Bradycardic Responses During Thermal Ablation for Hepatocellular Carcinoma: Impact of Procedural Pain Severity and Autonomic Imbalance

ABSTRACT Aim Bradycardic responses frequently occur during radiofrequency ablation (RFA) and microwave ablation (MWA) for hepatocellular carcinoma (HCC), but the impact of procedural pain severity and patient‐specific factors remains unclear. This study aimed to evaluate the incidence and risk factors for bradycardic responses, focusing on procedural pain and autonomic regulation. Methods This retrospective study included 267 patients with solitary HCC who underwent RFA or MWA between 2019 and 2024. Bradycardic responses were defined as a ≥ 30% decrease in heart rate from baseline or < 50 bpm. Patients were categorized by procedural pain severity using patient‐controlled analgesia (PCA) bolus administration. Risk factors for bradycardia were assessed by logistic regression. Results Bradycardic responses occurred in 70 patients (26.2%). Severe procedural pain (odds ratio [OR], 2.26 and p = 0.007) and primary HCC (OR, 2.68 and p = 0.002) were independent risk factors. In patients without severe pain, absence of angiotensin II receptor blocker (ARB) use increased bradycardia risk (OR, 0.14 and p = 0.013). Most bradycardic events (61.4%) occurred within 3 min of ablation initiation. Conclusions Bradycardic responses during RFA and MWA are common and linked to procedural pain severity and autonomic imbalance. Comprehensive management, including pain control, medication review, and addressing procedural anxiety through counseling or sedation, may reduce risks and enhance procedural safety.