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.

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

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.

A strong linear trend between log₁₀cTnI and ΔA-a was observed (r²=0.76) with a statistically significant Spearman correlation coefficient (r_s=0.75; p<0.0001) between cTnI and ΔA-a. A cTnI value of 0.5ng/ml discriminated mild CAP from moderate-severe CAP with an OR=208 (95% CI: 50.5–408; p<0.0001).

These data suggest that decreased blood O₂ levels as suggested by elevated ΔA-a may lead to acute myocardial damage and that cTnI may be useful as a biomarker to stratify risk in subjects with CAP.