Characterization of in vitro and in vivo lesions made by a novel multichannel ablation generator and a circumlinear decapolar ablation catheter.

INTRODUCTION: The aim of this study is to characterize ablation lesions using varying ratios of bipolar:unipolar energy and to show the feasibility of a circular decapolar pulmonary vein ablation catheter (PVAC) to create transmural lesions in an in vivo porcine superior vena cava (SVC) model. METHODS AND RESULTS: Ablations were performed on (1) isolated blocks of bovine myocardium, (2) thigh muscle preparations (4 pigs), and (3) the junction between SVC and right atrium (6 pigs). Radiofrequency (RF) energy was delivered simultaneously to all electrodes (target temperature 60 degrees C, maximum power 10 W/electrode) with various ratios of bipolar:unipolar energy. (1) In vitro PVAC resulted in circumscript lesions. Changing RF energy mode from unipolar only to bipolar:unipolar 1:1, 2:1 and 4:1 and bipolar only decreased lesion depth significantly (6.7 +/- 0.2 vs. 5.0 +/- 0.2, 4.1 +/- 0.3, 3.6 +/- 0.1 and 3.1 +/- 0.1 mm, P < 0.001). (2) Similar results were obtained in vivo (thigh muscle) showing less deep lesions with more bipolar energy modes (e.g., 5.4 +/- 1.3 for unipolar only vs. 4.1 +/- 0.8 mm for bipolar only, P < 0.05). (3) Ablation at the SVC did not result in device-related complications. All animals survived and were sacrificed after 7 +/- 1 days except for one pig, which died immediately postoperatively from an unknown cause. Macroscopy and microscopy showed circumferential transmural SVC lesions. CONCLUSIONS: Temperature-controlled, power-limited RF energy with the PVAC is feasible for creating circumferential transmural lesions (SVC) that sometimes extended to neighboring structures. Lesion depth can be titrated by varying the bipolar:unipolar energy ratio. This novel ablation system paves the way for single-catheter ablation of AF.

Surgical considerations of entire lumbar spine hardware removal via a minimally invasive approach.

A retrospective analysis of 13 patients who underwent endoscopic hardware removal to resolve residual foraminal stenosis issues was performed to determine the feasibility and validity of utilizing endoscopic techniques to entirely remove spinal hardware. Tubular retractors were utilized for the procedure with a diameter of 15 to 18 mm. Surgical times ranged from 58 to 268 minutes, with the largest time delay being the need to cut the crossbars in vivo due to stripped screws, bony overgrowth, or bent hardware. Entire hardware systems can be removed via an endoscopic approach. Blood loss averaged around 90 cc but surgical times were over an hour for most procedures. Endoscopic removal of entire hardware systems can be accomplished but it offers little advantage over conventional hardware removal. The main advantages include reduced trauma and the ability of the surgery to be performed on an outpatient basis.