SIGNAL-AVERAGED ECG ABNORMALITIES IN HEMODIALYSIS-PATIENTS - ROLE OF DIALYSIS

Background. Late potentials (LP) on the signal-averaged electrocardiog ram (SAECG) are predictive of malignant ventricular arrhythmias and su dden cardiac death in patients with ischaemic and non-ischaemic cardio myopathy. Cardiac dysfunction, both regional and global, as well as su praventricular and ventricular arrhythmias are reported in a high perc entage of patients with end-stage renal failure (ESRF). The aim of the study was to assess the prevalence of LP and the effects of haemodial ysis on the SAECG of ESRF patients. Methods. SAECG was recorded immedi ately before and within 30 min after the end of dialysis in 48 patient s 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 patie nts. 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 tha n or equal to 38 ms, RMS40 greater than or equal to 38 mu V at 40 Hz h igh pass bidirectional filter, and noise <0.7 mu V. Results. LP were d etected 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 gr eater wall motion score index-calculated on a 16 segment model-was rep orted 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 patien ts. At the end of dialysis, a significant prolongation of fQRS duratio n 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 di alysis-induced serum potassium reduction and fQRS changes at 40 Hz (r = -0.68, P < 0.001). Conclusions. LP were detected in a significant pr oportion of dialysis patients, probably related to underlying CAD with left ventricular dysfunction. Prolongation of fQRS after dialysis cou ld be explained by the acute reduction in serum potassium levels.