QRS vector analysis for optimizing timing of biventricular pacing in cardiac resynchronization therapy

In patients with heart failure and left bundle branch block (LBBB), cardiac
resynchronization therapy (CRT) improves cardiac pump function, clinical
status, and survival by restoring the LBBB induced asynchronous ventricular
contraction. However 30-50% of patients show little or no response to the
therapy. Optimal application of CRT using biventricular (BiV) pacing requires
appropriate programming of atrioventricular (AV)-delay and interventricular
(VV)-interval on an individual basis. However, extensive individual
optimization is often not practical or feasible in routine clinical practice.
Preliminary results from animal studies revealed a linear relation between
measurement of interventricular asynchrony and the QRS vector derived from the
surface ECG in BiV pacing. Moreover, the optimal improvement in left
ventricular (LV) pump function during BiV pacing was shown to be halfway the
minimum and maximum value of interventricular asynchrony as well as the QRS
vector.

The aim of the present study is to investigate whether the relation between QRS
vector, interventricular asynchrony and improvement in LV pump function is
present in CRT patients. Subsequently, we want to show that the QRS vector can
be used as a non-invasive and simple tool to optimize the configuration of the
BiV pacing device resulting in best hemodynamic improvement.

This study comprises an acute validation study, investigating QRS vector
analysis for optimization of BiV pacing in CRT patients by programming the best
suitable AV and VV delay.

During the proposed pacing protocol patients are exposed to a little physical
discomfort, because they have to lie down for approximately two hours. No
significant risks are identified and no psychological discomfort is associated
with participation.