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User question:

Aveir VR Leadless Pacemaker – Why It “Stops” When You Sleep Prone

Clinician-level overview – not a substitute for in-person follow-up with your electrophysiology team.

1 · What you observe vs. what the device is actually doing

Bedside finding	Inside the pacemaker	Typical cause
Pulse drops to 25-30 bpm while you lie face-down	Pacer output is inhibited (it thinks your heart just beat), or It does pace, but the pulse fails to “capture” the ventricle	1. Oversensing of muscle noise 2. Capture threshold temporarily rises above programmed output
Pulse returns to programmed 50 bpm once you roll onto your back	Normal pacing resumes	Posture removes the trigger

2 · Two proven, posture-dependent mechanisms

Mechanism	Why prone triggers it	Why supine fixes it
A. Loss of capture (threshold > programmed output)	Intrathoracic pressure and ventricular geometry change; tip may lift < 1 mm from myocardium. Thresholds can jump > 2 V in the “worst” posture.	Wall contact restored; threshold falls back below 3 V, so 3-3.5 V output captures again.
B. Oversensing of myopotentials	Prone breathing engages diaphragm / intercostal muscles; EMG looks like ventricular activity, so pacer withholds pulses.	Muscle noise disappears when supine, so sensing is clean and pacing resumes.

Abbott’s MRI-safety guide flags “unstable capture thresholds > 2.5 V @ 0.5 ms” and “diaphragmatic stimulation” as scenarios requiring special attention, confirming both mechanisms are recognised by the manufacturer.

3 · How your care team can pinpoint the culprit

Interrogate the Aveir in multiple positions. Measure capture threshold and R-wave amplitude in supine, prone, and side-lying.
Review night-time EGM logs.
- Spikes present but no QRS → loss of capture.
- No spikes, “ventricular sensed” markers → oversensing.
Check lead impedance & fluoroscopy to rule out micro-dislodgement.
Inspect auto-capture timing. If the daily capture test runs while you are prone, it may set output too low for the rest of the night.

4 · Programming or procedural fixes

Problem confirmed	Programming tweaks	Procedural options
Threshold rises in prone	Raise voltage or pulse-width ≥ 1 V above highest threshold Disable auto-output reduction	Retrieve/redeploy at better site Switch to transvenous lead if thresholds stay > 5 V
Oversensing	Reduce ventricular sensitivity (make it less sensitive) Enable noise-reversion or extend blanking	Rarely needed
Mixed picture	Combine above & schedule auto-capture test for midday when upright

5 · Practical tips while awaiting re-evaluation

Sleep on your back or side.
Use a pulse-oximeter or single-lead ECG recorder overnight for a few days; bring tracings to the clinic.
Keep a symptom log with time, body position, and heart rate.

6 · Key takeaway

Your Aveir VR is reacting – sometimes incorrectly – to posture-induced electrical or mechanical changes, not “turning off.” A posture-specific interrogation usually identifies the cause, and simple reprogramming (higher output or lower sensitivity) resolves the night-time pauses.