title: T vector and loop characteristics in coronary artery disease and during acute ischemia.
abstract: OBJECTIVE
  Three-dimensional characterization of the ventricular repolarization by the T vector and T vector loop morphology in coronary artery disease (CAD), and their response to short-term (no flow) ischemia induced by coronary occlusion during a percutaneous intervention (PCI).
  
  
  BACKGROUND
  The risk for sudden cardiac death is increased in conditions of acute or permanently heterogeneous ventricular repolarization, for which ischemia is a risk factor.
  
  
  METHODS
  Fifty-six CAD patients without visible collateral circulation were studied during an elective single-vessel PCI, and 10 healthy controls twice at rest. T vector parameters (Televation, Tazimuth, and QRS-T angle), and T loop parameters (Tarea, Tavplan, and Teigenv) were measured by vectorcardiography. ST vector magnitude (ST-VM) and its change (STC-VM) were used for reference.
  
  
  RESULTS
  At rest, T vector loop morphology (Tarea, Teigenv) was significantly different in CAD patients and controls, while T vector angles did not separate the groups. Ischemia induced significant changes in T loop parameters in the entire CAD group, whereas in the LAD subgroup significant changes were seen also in T vector angle. The T loop morphology was significantly different at baseline and a more pronounced response to ischemia (Tarea) was seen in patients with, than in those without, a history of hypertension.
  
  
  CONCLUSIONS
  T loop morphology, rather than the T vector angle, separated CAD patients from healthy controls. Coronary occlusion had significant impact on ventricular repolarization, as assessed by T vector and morphology analysis, and most prominently in the LAD group. Hypertensive patients appeared especially vulnerable to ischemia.
authors.affiliation: Department of Cardiology, Karolinska Institutet, Karolinska Hospital, Stockholm, Sweden.
authors.forename: Aigars
authors.initials: A
authors.lastname: Rubulis
authors.forename: Jens
authors.initials: J
authors.lastname: Jensen
authors.forename: Gunilla
authors.initials: G
authors.lastname: Lundahl
authors.forename: Jari
authors.initials: J
authors.lastname: Tapanainen
authors.forename: Liliane
authors.initials: L
authors.lastname: Wecke
authors.forename: Lennart
authors.initials: L
authors.lastname: Bergfeldt
mesh_terms: D000208:Acute Disease; D000328:Adult; D000368:Aged; D015906:Angioplasty, Balloon, Coronary / Q000009:adverse effects; D016022:Case-Control Studies; D003324:Coronary Artery Disease / Q000175:diagnosis / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D014672:Vectorcardiography