EP Staff Education Clinical Staff Ilyas Colombowala, MD, FACC, FHRS →
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Device

Pacemaker Interrogation Walkthrough

Step-by-step approach to a clinic pacemaker check — from connecting the programmer to printing the final report. Covers what each programmable parameter does, how to read counters and histograms, and the red flags that need an EP call.

Interrogation walk-through

  • ▸P — Pull the chart: device model, indication, programmed mode, last visit, any alerts since.
  • ▸B — Battery voltage, % remaining, RRT/ERI/EOL status, projected longevity.
  • ▸L — Per-lead impedance, capture threshold, sensing amplitude with trend comparison.
  • ▸S — Counters, histograms, AHRE/AT/AF burden, mode-switch episodes, stored EGMs.
  • ▸T — Manual capture threshold confirmation at 0.5 ms if auto-test is suspect.
  • ▸O — AV delay, % RV pacing, rate response, AV search / MVP behavior.
  • ▸P — Programming changes documented, re-interrogated, follow-up interval set, attending looped in if needed.

Common issues / troubleshooting

  • ▸Lead impedance drift suggesting microdislodgement or insulation breach
  • ▸Rising capture threshold from exit block or lead maturation issues
  • ▸Inappropriate mode switching from far-field R-wave oversensing
  • ▸High RV pacing burden in a patient with intact AV conduction
  • ▸Undetected AHRE in a patient with no documented AF history

We work through every interrogation using the PBL-STOP framework — a quick mental checklist so nothing gets missed. Seven letters, seven beats, and the order is deliberate: you build a picture of the device before you touch a single parameter, then change things at the end with eyes wide open.

Device overview

A modern pacemaker has three jobs: sense the intrinsic rhythm, pace when that rhythm fails to meet programmed criteria, and store diagnostic data we can review. The PBL-STOP walkthrough below applies to every clinic check and most remote downloads — it just gets faster with repetition.

PBL-STOP walkthrough

P — Presentation / Pre-interrogation review

Before the wand touches the pocket, know who you are looking at.

  • Device manufacturer, model, and serial — pulled from the implant card or last report
  • Indication for implant (sinus node dysfunction, complete heart block, post-AVN ablation, vasovagal)
  • Implant date and last office visit date
  • Programmed mode and lower rate at last visit
  • Any remote-monitoring alerts since the last in-person check
  • Current symptoms and medications, especially rate-slowing agents
  • A quick look at the most recent 12-lead, if available

This 60-second chart pass is what tells you whether the patient in front of you is supposed to be 100% V-paced or 0% V-paced — and it sets your expectations for every section below.

B — Battery / longevity

  • Voltage compared against the model-specific RRT/ERI cutoff
  • Percent remaining and projected months of service
  • Status indicator: BOL, MOL, ERI/RRT, EOS
  • Trend from prior visits — is depletion accelerating?
  • Drivers of accelerated depletion to call out:
    • High RV pacing burden (>40%) with high outputs
    • Elevated capture thresholds across leads
    • Chronic high-rate atrial pacing or rate-response use

Flag any device within 6 months of RRT for generator-change planning.

L — Lead measurements

Each lead, every visit, with the trend graph open:

  • Pacing impedance: expected 400–1200 ohms
    • Sudden drop suggests insulation breach
    • Sudden rise suggests conductor fracture or microdislodgement
  • Capture threshold at 0.5 ms pulse width
    • Atrial typical 0.5–1.5 V
    • Ventricular typical 0.5–1.0 V
    • Rise >1 V from baseline is a red flag
  • Sensing amplitude
    • P-wave typically >1.5 mV
    • R-wave typically >5 mV
    • Drop >50% from baseline warrants attention

Compare to the prior visit, not just absolute ranges — a stable-but-high threshold beats a “normal” value that just doubled.

S — Stored events / Sensed rhythm

This is where the device tells the story of the last 3–12 months.

  • Percent paced and percent sensed in each chamber
  • Rate histograms — sinus distribution, paced rate spread
  • Mode-switch episodes — count, total duration, longest episode
  • AHRE / AT / AF burden:

    • 6 minutes triggers an anticoagulation discussion

    • 24 hours moves that discussion to the top of the visit

  • Patient-activated events with surrounding EGM
  • Any noise reversion episodes (lead fracture or EMI clue)

Pull the EGM on anything atypical — the auto-classification is a starting point, not a verdict.

T — Threshold confirmation

For a pacemaker, the T step is manual capture-threshold confirmation when:

  • Auto-threshold trends are rising
  • The patient is pacing-dependent
  • Battery is approaching RRT and you are tightening outputs
  • A new lead is being followed in the first few months

Confirm capture at 0.5 ms by decrementing voltage until loss of capture, then incrementing until capture returns. Document the safety margin (typically programmed at 2× threshold).

O — Optimization

Where we make CRT-style fine adjustments — even on a dual-chamber pacer.

  • AV delay: shorten if intrinsic conduction can be encouraged; lengthen if fusion beats are degrading hemodynamics
  • Percent RV pacing: target as low as clinically appropriate in non-block patients
  • AV search / MVP / managed ventricular pacing: on for intact AV nodes, off for high-grade AV block
  • Rate response: on for chronotropic incompetence, off if the sinus node is doing its job
  • Mode switch sensitivity: tighten if mode switches are missing real AT, loosen if far-field R-wave is triggering false switches
  • Upper tracking and sensor rates: matched to the patient’s activity profile

P — Plan / Programming changes

Close the loop.

  • Document each parameter changed, the previous value, and the rationale
  • Re-interrogate after the change and confirm the device is behaving
  • Reset counters per institutional policy
  • Set the next remote transmission window and next in-office visit
  • Escalate to the EP attending for:
    • Acute impedance change with new symptoms
    • Battery at EOS or unexpectedly rapid depletion
    • New high-grade AV block in a patient programmed AAI or with MVP active
    • Syncope with no paced events on the device record
    • Pocket pain, swelling, or erythema regardless of interrogation findings

Red-flag findings

  • Impedance change >200 ohms from baseline
  • Capture threshold rise >1 V from baseline
  • P-wave or R-wave amplitude drop >50%
  • Battery at ERI/RRT — generator change within 90 days
  • AHRE >6 minutes without anticoagulation
  • 100% V-paced when intrinsic conduction was expected
  • Frequent noise reversion episodes

Last reviewed by Dr. Colombowala on May 22, 2026.

Not medical advice. This page is educational. Your situation may differ — discuss it with Dr. Colombowala or your treating physician before making decisions.