title: Hemodialysis causes changes in dynamic vectorcardiographic ischemia monitoring parameters.
abstract: OBJECTIVE
  The aim of this study was to establish whether changes in parameters reflecting myocardial ischemia QRS vector difference (QRS-VD), ST change vector magnitude (STC-VM) and ST vector magnitude (ST-VM6) during hemodialysis (HD) registered by MIDA (myocardial infarction dynamic analysis) are related to changes in blood volume (BV), extracellular water (ECW) and blood biochemistry.
  
  
  METHODS
  Fifteen hemodialysis (HD) patients were studied. Computerized vectorcardiography was used for on-line dynamic analysis of ST segment and QRS complex changes. BV changes were monitored non-invasively and continuously with the CRIT-LINE instrument. Bioelectric impedance analysis (BIA) was used for ECW estimation. Blood samples were taken before and after hemodialysis for hemoglobin (B-Hb), hematocrit (B-Hcr), sodium (P-Na), chloride (P-Cl), magnesium (P-Mg), potassium (P-K), ionized calcium (P-iCa), phosphate (P-Pi) and astrup measurement.
  
  
  RESULTS
  During dialysis treatment QRS-VD, ST-VM6 and STC-VM did not change in parallel. According to the linear mixed model, no statistically significant changes were noted in ST-VM6 during dialysis (time effect p = 0.5635). On the other hand, QRS-VD and STC-VM showed a statistically significant linear trend (time effect 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.
  
  
  CONCLUSIONS
  During HD treatment changes in the vectorcardiographic ischemia monitoring parameters QRS-VD and STC-VM are mostly related to ECW and BV changes and may give a false positive impression of myocardial ischemia. The ST-VM6 trend is less markedly influenced by volume changes.
authors.affiliation: Department of Medicine, Tampere University Hospital, Finland.
authors.forename: S
authors.initials: S
authors.lastname: Ojanen
authors.forename: T
authors.initials: T
authors.lastname: Kööbi
authors.forename: A M
authors.initials: AM
authors.lastname: Koivisto
authors.forename: P
authors.initials: P
authors.lastname: Korhonen
authors.forename: J
authors.initials: J
authors.lastname: Mustonen
authors.forename: A
authors.initials: A
authors.lastname: Pasternack
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000175:diagnosis* / Q000503:physiopathology*; D006435:Renal Dialysis; D014672:Vectorcardiography