Reflex Syncope With Complete Heart Block Triggered by Swallowing in a Patient on Immune Checkpoint Inhibitor Therapy

Immune checkpoint inhibitors (ICIs) are now standard of care for most advanced solid tumors. While effective, they are associated with immune-related adverse events (irAEs), including rare autonomic complications. We present a patient with metastatic lung adenocarcinoma receiving nivolumab and ipilimumab who developed reflex syncope with reproducible complete heart block (CHB) triggered by swallowing and food proximity. Barium esophagram revealed esophageal dysmotility, a small hiatal hernia, and distal esophageal narrowing. ICI therapy was held, and a dual-chamber pacemaker resolved the syncopal episodes. The overlap between structural esophageal pathology, possible ICI-associated autonomic dysregulation, and situational syncope complicates diagnosis and management. Clinicians should maintain vigilance for autonomic manifestations, especially new-onset bradyarrhythmias or syncope, in patients on immunotherapy.