William S. Yamanashi

Why a large tip electrode makes a deeper radiofrequency lesion: effects of increase in electrode cooling and electrode-tissue interface area.

Increase in RF Lesion Depth with Larger Electrode. Introduction: Increasing electrode size allows an increase in radiofrequency lesion depth. The purpose of this study was to examine the roles of added electrode cooling and electrode‐tissue interface area in producing deeper lesions.

777-1 Effective Delivery of Radiofrequency Energy Through the Coronary Sinus without Impedance Rise Using a Saline Irrigated Electrode

Some left free-wall and posteroseptal accessory pathways (AP) are located relatively close to the coronary sinus (CS) or its branches. Limitations of ablation from the venous system include rapid occurrence of an impedance rise at low power and the risk of perforation, due to high electrode temperature. We hypothesized that saline irrigation through the ablation electrode will maintain a low electrode temperature and allow safe application of higher RF power. In 14 dogs (18–22xa0kg), a 7F deflectable catheter with a lumen and a 5xa0mm tip electrode containing a thermistor and 6 irrigation holes was inserted into the CS. During saline irrigation (60xa0ml/min), two RF applications were delivered for 60xa0seconds or until an impedance rise. One application was placed in lateral-anterolateral CS and one was placed in the orifice or proximal segment of the middle cardiac vein. CS angiography was performed before and immediately after ablation and 6 days later (just before sacrifice). n Voltage (V) Power (W) Imp Rise Elect Temp (°C) Lesion Diameter (mm) 10 50 24xa0±xa03 0/10 31xa0±xa03 2.8xa0±xa00.8 18 66 45xa0±xa05 3/18 34xa0±xa05 7.6xa0±xa01.4 Impedance rise occurred with electrode temperaturexa0lxa040xa0°C and an audible pop and no thrombus formation. Lesions involving the epicardial surface of both the left atrium and ventricle (Fig) were found in 17/18 sites at 66xa0V but only 1/10 sites at 50xa0V. Necrosis did not extend to the endocardium at any of the 28 sites, eliminating risk of thromboembolism. CS angiography showed Download : Download high-res image (113KB) Download : Download full-size image patent veins and no evidence of perforation after ablation and at 6 days in all 14 dogs. Segmental necrosis of the adventitia and media (but not intima) of the LCx coronary artery (bold arrow) was present in 8/18 lesions of 66 V and 0/10 at 50xa0V. Conclusions Electrode cooling by saline irrigation allows high power (66xa0V, 45xa0W) RF application in the CS and venous branches, producing lesions likely to ablate epicardial left free-wall and posteroseptal AP. The significance of segmental medical necrosis (normal intima) of LCx is unknown.

Five-year survival in breast cancer treated with adjuvant immunotherapy

In this follow-up report of the treatment of primary breast cancer with adjuvant immunotherapy, a total of 95 patients were studied: 46 patients with stage I breast cancer and 49 patients with stage II breast cancer. All patients underwent standard surgical treatment and received immunotherapy as adjuvant treatment. Patients received a primary series of eight doses (1 mL of tumor-associated antigen preparation given as 0.2 mL intradermally and 0.8 mL subcutaneously) given over 8 weeks, and then booster injections every 3 months for at least 2 years. The 5-year survival with adjuvant immunotherapy was 83% for those with negative axillary nodes and 53% for those with positive nodes; this compares favorably with national 5-year survival statistics from two other studies (node-negative, 72% and 83%; node-positive, 51% and 59%). Based on these data, the addition of immunotherapy to other adjuvant therapies in randomized prospective trials seems both reasonable and justified.

705-5 Comparison of Radiofrequency Lesions in the Canine Left Ventricle Using a Saline Irrigated Electrode Versus Temperature Control

The maximum power deliverable by present radiofrequency (RF) ablation systems is limited by an impedance rise which occurs when the temperature at the electrode-tissue interface reaches 100 z C. The limitation in power limits the depth and diameter of the lesion. The present method to avoid an impedance rise and maximize power delivery utilizes a thermistor in the ablation electrode. The power is varied to maintain a target temperature and prevent the temperature from exceeding 90–95 z C (temperature control approach-TC). An alternative approach utilizes saline irrigation of the ablation electrode (active cooling) to prevent an impedance rise at high power (IR approach). The purpose of this study was to compare LV lesion size produced by the IR and TC approaches. In 15 anesthetized dogs (18–22xa0kg), a 7F deflectable catheter with a lumen and 5xa0mm tip electrode containing a thermistor and 6 Irrigation holes (located radially, 1xa0mm from tip) was inserted into a carotid artery and advanced to the LV under fluoroscopic guidance. RF current was applied at one site by manually controlling voltage (30–80xa0V) to maintain the electrode temperature at 80–90 z C (TC) and at a second site using saline irrigation (60xa0ml/min) and constant voltage of 90xa0V (IR). In 3 additional dogs with remote myocardial infarction (3–6 months), a total of 4 RF lesions was made at the border of the scar, all by IR approach (IR MI). The 15 dogs were sacrificed 6 days after ablation and the 3 dogs with infarction were sacrificed 4 hours after ablation Results. Voltage (V) Power (W) Imp Rise Elect tem (°C) Lesion Depth Diameter (mm) TC 15 57xa0±xa013 36xa0±xa017 3/15 84xa0±xa03 9.3xa0±xa02.0 12.7xa0±xa02.4 IR 15 90xa0±xa00 * 88xa0±xa08 * 6/15 38xa0±xa04 * 12.1xa0±xa02.4 * 20.5xa0±xa02.8 * IR MI 4 90xa0±xa00 81xa0±xa010 3/4 36xa0±xa03 8.6xa0±xa01.0 16.0xa0±xa02.4 * pxa0lxa00.01; TC vs. IR All impedance rises occurred after g30 seconds and with electrode temperature l80°C and an audible pop, suggesting release of steam from below the endocardial surface instead of boiling at the electrode-tissue interface. Conclusions 1) Electrode cooling by saline irrigation allows sustained RF energy at high power; producing larger and deeper lesions in normal LV myocardium; 2) the deeper lesions with a cooler electrode suggests direct resistive heating occurs relatively far from the electrode; and 3) reasonable lesions can be obtained in infarcted LV using irrigation.

Wound healing in rabbits: comparison of four methods of incision

A comparative wound healing study was performed to test the efficacy of using an electromagnetic field focusing device (EFF) as an incisional tool, and to compare it to wounds created using a scalpel, an Nd:YAG laser, and an electrosurgical device. Rabbits were aseptically incised using each modality. The wounds were allowed to heal for periods of 7, 14, and 21 days, and then the tissue was collected for histopathological analysis and tensile strength tests. The results indicated that the scalpel wounds healed faster and with fewer complications. The other three modalities resulted in thermal damage and necrosis that delayed healing.