Table 3

Biventricular Pacing and QRS Duration

StudyYearNo. of PatientsForm of Prolonged QRSMean Follow-Up (months)Mean QRS Before CRT (ms)Mean QRS After CRT (ms)Previous QRS vs. QRS After CRTp ValueClinical and Hemodynamic ImprovementRelationship Between QRS Shortening and Clinical ImprovementCorrelation of Spontaneous QRS Duration and Clinical Response
Bonanno et al. (51)200437NS8 ± 8189 ± 35162 ± 13<0.001NYHA↓, LVEF↑NSNS
Molhoek et al. (52)200461100% LBBB6177 ± 30161 ± 24<0.01NYHA↓, LVEF NSNoNo
Penicka et al. (53)200449 100% “LBBB-like”6NYHA↓, LVEF↑NoYes
 Responders27190 ± 30152 ± 37<0.01YesNo
 Non-responders22171 ± 27154 ± 30<0.01NoNo
Yu et al. (54)200458NoNo
 QRS 120 to 150 ms27
  • 15% LBBB

  • 85% IVCD

3134 ± 14NSNSNYHA↓, LVEF↑
 QRS >150 ms31
  • 87% LBBB

  • 13% IVCD

3172 ± 22NSNSNYHA↓, LVEF↑
Achilli et al. (55)200352NS18 ± 9151 ± 31124 ± 10<0.001NYHA↓, LVEF↑NSNS
Bax et al. (56)200322100% LBBB3172 ± 33158 ± 26<0.05NYHA↓, LVEF↑NSNS
Chan et al. (57)200363NS3182 ± 31151 ± 25<0.001NYHA↓, LVEF↑YesNS
Duncan et al. (58)200334IVCD12172 ± 19159 ± 330.04NYHA↓, LVESD↓, LVEDD↓, LVEF NSNSNS
Gasparini et al. (59)2003104
  • 85% LBBB

  • 8% RBBB

  • 7% Other

9165 ± 37143 ± 380.013NYHA and LVEF improved but statistical data nsNSNS
Gasparini et al. (25)2003158NS11NSNo
 QRS 110 to 150 ms30NS130 ± 15133 ± 15NSNYHA↓, LVEF↑NS
 QRS ≥150 ms128NS184 ± 22152 ± 17<0.0001NYHA↓, LVEF↑NS
Toussaint et al. (60)200334100% LBBB20 ± 7179 ± 18159 ± 16<0.0001NYHA↓, LVEF↑NoNo
Young et al. (61)2003187
  • 13% RBBB

  • Rest NS

6165 ± 22−20<0.001NYHA↓ Trend ↓LV Vols, LVEF NSNSNo
Yu et al. (62)200330
  • 57% LBBB

  • 43% IVCD

3167 ± 33145 ± 250.001NYHA↓, LVEF↑NoNo
Abraham et al. (63)2002228NS6167 ± 21Median decrease of 20 ms<0.001NYHA↓, LVEF↑NSNo
Ansalone et al. (64)200231100% LBBB>1 week and <1 month160 ± 27123 ± 24<0.001NYHA↓, LVEF↑NoNS
Martinelli-Filho et al. (65)200224100% LBBB24.5180.7177.4nsNYHA↓, LVEF↑NSNS
Gras et al. (66)2002103NS12178 ± 28152 ± 24<0.001NYHA↓, LVEF↑NSNS
Linde et al. (67)200248
  • 87% LBBB

  • Rest NS

12176 ± 19156 (from figure only)<0.05NYHA↓, LVEF↑NSNS
Lunati et al. (68)200252“Majority LBBB”12 ± 5194 ± 33159 ± 19<0.0001NYHA↓, LVEF↑NSNo
Pitzalis et al. (69)200220100% LBBB1169 ± 16132 ± 12<0.0001LVEF↑, NYHA NSNSNo
Reuter et al. (70)20021020% RBBB12184 ± 38168 ± 25<0.01NYHA↓, LVEF↑NoNo
Ricci et al. (71)200248NS9 ± 4154 ± 29120 ± 18<0.001NYHA↓, LVEF↑NSNS
Saxon et al. (72)200253
  • 63% LBBB

  • 3% RBBB

  • 34% Other

4177 ± 34157 ± 320.12 nsLVEF not ↑, LVEDD↓, LVEDD↓, LVESV↓, NYHA NSNoNo
Sogaard et al. (73)200220
  • 90% LBBB

  • 10% RBBB

12.6189 ± 23NSNSNYHA↓, LVEF↑NSNo
Yu et al. (74)200225NS3162 ± 30142 ± 200.001NYHA↓, LVEF↑NSNS
Alonso et al. (75)2001102NS15 ± 13185 ± 26158 ± 19<0.001NYHA↓, LVEF↑NSNS
Ansalone et al. (76)200121100% LBBB>1 week and <1 month158 ± 31122 ± 270.00006NYHA↓, LVEF↑NSNS
Cazeau et al. (77)200148NS3174 ± 20157 ± 30<0.002NYHA NS, LVEF NS QOL↑, 6WD↑NSNS
Leclercq et al. (78)2000
  • 37

  • 22, SR

  • 15, AF

  • 80% “LBBB aspect”

  • 20% PM

14 ± 9181 ± 23About 10% reductionNSNYHA↓, LVEF↑ only in the AF groupNSNS
Leclercq et al. (79)20005040% PM15 ± 10197 ± 32162 ± 29<0.001NYHA↓NSNS
Rest “LBBB aspect”LVEF↑
Reuter et al. (80)200047NS8193 ± 40168 ± 29<0.01NYHA↓, LVEF not ↑NoNS
Toussaint et al. (81)200021NS121801640.001LVEF↓, NYHA NSNSNS
Alonso et al. (82)199926
  • 88% LBBB

  • 4% RBBB

  • 8% IVCD

8 ± 4179 ± 22154 ± 170.0004NYHA↓, LVEF NSYesNS
Gras et al. (83)199868NS3179143<0.001NYHA↓, LVEF not ↑NoNS
  • Studies with ≥20 patients;

  • p value comparing QRS duration before and after CRT;

  • p value is for the responder group (19 of 26 patients). There was no difference in QRS duration after CRT in the non-responder group (7 of 26 patients). Patients were not evaluated a single group. Acute studies are not included. Several articles in the Table provided no standard deviations on data.  AF = atrial fibrillation; CRT = cardiac resynchronization therapy; IVCD = intraventricular conduction delay; LBBB = left bundle branch block; LVEF = left ventricular ejection fraction; ms = milliseconds; No. = number; NS = not stated; ns = not statistically significant; NYHA = New York Heart Association; PM = previously implanted conventional pacemaker; pts = patients; RBBB = right bundle branch block; Vols = volumes; Year = year of publication.