Dialysis-dependent changes in ventricular repolarization

BACKGROUND: Epidemiological data suggest increased risk of sudden death during and immediately after hemodialysis. Microvolt T-wave alternans (mTWA) is an electrocardiogram (ECG) measure of abnormal ventricular repolarization, which can be used in sudden death risk stratification. The aim of this study was to determine whether mTWA measurements during dialysis indicate abnormal repolarization as a potential trigger to dialysis associated arrhythmias.

METHODS: Forty-eight-hour, 12-lead Holter ECG recordings were taken on a cohort of maintenance hemodialysis patients. Modified moving average mTWA was examined for 48 hours from the start of dialysis. Predialysis biochemistry was taken and echocardiography was performed on a nondialysis day.

RESULTS: Nineteen patients were analyzed (age 61 ± 14 years, time on dialysis 2.7 ± 2 years). mTWA increased during dialysis (P < 0.01) but returned to baseline 2 hours postdialysis (first hour mTWA = 10.1 ± 4.5μV, final hour mTWA = 12.2 ± 3.7μV, postdialysis mTWA = 10.3 ± 2.7μV, P = 0.015). The change in mTWA did not correlate with serum biochemistry or echocardiographic measurements of left ventricular mass and function. Peak mTWA and frequency of spikes in mTWA ≥ 65μV were not more common during dialysis compared to other times. Patients who showed greater frequency of spikes ≥65μV or increase in hourly mean mTWA during dialysis did not have a worse cardiovascular outcome over a mean follow-up of 2.6 years.

CONCLUSIONS: Though there were subtle changes in mTWA during dialysis, there was no association with mTWA abnormalities previously shown to be associated with worse outcome. The presence of abnormal mTWA did not correlate with outcome.