title: Electrical activation in the coronary sinus branches as a guide to cardiac resynchronisation therapy: rationale for a coordinate system.
abstract: BACKGROUND
  For successful cardiac resynchronisation therapy (CRT) a spatial and electrical separation of right and left ventricular electrodes is essential. The spatial distribution of electrical delays within the coronary sinus (CS) tributaries has not yet been identified.
  
  
  OBJECTIVE
  Electrical delays within the CS are described during sinus rhythm (SR) and right ventricular pacing (RVP). A coordinate system grading the mitral ring from 0° to 360° and three vertical segments is proposed to define the lead positions irrespective of individual CS branch orientation.
  
  
  METHODS
  In 13 patients undergoing implantation of a CRT device 6±2.5, (median 5) lead positions within the CS were mapped during SR and RVP. The delay to the onset and the peak of the local signal was measured from the earliest QRS activation or the pacing spike. Fluoroscopic positions were compared to localizations on a nonfluoroscopic electrode imaging system.
  
  
  RESULTS
  During SR, electrical delays in the CS were inhomogenous in patients with or without left bundle branch block (LBBB). During RVP, the delays increased by 44±32 ms (signal onset from 36±33 ms to 95±30 ms; p<0.001, signal peak from 105±44 ms to 156±30 ms; p<0.001). The activation pattern during RVP was homogeneous and predictable by taking the grading on the CS ring into account: (% QRS) = 78-0.002 (grade-162)(2), p<0.0001. This indicates that 78% of the QRS duration can be expected as a maximum peak delay at 162° on the CS ring.
  
  
  CONCLUSIONS
  Electrical delays within the CS vary during SR, but prolong and become predictable during RVP. A coordinate system helps predicting the local delays and facilitates interindividual comparison of lead positions irrespective of CS branch anatomy.
authors.affiliation: Division of Pacing and Electrophysiology, Clinic for Cardiology, Cardiovascular Center, University Hospital Zurich, Zurich, Switzerland. christoph.scharf@gmail.com
authors.forename: Christoph
authors.initials: C
authors.lastname: Scharf
authors.forename: Nazmi
authors.initials: N
authors.lastname: Krasniqi
authors.forename: Jens
authors.initials: J
authors.lastname: Hellermann
authors.forename: Mariette
authors.initials: M
authors.lastname: Rahn
authors.forename: Gabor
authors.initials: G
authors.lastname: Sütsch
authors.forename: Corinna
authors.initials: C
authors.lastname: Brunckhorst
authors.forename: Firat
authors.initials: F
authors.lastname: Duru
mesh_terms: D000368:Aged; D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D058409:Cardiac Resynchronization Therapy Devices; D054326:Coronary Sinus / Q000473:pathology / Q000503:physiopathology*; D004452:Echocardiography; D005500:Follow-Up Studies; D006329:Heart Conduction System / Q000000981:diagnostic imaging / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D016896:Treatment Outcome; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000628:therapy