Cardiac Troponins Mark Mortality Risk with Influenza

An elevated high-sensitivity cardiac troponin test (hsTnT) in patients hospitalized for influenza infection was associated with increased 30-day mortality rate after discharge, in the largest analysis to date of the cardiac-specific biomarker in patients with influenza.

Although the most common complication associated with influenza is pneumonia, Yogesh Sharma, MD, PhD, College of Medicine and Public Health, Flinders University, and colleagues pointed out that influenza may also lead to exacerbation of underlying medical problems, including cardiac conditions.

"Observational studies have suggested that influenza may be associated with an increased cardiovascular morbidity and mortality especially in older people (>85years) during winter months," the investigators observe.

To test this observation, Sharma and colleagues conducted a retrospective study of 617 patients, mean age 66.4 years, admitted to two tertiary hospitals in South Australia for influenza infection between January 2016 and March 2020. These patients had an hsTnT obtained during their admission, and their influenza diagnosis confirmed by polymerase-chain-reaction (PCR) test.

The patients were stratified by hsTnT result, with 294 having detectable hsTnT and 323 without.Of the 294 patients, 62 had substantially elevated troponin levels (>14ng/L) with significant changes in level consistent with myocardial injury.The other 232 patients in this group had chronically elevated, but relatively stable troponin levels.

In addition to the primary measure of mortality within 30 days after discharge, Sharma and colleagues evaluated complications during hospitalization and unplanned hospital readmissions.The regression analysis for association of mortality with elevated hsTnT was adjusted for a range of covariates including age, sex, smoking status, creatinine levels, comorbidities (on the Charlson Comorbidity Index [CCI]) and severity of illness (as assessed by factors such as CRP levels).

The investigators report that the 30-day mortality rate was significantly higher among patients with acute, but not chronic hsTnT elevation, than those without elevated cardiac troponin on admission (HR, 8.30; 95% CI, 1.80-17.84).They also noted that the patients with acute elevation had significantly higher number of complications during hospital admission, a longer duration of stay, and higher inpatient mortality.

The influenza patients who had an acute or chronic hsTnT elevation were found to have higher incidences of sepsis, septic shock and respiratory failure.The investigators noted, however, that other complications such as pneumonia, acute respiratory distress syndrome (ARDS) and myocarditis were not significantly different than in those with negative hsTnT.

"As this study is limited to influenza patients who needed hospitalization, so findings may not be applicable to those with only mild symptoms in the community," Sharma commented to HCPLive.

"Although, we suggest increased vigilance, especially in patients who have cardiovascular risk factors or where practitioners think that their patients' symptoms are suggestive of cardiac ischemia," Sharma said.

As the study found heightened mortality post hospital discharge, Sharma also advised increased surveillance during this period for the patients with identified risk.

"We suggest extended monitoring of patients who required hospitalization for influenza, where initial hsTnT was suggestive of an acute cardiac injury, with a goal of optimizing cardiovascular risk factors," Sharma indicated.

The study, "Prognostic Impact of High Sensitive Troponin in Predicting 30-day Mortality among Patients Admitted to Hospital with Influenza," was published online in IJC Heart & Vasculature.