Abstract 14676: Evidence for Electromechanical Coupling in Patients With Cardiac Resynchronization Therapy From Vectorcardiography and Echocardiography
Introduction: Experiments in dogs with left bundle branch block (LBBB) showed a strong relation between electrical (QRS-vector amplitude, QRSVampl) and mechanical interventricular dyssynchrony. We investigated this relation in patients with previously implanted devices for cardiac resynchronization therapy (CRT) using echocardiography and vectorcardiography.
Methods: To induce different degrees of left (LV) and right ventricular (RV) pre-excitation, single site LV pacing at many AV-delays was performed in 20 LBBB patients in sinus rhythm, and biventricular pacing at many VV-delays in 18 patients with complete AV-block. At all pacing settings 3D-vectorcardiograms and echocardiograms were recorded. QRSVampl was defined negative when the spatial vector direction differed <90° from LBBB or RV-pacing. Interventricular mechanical dyssynchrony (IVMD) was determined from Doppler recordings and septal strain from speckle tracking. Septal systolic rebound stretch (SRS) and pre-stretch (SPS) were assessed, representing mechanical indicators of early and late septal contraction, respectively. The lowest sum of SRS and SPS was regarded to reflect the most physiological septal strain pattern.
Results: The figure shows an example of changes in QRSVampl, IVMD, SRS and SPS at different VV-delays. For both groups combined, a strong correlation was found between QRSVampl and IVMD at all AV- and VV-delays (median R=0.90; IQR 0.85 - 0.94), SPS (R=0.85; 0.73 - 0.91) and SRS (R=0.75; 0.65 - 0.83). The AV- and VV-delay that provided the QRSVampl value halfway in between that during LV and RV pre-excitation ((A+B)/2; figure) corresponded with the (A+B)/2-value of IVMD and with the delay where the sum of SRS and SPS was lowest (differences 10ms; -20 - 35ms and 0ms; -10 - 20ms).
Conclusions: In CRT patients, a close relationship exists between electrical and mechanical interventricular dyssynchrony, providing good evidence for electromechanical coupling.
- © 2013 by American Heart Association, Inc.