QRS Amplitude and Volume Changes during Hemodialysis

Abstract

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.

Electrocardiographic Changes during Hemodiafiltration with Different Potassium Removal Rates

“…According to previous studies [2,3], the QRS amplitude significantly increased during HD (about 20%). QRS amplitude has often been assessed by means of vector difference, instead we simply used a QRS amplitude because HD mostly influences this feature [3].…”

“…ECG-derived parameters, such as QRS amplitude and ST depression, show significant variations during HD treatment [2,3], albeit without immediate clinical repercussions. Importantly, HD alters the duration and homogeneity of ventricular repolarization: the QT interval is found to be significantly prolonged by the end of the treatment, and the QT prolonging is more evident when complex ventricular premature beats occur [4].…”

Electrocardiography and Outcome in Patients with Diabetes Mellitus on Maintenance Hemodialysis

“…Furthermore, the QRS amplitude is dependent on various parameters influenced by hemodialysis; for example,. the QRS amplitude increases when body weight, end diastolic volume, potassium, and systolic arterial pressure decrease after hemodialysis (5,6), which might question the validity of LVH assessment by ECG indexes in hemodialysis patients. Finally, multicollinearity might have played a role because LVH is associated with hypertension and anemia; therefore, ECG-based diagnosis of LVH might have dropped out of the multivariate analysis (26).…”

“…Hard-copy ECGs, recorded at either 25 or 50 mm/s paper speeds were collected and processed in a central laboratory. An independent experienced cardiologist who was blind to all clinical information quantified and interpreted the ECGs according to prespecified criteria (Table 1), describing the following characteristics for each recording: (1) cardiac rhythm, (2) heart rate, (3) QRS axis, (4) presence of atrioventricular conduction defects, (5) complete RBBB, (6) complete LBBB, (7) signs of MI, (8) LVH, and (9) corrected QT interval. To validate this analysis, the same reader reanalyzed a random subsample of ECGs.…”

“…Although ECGs are extensively used diagnostic tools, appropriate systematic evaluations regarding the prognostic utility in hemodialysis patients are absent. This is of particular importance, since in this high-risk group ECG interpretation might be compromised by the fact that volume and electrolyte status can influence various ECG variables like the QRS complex, QT interval and P-wave (3,4,5,6).…”