title: Larger interventricular conduction time enhances mechanical response to resynchronization therapy.
abstract: BACKGROUND
  Previous studies have reported that the left ventricular (LV) pacing site is a major determinant of the hemodynamic response to cardiac resynchronization therapy (CRT). However, lead positioning in a lateral or posterolateral cardiac vein may not be optimal for every patient. The objective of this study was to assess the relationship between the right ventricular (RV)-to-LV conduction time and the systolic function during CRT on the basis of changes to LV pressure-volume loops.
  
  
  METHODS
  Left ventricular pressure and volume data were determined using a conductance catheter during CRT device implantation in 10 patients. Four endocardial LV sites were systematically assessed at four atrioventricular delays. The RV-to-LV conduction time was measured as the time interval between spontaneous peak R waves, recorded through the RV lead and the LV catheter.
  
  
  RESULTS
  The optimal pacing site varied among patients. However, the pacing site associated with the maximum RV-to-LV conduction time resulted in a stroke volume improvement comparable to the pacing site identified through individual hemodynamic optimization (41 ± 17 mL vs 44 ± 18 mL, P = 0.266). Moreover, the RV-to-LV conduction time recorded at each endocardial pacing site correlated positively with the increase in stroke volume (r = 0.537; P < 0.001), stroke work (r = 0.642; P < 0.001), and the pressure-derivative maximum (r = 0.646; P < 0.001) obtained with CRT.
  
  
  CONCLUSIONS
  An optimal acute response to CRT can be obtained by positioning the LV lead at the site associated with the maximum RV-to-LV conduction time. A significant correlation appears to exist between RV-to-LV conduction time and the improvement in systolic function with CRT.
authors.affiliation: Institute of Internal Medicine and Cardiology, University of Florence, Florence, Italy. lpadeletti@interfree.it
authors.forename: Luigi
authors.initials: L
authors.lastname: Padeletti
authors.forename: Paolo
authors.initials: P
authors.lastname: Pieragnoli
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Ricciardi
authors.forename: Laura
authors.initials: L
authors.lastname: Perrotta
authors.forename: Alessandro P
authors.initials: AP
authors.lastname: Perini
authors.forename: Gino
authors.initials: G
authors.lastname: Grifoni
authors.forename: Ilaria
authors.initials: I
authors.lastname: Ricceri
authors.forename: Margherita
authors.initials: M
authors.lastname: Padeletti
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Lionetti
authors.forename: Sergio
authors.initials: S
authors.lastname: Valsecchi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D015150:Echocardiography, Doppler; D004562:Electrocardiography; D004699:Endocardium / Q000503:physiopathology; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006333:Heart Failure / Q000503:physiopathology* / Q000628:therapy*; D006352:Heart Ventricles / Q000503:physiopathology*; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D016014:Linear Models; D008297:Male; D013318:Stroke Volume / Q000502:physiology; D016896:Treatment Outcome