This situation with an Abbott Aveir VR leadless pacemaker, where it stops working in a supine position and then recovers in other positions, is concerning and requires immediate medical attention. While I can't provide a definitive diagnosis or medical advice, here's a breakdown of what could be happening and why it's so important to see a cardiologist:
Possible Explanations for Positional Malfunction:
Device Dislodgement or Unstable Fixation:
Sensing Issues:
Threshold/Impedance Changes:
Hardware/Software Malfunction (Less likely to be strictly positional):
Why this is Serious and Requires Immediate Action:
In summary, the most likely explanation for this positional malfunction of an Abbott Aveir VR leadless pacemaker is an issue with the device's stability or electrical contact within the heart, possibly due to subtle dislodgement or changes in sensing caused by body position. This is a critical situation that demands urgent medical attention to prevent potentially life-threatening cardiac events.
GPT 3o:
Posture-dependent rise in capture threshold (“positional loss of capture”)
In several case-series, the threshold of a leadless pacemaker has been shown to increase markedly when the patient moves from prone/side-lying to the supine position. Small changes in ventricular geometry stretch the septal wall, slightly separating the electrode helix or tines from viable myocardium. If the programmed output is only a narrow margin above this higher threshold, the first few stimuli in supine fail to capture and the device appears to “stop.” When the patient rolls prone (the heart falls anteriorly toward the sternum) the contact pressure returns, the threshold falls back below the programmed 1.5 V, and capture resumes. (PMC)
Bradycardia-associated threshold increase amplifies the effect
At very slow intrinsic rates during early sleep, diastolic filling and wall tension further reduce tissue–electrode contact and can raise threshold by another 0.2-0.4 V. This phenomenon has been described specifically in leadless systems. (PMC)
Occasional oversensing of diaphragmatic/myopotential noise in supine
In the same posture the horizontal diaphragm and abdominal musculature can generate low-frequency signals that the ventricular channel misinterprets as R-waves, so the pacemaker inhibits output exactly when capture is already marginal. The result on surface ECG looks like an irregular, slow idioventricular or junctional rhythm (“total arrhythmia-bradyarrhythmia”). (Patient Information)
Why it works perfectly after four hours
Auto-capture safety check (manual or scheduled) – Aveir VR verifies threshold once every 24 h (and at power-on reset). If it detects loss of capture it automatically doubles the output for the remainder of the interval, so by the time the patient awakens the device is pacing at a higher amplitude and works in every position.
Physiological changes – Vagal tone and filling pressures fall as sleep cycles progress; myocardial excitability rises slightly; the threshold gap narrows even without the safety factor.
| Step | Test | What you’re looking for |
|---|---|---|
| 1 | Bedside threshold test in different positions (supine, prone, right/left lateral) | ≥0.5 V step-up in threshold in supine only → positional loss of capture |
| 2 | 12-hour Holter synchronized with device EGMs | Oversensing markers (“NFG”, “noise”) or inhibition without spike → myopotential/EMI |
| 3 | Interrogate daily “trend” data | Sudden auto-rise in output that coincides with the first night block |
| 4 | Chest CT or 3-D echo (if thresholds are very labile) | Confirm the capsule is still seated and look for excessive fibrotic capsule |
| Goal | Programming change | Rationale |
|---|---|---|
| Guarantee capture all night | Raise output to threshold + 1 V or extend pulse width to 0.6 ms | 2× safety margin eliminates failure even if threshold drifts overnight |
| Reduce oversensing | Lengthen post-ventricular blanking, lower sensitivity from 0.18 mV → 0.3 mV | Filters out diaphragmatic potentials without missing R-waves |
| Detect episodes automatically | Turn on “Capture Verification Alerts” in Merlin | Remote alert the next morning if loss-of-capture >30 s |
| Long-term | If thresholds keep rising (≥3 V @ 0.4 ms) despite reprogramming, discuss:• relocation of a new Aveir VR to mid-septum or• enrollment in ASCEND CSP trial for leadless conduction-system pacing | Both options regain low thresholds and reset projected battery life |
Nothing is “wrong” with the battery or electronics – the problem is the interface between the pacemaker and the heart changing with posture and very low heart rates.
Raising the night-time output or pulse width today is low-risk and buys time while you and the EP team decide whether a new implant site or a CSP device is worthwhile.
Keep using remote monitoring; it will flag any future loss-of-capture episodes, so you don’t have to wait six months for the next in-office check.
Next practical step: ask your EP to perform a supine-vs-prone threshold scan at the beginning of your next visit and re-program the safety margin accordingly.