title: Twelve-lead electrocardiographic characteristics of the aortic cusp region guided by intracardiac echocardiography and electroanatomic mapping.
abstract: BACKGROUND
  The most common site of origin of idiopathic ventricular tachycardia (VT) is the right ventricular outflow tract. Idiopathic VT also can arise from the left ventricular outflow tract and the surrounding structures. Morphologic descriptions of 12-lead ECG characteristics of the aortic cusp region are limited.
  
  
  OBJECTIVE
  The purpose of this study was to define unique ECG characteristics of the aortic cusp region by performing a systematic analysis of pacemapping of this region in patients with structurally normal hearts.
  
  
  METHODS
  A combination of electroanatomic mapping, intracardiac echocardiography, and fluoroscopic guidance was used to study a total of 30 patients with structurally normal hearts undergoing left-sided ablation procedures. Each of the aortic valve cusps and the aortomitral continuity were paced at threshold and analyzed offline to determine unique ECG characteristics.
  
  
  RESULTS
  Pacing from the left coronary cusp typically produced a multiphasic QRS morphology consistent with an M or W pattern in lead V(1) with a precordial transition (R>S) no later than V(2). Pacing from the right coronary cusp typically resulted in a left bundle-type pattern with a broad small R wave in V(2) and a precordial transition generally at V(3). Pacing from the aortomitral continuity resulted in a qR pattern that was not observed anywhere else in the left ventricular outflow tract. When comparing the right coronary cusp and left coronary cusp, the precordial transition was earlier in the left coronary cusp than in the right coronary cusp. Pacing the noncoronary cusp uniformly resulted in atrial capture.
  
  
  CONCLUSIONS
  When considering ablation of idiopathic VT, the aortic cusps and aortomitral continuity must be considered as possible foci. The 12-lead ECG, a readily and easily obtainable source of information, has useful characteristics for differentiating VTs arising from the cusp region.
authors.affiliation: Cardiovascular Division, Section of Electrophysiology, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA. david.lin@uphs.upenn.edu
authors.forename: David
authors.initials: D
authors.lastname: Lin
authors.forename: Leonard
authors.initials: L
authors.lastname: Ilkhanoff
authors.forename: Edward
authors.initials: E
authors.lastname: Gerstenfeld
authors.forename: Sanjay
authors.initials: S
authors.lastname: Dixit
authors.forename: Stuart
authors.initials: S
authors.lastname: Beldner
authors.forename: Rupa
authors.initials: R
authors.lastname: Bala
authors.forename: Fermin
authors.initials: F
authors.lastname: Garcia
authors.forename: David
authors.initials: D
authors.lastname: Callans
authors.forename: Francis E
authors.initials: FE
authors.lastname: Marchlinski
mesh_terms: D000328:Adult; D000368:Aged; D001021:Aortic Valve / Q000033:anatomy & histology*; D018780:Body Surface Potential Mapping; D017115:Catheter Ablation; D004452:Echocardiography / Q000379:methods*; D004562:Electrocardiography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017180:Tachycardia, Ventricular / Q000628:therapy