Philadelphia, PA - Results from a new study have shown that the use of intracardiac echocardiography to provide real-time esophageal imaging can be used to monitor lesion development during AF ablation procedures, thus reducing the risk of atrioesophageal fistulas, a rare but deadly complication of the procedure [1].

Writing in the September 2006 issue of Heart Rhythm, lead investigator Dr Jian-Fang Ren (University of Pennsylvania, Philadelphia) and colleagues write that "this study demonstrates that the esophagus can be imaged, and intracardiac echocardiography appearance of ablation lesions and possible esophageal involvement can be modified by adjusting the power, temperature, and duration of lesion application."

In their paper, Ren and colleagues report that a patient, a 47-year-old woman with paroxysmal AF, experienced an atrioesophageal fistula and died as a result of the complication at their center. Two weeks after an uncomplicated ablation procedure, the woman developed fever, nausea, and vomiting, with and without blood. An autopsy revealed a 1- to 2-mm fistula between the left atrial posterior wall and the esophagus.

The group hypothesized that intracardiac echocardiography could provide real-time anatomic imaging of the esophagus to monitor lesion development and control the radiofrequency energy deployed during left atrial ablation for AF. The investigators retrospectively reviewed the stored intracardiac echocardiography images of 79 patients and analyzed 73 patients whose images were prospectively obtained after the death of the 47-year-old woman. In these prospective cases, the radiofrequency duration was titrated based on the results of the intracardiac echocardiography .

Ren and colleagues report that intracardiac echocardiography was able to image the longitudinal extent of contact between left atrium and esophagus in all patients. They report that radiofrequency ablation induced morphologic changes in the atrial wall, including swelling, dimpling, crater formation, and echocardiographic enhancement.

Before the death of the 47-year-old patient, the use of either an 8-mm ablation or cooled-tip catheter was used with high-power and high-temperature settings, resulting in morphologic changes that were contiguous with the esophagus. Following this index case, however, lower-power and -temperature settings, as well as shorter duration, all guided by the real-time monitoring, were used to generate lesions in the left atrial poster wall only. In addition, when intracardiac echocardiography was used to titrate lesion duration, termination of energy delivery within 30 seconds was required in more than 30% of lesions because of accelerated bubble formation or the development of lesion-induced echogenicity. Importantly, pulmonary vein isolation was still achieved in all 73 patients.

The group cautions, however, as does Dr Hugh Calkins (Johns Hopkins University Medical Center, Baltimore, MD) in an accompanying editorial [2], that because of the low incidence of esophageal fistula formation, further study will be needed to determine whether the imaging modality can completely eliminate the risk.

"There is no question that those involved with catheter ablation of AF urgently need a method to protect the esophagus and prevent further atrioesophageal fistulas," writes Calkins. "Based on the results of this study, it appears that intracardiac echocardiography may have promise in this regard. But it is also important to recognize that this study does not prove that an intracardiac echocardiography-based strategy will prevent the development of this complication in the future. With an incidence of only 0.1%, the absence of esophageal injury with intracardiac echocardiography monitoring in 73 consecutive patients is hardly compelling."