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 <7.36, and alkalosis 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.