Various degrees of esophageal injury have been described after radiofrequency ablation performed for treatment of atrial fibrillation. The main mechanism of injury is thermal and may lead to a range of esophageal mucosal changes, some clinically insignificant, however when deep ulceration occurs, this may be further complicated by perforation and mediastinitis, a rare but life threatening sequelae. We present a case of a severe esophageal injury leading to mediastinitis, with interesting endoscopic findings. Various degrees of esophageal injury have been described after treatment of atrial fibrillation. The main mechanism of injury is thermal and may lead to a range of esophageal mucosal changes, some clinically insignificant, however when deep ulceration occurs, this may be further complicated by perforation and mediastinitis, a rare but life threatening sequelae. We present a case of a severe esophageal injury leading to mediastinitis, with interesting endoscopic findings.