QRS and T loops area changes during haemodialysis

We studied 58 patients, age 59±13 years, 52% males, with renal disease duration 9.7±6.7 years and haemodialysis (HD) duration 5.2±4.4 years. Digital ECGs were recorded before and after HD. Serum electrolytes (potassium-K, sodium-Na, phosphorus-Ph and calcium-Ca), urea and creatinine levels were evaluated. Percentage change of the above mentioned parameters during HD was estimated. Orthogonal X; Y and Z leads were derived from the standard 12-leads and VCG parameters changes in response to HD were analysed. QRS loop area increased significantly after HD, while T loop area did not change significantly. Maximal QRS vector increased significantly, maximal T vector decreased significantly, and QRS-T angle remained relatively the same. The increase of QRS area did not show a significant correlation with any of the demographic factors, clinical characteristics and laboratory parameters. The increase of maximal QRS vector was inversely correlated with HD duration in years (p = 0.002). The decrease of T loop area and maximal T vector correlated negatively with Na shift during HD (p = 0.02 and p = 0.03, respectively). The decrease of maximal T vector correlated positively with the change in K concentration (p = 0.04).