title: The prognostic impact of pre-implantation hyponatremia on morbidity and mortality among patients with left ventricular dysfunction and implantable cardioverter-defibrillators.
abstract: OBJECTIVE
  Hyponatremia is commonly observed among patients with left ventricular (LV) dysfunction and is a marker for adverse outcomes. We aimed to determine the prognostic significance of pre-implant hyponatremia on the outcomes of death, acute decompensated heart failure (ADHF) and appropriate implantable cardioverter-defibrillator (ICD) therapy for ventricular arrhythmias among patients with ICDs.
  
  
  RESULTS
  The study population consisted of patients with an ejection fraction ≤40% undergoing ICD implantation (n = 911) for the primary or secondary prevention of sudden cardiac death from 1997 to 2007. The predictive value of the severity of pre-implantation hyponatremia stratified into mild hyponatremia (n = 268, sodium 134-136 mmol/L), moderate hyponatremia (n = 105, sodium 131-133 mmol/L), and severe hyponatremia (n = 31, sodium ≤130 mmol/L) on the risk of death, ADHF, and appropriate ICD therapy for ventricular arrhythmias as compared with patients a normal serum sodium (n = 507, sodium ≥ 137 mmol/L), was calculated using multivariable Cox proportional hazards analyses. During a mean follow-up of 775 ± 750 days as the severity of hyponatremia (from a normal sodium to severe hyponatremia) increased an incremental incidence of death (25% to 61%, P < 0.001) and ADHF (11% to 26%, P = 0.004) was observed with a reduced incidence of ICD therapy for ventricular tachycardia/ventricular fibrillation (37-29%, P = 0.037). Compared with the normal sodium cohort, patients with severe hyponatremia demonstrated an increased risk of death [adjusted hazard ratio (AHR) 2.69 (95% confidence interval, CI 1.57-4.59), P = 0.004] and ADHF [AHR 2.98 (95% CI 1.41-6.30), P = 0.004], with a lower probability of appropriate ICD therapy [AHR 0.68 (95% CI 0.27-0.88), P = 0.031].
  
  
  CONCLUSIONS
  Hyponatremia is commonly observed among ICD recipients with LV dysfunction. Patients with an increasing severity of hyponatremia are at increased risk of death and HF related morbidity with a reduced incidence of appropriate ICD therapy particularly among patients with severe hyponatremia.
authors: Division of Cardiology, Section of Heart Rhythm Management and the Evidence Based Practice Center, Hartford Hospital, University of Connecticut School of Medicine, 80 Seymour Street, Hartford, CT 06102-5037, USA.
authors: Sanjeev P
authors: SP
authors: Bhavnani
authors: Anupam
authors: A
authors: Kumar
authors: Craig I
authors: CI
authors: Coleman
authors: Danette
authors: D
authors: Guertin
authors: Ravi K
authors: RK
authors: Yarlagadda
authors: Christopher A
authors: CA
authors: Clyne
authors: Jeffrey
authors: J
authors: Kluger
mesh_terms: D000368:Aged; D015897:Comorbidity; D003237:Connecticut; D017147:Defibrillators, Implantable / Q000706:statistics & numerical data*; D005260:Female; D006333:Heart Failure / Q000401:mortality* / Q000517:prevention & control*; D006801:Humans; D007010:Hyponatremia / Q000175:diagnosis* / Q000401:mortality*; D015994:Incidence; D008297:Male; D011300:Preoperative Care / Q000379:methods / Q000706:statistics & numerical data; D011379:Prognosis; D019919:Prosthesis Implantation / Q000401:mortality; D018570:Risk Assessment; D016019:Survival Analysis; D016896:Treatment Outcome; D018487:Ventricular Dysfunction, Left / Q000401:mortality* / Q000517:prevention & control*
keywords: Hyponatremia; Implantable cardioverter defibrillator; Mortality; Outcomes; Risk stratification; Shocks