The primary purpose of the study is to evaluate if patients with a standard indication for permanent ventricular pacing, left ventricular ejection fraction without limit, or any QRS duration will profit from the prevention of ventricular desynchronisation.

The study will be performed as a controlled, single-blind, international, multicenter, prospective, randomized, parallel group design.

In order to pragmatically examine the effectiveness of biventricular pacing in patients with an indication for ventricular pacing, the study group with biventricular pacing is compared to a control group with standard pacemakers which only allow univentricular (right ventricular) stimulation, as it has been the standard outside of clinical studies until so far.

Inclusion Criteria:

1. Presence of an indication for ventricular pacing according to the actual guidelines for the implantation of cardiac pacemakers and a need for frequent (or even permanent) ventricular pacing for:

   1. Permanent 3rd degree atrioventricular (AV)-block or
   2. Intermittent 3rd degree AV-block in combination with 1st degree AV-block with a pQ-interval ≥ 220 ms or
   3. 2nd degree AV-block type Mobitz II in combination with 1st degree AV-block with a pQ-interval ≥ 220 ms or
   4. 2nd degree AV-block type Mobitz I (if indicated) in combination with 1st degree AV-block with a pQ-interval ≥ 220 ms or
   5. 1st degree AV-block with a pQ-interval ≥ 220 ms and indication for ventricular pacing (includes indication for ventricular pacing based on long HV interval measured during invasive electrophysiological testing) or
   6. Sick-sinus-syndrome with symptomatic sinus bradycardia or sinus arrest as primary indication for device implantation in combination with long 1st degree AV-block with a pQ-interval ≥ 220 ms or
   7. Chronic (permanent) atrial fibrillation (flutter or tachycardia) with a spontaneous heart (ventricular) rate at rest ≤ 60/min or
   8. Chronic (permanent) atrial fibrillation (flutter or tachycardia) with a spontaneous heart (ventricular) rate at rest ≤ 75/min, if initiation or increase of pharmacological treatment with a relevant heart rate lowering effect (negative chronotropic effect) is planned for the time after pacemaker implantation (i.e. ß-blockers for heart failure and rate control)
   9. Patients scheduled for AV node ablation

2. Any QRS duration and morphology

3. Left ventricular ejection fraction (LVEF) without limit as measured by echocardiography (in at least one plane, either 4- or 2-chamber or apical long axis view)

4. Signed written informed consent of the patient or a first-degree relative for study participation after informing the patient/relative about the risks and the aim of the study

5. Willingness and ability to comply with the prescribed follow-up tests and schedule of evaluations.

6. Absence of an implanted ventricular pacing device (patients with atrial pacemakers and new need for ventricular pacing may be included)

Exclusion Criteria:

1. Implanted Cardioverter Defibrillator or consideration for implantation of an ICD due to arrhythmia indication. However, ICD implant for primary prevention of sudden cardiac death in patients with LVEF ≤ 35 % (in accordance with the actual guidelines for the implantation of arrhythmia devices[LVEF < 30%] and in accordance with the results of the SCD-Heft study [LVEF < 35%) will be allowed.
2. Implanted ventricular pacing device
3. Status 1 for cardiac transplantation and likelihood to receive transplantation within 2 years (these patients would not be expected to fulfill the follow-up requirements as outlined in this protocol)
4. Evidence of acute left ventricular dysfunction and high probability for its reversibility (e.g. acute myocarditis, tachycardiomyopathy)
5. Implanted prosthetic tricuspid valve
6. Severe musculoskeletal disorder(s)
7. Age below 18 years
8. Current or planned pregnancy in the next 6 months
9. Current or recent (within the past 30 days) participation in any other clinical investigation
10. Life expectancy of less than 6 months
11. Patient's inability to independently comprehend and complete the Quality of Life (QoL) questionnaire](streamdown:incomplete-link)

Study duration (5.7 years mean follow-up)

The sponsor assessed all events except the death cases without further information, duplicate events and uncomplicated device replacement due to end of life. 5628 events were reviewed and assessed by the sponsor. Subjects may experience more than one adverse event.