title: Midterm 'super-response' to cardiac resynchronization therapy by biventricular pacing with fusion: insights from electro-anatomical mapping.
abstract: OBJECTIVE
  Some authors recommend avoiding fusion with left ventricular (LV) intrinsic depolarization during cardiac resynchronization therapy (CRT). If fusion is still present during optimized biventricular (Biv) pacing and its long-term effects on the response to CRT are currently unknown. The aim of the study was to analyse the endocardial LV activation pattern induced by echocardiographically optimized Biv pacing and its influence on LV reverse remodelling.
  
  
  RESULTS
  Contact electro-anatomical mapping was performed in 15 heart failure (HF) patients with left bundle branch block and echocardiographically optimized CRT (seven ischaemic aetiology, 64 +/- 8 years, three women, New York Heart Association class 3 +/- 0.4, LV ejection fraction 25 +/- 5%). Left ventricular activation maps were performed in sinus rhythm (SR), during DDD right ventricular apical (RVA) and optimized Biv pacing. Fusion with intrinsic rhythm during pacing was considered when LV septal activation was produced at least partially by intrinsic depolarization, when compared with LV activation map during SR. Patients were considered responders to CRT if they had > or =10% reduction in LV end-systolic volume (LVESV) after 6 months of CRT. During SR, the LV breakthrough was mid-septal (n = 12), basal septum (n = 2), and apical (n = 1). During RVA pacing, LV breakthrough shifted apical in all patients. Right ventricular apical/Biv pacing proved fusion with intrinsic depolarization in 8 of 15 patients. The PR interval was shorter in patients with fusion RVA/Biv pacing (164 +/- 24 vs. 234 +/- 55 ms, P = 0.006). There was a trend for shorter LV activation time (LV(at)) in patients with fusion during RVA pacing (87 +/- 33 vs. 113 +/- 21 ms, P = 0.08) as well as during optimized Biv pacing (83 +/- 18 vs. 104 +/- 24 ms, P = 0.07), although LV(at) was similar in SR (100 +/- 22 vs. 106 +/- 20, P = NS). In patients with fusion, 6 months responder rate was significantly higher (100 vs. 28.5%, P < 0.007) as was the degree of LVESV reduction (39 +/- 17 vs. 1.0 +/- 14%, P < 0.001).
  
  
  CONCLUSIONS
  Biventricular pacing with fusion may substantially increase the structural responder rate probably by shortening LV(at).
authors.affiliation: Cardiology Department, Arrhythmia Section, Hospital Clinic, Thorax Institute, University of Barcelona, Villarroel 170, Barcelona, Catalonia, Spain.
authors.forename: Radu
authors.initials: R
authors.lastname: Vatasescu
authors.forename: Antonio
authors.initials: A
authors.lastname: Berruezo
authors.forename: Lluis
authors.initials: L
authors.lastname: Mont
authors.forename: David
authors.initials: D
authors.lastname: Tamborero
authors.forename: Marta
authors.initials: M
authors.lastname: Sitges
authors.forename: Etel
authors.initials: E
authors.lastname: Silva
authors.forename: Jose María
authors.initials: JM
authors.lastname: Tolosana
authors.forename: Bárbara
authors.initials: B
authors.lastname: Vidal
authors.forename: David
authors.initials: D
authors.lastname: Andreu
authors.forename: Josep
authors.initials: J
authors.lastname: Brugada
mesh_terms: D000368:Aged; D018780:Body Surface Potential Mapping / Q000379:methods*; D002037:Bundle-Branch Block / Q000150:complications / Q000175:diagnosis* / Q000517:prevention & control*; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D005260:Female; D006333:Heart Failure / Q000175:diagnosis* / Q000209:etiology / Q000517:prevention & control*; D006801:Humans; D008297:Male; D016896:Treatment Outcome