Hemodialysis causes changes in dynamic vectorcardiographic ischemia monitoring parameters

Aims: The aim of this study was to establish whether changes in parameters reflecting myocardial ischemia QRS vector difference (QRS-VD), ST change ve ctor magnitude (STC-VM) and ST vector magnitude (ST-VM6) during hemodialysi s (HD) registered by MIDA (myocardial infarction dynamic analysis) are rela ted to changes in blood volume (BV), extracellular water (ECW) and blood bi ochemistry, Patients and methods. Fifteen hemodialysis (HD) patients were s tudied. Computerized vectorcardiography was used for on-line dynamic analys is of ST segment and QRS complex changes. BV changes were monitored non-inv asively and continuously with the GRIT-LINE instrument. Bioelectric impedan ce analysis (BIA) was used for ECW estimation. Blood samples were taken bef ore and after hemodialysis for hemoglobin (B-Hb), hematocrit (B-Hcr), sodiu m (P-Na), chloride (P-Cl) magnesium (P-Mg), potassium (P-K), ionized calciu m (P-iCa), phosphate (P-Pi) and astrup measurement. Results: During dialysi s treatment QRS-VD, ST-VM6 acid STC-VM did not change in parallel. Accordin g to the linear mixed model, no statistically significant changes were note d in ST-VM6 during dialysis (time effect p = 0.5635). On the other hand, QR S-VD and STC-VM showed a statistically significant linear trend (time effec t for QRS-VD p = 0.0001 and for STC-VM p = 0.0004). Changes in both ECW and BV affected the change in QRS-VD and in STC-VM. Conclusion: During HD trea tment changes in the vectorcardiographic ischemia monitoring parameters QRS -VD and STC-VM are mostly related to ECW and BV changes and may give a fals e positive impression of myocardial ischemia. The ST-VM6 trend is less mark edly influenced by volume changes.