The prognostic significance of serum sodium in a population undergoing cardiac resynchronisation therapy

Abstract

PurposeTo determine the prognostic implications of changes towards hyponatremia at varying time-points in the treatment of patients undergoing cardiac resynchronisation therapy (CRT). MethodsA retrospective series of 249 patients was studied from 2002 to 2013. The population was categorized on the basis of serum sodium profile at baseline, at 1 month and at 6 month follow up visits following successful CRT implantation. The composite endpoint was all-cause mortality and heart failure hospitalisation (defined by the need for intravenous diuretic therapy) following CRT implantation. ResultsA total of 249 patients (67.8±12.5 years; NYHA class III/IV 75; LVEF 27.2±8.8%) were followed up for a median of 5.5 years. Hyponatremia at baseline, 1 month or 6 months follow up did not predict the composite endpoint. 26% of patients showed hyponatremia at baseline prior to CRT implantation, while it was present in 19.9% of patients 1 month (p=0.003) and in 16% (p<0.001) 6 months after CRT implantation. There was a significantly worse outcome for those patients who developed hyponatremia 6 months after CRT implantation. In multivariate analysis, the intake of loop diuretics (HR 1.76 [1.04–2.95], p=0.03) and renal impairment (urea>7.0mmol/l) (HR 1.61 [1.05–2.46], p=0.03) at baseline were associated with an increased risk of unplanned heart failure hospitalisation and all-cause mortality after CRT implantation. ConclusionsA change towards hyponatremia when observed 6 months after CRT implantation may predict a worse clinical outcome. Additionally, renal impairment and higher diuretic doses are associated with an increased risk of mortality in the population analysed.