1) How should outputs be programmed acutely and chronically?
Start with a conservative safety margin above measured LBB capture threshold; after stabilization, re‑assess to maintain selective or nonselective LBB capture with adequate safety while preserving battery life.
2) What signals threshold drift?
Rising capture thresholds, widening QRS or loss of LBB‑like morphology, and output‑dependent loss of transitions; investigate lead micro‑dislodgement, fibrosis, or metabolic factors (e.g., potassium, acid–base).
3) How to verify ongoing conduction system capture in clinic?
Use output step‑downs, analyze V6 R‑wave peak time stability, compare ECG to implant baseline, and confirm sensing/capture with device diagnostics where available.
4) What about nocturnal or circadian threshold variation?
Autonomic tone and myocardial excitability vary across 24 hours; consider capture management features, nighttime output margins, and review comorbidities (sleep apnea, electrolyte shifts).
5) Which follow‑up metrics are useful?
ECG morphology, capture thresholds, impedance trends, symptom logs (exercise tolerance, palpitations), and biomarkers (e.g., NT‑proBNP in HF patients) guide programming and escalation.