Elevated cardiac troponin raises risk of cardiac mortality in CAP patients

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Elevated cardiac troponin T (cTnT), a dependable marker for myocardial infarction, is also strongly prognostic of cardiac mortality observed in association with community-acquired pneumonia (CAP), according to a study. cTnT is a cardiac regulatory protein with high sensitivity and specificity to cardiac muscle enzyme measurements that quantify cardiac muscle damage.

In the current study, the investigators led by Dr Stefan MT Vestjens of the department of internal medicine at St Antonius Hospital in Nieuwegein in the Netherlands, retrospectively extracted data from 295 hospitalised participants in an earlier randomised placebo-controlled trial of adjunctive dexamethasone treatment for CAP conducted in the Netherlands from November 2007 to September 2010.

The cohort was comprised of 167 men and 128 women (median age 67) diagnosed with CAP; the most common comorbid conditions included smoking (27.1%), heart disease (16.6%), diabetes mellitus (14.2%), chronic renal failure (9.2%) and neoplastic diseases (6.4%).

Of the study participants, 132 (44.7%) had elevated cTnT levels of 14 ng/L or greater, designated as “elevated”, measured from blood samples taken from the participants upon admission. Overall, short-term survival was poor in this group: 15 out of 16 patients who died soon after admission were among the patients with elevated cTnT levels, 19 patients (6.4%) died before day 30, and another 49 patients (16.4%) died within 1 year of hospitalisation.

High cTnT levels had a negative impact on both morbidity and mortality that increased exponentially at the highest levels. Intensive care unit (ICU) admission went from 3.1% and 4.7% at 14 ng/L and 14-28 ng/L, respectively, to 11.8% at >28 ng/L. Early death in the hospital increased from 0.6% and 1.6% to 20.6%, and 30-day mortality rose from 0.6% and 1.6% to 22.1%. No other factor or comorbidity was so significantly associated with 30-day mortality. At 1 year, mortality increased from 3.1% at levels below 14 ng/L to 12.5% at 14-28 ng/L, and 52.9% at 28 ng/L.

This study was the first to assess long-term mortality, which was 32% from all causes at 4.1 years post-hospitalisation, and directly associated with high cTnT upon admission. The impact of the highest cTnT levels on long-term mortality was most striking: increasing from 6.1% below 14 ng/L to 13.7% at 14-28 ng/L, and 72.1% at 28 ng/L and above.

Elevated cTnT was strongly prognostic of both short- and long-term mortality in CAP compared with other measures used to predict survival in CAP, including the Pneumonia Severity Index (PSI) and CURB-65 (confusion, urea, respiratory rate, blood pressure in patients older than 65). Patients with high cTnT were older and had more comorbidies, captured as part of the PSI rating; therefore, patients with a higher PSI also had higher cTnT levels. The use of antiplatelet therapy also increased long-term mortality in the presence of even moderately elevated cTnT levels (≥14 ng/L). One surprising trend was that cTnT was less likely to be elevated in smokers in the study than nonsmokers.

The investigators suggested that elevated cTnT in patients admitted with CAP warrants diagnostic consideration of cardiac risks and modified treatment plans to reduce risks of all-cause mortality.

Abstract
Background and objective: Mortality after hospitalization with community-acquired pneumonia (CAP) is high, compared with age-matched controls. Available evidence suggests a strong link with cardiovascular disease. Our aim was to explore the prognostic value of high-sensitivity cardiac troponin T (cTnT) for mortality in patients hospitalized with CAP.
Methods: CTnT level on admission was measured (assay conducted in 2015) in 295 patients hospitalized with CAP who participated in a randomized placebo-controlled double-blind trial on adjunctive dexamethasone treatment. Outcome measures were short- (30-day) and long-term (4.1-year) mortalities.
Results: CTnT levels were elevated (≥14 ng/L) in 132 patients (45%). Pneumonia severity index (PSI) class was 4–5 in 137 patients (46%). Short- and long-term mortality were significantly higher in patients with elevated cTnT levels. cTnT level on admission combined with PSI classification was significantly better in predicting short-term mortality (area under the operating curve (AUC) = 0.903; 95% CI = 0.847–0.960), compared with PSI classification alone (AUC = 0.818; 95% CI = 0.717–0.919). An optimal cTnT cut-off level of 28 ng/L was independently associated with both short- and long-term mortality (OR = 21.9; 95% CI = 4.7–101.4 and 10.7; 95% CI = 5.0–22.8, respectively).
Conclusion: Elevated cTnT level on admission is a strong predictor of short- and long-term mortalities in patients hospitalized with CAP.

Authors
Stefan MT Vestjens, Simone MC Spoorenberg, Ger T Rijkers, Jan C Grutters, Jurriën M Ten Berg, Peter G Noordzij, Ewoudt MW van der Garde, Willem Jan W Boss

Infectious Disease Advisor material
Respirology abstract


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