BIO|Adapt study is designed to provide evidence for the clinical benefit of the CRT AutoAdapt feature. This feature provides continuous adaptation of AV delay and biventricular pacing modality. However, additional clinical data on the short and mid-term improvement of CRT-D patients by the CRT AutoAdapt feature are needed.

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.

Inclusion Criteria:

• Indication for de novo implantation or upgrade to a CRT-D device
• Enrolled in BIO|STREAM.HF but not yet implanted with or upgraded to CRT-D
• LVEF < 35%
• QRS > 120 ms
• NYHA II-IV
• Atrial heart rate during sinus rhythm at rest below 100 bpm
• Patient is able to understand the nature of the study and willing to provide written informed consent to this submodule

Exclusion Criteria:

• Planned implantation or previous implantation with a BIOTRONIK DX ICD lead
• History of persistent/permanent AF
• History of complete AV-block