Thermodynamic Evaluation of 4 Open-Irrigated Catheters. Introduction: New generation open-irrigated catheters aim to improve irrigation efficiency. This may change lesion patterns, challenging operators. Indeed, safety issues have recently arisen. We aimed to experimentally assess 4 open-irrigated catheters, comparing lesion size, safety, and heat transfer. Methods: The thigh lesion model was employed in 6 anesthetized pigs to assess the morphology of perpendicular and tangential lesions (n = 140) created by the newer catheters ThermoCool R SF, CoolFlex TM , and Blazer TM Open-Irrigated, and the standard ThermoCool R , at a constant power of 30 W (60 seconds). To evaluate the propensity for deep-tissue overheating, a set of 120 applications were performed at 50 W (180 seconds) comparing pop rates. Thermal assessment of the lesion generation process (20 W, 60 seconds, n = 32) was performed with an infrared camera on bovine ventricular tissue.Results: At 30 W, the newer catheters showed lower temperature readings compared with the ThermoCool R . No major efficacy or safety differences were found at tangential applications; however, at perpendicular applications: (1) the SF at 17 mL/min better preserved the superficial layers and focused its maximum thermal effect deeper, but at recommended flow rates (8 mL/min) it generated the largest superficial lesions; (2) CoolFlex TM created smaller lesions than SF and readily induced steam pops at 50 W without temperature control; and (3) no major differences were found comparing Blazer TM Open-Irrigated and ThermoCool R .Conclusions: The lower temperature readings in the newer catheters make them more prone to deliver the maximum programmed power. Under experimental conditions, the SF catheter focuses its maximum effect deeper and the CoolFlex TM can be more prone to induce steam pops at high power settings.

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Upon KATP-channel opening, VF consisted of rapid and highly organized domains mainly due to stationary rotors, surrounded by poorly organized areas. A 'beat phenomenon' due to the quasi-periodic onset of drifting rotors was observed. These findings demonstrate the feasibility of a VF driven by stable rotors in hearts whose size is similar to the human heart. Our model also showed that complex fractionation does not seem to localize stationary rotors.

Intravascular beta-radiation can induce transmural necrosis and fibrosis of PV myocardial sleeves without PV stenosis and other unwanted effects, which supports a potential usefulness of this energy source in the treatment of AF.