title: Overdrive pacing from downstream sites on multielectrode catheters to rapidly detect fusion and to diagnose macroreentrant atrial arrhythmias.
abstract: BACKGROUND
  Entrainment criteria for macroreentrant arrhythmias are based on detecting fusion between tachycardia and paced wavefronts, but this is often difficult for atrial tachycardias (AT) after ablation of atrial fibrillation.
  
  
  RESULTS
  With the use of a multipolar catheter, pacing was performed from electrodes within the coronary sinus showing activation later than adjacent electrodes (downstream overdrive pacing) during 66 ATs in 62 patients: 20 cavotricuspid isthmus-dependent ATs, 20 perimitral ATs, 13 focal ATs with sequential coronary sinus activation, and 13 other macroreentrant left atrial ATs. The paced cycle length was 10 to 30 milliseconds below the tachycardia cycle length (TCL), and activation at the neighboring upstream electrodes was assessed. Downstream overdrive pacing at 48 sites close to a macroreentrant circuit (PPI-TCL <40 milliseconds, where PPI is postpacing interval) produced constant fusion demonstrated by a long stimulus to upstream atrial electrogram interval (S-Au) >75% TCL and was consistent with orthodromic activation of the upstream site despite its close proximity to the pacing site. In contrast, downstream overdrive pacing at 18 sites during focal AT or remote from the macroreentrant AT circuit (PPI-TCL >40 milliseconds) always demonstrated a comparatively short S-Au <25% of TCL (12±4% versus 89±4% of TCL; P<0.001), consistent with direct activation.
  
  
  CONCLUSIONS
  Selection of a downstream activation site for overdrive pacing can facilitate rapid recognition of macroreentry and proximity to the reentry circuit using a single multielectrode catheter by recognizing a PPI-TCL <40 milliseconds and S-Au >75% of TCL. Recognition of intracardiac constant fusion with this method is a novel criterion for transient entrainment.
authors.affiliation: From the Cardiovascular Division, Brigham and Women's Hospital, Boston, MA.
authors.forename: Chirag R
authors.initials: CR
authors.lastname: Barbhaiya
authors.affiliation: From the Cardiovascular Division, Brigham and Women's Hospital, Boston, MA.
authors.forename: Saurabh
authors.initials: S
authors.lastname: Kumar
authors.affiliation: From the Cardiovascular Division, Brigham and Women's Hospital, Boston, MA.
authors.forename: Justin
authors.initials: J
authors.lastname: Ng
authors.affiliation: From the Cardiovascular Division, Brigham and Women's Hospital, Boston, MA.
authors.forename: Usha
authors.initials: U
authors.lastname: Tedrow
authors.affiliation: From the Cardiovascular Division, Brigham and Women's Hospital, Boston, MA.
authors.forename: Bruce
authors.initials: B
authors.lastname: Koplan
authors.affiliation: From the Cardiovascular Division, Brigham and Women's Hospital, Boston, MA.
authors.forename: Roy
authors.initials: R
authors.lastname: John
authors.affiliation: From the Cardiovascular Division, Brigham and Women's Hospital, Boston, MA.
authors.forename: Laurence M
authors.initials: LM
authors.lastname: Epstein
authors.affiliation: From the Cardiovascular Division, Brigham and Women's Hospital, Boston, MA.
authors.forename: William G
authors.initials: WG
authors.lastname: Stevenson
authors.affiliation: From the Cardiovascular Division, Brigham and Women's Hospital, Boston, MA. gfmichaud@partners.org.
authors.forename: Gregory F
authors.initials: GF
authors.lastname: Michaud
mesh_terms: D000368:Aged; D001282:Atrial Flutter / Q000175:diagnosis / Q000601:surgery / Q000628:therapy; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D017115:Catheter Ablation; D004567:Electrodes, Implanted; D022062:Electrophysiologic Techniques, Cardiac / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012189:Retrospective Studies; D013611:Tachycardia, Atrioventricular Nodal Reentry / Q000175:diagnosis* / Q000601:surgery / Q000628:therapy*; D013612:Tachycardia, Ectopic Atrial / Q000175:diagnosis* / Q000601:surgery / Q000628:therapy*
keywords: arrhythmias, cardiac; atrial fibrillation; atrial flutter; catheter ablation; electrophysiology