Esophageal cooling for protection during left atrial ablation: a systematic review and meta-analysis

Abstract

Purpose: Thermal damage to the esophagus is a risk from radiofrequency (RF) ablation of the left atrium for the treatment of atrial fibrillation (AF). The most extreme type of thermal injury results in atrio-esophageal fistula (AEF) and a correspondingly high mortality rate. Various strategies for reducing esophageal injury have been developed, including power reduction, esophageal deviation, and esophageal cooling. One method of esophageal cooling involves the direct instillation of cold water or saline into the esophagus during RF ablation. Although this method provides limited heat-extraction capacity, studies of it have suggested potential benefit. We sought to perform a meta-analysis of published studies evaluating the use of esophageal cooling via direct liquid instillation for the reduction of thermal injury during RF ablation.

Methods: We searched PubMed for studies that used esophageal cooling to protect the esophagus from thermal injury during RF ablation. We then performed a meta-analysis using a random effects model to calculate estimated effect size with 95% confidence intervals, with an outcome of esophageal lesions stratified by severity, as determined by post-procedure endoscopy.

Results: A total of 9 studies were identified and reviewed. After excluding preclinical and mathematical model studies, 3 were included in the meta-analysis, totaling 494 patients. Esophageal cooling showed a tendency to shift lesion severity downward, such that total lesions did not show a statistically significant change (OR 0.6, 95% CI 0.15 to 2.38). For high-grade lesions, a significant OR of 0.39 (95% CI 0.17 to 0.89) in favor of esophageal cooling was found, suggesting that esophageal cooling, even with a low-capacity thermal extraction technique, reduces the severity of lesions resulting from RF ablation.

Conclusions: Esophageal cooling reduces the severity of the lesions that may result from RF ablation, even when relatively low heat extraction methods are used, such as the direct instillation of small volumes of cold liquid. Further investigation of this approach is warranted, particularly with higher heat extraction capacity techniques.

Keywords: Atrial fibrillation; Atrio-esophageal fistula; Esophageal cooling; Esophageal injury; Radiofrequency ablation.

Conflict of interest statement

EK declares equity interest in Attune Medical, manufacturer of an esophageal cooling device; MG, PS, CT, JG, and BC serve as Principal Investigators for studies of esophageal cooling sponsored by Attune Medical, which includes institutional support and travel reimbursements. SM has provided consulting services for Attune Medical. All other authors declare no relevant conflicts of interest.

Figures

Fig. 1

Results from John et al. Patients in the treatment group were actively cooled by injecting a 20 mL bolus of ice-cold saline via orogastric tube into the upper esophagus if/when the LET increased by 0.5 °C above baseline. Grade III and grade IV lesions are shown separately

Fig. 2

Results from Kuwahara et al. Patients in the treatment group were actively cooled by injecting 5 mL of ice water prior to RF energy delivery and subsequently when the LET reached 42 °C. The Grade III/IV lesion category represents all lesions qualitatively graded as “severe,” with mild lesions in Grade I and moderate lesions in Grade II

Fig. 3

Results from Sohara et al. Patients in group A received only LET monitoring without cooling of the esophagus. Patients in groups B and C received LET monitoring with esophageal cooling when the LET exceeded 43 °C and 39 °C, respectively. Cooling was by infusion of cooled saline mixed with Gastrografin. The Grade III/IV lesion category represents all lesions graded as ulcers (scored as 3 or 4 by Sohara et al.)

Fig. 4.

Forest plot comparing the outcome of all lesions in the three clinical studies. Events are the occurrence of grade I, II, III, and IV lesions

Fig. 5.

Forest plot comparing the outcome of low-grade lesions in the three clinical studies. Events are the occurrence of grade I and II lesions

Fig. 6

Forest plot comparing the outcome of severe lesions. Events are the occurrence of grade III/IV lesions