division of Cardiology, Providence).

MINS Common Worldwide

MINS accounts for a third of the 2 million total postsurgical deaths that occur worldwide annually, said Devereaux.

Although the US Food and Drug Administration (FDA) recently approved the use of hs-TnT assays, "little is known" about the relationship between the measures, MINS, and mortality, he added.

The VISION trial enrolled patients from 23 centers in 13 countries. Of these, 21,050 had their hs-TnT levels measured 6 to 12 hours postsurgery and 1, 2, and 3 days afterward and completed a 30-day follow-up visit. All were 45 years or older (mean age 63 years; 51% men). The most common surgery type was low risk (35%), followed by major general (20%) and major orthopedic (16%).

The absolute risk for 30-day mortality needed to be at least 3% and the adjusted hazard ratio (HR) needed to be at least 3.0 to be considered significant in this study. The 30-day mortality  for the entire patient population was 1.2% (95% CI 1.1%–1.4%).

Association Between Peak Postoperative hs-TnT Levels and 30-Day Mortality

hs-TnT Threshold (ng/L) Patients (%) Mortality Rate (%) HR (95% CI) P
>20 to <65 18.6 3.0 23.6 (10.3-54.1) <0.001
>65 to <1000 5.1 9.1 70.3 (30.6-161.7) <0.001
>1000 0.2 29.6 227.0 (87.4-589.9) <0.001
*Compared with the reference group (<5 ng/L; 24.4% of the participants)

In addition, an absolute change from baseline of at least 5 ng/L had an adjusted HR of 4.7 for 30-day mortality (95% CI 3.5–6.3).

Other postoperative variables associated with 30-day mortality included stroke (HR 5.2), sepsis (HR 5.0), MINS (HR 3.7), and major bleeding (HR 2.8).

MINS occurred in 3904 of the participants (17.9%), with 94.1% occurring by the second day postsurgery. And although MINS has been universally defined as elevated hs-TnT with at least one ischemic feature, 93.1% of the MINS patients had no ischemic symptoms.

The odds ratio for a composite of nonfatal cardiac arrest, CHF, coronary revascularization, and mortality among patients with MINS was 8.5 (95% CI 6.9–10.3).

"Given that . . . 13.8% of patients had their peak value before surgery suggests that physicians should consider obtaining preoperative troponin measurements in patients whom they plan to measure after surgery," said Devereaux.

He reported that the investigators have started a new trial that will assess whether hs-TnT-based anticoagulation after noncardiac surgery may prevent postoperative deaths.

"Important Data," but What Now?

After the presentation, session panelist Dr Robert O Bonow (Northwestern University Feinberg School of Medicine, Chicago, IL) noted that these are "important data." But he had questions about the patients' baseline characteristics, especially whether prior MI or heart failure had any influence on the findings.

"In our adjusted models, we did adjust for all baseline cardiovascular history. If you look at this broad population, only about 8% had known coronary heart disease and only 5% had known heart failure," answered Devereaux.

"One of the challenges is that patients undergoing noncardiac surgery are very mobile before surgery. And because of a lack of symptoms, there's an underappreciation of the risks."

At a press briefing later in the day, official discussant Dr Alistair Phillips (Cedars-Sinai Medical Center, Los Angeles, CA) called this "very important work" because of two things.

"It informs about what are normal values and higher values with risk stratification with the new [high-sensitivity] troponin test," said Phillips. "But most important is it's helping to find those who have a risk of having MINS, which is not being detected in a large percentage of patients."

ACC 2017 vice chair Dr Andrew Kates (Washington University School of Medicine, St Louis, MO) told heartwire that it was interesting to see the elevated risk associated with elevated troponin levels after this type of surgery.

"I think one of the challenges is going to remain identifying the appropriate patient population in whom it should be checked. Also: what do we do with the results?" wondered Kates.

"I think many clinicians will ask: how do we evaluate these patients from a functional standpoint? Do they require stress testing or additional ischemic evaluation? And how routinely should we be checking these levels presurgery as part of the preop evaluation?"

He added that in the recently released findings from the FOURIER trial, the investigators noted the importance of the absolute reduction in LDL-C levels as well as the percentage of reduction. In VISION, "it seems to be important to see the change in troponin values from baseline and not just the elevation itself," said Kates.

"The challenge basically now is: what do we do? How we put all of this in clinically is something we need to think through."

The study received the troponin T assay from Roche Diagnostics but the company "was not involved with the study data or analyses." Devereaux has received research funds or grants from Abbot Diagnostics, Boehringer Ingelheim, and Roche Diagnostics. Poppas reports having GE stock. Bonow is on the data safety monitoring board for the Harvard Clinical Research Institute and has received "other funds" from Gilead and the Journal of the American Medical Association. Phillips and Kates have reported no relevant financial relationships.

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