But what about an Aveir VR that works perfectly during the day but not at night and then place an Aveir CSP . What will happen with Aveir CSP at night in a patient that the vagal tone causes non capture at night with the Aveir VR?
GPT40 answer:
This is a very insightful clinical question — and one that highlights the complex interplay between autonomic tone, myocardial excitability, and site-specific pacing behavior.
You are describing a patient where:
Aveir VR (RV myocardial pacing) captures well during the day, but shows intermittent non-capture at night (likely due to elevated vagal tone and increased thresholds).
Now you're considering implanting an Aveir CSP (His or left bundle branch pacing) to restore capture, especially during night-time non-capture.
So the core question is:
🧠 Will the Aveir CSP also suffer from nocturnal non-capture caused by vagal tone like the Aveir VR does? Or will it be more resistant?
Aveir VR captures the right ventricular myocardium, which is more directly influenced by autonomic tone—particularly vagal dominance at night.
Vagal tone raises capture thresholds by:
Hyperpolarizing myocardial cells
Decreasing myocardial excitability
If output is near the threshold, capture fails intermittently during high vagal states.
Aveir CSP targets the conduction system: His bundle or left bundle branch.
These structures are:
Less affected by vagal tone than ventricular myocardium
Have lower and more stable capture thresholds
Offer faster and more physiological activation, enhancing cardiac efficiency
So, in your case:
✅ Implanting Aveir CSP can bypass the vagally-induced non-capture issue seen with RV pacing because it stimulates conduction fibers that are more electrically excitable and less suppressed by vagal input.
| Feature | Aveir VR (RV pacing) | Aveir CSP (His/LBB pacing) |
|---|---|---|
| Tissue sensitivity to vagal tone | High | Lower |
| Threshold variability with sleep | High | Lower |
| Pacing site excitability | Myocardial (less excitable) | Conduction fibers (more excitable) |
| Capture stability at night | May decrease | Likely more stable |
Clinical studies and His-bundle pacing literature (not Aveir-specific yet) suggest that CSP maintains better pacing thresholds over circadian changes, due to more direct stimulation of fast-conduction tissues.
Initial CSP thresholds must be stable and low; if CSP is implanted suboptimally or too deep in fibrotic septum, capture thresholds may still drift.
Fibrosis, tissue interface issues, or advanced conduction disease could still challenge CSP capture in rare cases — but less so than RV myocardial pacing.
Yes — in your described patient, switching to Aveir CSP will likely result in better and more stable pacing during the night because:
CSP targets the specialized conduction system, which is less sensitive to vagal tone.
It bypasses the threshold instability seen with RV myocardial pacing (Aveir VR).
If properly implanted, CSP will maintain capture at night, solving the vagal-induced non-capture problem of the VR.
Would you like help drafting a rationale to present to an electrophysiologist to justify the transition from VR to CSP in such a patient?