Cardiac troponin I levels and alveolar-arterial oxygen gradient in patients with community-acquired pneumonia.

Background: Patients with community-acquired pneumonia (CAP) appear to have cardiac stress as demonstrated by elevated B-type natriuretic peptide (BNP). We hypothesised that myocardial stress and decrease in oxygenation might also lead to elevations of cardiac troponin I (cTnI) levels in serum.

Objective: The aim of this study was to see if cTnI was associated with the alveolar-arterial oxygen gradient (DeltaA-a), a marker of severity in CAP.

Methods: Retrospective cohort study of 901 CAP patients with no evidence of acute coronary syndrome presenting to a large, tertiary-care, urban teaching hospital over a 3-year period.

Results: A strong linear trend between log(10)cTnI and DeltaA-a was observed (r(2)=0.76) with a statistically significant Spearman correlation coefficient (r(s)=0.75; p<0.0001) between cTnI and DeltaA-a. A cTnI value of 0.5 ng/ml discriminated mild CAP from moderate-severe CAP with an OR=208 (95% CI: 50.5-408; p<0.0001).

Conclusions: These data suggest that decreased blood O(2) levels as suggested by elevated DeltaA-a may lead to acute myocardial damage and that cTnI may be useful as a biomarker to stratify risk in subjects with CAP.