The magnitude of clinical and hemodynamic benefit of CRT varies significantly among its
recipients. Many studies report that approximately one-third of the implanted population
show no clinical improvement at follow-ups. There are many clinical factors that are
associated with the CRT response and the grade of benefit, such as type of
cardiomyopathy, severity of electrical conduction abnormalities, dyssynchrony, and scar
burden. In addition, there are device-related factors such as lead location, insufficient
ventricular pacing percentage (%V), and suboptimal atrial-ventricular (AV) and ventricle-
ventricle (VV) timing.
The main finding in such CRT non-responders is a suboptimal AV-timing (47%). The
optimization of AV and VV intervals during biventricular (BiV) pacing is an option to
maximize the positive effects of CRT, by taking advantage of the full atrial contraction
for optimal filling of the ventricles. Optimization is usually accomplished by using
echocardiography or other methods. However, such methods are time consuming for the
hospitals and may not provide a benefit for every patient.
The most common pacing mode for CRT therapy is BiV pacing, but many acute and chronic
randomized clinical studies have demonstrated that left-ventricular (LV) pacing can be at
least as effective as BiV pacing. In patients with sinus rhythm and normal
atrioventricular (AV) conduction, pacing the left ventricle only with an appropriate AV
interval can result in an even superior LV and right ventricular (RV) function compared
with standard BiV pacing. LV pacing has been proposed as an alternative approach to apply
cardiac resynchronization as it has been shown that LV pacing induces short-term
hemodynamic benefits compared to BiV pacing.
Different algorithms have been developed by different manufactures to provide continuous
automatic CRT optimization, allowing a more physiologic ventricular activation and
greater device longevity in patients with normal AV conduction due to the reduction of
unnecessary RV pacing. Studies with the Medtronic Adaptive cardiac resynchronization
therapy (aCRT) algorithm, that provides automatic ambulatory selection between
synchronized LV or BiV pacing with dynamic optimization of atrioventricular and
interventricular delays, have shown that the algorithm is safe and as effective as BiV
pacing with comprehensive echocardiographic optimization.
The CRT AutoAdapt feature by BIOTRONIK optimizes the CRT therapy settings of the device
automatically and continuously. This algorithm adjusts the AV delay and sets the
ventricular pacing configuration to BiV or LV. The settings are based on intracardiac
conduction times, which are measured every 60 seconds to select the optimal
configuration.
The objective of this study is to show non-inferiority of this feature compared to
standard echo-based optimization with regard to clinical benefit.