Background: According to several studies the QRS amplitude of the ECG increases during hemodialysis. The detailed background to this phenomenon has not been defined. Two main mechanisms have been suggested: myocardial ischemia and volume changes. New noninvasive technologies make possible a comparison of QRS complex changes synchronously with myocardial ischemia and extracellular water (ECW)/blood volume (BV) changes during hemodialysis. Methods: In this study hemodialysis-related changes in body weight, biochemical blood variables, BV, ECW, ST segment and QRS complex were analyzed in 15 patients (age 36–76, time on dialysis 0–6 years) undergoing chronic hemodialysis treatment. QRS complex and ST segment changes were measured using a dynamic vectorcardiographic monitoring system. The ECG parameters measured were QRS vector difference (QRS-VD) and ST vector magnitude (ST-VM6). Bioimpedance analysis was used to detect changes in the ECW. Continuous measurement of BV changes was implemented using an on-line optical reflection method based on the reflection of infrared light by erythrocyte membranes. Blood hemoglobin (B-Hb), hematocrit (B-Hcr), plasma sodium (P-Na), chloride (P-Cl), magnesium (P-Mg), potassium (P-K), ionized calcium (P-iCa), phosphate (P-Pi), creatinine (P-Crea) and urea (S-Urea) were monitored. Results: The mean QRS-VD increase during the dialysis session was almost fourfold (372 ± 300%) from 4.16 ± 2.40 to 15.60 ± 7.0 μVs (p < 0.001). This change was due to a change in amplitude, since the duration of the QRS complex did not alter significantly. The correlation between the changes in QRS-VD and body weight from the start to the end of the dialysis session was moderate and statistically significant (r = –0.55, p < 0.05). The correlation between the changes in QRS-VD and ECW varied from r = –0.67 to –0.97, being statistically significant in all patients (p < 0.001). The correlation between BV and QRS-VD was assessed at one minute intervals during the dialysis and varied from r = –0.22 to –0.98, being significant in 14 of the 15 patients (p < 0.001). Significant ST segments alterations (ST-VM6 elevation > 100 μV) did not occur during dialysis. Laboratory parameters reflecting volume and osmotic changes during hemodialysis correlated with QRS-VD change: B-Hcr (r = 0.56, p < 0.05), B-Hb (r = 0.63, p < 0.05), P-Na (r = 0.62, p < 0.05) and S-Urea (r = –0.62, p < 0.05). Conclusions: The increase in QRS complex amplitude during hemodialysis is correlated to reduced ECW. The mechanism involved is most probably augmentation of electrical resistance of the tissues around the heart caused by loss of interstitial fluid.

Background Knowledge of arrhythmias in patients with end-stage renal disease (ESRD) is mainly based on ambulatory electrocardiography (ECG) studies and observations during haemodialysis. We used insertable cardiac monitors to define the prevalence of arrhythmias, focusing on bradyarrhythmias, in ESRD patients treated with several dialysis modes including home therapies. Moreover, we assessed whether these arrhythmias were detected in baseline or ambulatory ECG recordings. Methods Seventy-one patients with a subcutaneously insertable cardiac monitor were followed for up to three years. Asystole (≥4.0 secs) and bradycardia (heart rate &lt;30 bpm for ≥4 beats) episodes, ventricular tachyarrhythmias and atrial fibrillation were collected and verified visually. A baseline ECG and a 24-48-hour ambulatory ECG were recorded at recruitment and once a year thereafter. Results At recruitment, forty-four patients were treated in in-center haemodialysis, 12 in home haemodialysis and 15 in peritoneal dialysis. During a median follow-up of 34.4 months, 18 (25.4%) patients had either an asystolic or a bradycardic episode. The median length of each patient’s longest asystole was 6.6 seconds and that of a bradycardia 13.5 seconds. Ventricular tachyarrhythmias were detected in 16 (23%) patients, and atrial fibrillation in 34 (51%) patients. In-center haemodialysis and type II diabetes were significantly more frequent among those with bradyarrhythmias whereas no bradyarrhythmias were found in home haemodialysis. No bradyarrhythmias were evident in baseline or ambulatory ECG recordings. Conclusions Remarkably many patients with ESRD had bradycardia or asystolic episodes, but these arrhythmias were not detected by baseline or ambulatory ECG.

The pharmacokinetic parameters describing the fate of one intravenous clodronate (disodium dichloromethane diphosphonate) dose was studied in 24 normal subjects and in 24 patients with different degrees of renal insufficiency. The aim of the study was to derive data for adjustment of dosage in relation to renal function. Disodium clodronate in serum and urine samples was analyzed by capillary gas chromatography with mass-selective detection. The renal clearance (CLR) of clodronate was highly dependent on renal function and declined successively with declining glomerular filtration rate (GFR). Plasma clearance (CLP) declined, too, but to a lesser degree than CLR. The impairment of renal function resulted in decreased cumulative urinary elimination of clodronate and increased total areas under the serum concentration-time curve (AUC0-infinity). Hence, as the renal elimination of clodronate diminishes with decreasing GFR, there is a related retention of the substance. As a result of the present study, the following dosages are recommended: creatinine clearance (CLCr) from 50 to 80 ml/minute, 75-100% of normal dose; CLCr 12-50 ml/minute, 50-75% of normal dose; and ClCr < 12 ml/minute, 50% of normal dose. The results must be interpreted with caution in patients with malignancy and severe skeletal disease, in whom the nonrenal clearance may vary markedly.

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UF affects the parameters Emax, Amax and IVRT used to evaluate LV diastolic function. The changes in Emax and Amax during the HD phase are due to fluid refilling from tissues into the blood space, HD as such having no effect on Doppler indices. However, isolated UF or HD does not affect the Emax/Amax ratio. Emax and IVRT seem to be the most volume-sensitive parameters.