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The prognostic impact of pre-implantation hyponatremia on morbidity and mortality among patients with left ventricular dysfunction and implantable cardioverter-defibrillators

Sanjeev P. Bhavnani, Anupam Kumar, Craig I. Coleman, Danette Guertin, Ravi K. Yarlagadda, Christopher A. Clyne, Jeffrey Kluger
DOI: http://dx.doi.org/10.1093/europace/eut211 47-54 First published online: 16 August 2013

Abstract

Aims 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.

Methods and 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].

Conclusion 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.

  • Implantable cardioverter defibrillator
  • Mortality
  • Shocks
  • Risk stratification
  • Outcomes
  • Hyponatremia
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