13.2 CIED Interrogation Workflow, Programmer Operation & Peri-Procedural Reprogramming
Key Takeaways
- Task B6 requires interrogating cardiac implantable electronic devices as a distinct intra-procedural objective, separate from implant assistance.
- Programmers are manufacturer-specific and communicate through an inductive wand or radiofrequency telemetry; there is no universal programmer.
- Pacing dependence is determined by decrementing the pacing rate to observe an underlying rhythm, not by assuming the mode implies dependence.
- Pacemaker-dependent patients are reprogrammed to an asynchronous mode before electrocautery or MRI, and ICD tachytherapy is suspended.
- Every device reprogrammed for a procedure must be restored and re-interrogated afterward with thresholds, sensing, and impedances documented.
13.2 CIED Interrogation Workflow, Programmer Operation & Peri-Procedural Reprogramming
CCI lists "Interrogate Cardiac Implantable Electronic Devices (CIEDs)" as task B6, and separately lists CIED programmer function and operation(s), basic CIED programming, and basic CIED function in the knowledge list. In an EP lab a device is interrogated before nearly every case in a device patient, again after any external shock or cautery exposure, and always before discharge.
1. The Programmer and Telemetry
A programmer is a manufacturer-specific computer that communicates with an implanted device. There is no universal programmer: an Abbott device requires an Abbott programmer, a Medtronic device a Medtronic programmer, and so on. Identifying the manufacturer is therefore the first step in any device encounter.
| Identification method | Detail |
|---|---|
| Patient identification card | Manufacturer, model, serial number, implant date, implanting physician |
| Chest radiograph | Radiopaque alphanumeric identifier stamped in the header; distinctive generator shape and lead architecture |
| Institutional or manufacturer registry | Device tracking database lookup |
| Manufacturer support line | 24-hour technical support for every major manufacturer |
| Trial-and-error interrogation | Attempting each available programmer — the slowest option, used only when nothing else identifies the device |
Telemetry is either inductive, requiring a wand held directly over the generator, or radiofrequency (wireless), which works over a few metres. Inductive telemetry is more robust in an electrically noisy lab; radiofrequency telemetry is convenient but can drop out. Sterile-field interrogation during a procedure uses a wand inside a sterile sleeve.
2. The Systematic Interrogation Sequence
- Identify manufacturer, model, serial number, implant date, and indication.
- Establish telemetry and save the pre-existing ("initial") programmed settings before changing anything.
- Battery status — voltage, estimated longevity, and replacement indicators.
- Lead measurements — impedance, sensed amplitude, and pacing threshold for each lead.
- Programmed parameters — mode, rates, AV delays, outputs, sensitivities, refractory periods, and (for an ICD) detection zones and therapies.
- Diagnostics — percentage paced per chamber, rate histograms, mode switch episodes, arrhythmia counters, heart failure diagnostics.
- Stored episodes — electrograms and markers for arrhythmias and delivered therapies.
- Determine pacing dependence.
- Reprogram as clinically required.
- Print or save the final report to the medical record, and restore original settings when the procedural need has passed.
Battery status terminology
| Indicator | Meaning |
|---|---|
| BOL — beginning of life | Full battery |
| ERI / RRT — elective replacement indicator / recommended replacement time | Schedule replacement; typically ~3 months of normal function remain |
| EOL / EOS — end of life / end of service | Urgent; device may cease reliable therapy |
At ERI, devices typically change behavior in a manufacturer-specific way — often reverting to a fixed VVI rate, disabling rate response, and lengthening the magnet rate — and those changes are themselves the clue on an ECG.
Normal measured values
| Parameter | Normal | Abnormal suggests |
|---|---|---|
| Pacing lead impedance | ~300-1,200 Ω (varies by lead) | > 2,000 Ω or an abrupt rise = conductor fracture / loose set screw; < 200 Ω or an abrupt fall = insulation breach |
| High-voltage (shock) coil impedance | ~20-100 Ω | Out of range suggests coil or connection failure |
| Atrial sensed P wave | > 1.5-2.0 mV | Undersensing risk |
| Ventricular sensed R wave | > 5 mV | Undersensing risk; ICD needs adequate R waves for VF detection |
| Atrial threshold | < 1.5 V at 0.5 ms | Exit block, dislodgement, perforation |
| Ventricular threshold | < 1.0-1.5 V at 0.5 ms | Same |
Trends matter more than single values. A ventricular threshold of 1.2 V is unremarkable in isolation but alarming if it was 0.5 V three months ago. Interrogation reports plot these trends, and reading the trend is the skill being tested.
