The prognostic value of arterial blood gas analysis in high-risk acute heart failure patients: an analysis of the Korean Heart Failure (KorHF) registry

Aims In acute heart failure (AHF) patients, pulmonary oedema and low tissue perfusion may lead to changes in the acid–base balance, which may be associated with worse outcomes. Methods and results In this prospective nationwide cohort study from 24 academic hospitals, arterial blood gas (ABG) was measured in 1982 AHF patients at hospital admission. Acidosis was defined as pH 7.44. Mortality was stratified according to ABG results. Overall, 19% had acidosis, 37% had normal pH, and 44% had alkalosis. The most common type of acidosis was the mixed type (42%) followed by metabolic acidosis (40%), and the most common type of alkalosis was respiratory alkalosis (58%). At 12 months' follow‐up 304 patients (15%) died. Patients with acidosis had higher mortality (acidosis 19.5%, neutral pH 13.7%, alkalosis 14.9%; P = 0.007). In the Cox proportional‐hazards regression model, acidosis was a significant predictor of mortality (hazard ratio 1.93; 95% confidence intervals 1.27–2.93) along with N‐terminal pro‐brain type natriuretic peptide (NT‐proBNP), among others. In contrast, alkalosis was not associated with increased mortality. pH had an incremental prognostic value over NT‐proBNP (net reclassification improvement 30%; P < 0.001), and ABG analysis identified extra patients at increased risk for mortality among patients with an NT‐proBNP level less than the median (12‐month mortality 17.5% vs. 9.9%; P = 0.009). Conclusion In high‐risk AHF patients, the most common acid–base imbalance is respiratory alkalosis. Acidosis is observed in every fifth patient and is a significant predictor of mortality. pH provides an additional prognostic value and may be used to optimize risk stratification in high‐risk AHF patients.