Inclusion Criteria:  Patient with class I or II indication for implantation of a CRT-D device according to current ESC guidelines Patient newly implanted with a MicroPort CRM Platinium CRT-D SonR or Platinium CRT-D device within 2 months before the Investigational Procedure Patient in sinus rhythm with a preserved atrio-ventricular conduction, and PR interval=220 +/- 30 ms on surface ECG Patient has reviewed, signed and dated the study informed consent form  Exclusion Criteria:  Patient with permanent or persistent atrial fibrillation or atrial flutter Patient presenting with a permanent or frequent paroxysmal high degree atrio-ventricular block Device upgrade or replacement Minor patient (i.e. under 18 years of age), or patient under guardianship or kept in detention Patient unavailable for the scheduled Investigational Procedure, not able to understand the purpose of this study or refusing to cooperate