The patients had daily Ws and ECGs recorded and printed routinely with the placement of the limb electrodes on the wrists and ankles, however, for the purposes of this study, the ECGs and Ws from hospital admission and at the point of half-PW gain (HF-W), and PW for the patients with AN, the hospital admission and discharge data for the control subjects, the prehemodialysis and posthemodialysis data for the patients undergoing this procedure, and the data from hospital admission and discharge for the patients with CHF were employed. An ECG unit (PageWriter XLi ECG, model M1700A; Philips; Amsterdam, the Netherlands) was used that acquires data simultaneously and digitally from all 12 ECG leads, instead of acquiring data from a few leads and calculating the rest of them online.5
Calibration of the unit was 1.0 mV = 1.0 cm. Measurements of the sum of the highest positive plus the lowest negative deflections of the QRS complex in all 12 ECG leads of all study ECGs were made to the nearest 0.5 mm, employing hard copies and using manual calipers and a magnifying glass (Fig 1
). For ECGs with atrial fibrillation, the average of measurements of three consecutive heart beats was used. Since the six limb leads can be calculated from leads 1 and 2, as per Einthoven law (leads 1 + 3 = 2), and the aV leads, as per formulas (lead aVR = 1/2[1 + 2], aVL = 1 − 1/2, , lead aVF = 2 − 1/2, , and lead aVR + aVL + aVF = 0),,2,6–7
the ΣQRS2 was employed as a variable, along with the ΣQRS12 and ΣQRS6. It should be emphasized here that the use of ΣQRS2 as an ECG system is employed with the full realization that for the derivation of the remaining four limb leads, through the above-described formulas, the values of leads 1 and 2 are treated algebraically in serial online measurements from the entire duration of the QRS complex in ECG machines,,5
while in the present work the sum of the peak-to-peak (ie, positive-to-negative) amplitude values of the QRS complex of these two leads is implemented. Moreover, it should be understood that the same measurement approach was used for all three ECG systems. ΣQRS12, ΣQRS6, and ΣQRS2 were calculated from the day of admission, the HF-W point, and the PW point for each of the 28 patients (Fig 1)
. Obviously, the HF-W point was determined after the PW was attained, and it represented a W value that was closest to one half of the PW gained. The mean (± SD) PW gain of the 28 patients with AN was 23.9 ± 14.8 lbs, and the mean HF-W gain was 16.9 ± 10.7 lbs. The corresponding ECG for the day when the HF-W was reached was used in the analysis. Similar calculations were employed for the hospital admission and discharge ECGs of the control subjects, the preprocedural and postprocedural tracings of patients who underwent hemodialysis, and the pretreatment and posttreatment tracings of the patients with CHF. The mean intraobserver variability of ΣQRS12 in 10 random ECGs has been found previously to be 0.41 ± 3.34%.,1
The mean frontal QRS complex axis (in degrees), as calculated by the automated ECG interpretation program,5
also was employed as a variable at all study time points in all patients.