Hi. Great question. And I look forward to others chiming in here to share their expertise. I am not an expert on pacemakers. Although, the way I understand it, CRT-P is a type of pacemaker that makes sure both your ventricles pace at the same time. A DDDR pacemaker is a mode that makes sure that both your atria and your ventricles pace in uniform fashion. And this is supposed to work whether you are at rest or exerting yourself. Keep in mind that is how I understand it. Your doctor may have a better way of explaining the difference. Which one your doctor decides to use, I think, depends on the type of arrhythmia that you have. So, to get a better understanding of which pacemaker is best for you, it may be a good idea to have that discussion with your doctor. I would think that your doctor should have access to information (i.e. pamphlets or websites) to help you learn and understand both your heart condition and the pacemaker options available to treat it. What do you think? John. heart-failure.net community moderator