title: Electrocardiographic determinants of the polymorphic QRS morphology in idiopathic right ventricular outflow tract tachycardia.
abstract: BACKGROUND
  Premature ventricular contractions (PVCs) arising from the right ventricular outflow tract (RVOT) can trigger polymorphic ventricular tachycardia (PVT) or ventricular fibrillation (VF) in patients with no structural heart disease. We aimed to clarify the ECG determinants of the polymorphic QRS morphology in idiopathic RVOT PVT/VF.
  
  
  RESULTS
  The ECG parameters were compared between 18 patients with idiopathic PVT/VF (PVT-group) and 21 with monomorphic VT arising from the RVOT (MVT-group). The coupling interval (CI) of the first VT beat was comparable between the 2 groups. However, the prematurity index (PI) of the first VT beat was smaller in the PVT-group than in the MVT-group (P < 0.001). Furthermore, the QT index, defined as the ratio of the CI to the QT interval of the preceding sinus complex, was also smaller for the PVT/VF in the PVT-group than that for the VT in the MVT-group (P < 0.01). In the PVT-group, the CI of the first VT beat was comparable between that of VT and isolated PVCs, but the PI of the first VT beat was shorter for VT than isolated PVCs (P < 0.05). The PI was the only independent determinant of the polymorphic QRS morphology (odd ratio = 2.198; 95% confidence interval = 1.321-3.659; P = 0.002).
  
  
  CONCLUSIONS
  The smaller PIs of the first VT beat may result in a polymorphic QRS morphology.
authors.affiliation: Cardiovascular Division, Institute of Clinical Medicine, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan.
authors.forename: Miyako
authors.initials: M
authors.lastname: Igarashi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Tada
authors.forename: Kenji
authors.initials: K
authors.lastname: Kurosaki
authors.forename: Hiro
authors.initials: H
authors.lastname: Yamasaki
authors.forename: Daiki
authors.initials: D
authors.lastname: Akiyama
authors.forename: Yukio
authors.initials: Y
authors.lastname: Sekiguchi
authors.forename: Kenji
authors.initials: K
authors.lastname: Kuroki
authors.forename: Takeshi
authors.initials: T
authors.lastname: Machino
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Murakoshi
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Nakata
authors.forename: Keisuke
authors.initials: K
authors.lastname: Kuga
authors.forename: Akihiko
authors.initials: A
authors.lastname: Nogami
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Aonuma
mesh_terms: D000200:Action Potentials; D000328:Adult; D000368:Aged; D001145:Arrhythmias, Cardiac / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery; D017115:Catheter Ablation; D004562:Electrocardiography; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D006352:Heart Ventricles / Q000503:physiopathology* / Q000601:surgery; D006801:Humans; D007564:Japan; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D017180:Tachycardia, Ventricular / Q000175:diagnosis / Q000503:physiopathology; D013997:Time Factors; D014693:Ventricular Fibrillation / Q000175:diagnosis / Q000503:physiopathology; D016278:Ventricular Function, Right; D018879:Ventricular Premature Complexes / Q000175:diagnosis / Q000503:physiopathology