lvad beats

Hi everyone! My farher was implanted by a heartmate 3, three months ago. He is slowly recovering from the surgery and getting used to the device. Yet he always feels something like mehanical 'beats' in the thorax. He can't decide whether its origin is the heartmate or maybe the pacemaker he already had before. This feeling is new to him and very uncomfortable. The doctors can't find the reason. Does anyone have any idea of what these beats are? Any change of the device parameters can maybe improve this issue? Thank you so much and loth of health.