A DDD pacemaker is a mechanical pacemaker placed in both the atria and ventricles, with sensors to monitor the heart's rhythm in both locations. It acts on demand, triggering a heartbeat when the heart does not do so spontaneously. This type of pacemaker is widely used for permanent pacemaking, and the programming can be adjusted to meet the needs of the patient, depending on the specific condition a patient has and the reason the pacemaker is being implanted.
In pacemaker classification, each letter provides information about the functions of the pacemaker. The first letter tells the user which chamber of the heart is paced by the device. A indicates the atria, V is for the ventricles, and D symbolizes both chambers. The second letter provides information about which chambers are sensed by the pacemaker, with the same letter codes along with 0, meaning no sensing function is available. The third letter indicates what the device does in response to the sensations it receives. It may be 0, reflecting the lack of sensing, I for inhibit to show that the pulse from the pacemaker can be suppressed, T for trigger to indicate that a pulse will be triggered, and D, indicating that the pacemaker can trigger and inhibit.
The DDD pacemaker acts on demand, taking action appropriate to what is happening inside the patient's heart at any given time. The internal clock on the device can be programmed to meet the patient's needs, and most devices also have sensors designed to help the pacemaker adjust to the patient's level of activity. When people are working hard and need a higher heart rate, the pacer can speed up, ramping back down as the they cool down and resumes more sedentary activities.
Before the pacemaker is implanted, it is checked to confirm it is working properly. After installation, it is programmed and tested. It will regulate the patient's heartbeat, addressing health problems caused by an abnormal rhythm. Pacemakers can be reprogrammed externally, as well as being checked for errors if a patient reports problems like irregular heart rate or discomfort in the chest. Diagnostics may reveal the need for reprogramming or a new pacemaker.
Understanding the letter designations on a pacemaker can be helpful for a patient who wants to understand what the device does. The DDD variety provides a highly flexible set of modes, but may not necessarily be needed in all patients.