Abstract 12042: Elevated Levels of Bicarbonate Predict Adverse Outcomes in Patients With Chronic Heart Failure

Background: The bicarbonate (HCO3 ^- ) buffer system plays a crucial role in maintaining acid-base homeostasis, and HCO3 ^- levels are affected by multiple factors in heart failure. Recently, a sub-analysis of the ADVOR trial for acute heart failure revealed that patients with elevated serum HCO3 ^- levels experienced beneficial effects of decongestion by acetazolamide. However, the significance of HCO3 ^- levels in chronic heart failure has not been fully understood.

Aim: We sought to clarify whether HCO3 ^- levels have clinical relevance or prognostic impact in patients with chronic heart failure.

Methods and Results: We conducted a prospective study involving hospitalized patients with stage C/D heart failure and measured HCO3 ^- levels in arterial blood gas samples prior to discharge. We enrolled a total of 718 patients (mean 68.3 years old and 62.1% male), with neutral pH ranging from 7.35 to 7.45, and found that 132 (18.4%) had HCO3 ^- levels exceeding 26 mmol/L. Patients with HCO3 ^- > 26 mmol/L were more likely to be male and to use loop diuretics, and had higher serum sodium, as well as lower potassium levels, compared to those with HCO3 ^-

26 mmol/L, whereas there were no differences in B-type natriuretic peptide levels or left ventricular ejection fraction between the two groups. In a Kaplan-Meier analysis, patients with HCO3 ^- > 26 mmol/L had lower event-free survival rates from cardiac deaths and decompensated heart failure as well as the composite of the cardiac events over a median follow-up period of 1540 days ( Figure ). In a multivariable Cox proportional hazard model after adjusting confounding variables, the presence of HCO3 ^- > 26 mmol/L was independently associated with increased risks of the composite of cardiac events (hazard ratio, 1.64; P < 0.01).

Conclusion: Elevated HCO3 ^- levels may indicate enhanced proximal nephron activation and resistance to loop diuretics, which predicted adverse outcomes in patients with chronic heart failure, even within a normal pH range.