Abstract 88: Preoperative Hyponatremia is Associated with Increased Risk of Heart Failure Hospitalization and Mortalityamong Veterans Undergoing Cardioverter-Defibrillator Implantation

Abstract

Introduction: It is unknown whether hyponatremia is associated with risk of heart failure hospitalization or mortality among patients undergoing implantable cardioverter-defibrillator (ICD) implantation. This study was undertaken to assess whether or not hyponatremia is an independent risk factor for heart failure hospitalization or mortality following ICD implantation. Methods: The Outcomes among Veterans with Implantable Defibrillators (OVID) registry is a prospectively identified national cohort of VA patients who underwent ICD implantation between 2003 and 2009. There were 3,918 patients who were identified and having serum sodium measured at the time of implantation. Hyponatremia was the primary exposure and was defined by a serum sodium of less than 135 milliequivalents per liter (mEq/L). We assessed the association of hyponatremia with heart failure hospitalization and mortality using Cox proportional hazards regression adjusted for demographics, comorbidities, and type of device. Results: The mean serum sodium was 138.5 mEq/L and 579 patients (15.0%) had hyponatremia. Over a mean follow up time of 2.52 years, the rate of heart failure hospitalization was 14.1 per 100 person-years, and mortality was 9.6 per 100 person-years for subjects with hyponatremia at the time of implantation, compared to 10.0 per 100 person-years and 6.5 per 100 person-years, respectively, for those without hyponatremia. After multivariable analysis, hyponatremia at the time of implantation was associated with increased risk of both heart failure hospitalization (adjusted HR, 1.29; 95% CI, 1.06 - 1.57; P = 0.012) and mortality (adjusted HR, 1.31; 95% CI, 1.05 - 1.64; P = 0.016). Conclusions: Preoperative hyponatremia is associated with a modestly increased risk of both subsequent heart failure hospitalization and mortality among veterans undergoing ICD implantation. Further studies should assess whether hyponatremia at the time of ICD implantation is a modifiable risk factor that can be optimized or whether it is a representation of overall health status.