title: Toward understanding response to cardiac resynchronization therapy: left ventricular dyssynchrony is only one of multiple mechanisms.
abstract: OBJECTIVE
  To date, most published echocardiographic methods have assessed left ventricular (LV) dyssynchrony (DYS) alone as a predictor for response to cardiac resynchronization therapy (CRT). We hypothesized that the response is instead dictated by multiple correctable factors.
  
  
  RESULTS
  A total of 161 patients (66 +/- 10 years, EF 24 +/- 6%, QRS > 120 ms) were investigated pre- and post-CRT (median of 6 months). Reduction in NYHA Class >/=1 or LV reverse remodelling (end-systolic volume reduction >/= 10%) defined response. Four different pathological mechanisms were identified. Group1: LVDYS characterized by a pre-ejection septal flash (SF) (87 patients, 54%). Elimination of SF (77 of 87 patients) resulted in reverse remodelling in 100%. Group 2: short-AV delay (21 patients, 13%) resolution (19 of 21 patients) resulted in reverse remodelling in 16 of 19. Group 3: long-AV delay (16 patients, 10%) resolution (14 of 16 patients) resulted in NYHA Class reduction >/=1 in 11 with reverse remodelling in five patients. Group 4: exaggerated LV-RV interaction (15 patients, 9%) reduced post-CRT. All responded clinically with fall in pulmonary artery pressure (P = 0.003) but did not volume respond. Group 5: patients with none of the above correctable mechanisms (22 patients, 14%). None responded to CRT.
  
  
  CONCLUSIONS
  CRT response is dictated by correction of multiple independent mechanisms of which LVDYS is only one. Long-axis DYS measurements alone failed to detect 40% of responders.
authors.affiliation: Department of Cardiology, St George's Hospital, Blackshaw Road, SW17 0QT London, UK. chirineparsai@hotmail.com
authors.forename: Chirine
authors.initials: C
authors.lastname: Parsai
authors.forename: Bart
authors.initials: B
authors.lastname: Bijnens
authors.forename: George Ross
authors.initials: GR
authors.lastname: Sutherland
authors.forename: Aigul
authors.initials: A
authors.lastname: Baltabaeva
authors.forename: Piet
authors.initials: P
authors.lastname: Claus
authors.forename: Maciej
authors.initials: M
authors.lastname: Marciniak
authors.forename: Vince
authors.initials: V
authors.lastname: Paul
authors.forename: Mike
authors.initials: M
authors.lastname: Scheffer
authors.forename: Erwan
authors.initials: E
authors.lastname: Donal
authors.forename: Geneviève
authors.initials: G
authors.lastname: Derumeaux
authors.forename: Lisa
authors.initials: L
authors.lastname: Anderson
mesh_terms: D000368:Aged; D001145:Arrhythmias, Cardiac / Q000503:physiopathology / Q000628:therapy*; D002304:Cardiac Pacing, Artificial; D002306:Cardiac Volume; D018618:Echocardiography, Doppler, Color; D005260:Female; D006333:Heart Failure / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction; D011446:Prospective Studies; D013318:Stroke Volume; D018487:Ventricular Dysfunction, Left / Q000503:physiopathology / Q000628:therapy*; D020257:Ventricular Remodeling