Signal-averaged ECG abnormalities in haemodialysis patients. Role of dialysis

Background. Late potentials (LP) on the signal-averaged electrocardiogram (SAECG) are predictive of malignant ventricular arrhythmias and sudden cardiac death in patients with ischaemic and non-ischaemic cardiomyopathy. Cardiac dysfunction, both regional and global, as well as supraventricular and ventricular arrhythmias are reported in a high percentage of patients with end-stage renal failure (ESRF). The aim of the study was to assess the prevalence of LP and the effects of haemodialysis on the SAECG of ESRF patients. Methods. SAECG was recorded immediately before and within 30 min after the end of dialysis in 48 patients in sinus rhythm, free of conduction disturbances on ECG and of signs of congestive heart failure. Serum electrolytes were sampled together with the SAECG recordings. An echo-Doppler exam was performed within 2 weeks of the study. SAECGs were adequate for analysis in 45/48 patients. LP were present when at least two of the following criteria were fulfilled: QRS duration less than or equal to 115 ms, LAS(40) less than or equal to 38 ms, RMS40 greater than or equal to 38 mu V at 40 Hz high pass bidirectional filter, and noise <0.7 mu V. Results. LP were detected in 12/45 patients (25%) on the SAECG before dialysis; of these 12 patients, seven had a history of a previous myocardial infarction and two had documented coronary artery disease (CAD). A significant greater wall motion score index-calculated on a 16 segment model-was reported in patients with LP (1.20 +/- 0.20 vs 1.01 +/- 0.03, P < 0.01), while left ventricular mass was comparable in the two groups of patients. At the end of dialysis, a significant prolongation of fQRS duration was found both at 25 and 40 Hz filters (from 98 +/- 11 to 106 +/- 16 ms and from 97 +/- 12s to 102 +/- 13 ms, respectively, P < 0.001). A significant inverse relationship was seen between the percentage of dialysis-induced serum potassium reduction and fQRS changes at 40 Hz (r = -0.68, P < 0.001). Conclusions. LP were detected in a significant proportion of dialysis patients, probably related to underlying CAD with left ventricular dysfunction. Prolongation of fQRS after dialysis could be explained by the acute reduction in serum potassium levels.