Objective: Although the advent of ablation technology has simplified and shortened surgery for atrial fibrillation, only bipolar clamps have reliably been able to create transmural lesions on the beating heart. Currently, there are no devices capable of reproducibly creating the long linear lesions in the right and left atria needed to perform a Cox-Maze procedure. This study evaluated the performance of a novel suction-assisted radiofrequency device that uses both bipolar and monopolar energy to create lesions from an epicardial approach on the beating heart.
Methods: Six domestic pigs underwent median sternotomy. A dual bipolar/monopolar radiofrequency ablation device was used to create epicardial linear lesions on the superior and inferior vena cavae, the right and left atrial free walls, and the right and left atrial appendages. The heart was stained with 2,3,5-triphenyl-tetrazolium chloride, and each lesion was cross-sectioned at 5-mm intervals. Lesion depth and transmurality were determined.
Results: Transmurality was documented in 94% of all cross sections, and 68% of all ablation lines were transmural along their entire length. Tissue thickness was not different between the transmural and nontransmural cross sections (3.1 ± 1.3 and 3.4 ± 2.1, P = 0.57, respectively), nor was the anatomic location on the heart (P = 0.45 for the distribution). Of the cross sections located at the end of the ablation line, 11% (8/75) were found to be nontransmural, whereas only 4% (8/195) of the cross sections located within the line of ablation were found to be nontransmural (P = 0.04). Logistic regression analysis demonstrated that failure of the device to create transmural lesions was associated with low body temperature (P = 0.006) but not with cardiac output (P = 0.54).
Conclusions: This novel device was able to consistently create transmural epicardial lesions on the beating heart, regardless of anatomic location, cardiac output, or tissue thickness. The performance of this device was improved over most devices previously tested but still falls short of ideal clinical performance. Transmurality was lower at the end of the lesions, highlighting the importance of overlapping lines of ablation in the clinical setting.
From the Division of Cardiothoracic Surgery, Department of Surgery, Washington University School of Medicine, Barnes-Jewish Hospital, St Louis, MO USA.
Accepted for publication June 19, 2013.
Supported by grants from the National Institutes of Health (R01 HL032257 and 5 T32 HL007776) and by a research grant from Estech, San Ramon, CA USA.
Presented at the Annual Scientific Meeting of the International Society for Minimally Invasive Cardiothoracic Surgery, June 12–15, 2013, Prague, Czech Republic.
Disclosures: Ralph J. Damiano, Jr, MD, receives research funding from Edwards Lifesciences, Corp, Irvine, CA USA, and Atricure, Inc, West Chester, OH USA, and acts as a consultant to Atricure, Inc, West Chester, OH USA, and Medtronic, Inc, Minneapolis, MN USA. Richard B. Schuessler, PhD, receives research funding from Atricure, Inc, West Chester, OH USA. Lindsey L. Saint, MD; Christopher P. Lawrance, MD; Shoichi Okada, MD; Toshinobu Kazui, MD, PhD; and Jason O. Robertson, MD, declare no conflicts of interest.
Address correspondence and reprint requests to Ralph J. Damiano, Jr, MD, Division of Cardiothoracic Surgery, Department of Surgery, Washington University School of Medicine, Barnes-Jewish Hospital, Campus Box 8234, 660 South Euclid Ave, St Louis, MO 63110 USA. E-mail: firstname.lastname@example.org.