Elevated blood bicarbonate levels and long-term adverse outcomes in patients with chronic heart failure

The bicarbonate (HCO₃ ^-) buffer system is crucial for maintaining acid-base homeostasis and blood pH. Recent studies showed that elevated serum HCO₃ ^- levels serve as an indicator of the beneficial effects of acetazolamide in improving decongestion in acute heart failure. In this study, we sought to clarify the clinical relevance and prognostic impact of HCO₃ ^- in chronic heart failure (CHF).

This cohort study enrolled 694 hospitalized patients with CHF (mean age 68.6 ± 14.6, 62% male) who underwent arterial blood sampling and exhibited neutral pH ranging from 7.35 to 7.45. We characterized the patients based on HCO₃ ^- levels and followed them to register cardiac events.

Among the patients, 17.3% (120 patients) had HCO₃ ^- levels exceeding 26 mmol/L. Patients presenting HCO₃ ^- > 26 mmol/L were more likely to use loop diuretics and had higher serum sodium and lower potassium levels, but left ventricular ejection fraction did not differ compared with those with HCO₃ ^- between 22 and 26 (379 patients) or those with HCO₃ ^- < 22 mmol/L (195 patients). During a median follow-up period of 1950 days, Kaplan-Meier analysis revealed that patients with HCO₃ ^- > 26 mmol/L had the lowest event-free survival rate from either cardiac deaths or heart failure-related rehospitalization (P < 0.01 and 0.03, respectively). In the multivariable Cox model, the presence of HCO₃ ^- > 26 mmol/L independently predicted increased risks of each cardiac event with a hazard ratio of 2.31 and 1.69 (P < 0.01 and 0.02, respectively), while HCO₃ ^- < 22 mmol/L was not associated with these events (hazard ratios, 0.99 and 1.19; P = 0.98 and 0.43, respectively).

Elevated blood HCO₃ ^- levels may signify enhanced proximal nephron activation and loop diuretic resistance, leading to long-term adverse outcomes in patients with CHF, even within a normal pH range.