Figure 2. CT scan showed the anatomic relation of esophagus and LA
Extremely cold temperature and isolation duration prolongation of the left side PVs could be blamed for esophageal injury [8][9].Studies have demonstrated that there is a significant correlation between LET and the incidence of esophageal injury after cryoballoon ablation[10][11]. Wilber SU,et al suggeested that preventive measures should be taken when the ablation process exceeds 4 minutes, and more than 2 applications should be deployed to a single PV antrum and the also when the lowest temperature of the balloon reaches -60 ℃[12].Furthermore,A recent review by Montreal Heart Institute recommended several strategies, including terminating the freezing at extremely cold temperature(I.E. -50℃–60℃),applying LET and aborting the procedure when the esophageal temperature is colder than 10-12℃[13]. A single-center study[14] asserted that a single transducer probe does not provide reliable indicators,multi-sensor high sampling rate LET monitoring may be more precise alternative approach. However the threshold of LET has not been decided yet, there is research reporting about cutoff value of 12℃[15] . Ablation termination with “double stop” technique under a low threshold which can benefit in more instant tissue rewarming, limiting the extent of cold-induced collateral injury,is also considered as a preventive option[13].In our case no LET monitoring was performed, and cryoballooon temperature was not properly controlled, this might also explain the injury.
Although epicardial and mediastinal fat can somehow play roles in insulating the esophagus against thermal injury. Sakher Y[14] et al reported that obesity and increased body mass index were in correlation with incidence of post-ablation esophageal injury. This might because overall body fat may not always indicate mediastinal or epicardial obesity.Thus weight control in AF patients may be beneficial not only in rhythm control but also in esophageal protection.Our patient was slightly overweight when she underwent the ablation ,this might be another predisposing factor of her esophageal injury.
Other feasible strategies such as pharmacological prophylaxis(PPIs or H2 blockers starting before the ablation and continuing 4-8 weeks after ablation), Patient education on symptoms associated with severe esophageal thermal injury (prolonged thoracic pain, dysphagia,swallowing related pain, fever) is important for early detection.