The clinical significance of hyperkalaemia-associated repolarization abnormalities in end-stage renal disease

Background. Hyperkalaemia is a common potentially fatal complication of chronic kidney disease (CKD). It may manifest as electrocardiogram (ECG) changes, the earliest of which is T-wave 'tenting'. However, this occurs in less than half of episodes of hyperkalaemia. The aim of this study was to determine what other clinical features relate to the probability of T-wave tenting; and if there is a longer-term survival difference between patients who develop tenting and those who do not. Method. One hundred and forty-five patients with endstage renal disease who had standard 12-lead ECG and concurrent serum potassium measurement were enrolled. The presence of tenting and the ratio of the amplitude of the tallest precordial T-wave and R-wave were determined (T:R). Results. Tenting was as common in normal range serum potassium as hyperkalaemia (33 versus 31%) and less common than in left ventricular hypertrophy (44%). T:R was less sensitive (24 versus 33%) but more specific (85 versus 67%) than tenting at correctly identifying hyperkalaemia 6.0 mmol/L. Tenting became less common with increasing age. Dialysis patients were more likely to show increased T: R that pre-dialysis Stage 5 CKD. Elevated T:R was not associated with worse cardiovascular outcome but was associated with increased risk of sudden death over a mean follow-up of 3.8 years (hazard ratio = 8.3, P = 0.021). Conclusions. The reason for the variability in T-wave changes is not clear. The ratio of precordial T-wave to Rwave amplitude is a more specific measure than tenting but both are poorly sensitive at detecting hyperkalaemia. The greater risk for sudden death may represent a susceptibility to cardiac arrhythmia during repolarization.