Pre-Operative Hyponatremia as a Risk Factor for Mortality in Patients after Left Ventricular Assist Device Implantation

Abstract

Hyponatremia is a recognized risk factor for adverse outcomes in heart failure and after cardiac surgery. We hypothesized that hyponatremia would be associated with poorer short-term and longer-term survival in patients after continuous-flow left ventricular assist device (CF-LVAD) placement. Patients who received a CF-LVAD between January 2012 and December 2017 were identified in a single-center database. Sodium values within 14 days of LVAD insertion were averaged; hyponatremia was defined as Na < 135mEq/L. Baseline characteristics, post-operative complications and mortality were analyzed. Patients who required pre-operative dialysis were excluded from the study. The effect of pre-operative hyponatremia on short-term outcomes and long-term survival was analyzed. Out of 322 patients, 49.7% (n=160) were found to have hyponatremia prior to LVAD insertion. There were no significant differences in comorbidities between groups. Pre-operative hyponatremia was associated with increased length of post-operative stay (38 vs 30 days, p=0.02). Though there was no difference in short-term (90-day) mortality, hyponatremia was associated with increased long-term, five-year mortality (61% vs 44%, p=0.03) (Figure 1). On binary logistic regression analysis, hyponatremia (OR 1.88 95% CI [1.073-3.315], p=0.03), increased age (OR 1.03 95% CI [1.007-1.053], p=0.01), elevated neutrophil-lymphocyte ratio (OR 1.064 95% CI [1.004-1.128], p=0.037), decreased albumin (OR 0.94 95% CI [0.887-0.992], p=0.03), and elevated mean right atrial pressure/pulmonary capillary wedge pressure ratio (OR 4.69 95% CI [1.762-12.473], p=0.002) were independent risk factors of mortality. Pre-operative hyponatremia is associated with increased mortality after LVAD implantation and can be used as a marker or added to existing risk scores to further risk stratify patients. Whether hyponatremia correction improves long-term survival should be investigated.