RESUMO
AIMS: 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). METHODS: 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. RESULTS: 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). CONCLUSIONS: 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.
RESUMO
BACKGROUND: The immune systems and chronic inflammation are implicated in the pathogenesis of dilated cardiomyopathy (DCM) and heart failure. However, the significance of neutrophil extracellular traps (NETs) in heart failure remains to be elucidated. METHODS: We enrolled consecutive 62 patients with heart failure with idiopathic DCM who underwent endomyocardial biopsy. Biopsy specimens were subjected to fluorescent immunostaining to detect NETs, and clinical and outcome data were collected. Ex vivo and in vivo experiments were conducted. RESULTS: The numbers of NETs per myocardial tissue area and the proportion of NETs per neutrophil were significantly higher in patients with DCM compared with non-DCM control subjects without heart failure, and the numbers of NETs were negatively correlated with left ventricular ejection fraction. Patients with DCM with NETs (n=32) showed lower left ventricular ejection fraction and higher BNP (B-type natriuretic peptide) than those without NETs (n=30). In a multivariable Cox proportional hazard model, the presence of NETs was independently associated with an increased risk of adverse cardiac events in patients with DCM. To understand specific underlying mechanisms, extracellular flux analysis in ex vivo revealed that NETs-containing conditioned medium from wild-type neutrophils or purified NET components led to impaired mitochondrial oxygen consumption of cardiomyocytes, while these effects were abolished when PAD4 (peptidyl arginine deiminase 4) in neutrophils was genetically ablated. In a murine model of pressure overload, NETs in myocardial tissue were predominantly detected in the acute phase and persisted throughout the ongoing stress. Four weeks after transverse aortic constriction, left ventricular ejection fraction was reduced in wild-type mice, whereas PAD4-deficient mice displayed preserved left ventricular ejection fraction without inducing NET formation. CONCLUSIONS: NETs in myocardial tissue contribute to cardiac dysfunction and adverse outcomes in patients with heart failure with DCM, potentially through mitochondrial dysfunction of cardiomyocytes.