3. Determining Pacing Dependence
Pacing dependence cannot be inferred from the mode or from the percentage paced. A patient can be 100% paced and still have a stable underlying escape rhythm; another can be 40% paced and have no escape at all.
The determination is made by decrementing the programmed lower rate (or briefly programming to VVI at 30 bpm) and observing whether an intrinsic rhythm emerges, with the patient monitored, pads on, and the programmer ready to restore pacing immediately. A patient with no escape rhythm, or an escape below about 30-40 bpm that is hemodynamically inadequate, is pacemaker-dependent.
That single determination drives every subsequent peri-procedural decision.
4. Peri-Procedural Reprogramming
| Situation | Pacemaker | ICD |
|---|---|---|
| Electrocautery (monopolar), pacing-dependent | Asynchronous: VOO or DOO | Asynchronous pacing plus suspend tachytherapy |
| Electrocautery, not pacing-dependent | Often no change; monitor | Suspend tachytherapy |
| External cardioversion / defibrillation | Pads ≥ 8 cm from the generator, ideally anteroposterior; interrogate afterward | Same; interrogate afterward |
| MRI (conditional system) | Enable MRI mode, asynchronous if dependent | Enable MRI mode, tachytherapy off |
| Radiation therapy | Dose limits to the generator; relocate the device if it lies in the treatment field | Same, plus therapy suspension during fractions if indicated |
| Lithotripsy, RF ablation, TENS, electroconvulsive therapy | Case-specific; asynchronous if dependent | Suspend tachytherapy |
Suspending tachytherapy is accomplished either by programming detection off (preferred, because it is precise and documented) or by applying a magnet over the ICD. The magnet's effect must be understood exactly, because the two device types behave differently:
| Magnet over a... | Effect |
|---|---|
| Pacemaker | Asynchronous pacing (VOO/DOO/AOO) at a manufacturer-specific magnet rate; the magnet rate itself indicates battery status |
| ICD | Suspends tachyarrhythmia detection and therapy only. Bradycardia pacing does not change and does not become asynchronous |
A pacemaker-dependent ICD patient undergoing electrocautery therefore cannot be managed with a magnet alone: the magnet stops inappropriate shocks but leaves the bradycardia pacing susceptible to oversensing and inhibition. That patient requires programming.
The mandatory closing step: any device reprogrammed for a procedure is restored and re-interrogated before the patient leaves monitored care, with thresholds, sensing, and impedances documented and compared with the pre-procedure values. Leaving a device asynchronous, in MRI mode, or with therapies off is a well-documented and entirely preventable adverse event, and it is the reason the patient stays on continuous monitoring until restoration is confirmed.
5. Special Intra-Procedural Situations
Radiofrequency ablation in a device patient. RF current can be oversensed, and lesions near a lead can raise thresholds. Practice includes suspending tachytherapy in an ICD, programming asynchronously in a dependent patient, keeping the RF dispersive pad positioned so the current vector does not cross the generator or leads, and interrogating fully afterward.
Cryoablation near a lead can cause transient threshold rise and undersensing during the freeze, which typically recovers on rewarming but must be watched in a dependent patient.
External cardioversion in a device patient uses pads at least 8 cm from the generator, preferably in an anteroposterior orientation, at the lowest effective energy. Post-shock interrogation checks for parameter reset, threshold change, and impedance change.
Power-on reset occurs when strong interference causes the device to revert to factory backup settings — typically a fixed-rate VVI mode with nominal outputs, and with tachytherapy off in an ICD. It is recognized on interrogation as a set of parameters nobody programmed, along with a reset event marker in the diagnostics, and it requires full reprogramming to the patient's intended settings.
A patient with a dual-chamber ICD requires monopolar electrocautery for an unrelated procedure and is pacemaker-dependent. A colleague proposes taping a magnet over the device for the duration. Why is this inadequate?
Interrogation of a pacemaker before a scheduled ablation shows the patient is paced 98 percent of the time in DDD mode. What does this establish about pacing dependence?
Post-procedure interrogation of a pacemaker exposed to prolonged monopolar electrocautery reveals VVI mode at 65 beats per minute with nominal outputs and rate response off, although the patient was implanted and programmed as DDDR at 60 with a rate-adaptive sensor. Diagnostics show a reset event marker. What has occurred?