title: U wave features in body surface potential mapping in post-myocardial infarction patients.
abstract: BACKGROUND
  The data on U wave features in post-myocardial infarction (MI) remain sparse. We employed 120-lead body surface potential mapping (BSPM) to explore the U wave in patients with remote MI.
  
  
  METHODS
  Sixty post-MI patients and 46 healthy controls were examined. After signal averaging, the polarity changes of U wave related to the T wave were analyzed, and the spatial and temporal U wave parameters were computed.
  
  
  RESULTS
  Four types of patterns based on T and U polarity were recognized. A pattern with positive T and U waves was related to better ventricular function. The study groups did not differ as regards to Tend-Uapex and Tapex-Uapex intervals whereas Uapex-Uend was significantly longer in MI patients (110 ± 20 ms vs. 100 ± 13 ms, P = 0.004). MI patients had significantly higher U wave maximum amplitude (70 ± 30 μV vs. 50 ± 20 μV, P < 0.001), and U integral area (3.96 ± 1.50 μV·s vs. 3.17 ± 0.99 μV·s, P = 0.002), but lower corresponding T wave parameter values, thus resulting into higher U/T maximum amplitude and area ratios (0.16 ± 0.10 vs. 0.09 ± 0.04, P < 0.001; and 0.13 ± 0.06 vs. 0.09 ± 0.03, P < 0.001). In comparison to 12-lead ECG, BSPM covering the entire thorax enhanced the detection of U waves.
  
  
  CONCLUSIONS
  MI tends to increase the U amplitude and prolong the later part of U wave duration thus augmenting the U wave. The size and location of infarction were associated with specific T and U wave polarity patterns.
authors.affiliation: Department of  Cardiology, Helsinki University Central Hospital, Helsinki, Finland; BioMag Laboratory, Helsinki University Central Hospital, Helsinki, Finland.
authors.forename: Bei
authors.initials: B
authors.lastname: Wang
authors.forename: Petri
authors.initials: P
authors.lastname: Korhonen
authors.forename: Ilkka
authors.initials: I
authors.lastname: Tierala
authors.forename: Helena
authors.initials: H
authors.lastname: Hänninen
authors.forename: Heikki
authors.initials: H
authors.lastname: Väänänen
authors.forename: Lauri
authors.initials: L
authors.lastname: Toivonen
mesh_terms: D000704:Analysis of Variance; D001145:Arrhythmias, Cardiac / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology*; D018780:Body Surface Potential Mapping / Q000379:methods*; D053840:Brugada Syndrome; D000075224:Cardiac Conduction System Disease; D005260:Female; D006329:Heart Conduction System / Q000002:abnormalities* / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology*; D012372:ROC Curve; D012815:Signal Processing, Computer-Assisted
keywords: U wave; body surface potential mapping; myocardial infarction; repolarization