Therapy Cool Flex RF Ablation Catheter Pre-Clinical Results

Transcription

1 Irrigated Ablation Catheter RF Ablation Catheter Pre-Clinical

2 RF Ablation Catheter Pre-Clinical Introduction The catheter (Figure 1) is an entirely new concept in irrigated ablation catheters. It possesses a unique electrode design that allows the ablation tip to flex and compress to the motion of the heart. Irrigation is provided through dozens of slits that are uniformly spread throughout the electrode providing radial cooling. Four additional ports on the distal tip enhance cooling when the catheter is in a perpendicular orientation. Furthermore, the tip design allows for cooling that goes beyond bathing the entire tip in saline. The dovetail pattern creates preferential flow that directs the saline toward the tissue when the catheter is flexed (Figure 2). One millimeter band electrodes and close spacing is designed to enhance signal quality. Features Type Catheter Diameter Usable Length Number of Electrodes Tip Electrode Band Electrodes Electrode Spacing Temperature Sensor Curve Type/ Configuration Handle and Connector Specification Steerable ablation catheter 7 F 110 cm 4 (one tip and three bands) 4 mm (four open holes at distal tip and multiple lateral slits for irrigation) 1 mm (three) mm Thermocouple Type T Unidirectional/ M, L, XL, L1 Push/pull handle mechanism, male/female Redel connector from cable to catheter Table 1: Cool Fled catheter specifications Figure 1: Cool Fled catheter tip Figure 2: Irrigation distribution through the fleded tip of Cool Fled catheter. Note higher fluid output through the side of the tip which is more fleded as would be found if it were against the endocardial surface Page 2

3 Pre-clinical Testing The following is the summary of pre-clinical tests performed using the ablation catheter, studying its safety and performance. Comparative BenTh Study on PorTine Heart Tissue 1 This study compared dimensions of lesions created using the catheter with Cool Path and Cool Path Duo catheters (CE Marked) on porcine heart tissue across a range of radiofrequency power settings. Figure 3: Irrigation pattern through the Cool Path catheter (sid ports for irrigation) Lesions were created at six different power settings from W, with 45 C for 60 seconds at one location, and with a flow rate of 17 ml/min. Catheters were placed in the parallel and perpendicular orientations with approximately 5 grams of pressure. A total of 360 lesions 120 with each catheter type were created. Lesion dimensions including maximum depth, maximum diameter, depth at maximum diameter, and diameter at the surface were measured. Figure 4: Irrigation pattern through the Cool Path Duo catheter (twelve ports for irrigation) A statistical comparison showed lesions were comparable to those of the Cool Path and Cool Path Duo catheters. There were two instances of steam pops with Cool Path Duo and three with Cool Path. None were produced with the. Incidences of Steam Pops Cool Path 3 Cool Path Duo 2 0 Table 2: Incidences of steam pops Figure 5: Irrigation pattern through the Cool Fled catheter (multiple lateral slits and four top ports for irrigation) 1. Data on file at St. Jude Medical, Report and Page 3

4 Average Depth (mm) Average Depth in Parallel Orientation Lesions were created at power settings of 25, 30, 35, 40, 45 and 50 W at 45 C for 60 seconds, with a flow rate of 17 ml/min. Catheters were placed in a parallel and perpendicular orientation with 5-10 grams of pressure. A total of 120 lesions 60 with each catheter type were created. Lesion dimensions, such as maximum depth, maximum diameter, depth at maximum diameter, and diameter at the surface, were measured and average temperature, as well as adverse events recorded W 30 W 35 W Cool Path 40 W 45 W Cool Path Duo 50 W Figure 6: Average lesion depth comparison in parallel orientation Average Depth (mm) Average Depth in Perpendicular Orientation A statistical comparison showed average lesion depths were comparable to those of the Cool Path Duo catheters at 30 and 40 W (Figure 6 and 7). A statistical comparison at 50 W was not possible due to incidences of premature termination of the RF application as a result of steam pops. Power Cool Path Duo ( C) ( C) 30 W 32.8 ± ± W 34 ± ± W 34.8 ± ± 0.8 Table 3: Average tip temperature in parallel orientation 0 25 W 30 W 35 W Cool Path 40 W 45 W Cool Path Duo Figure 7: Average lesion depth comparison in perpendicular orientation Comparative In-vivo Study on Thigh MusTle Preparation 2 50 W This study compared dimensions of lesions created using the catheter and the Cool Path Duo catheter in a porcine thigh muscle preparation and evaluated the incidences of thrombus formation and steam pops across a range of radiofrequency power settings. Temperature ( C) Average Tip Temperature in Parallel Orientation W 40 W 50 W Cool Path Duo Figure 8: Average tip temperatures: parallel orientation Data on file at St. Jude Medical, Report Page 4

