Practical safety thresholds for pulsed-field ablation near the sinus node and his bundle: an in vivo swine study
M Honda, M Takigawa, M Negishi, R Tateishi, I Kawamura, K Goto, T Nishimura, K Yamao, S Tao, S Miyazaki, T SasanoAbstract
Background
Pulsed-field ablation (PFA) is established for pulmonary vein isolation for tissue selectivity, but quantitative safety margins around the cardiac conduction system remain unclear. As PFA expands to non-PV targets and complex atrial tachycardias, energy is delivered near the sinus node (SN) and the His bundle (HB), yet practical safety strategies remain undefined.
Purpose
To identify determinants of electrophysiological responses near the SN and HB and derive a practical safety strategy for PFA delivery.
Methods
Nine swine underwent 161 applications around the SN and 67 around the HB using a circular over-the-wire PFA catheter. SN localization used a right atrial LAT map discretized into 5-ms bins; the earliest 5-ms bin defined the SN, and P-EGM lead (ms) was the interval from P-wave onset to the local electrogram (negative if local preceded the P-wave) (Fig. 1A). HB sites were 3D tags with a clear His potential; distance was measured (Fig. 1B). At each site a single test shot (1-shot) was delivered, then three additional shots at the same site (4-shot); applications proceeded distal-to-proximal in 1-mm steps relative to SN/HB. SN responses were sinus tachycardia (≥10-bpm increase), sinus bradycardia (≥10-bpm decrease), or sinus arrest (asystole ≥3 s). HB responses were first-degree atrioventricular block (PR ≥200 ms) or complete AV block. Responses were classified as transient if SN or HB recovered within 30 minutes, and as persistent if recovery did not occur within 30 minutes. A warning sign was defined as any 1-shot response that preceded persistence after completion of the 4-shots. Sinus change was defined as the emergence of a new earliest activation site after sinus arrest.
Results
SN. Distance, P-EGM lead, and shot number independently predicted any SN response (Fig. 2A); for persistent bradycardia/arrest, distance and 4-shot remained strongest. ROC for distance: AUC 0.877 for any response (cutoff 5.0 mm; Se 0.93; Sp 0.72) and 0.887 for persistent injury (5.0 mm; Se 1.00; Sp 0.65). ROC for P-EGM lead: AUC 0.835 (cutoff −20 ms; Se 0.86; Sp 0.72) and 0.824 (cutoff −29 ms; Se 0.75; Sp 0.80). Four-shot increased risk across distance strata. After persistent arrest, sinus change occurred in 86% at the first change, then 50% and 0%; limit further shots. HB. Distance performed best (AUC 0.944); using 5 mm preserved 100% sensitivity (Sp 0.55), and no events occurred beyond 5 mm in either 1-shot or 4-shot sets (Fig. 2B). Warning signs preceded 5/6 (83.3%) persistent HB injuries, but ~17% persisted without warning.
Conclusions
In swine, conduction-system risk near SN/HB is governed by proximity and dose. Strategy: (i) SN—avoid when distance ≤5 mm or P-EGM lead ≤−20 ms; if uncertain, use a 1-shot test and stop for any warning sign or sinus change. (ii) HB—avoid when distance ≤5 mm and at His-positive sites; if distance is uncertain, a 1-shot test may be considered, but distance—not warnings—remains the primary criterion.Figure 1Figure 2