8 Pacemaker, Defibrillator, and Lead Codes and Headers
Devices are used for more indications in the treatment of patients with bradyarrhythmias, tachyarrhythmias, and congestive heart failure, and more algorithms are developed either to stimulate multiple chambers (cardiac resynchronization) or to minimize unnecessary pacing when possible.1,2 It is noteworthy that, unlike some therapies, the generic pacemaker codes have withstood the test of time.
Pacemaker Codes
Three-Position Ichd Code (1974)
In 1974 the Inter-Society Commission for Heart Disease Resources (ICHD) proposed a three-position code to allow a uniform system to describe the functionality of a pacemaker platform.3 The goal was to create a generic code that would work among all platforms; it would also allow for concise description of what was becoming a more complex issue. The first letter of the code was to distinguish the chamber(s) being paced. The second letter was to determine the chamber(s) that were sensed for intrinsic electrical depolarizations and to start the timer for determining the next paced beat delivery. The third letter of the code was to describe how the pacing was to be affected by a sensed event (i.e., inhibiting pacing or triggering pacing in response to sensing).
Position one can be the atrium (A), the ventricle (V), or both atrium and ventricle (D) for location of pacing. Position two again represents atrium (A), the ventricle (V), or both (D), meaning sensing can occur for spontaneous electrical depolarizations in either chamber. The third position describes whether sensing leads to inhibition of pacing (I), triggering the delivery of a pacing stimulus (T), or both inhibition and triggering (D). Tables 8-1 and 8-2 outline the options and different pacing configurations.
First Letter | Second Letter | Third Letter |
---|---|---|
Chambers paced | Chambers sensed | Mode of response |
* Letters used: A, atrium; D, double-chamber; I, inhibited; O, not applicable; T, triggered; V, ventricle.
Adapted from Parsonnet V, Furman S, Smyth NPD: Implantable cardiac pacemakers: Status report and resource guideline. Pacemaker Study Group, Inter-Society Commission for Heart Disease Resources (ICHD). Circulation 50:A-21, 1974. Copyright 1974 American Heart Association.
Mode | Description |
---|---|
VOO | Asynchronous ventricular pacing; no sensing function |
AOO | Asynchronous atrial pacing; no sensing function |
DOO | Dual-chamber (AV-sequential) asynchronous pacing; no sensing function |
VVI | Ventricular pacing inhibited by ventricular sensing |
VVT | Ventricular pacing triggered instantaneously by ventricular sensing |
AAI | Atrial pacing inhibited by atrial sensing |
AAT | Atrial pacing triggered instantaneously by atrial sensing |
VAT | Ventricular pacing triggered after a delay by atrial sensing |
DVI | Dual-chamber (AV-sequential) pacing inhibited by ventricular sensing |
AV, Atrioventricular.
Modified from Parsonnet V, Furman S, Smyth NPD: Implantable cardiac pacemakers: status report and resource guidelines. Pacemaker Study Group, Inter-Society Commission for Heart Disease Resources (ICHD). Circulation 50:A21, 1974. Copyright 1974 American Heart Association.
Five-Position Ichd Code (1981)
Table 8-3 shows the different options for all five positions, but as one would surmise, it is now assumed all devices can store information and can be programmed, thus obviating the need for that nomenclature. Currently, pacing platforms that provide antitachycardia pacing are typically identified based on the specifics of the device platform rather than an additional letter in the code (e.g., Medtronic EnRhythm pacing platform allows atrial antitachycardia pacing therapy). Using this convention, a single-chamber pacing system today would be described as VVIM to designate multiprogrammability or VVIC to designate the presence of telemetry (communication). In reality, this fourth letter is implied due to the presence of telemetry and multiprogrammability in all of our current platforms. Table 8-4 provides examples of the many different ways to describe pacemaker function that are highly descriptive of the available features on pacing systems, but not readily used in day-to-day management of pacemakers.
Mode | Description |
---|---|
VDD,M (VDDM) | Ventricular antibradycardia pacing inhibited by ventricular sensing, triggered after delay by atrial sensing; multiprogrammable device; no antitachyarrhythmia (antitachycardia) function. |
DDD,M (DDDM) | Dual-chamber (AV-sequential) antibradycardia pacing inhibited by sensing in either chamber, with ventricular pacing triggered after delay by sensing in atrium after ventricular event; multiprogrammable device; no antitachycardia function. |
VVI,MB (VVIMB) | Ventricular antibradycardia pacing inhibited by ventricular sensing; multiprogrammable device; pacing bursts for ventricular tachycardia, means of activation unspecified. |
AAR,ON (AARON) | No antibradycardia function; nonprogrammable device; normal-rate competition for termination of atrial tachycardia, activated by atrial sensing. |
AOO,OE (AOOOE) | Asynchronous atrial antibradycardia pacing; nonprogrammable device; externally activated atrial antitachycardia pacing, nature unspecified. |
AV, Atrioventricular.
Modified from Parsonnet V, Furman S, Smyth NPD: Revised code for pacemaker identification. PACE 4:400, 1981.
NASPE/BPEG Generic (NBG) Pacemaker Code
The Mode Code Committee of the North American Society of Pacing and Electrophysiology (NASPE), now known as the Heart Rhythm Society, in cooperation with the British Pacing and Electrophysiology Group (BPEG), developed a code in 1987 (Table 8-5).4