Nerve sprouting induced by radiofrequency catheter ablation in dogs.

Abstract

OBJECTIVES: The purpose of this study was to test the hypothesis that radiofrequency (RF) catheter ablation results in cardiac nerve sprouting. BACKGROUND: Nerve sprouting plays a role in cardiac arrhythmogenesis. Whether or not nerve sprouting occurs after RF catheter ablation is unclear. METHODS: We performed RF catheter ablation in the right atrium (RA) and right ventricle (RV) in 10 dogs, which then were sacrificed in 2 hours (acute group, n = 5) or 1 month (chronic group, n = 5). Seven normal dogs were used as control. Immunohistochemical staining for growth-associated protein 43 (GAP-43) was performed to measure growing (sprouting) nerves. RESULTS: A significant increase of GAP-43 immunoreactive nerve fiber density was observed at the RA ablation sites in 2 hours (4,410 +/- 1,379 microm(2)/mm(2)) and in 1 month (2,948 +/- 666 microm(2)/mm(2)) after ablation compared to controls (1,377 +/- 471 microm(2)/mm(2), P = .0001). At remote sites (>2 cm away from ablation sites) of RA, RF ablation also resulted in robust nerve sprouting in both the acute group (5,846 +/- 3241 microm(2)/mm(2)) and the chronic group (6,030 +/- 2226 microm(2)/mm(2)). RF ablation in the RV did not increase nerve density at the ablation sites, but nerve density was increased at remote sites in 2 hours (1,345 +/- 451 microm(2)/mm(2), P = .0136) that was reduced down to the normal control level (722 +/- 337 microm(2)/mm(2)) in 1 month. CONCLUSIONS: Nerve sprouting occurred within 2 hours after RF ablation in both the RA and RV and persisted for at least 1 month in the RA but not the RV. The increased GAP-43(+) nerve densities developed at both the ablation and the remote sites.

AI evidence extraction

Main findings

In 10 dogs receiving RF catheter ablation, GAP-43(+) nerve fiber density increased at right atrium ablation sites at 2 hours and 1 month compared with controls, and robust sprouting was also observed at remote right atrium sites (>2 cm) in both timepoints. In the right ventricle, nerve density did not increase at ablation sites, but increased at remote sites at 2 hours and returned to control levels by 1 month.

Outcomes measured

• Cardiac nerve sprouting (GAP-43 immunoreactive nerve fiber density) at ablation sites and remote sites in right atrium and right ventricle

Limitations

• Animal study (dogs); generalizability to humans not established in abstract
• Small sample sizes per group (n=5 acute, n=5 chronic; 7 controls)
• RF exposure parameters (e.g., frequency, power, SAR) not reported in abstract
• Outcome is a histologic marker (GAP-43) rather than clinical arrhythmia outcomes

Suggested hubs

• occupational-exposure (0.2)
  RF catheter ablation is a medical RF source; could be relevant to procedural/clinical RF exposure contexts, though not explicitly occupational in abstract.

{
    "study_type": "animal",
    "exposure": {
        "band": "RF",
        "source": "radiofrequency catheter ablation",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": "assessed at 2 hours (acute) and 1 month (chronic) post-ablation"
    },
    "population": "Dogs",
    "sample_size": 17,
    "outcomes": [
        "Cardiac nerve sprouting (GAP-43 immunoreactive nerve fiber density) at ablation sites and remote sites in right atrium and right ventricle"
    ],
    "main_findings": "In 10 dogs receiving RF catheter ablation, GAP-43(+) nerve fiber density increased at right atrium ablation sites at 2 hours and 1 month compared with controls, and robust sprouting was also observed at remote right atrium sites (>2 cm) in both timepoints. In the right ventricle, nerve density did not increase at ablation sites, but increased at remote sites at 2 hours and returned to control levels by 1 month.",
    "effect_direction": "harm",
    "limitations": [
        "Animal study (dogs); generalizability to humans not established in abstract",
        "Small sample sizes per group (n=5 acute, n=5 chronic; 7 controls)",
        "RF exposure parameters (e.g., frequency, power, SAR) not reported in abstract",
        "Outcome is a histologic marker (GAP-43) rather than clinical arrhythmia outcomes"
    ],
    "evidence_strength": "low",
    "confidence": 0.7800000000000000266453525910037569701671600341796875,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "radiofrequency",
        "catheter ablation",
        "nerve sprouting",
        "GAP-43",
        "right atrium",
        "right ventricle",
        "cardiac innervation",
        "dogs"
    ],
    "suggested_hubs": [
        {
            "slug": "occupational-exposure",
            "weight": 0.200000000000000011102230246251565404236316680908203125,
            "reason": "RF catheter ablation is a medical RF source; could be relevant to procedural/clinical RF exposure contexts, though not explicitly occupational in abstract."
        }
    ]
}

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