The North American Society of Pacing and Electrophysiology (NASPE) and the British Pacing and Electrophysiology Group (BPEG) categorize pacemakers according to what is known as the Generic Code (NBG Code). A DDDR pacemaker is a term that is used to code a certain type of pacemaker according to the criteria set forth in the NBG Code. Specifically, a DDDR pacemaker is a type of pacemaker that paces and senses both chambers of the heart and is capable of adjusting the pacing rate automatically. According to the NASPE and BPEG, the DDDR pacemaker can also be referred to as the DDDRO pacemaker.

DDDR is an acronym where each letter corresponds to a specific mode of functioning. The first and second letters are used to denote the chambers of the heart in which pacing will occur and the chambers in which the pacemaker can detect cardiac depolarization as it happens, respectively. These two letters can either be A for atrium, V for ventricle, or D, meaning that the pacemaker is capable of dually pacing and/or sensing cardiac depolarization in both the atrium and the ventricle. The third letter denotes the ability of the pacemaker to either trigger pacing when needed, which is denoted with a T, inhibit pacing when it is not needed, which is denoted with an I, or is able to both trigger and inhibit pacing as needed, which is denoted with a D. Finally, the fourth letter is used to indicate the ability of the pacemaker to involuntarily adjust the pacing rate and can be denoted with an R for the presence of a rate modulator or O for the absence of a rate modulator.

There is a fifth letter that is often part of the pacemaker label as put forth by the NASPE and BPEG. This fifth letter denotes whether or not the pacemaker is capable of pacing more than one site in the atrium or ventricle. It also signifies whether or not the pacemaker is capable of pacing in the right ventricle as well as in the left ventricle or in the right atrium as well as in the left atrium or any combination of the atrium and ventricles. It is denoted with an O for the absence of multisite pacing, an A for the presence of multisite atrium pacing, a V for the presence of multisite ventricle pacing or a D for the capability of multisite pacing in both the atrium and ventricle chambers.

Typically, a DDDR pacemaker is synonymous with a DDDRO pacemaker. The DDDR pacemaker is thus capable of pacing and sensing cardiac depolarization in both chambers of the heart, is equipped with the ability to trigger as well as inhibit pacing and can adjust the pacing rate automatically. In general, however, the DDDR pacemaker is not capable of multisite pacing. Those DDDR pacemakers that are capable of this type of pacing are typically referred to as DDDRA, DDDRV or DDDRD pacemakers.