Abstract 14341: A Depressed Cardiac Output in Patients With Advanced Heart Failure is Not Accompanied by Increased Plasma Lactate Levels in the Majority of Patients: Is it Time for a New Definition of Heart Failure?

Abstract

Introduction: Heart failure (HF) has been defined as a condition in which the heart is unable to deliver sufficient oxygen to match the needs of the metabolizing tissues. This definition, which was based on observations in patients with terminal HF, has never been validated. Moreover, the application of this definition led to the use of inotropes , and discouraged the use of beta-blockers, delaying the development of appropriate HF therapies. Methods: To determine whether the heart was unable to meet the metabolic demands of the body, we retrospectively analyzed Arterio-Venous oxygen difference (AV O2) and plasma lactate levels in NYHA class IV heart failure patients that subsequently received a Left Ventricular Assist Device (LVAD). Results: We identified 359 patients with a right heart catheterization (RHC) performed prior to LVAD implantation. Plasma lactate was available for 96 patients. RHC showed that 93% of the patients had an AV O2 difference above normal (> 5 ml/100 ml). Among patients with measured lactate levels the prevalence of elevated lactate (> 2.1 mmol/L) was only 25% (95% CI 16.7-34.9). AV O2 was widened in all patients with elevated lactate, but plasma lactate did not correlate with AV O2 (R=0.02) and only 27% of patients with increased AV O2 had elevated plasma lactate ( Figure ). Patients with widened AV O2 and elevated lactate were sicker than patients with widened AV O2 and normal lactate, as shown by a higher prevalence of low INTERMACS class, elevated INR and reduced serum albumin. However, there was no obvious hemodynamic difference between the two groups. Conclusions: Approximately 75% of the patients in this NYHA class IV HF sample with a depressed cardiac output had normal lactate levels, suggesting that cardiac output was sufficient to meet the metabolic demands of the body. Given that approximately 4% of HF patients are NYHA class IV, these findings suggest that the classic definition of heart failure may be valid in only 1% of the total heart failure population.