5 Power Temperature ( C) Cool Path Duo ( C) 32.9 Average Tip Temperature in Perpendicular Orientation ( C) 30 W 32.9 ± ± W 33.8 ± ± W 33.8 ± ± 1.2 Table 4: Average tip temperature in perpendicular orientation W 40 W 50 W Cool Path Duo 29.6 Figure 9: Average tip temperatures: perpendicular orientation In-vivo Study on Canine EndoTardial Tissue 3 This study demonstrated the ability of the catheter to create linear lesions in the canine endocardial tissue and evaluated the acute and chronic effects of those lesions. Testing was performed on five acute and five chronic animals. The ablation parameters were 30 W, 40 C, 17 ml/min flow rate, and 999 seconds of potential RF application with no more than 60 seconds at one location. A total of 33 lesions 16 acute and 17 chronic were created in the right and left atrium. Lesions were microscopically examined, and their dimensions were measured soon after the procedure in acute animals and about 29 days post-procedure in the chronic animals. On average, the catheter tip was approximately 5 C cooler than the Cool Path Duo catheter tip (Figure 8 and 9). This may be due to more evenly distributed cooling along the entire length of the catheter tip. There were 68% less incidences of steam pops and 50% less incidences of charring with Cool Flex as compared to Cool Path Duo. Most of the steam pops occurred at 40 and 50 W. Ablation was feasible in the right and left atrial regions without damaging adjacent tissue or other structures. The average lesion depth was 5 mm (range of 1-8 mm) in acute animals and 4 mm (range of 1-13 mm) in chronic animals. There were five incidences of steam pops and no instances of coagulum or charring. No clinical pathology abnormalities that would have affected the outcomes of the study were found. Most ablation sites appeared to exhibit transmural lesions in the samples (Table 6). Steam Pops Cool Path Duo Cool Path Duo Charring 30 (n=20) (n=20) (n=20) Total 22/60 (36.7%) 7/60 (11.7%) 38/60 (63.3%) 19/60 (31.7%) Table 5: Incidence of steam pops and charring 3. Data on file at St. Jude Medical, Reports and Page 5

6 Parameter Total Lesions Created # of Steam Pops # of Chars and Coagulum Acute Animals Chronic Animals (Evaluated 29 Days Post-procedure) Average Power 29 W 25 W Average Temperature Lesion Depth in RA Lesion Depth in LA 34 C 35 C 5.1 ± 2.1 mm (9/11 lesions were transmural) 4.4 ± 1.9 mm (4/5 lesions were transmural) 5.2 ± 3.3 mm (6/9 lesions were transmural, depth of two lesions could not be measured) 2.7 ± 0.8 mm (6/6 lesions were transmural) A fixture capable of controlled angle positioning was used to orient the catheters at 30, 45, 60, 75 and 90 degrees relative to a tissue-like silicone sheet supported on a digital scale. The catheter tip was placed in zero gram contact with the silicone surface. The catheter tip was then vertically lowered in 0.1 mm increments and the balance reading recorded until 200 g of force were registered. The sample size was 10 for each catheter type and orientation. The data revealed that operators can engage a larger amount of tissue surface area with the same amount of applied force using the catheter. This is true for any displacement greater than 0.2 mm and over the entire study range of degrees of tip orientation (see Figure 12 and 13). Table 6: In-vivo study data Conclusion The results from pre-clinical testing show that the unique properties of the tip produce comparable lesions to that of the Cool Path and Cool Path Duo ablation catheters. may result in a lower incidence of steam pops and charring. The average tip temperature of measured approximately 5 C cooler than that of the Cool Path Duo. This may be due to more evenly distributed cooling along the entire length of the catheter tip. Figure 12: Resultant force versus catheter displacement at 30 angle Comparative ForTe Transmission Evaluation 4 This bench test compared the force transmission of the catheter ablation tip to that of a conventional rigid 4mm irrigated catheter tip. Figure 13: Resultant force versus catheter displacement at 90 angle 4. Data on file at St. Jude Medical, Report Page 6

7 Finite Element Analysis on Flow Distribution 5 This computer simulation estimated the flow area and distribution of fluid output of the catheter ablation tip. A Finite Element Analysis (FEA) was performed using software specifically developed for this application. The physical dimensions and mechanical properties of the flexible catheter tip were used to develop the simulation model for this FEA. The computation method used for this test generated the mesh for the purposes of the structural simulation, which was then applied to identify the flow surfaces of the Flex tip. Figure 14: Cumulative Flow Area for Fleded Tip The flow distribution analysis showed that up to 70% of flow exits from expanded side of flexed catheter tip (Figure 14). This means that the design of the catheter tip accommodates the direction of the fluid flow in a flexed position toward the tip-to-tissue interface where cooling is most needed and most effective (Figure 15). Figure 15: Fluid Velocity at Cross Section of Cool Fled Tip 5. Data on file at St. Jude Medical, Report Page 7

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