Balloon surface temperature–controlled ablation using a second-generation radiofrequency HotBalloon: an in vivo feasibility study

Figures

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  Figure 1. Principles of the first- and second-generation RHB and their impact on the efficacy and safety of energy applications. (A) With the first-generation RHB, energy output is regulated by the balloon’s central temperature. (B) With the second-generation RHB, an additional temperature sensor was attached 15 mm from the proximal end of the balloon, and BST-controlled ablation became available. BST, balloon surface temperature.

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  Figure 2. Study design of Protocols 1 and 2. (A) Study design of the Protocol 1 verifying the accuracy of the BST-monitoring system. (B) Study design of the Protocol 2. The left diagram shows the Phase 1 study evaluating acute electrophysiological and pathological findings. The right diagram shows the Phase 2 study evaluating chronic electrophysiological and pathological findings. BST, balloon surface temperature; PV, pulmonary vein.

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  Figure 3. Method and result of the Protocol 1. (A) Thermocouple implantation in the epicardial surface of the SVC and RA junction. (B) Fluoroscopy image of energy application at the SVC–RA junction. Two thermocouples were positioned just opposite the RHB (arrow). (C) Representative scatterplots of the epicardial temperature, temperature recorded at the BST-monitoring system, and BCT during energy application. (D) Scatterplots showing the correlation between the epicardial temperature of the SVC–RA junction and the BST. AP, anterior-posterior; SVC, superior vena cava.

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  Figure 4. Histological illustrations of the lesions using PTAH staining. The white and grey boxes show a longitudinal section of the LSPV and RSPV. The white box (A) shows transmural injury, and the grey box (B) shows non-transmural injury. LA, left atrium; LAA, left atrial appendage; LSPV, left superior pulmonary vein; RSPV, right superior pulmonary vein.

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  Figure 5. Acute electrophysiological and pathological findings after energy application using four different BSTs. (A) Acute electrical isolation rate of target veins. (B) Transmural ratio. (C) Lesion depths. Representative resected slides stained by PTAH staining (D: 51°C, E: 54°C, F: 57°C, G: 60°C). Of note, energy application with a higher BST resulted in uniform myocardial injury. An apparent positive association between BST and lesion depth was observed, but actual lesion depth was difficult to measure when the transmural lesion was achieved. Hence, a statistical comparison of lesion depth between each BST was not performed.

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  Figure 6. Chronic electrophysiological and pathological findings comparing energy application using BSTs of 57 and 60°C. (A) Electrical isolation rate during the ablation and after 8 weeks. Energy application with a BST of 60°C created durable lesions, while energy application with a BST of 57°C resulted in a 44% reconnection rate. (B) The transmural ratio was significantly greater after energy application at a BST of 60°C. (C) Lesion depths. (D and E) Representative resected slides of the chronic phase stained by PTAH staining.

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  Figure 7. Representative voltage map in the LA and PV for acute and chronic evaluation. (A) Voltage maps of ablation with a BST of 57°C in the acute and chronic phases. (B) Voltages map of ablation with a BST of 60°C in the acute and chronic phases. For details, see text. LIPV; left inferior pulmonary vein; LSPV, left superior pulmonary vein; RSPV, right superior pulmonary vein.