How does the Aveir VR handle intermittent myocardial capture that might occur during certain sleep positions - does it automatically adjust output parameters or temporarily modify pacing modes?
GPT 3o:
Short answer — it doesn’t.
Unlike many modern trans-venous generators (and unlike Medtronic’s Micra VR/AV), the single-chamber **Aveir VR has no automatic-capture-verification or adaptive-output algorithm. When the pulse it delivers in a particular body position fails to depolarise the ventricle, the device simply keeps pacing at the same programmed amplitude and pulse-width until capture happens to return — or the patient moves. (abcfarma.net)
No capture-sensing circuit. The LP can sense intrinsic electrical events, but it cannot discriminate “electrical-stimulus-without-mechanical-response” the way impedance-based or evoked-response systems do.
Energy budget. Autocapture requires additional hardware and frequent test pulses; Abbott chose maximum battery longevity (243 mAh ≈17 y at 1.5 V, 0.4 ms) instead. (cardiovascular.abbott)
Fixed-output philosophy inherited from Nanostim. The helix-fixation design lets operators map the implant site and then program a comfortable safety margin (e.g., ≥2× threshold); after that the output is static unless a clinician re-programs it. (cardiovascular.abbott)
| Step | What the pacemaker does | What the patient sees/feels |
|---|---|---|
| 1. Position change raises the true capture threshold above the fixed output (e.g., 1.5 V → >2.0 V). | Continues to fire at the programmed output (e.g., 1.5 V @ 0.4 ms) because it has no feedback. | Idioventricular escape rhythm or brady-arrhythmia; possible presyncope, palpitations, or just a very low sleep HR. |
| 2. If intrinsic ventricular activity is absent for ≥ the lower-rate interval, Aveir will pace again – still at the same output – but those stimuli are “blank shots.” | --- | ECG shows pacing spikes with no QRS complexes. |
| 3. When posture, autonomic tone, or impedance returns the threshold below the programmed voltage, every pulse captures again and the rhythm normalises. | “Self-recovery” with no mode switch because nothing in the device has changed. | Heart rate returns to the base rate; symptoms resolve. |
| Feature | Why it can look adaptive | What it really is |
|---|---|---|
| Emergency-VVI (EVVI) or MRI fallback modes triggered by strong EMI | Device jumps to 6 V @ 0.6 ms (EVVI) or 5 V @ 1 ms (VOO MRI mode) at a higher rate — looks like it “boosted output” | A safety mode only for electromagnetic interference, not for threshold jumps (hrsonline.org) |
| i2i™ “automatic-safeguard modes” in the new Aveir DR dual-chamber system | Mode switches (DDD→DDI, VDD, etc.) when atrial–ventricular communication is lost | Protects AV synchrony; it does not adjust pulse amplitude for loss-of-capture (pmc.ncbi.nlm.nih.gov) |
Increase the night-time safety margin
Raise output to ≥2.5 V or widen pulse-width from 0.4 → 0.6 ms during sleep. The extra drain is small (≈3–5 mAh y⁻¹) but prevents nocturnal pauses.
Document thresholds in different positions
In-clinic programmer + real-time positional changes can confirm whether right-lateral decubitus (for example) raises threshold by >0.3 V.
Rule-out progressive fibrosis or micro-dislodgement
A sudden threshold jump that never falls may need re-implant or (if available at your centre) an Aveir CSP or dual-chamber upgrade.
Educate the patient
If they feel light-headed when rolling onto the right side, turning supine or prone usually restores capture in <60 s.
The Aveir VR will neither “bump the voltage” nor “switch modes” just because capture is intermittent in a certain sleep posture; it keeps pacing at the value you or the EP team programmed. The only automatic changes you’ll see are EMI-driven high-output fallback modes or the dual-chamber i2i safeguard modes in the newer DR platform—neither is capture-management.