Varzaly, J.A.Chapman, D.Lau, D.H.Edwards, S.Louise, J.Edwards, J.Mahajan, R.Worthington, M.Sanders, P.2018-12-132018-12-132018Interdisciplinary cardiovascular and thoracic surgery, 2018; 28(1):1-91569-92931569-9285http://hdl.handle.net/2440/116794OBJECTIVES: Atrial fibrillation is treated surgically by creating conduction block lesions. Radiofrequency (RF) lesions have reduced efficacy compared to ‘cut-and-sew’. Catheter ablation studies demonstrate a relationship between lesion depth and contact force. We hypothesized that contact force and lesion depth are dependent on design of the bipolar surgical RF clamps. METHODS: Hinged and parallel jaw style RF clamps were studied. Muscle samples were clamped with pressure-sensitive film at increasing tissue thicknesses. Films were analysed determining clamp pressure profiles. A sheep model was utilized for ablation testing using each clamp style until the device indicated transmurality. Separate muscle areas had 1, 2 or 3 burns applied. The muscle was excised, sectioned every 1 cm and stained for lesion depth and fat thickness analysis. RESULTS: Pressure profiling comparing the proximal and distal segments of each clamp style demonstrated only one statistically significant difference in the parallel clamp; the hinged clamp had statistically significant differences (P ≤ 0.03) for all tissue thicknesses. There was no evidence for differences in the proximal lesion depth of both clamps (P = 0.13) but deeper distally in the parallel clamp (10.17 mm vs 8.02 mm, P = 0.003). The logistic regression analysis demonstrated increased odds of transmurality with parallel clamps at 1, 2 or 3 burns (P = 0.03, P = 0.003 and P = 0.002). Every 1 mm increase in overlying fat decreased likelihood of transmurality by 11% (P < 0.05). CONCLUSIONS: The parallel and hinged clamps have different pressure profiles with higher likelihood of transmurality using the parallel clamp. Fat reduces the ability of RF to deliver a transmural lesion. These findings have implications for optimal surgical RF ablation technique.en© The Author(s) 2018. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices)Surgery; atrial fibrillation; ablation; contact force; lesion; radiofrequencyJournal article003009930310.1093/icvts/ivy1910004639612000142-s2.0-85058909797441211Lau, D.H. [0000-0001-7753-1318] [0000-0002-1564-439X]Edwards, S. [0000-0003-2074-1685]Louise, J. [0000-0001-5785-0290]Mahajan, R. [0000-0003-3375-5568]Sanders, P. [0000-0003-3803-8429]