Okumura, Yasuo

Introduction: Recently, there have been numerous strategies for treating atrial fibrillation, including the choice of catheters However, the thermal characteristics of each catheter, particularly in terms of safety, have not been fully understood. Hypothesis: Our aim was to characterize the thermal damage to collateral tissues during 50W-HPSD ablation and 90W/4sec-vHPSD ablation using three different ablation catheters. Methods: In 28 pigs, we implanted thermocouples on the superior vena cava, close to the phrenic nerve, and on the esophageal, close to the inferior vena cava. We performed endocardial ablation near the fiducial markers of the thermocouples using three different RF catheters: ablation index (AI)-guided HPSD (Qmode) and vHPSD ablation (Qmode+) with QDOTMICRO, lesion size index-guided HPSD ablation (targeting 5.0) with TactiCath Sensor Enabled (Tacti), and AI-guided HPSD ablation (targeting 400) with Thermocool Smart Touch (STSF). We measured tissue temperatures during ablation, including maximum tissue temperature (Tmax), time to maximum tissue temperature (t-Tmax), time to achieve a lethal temperature of 50°C (t-50°C), and time to return to baseline from Tmax (t-Tbase). Results: In terms of the frequency of esophageal injury, there were no significant differences among the different catheters. However, the depth of esophageal injury from the adventitia showed a significant difference. In terms of phrenic nerve injury, Tacti had the highest frequency compared to the other catheters (100%, p=0.0012). Tmax, t-Tmax, t-50°C, and t-Tbase showed significant differences, as shown in figure. Conclusions: The thermal effects on collateral tissues differ among the three different catheters and settings. STSF and Qmode result in a gradual increase in tissue temperature, while Tacti and Qmode+ lead to a rapid temperature increase. These distinct thermal distributions may contribute to the risk of phrenic nerve and esophageal injuries.

Background: Current mapping systems use simultaneous displays of overlapping 3D maps and pre-acquired CT images of the LA to “pseudo-register” data sets rather than specifically “register” each point of one mapping data set to the other. The appropriateness of the 2 data set match has not been validated. Since significant surface to surface mismatch errors may occur, this study was undertaken to quanititatively validate NavX map to CT registration and determine its suitability for guiding AF ablation. Methods: Sixty-four slice, multidetector CT scans were acquired in 8 dogs and segmented to establish subject-specific LA/PV volumes for importation into the EnSite mapping system. A detailed multi-surface geometry (NavX map) was collected by navigating a mapping catheter in target LA and PVs. Using a novel developmental registration algorithm the map was registered to LA/PV CT volume. Validation was performed using the registered 3D CT model for the guidance of ablation at the location of multiple implanted radio-opaque markers. Results: A total of 39 radio-opaque markers were implanted before CT including 9 LSPV, 8 RSPV, 7 RIPV, 9 LIPV, 3 roof, and 3 LAA locations. Subsequent registration of individual NavX maps to acquired 3D CT volume was successfully completed in all animals. RF ablations were performed at the predicted 3D registered model locations of the radio-opaque markers using 5 mm tip RF ablation catheter. Resulting mean lesion size was 5.3 x 6.5 mm. The lesions enveloped the point of marker attachment to the myocardium in 31/36 (86%) ablations. The average distance from the center of the RF lesion to the targeted site was 2.5 ± 1.5mm. 47 points were successfully navigated under fluorscopic and ICE guidance. All points were accurately portrayed on the 3D registered model. 3 points in the region of the RSPV floor did have minor offsets on the model due to technically difficult segmentation of the RSPV from the right pulmonary artery. Conclusion: These data demonstrate the feasibility of registering NavX derived geometries to CT data sets accommodating sources of cardiac, respiratory, and translational cycle dependent error. Catheter navigation precisely conducted using the registered model demonstrates accuracy within the range required for RF ablation.

Background: Current technologies to fully “register” surrogate maps onto 3D CT (CartoMerge, NavxMerge) or 3D ICE images (CartoSound) have emerged to guide ablation. The feasibility of navigation with the Hansen Robotic Catheter Sheath System (HRCS) has also been reported. Integrated 3D Image and contact force sensor with this robotic system may allow for feasibility and safety for guiding complex anatomic-based ablation. Methods: Circumferential pulmonary vein (PV) ablation with the robotic system guided by integrated 3D images (CartoMerge, NavxMerge or CartoSound) (n=3), were done and compared to manual manipulation guided by the integrated 3D images (CartoSound) (n=8). Each ablation was performed using contact force ranges of 10 –20 grams (20W, 17 ml/min flow, 30 seconds). Accuracy of PV ablation was assessed by comparing distance from the PV ostia (specific 4 sites) to the ablative points on the 3D image structures, and the corresponding distances of the actual ablative lesions at pathologic exam. Results: Using three integrated 3D image systems, circumferential PV ablation was successfully guided in 6 PVs (3 RSPVs and 3 LSPVs) with the robotic system. During all ablations with contact forces of 10 –20 grams, no impedance rises, pops or type 2 microbubbles were seen. Accuracy of the PV ablation was 0.22±0.84 mm (range 0 –2). The PV rings were 100% circumferential by electroanatomic mapping, yielding an 86±7% (range 80 –98%) uninterrupted circumferential ablative ring around each PV with 1.1 ± 0.4 gaps (3.0 ± 0.9 mm). These resulting parameters were equal to those in the integrated 3D image-based manual navigation (Accuracy: 0.5±0.9 (range 0 –2.5) mm, Gaps:1.3 ± 0.9 ( 2.6 ± 0.9 mm), circumferential lesions 88 ± 10% (range 70 –100). Conclusions: This feasibility study demonstrated successful integrated 3D image and contact force-guided robotic ablation. Contact sensor guided 3D volume construction and real time 3D images accurately replicated atrial and venous anatomy, resulting in successful circumferential ablation.

Introduction: Unstable scar related ventricular tachycardia (VT) is a common problem after myocardial infarction. Aggressive ablation may be limited, however, by incomplete scar penetration with available RF energy delivery technologies. The purpose of this study was to test the feasibility of full thickness linear ablation of infarcted ventricular substrate with a high penetration virtual electrode needle based electrode system. Methods: Chronic infarcted (> 2months) mongrel dogs (35–40 kg) underwent percutaneous catheter ablation of the LV with a saline-injection needle catheter employing an 8 mm 20-GA tip. Constant power at 40W was delivered for 90 sec via the virtual electrode needle during infusion of saline 10 ml/h at 50°C. The lines were created under electroanatomic map guidance and intracardiac ultrasound (ICE). The ejection fraction was monitored immediately before and after the ablation. One week after ablation, the dogs where restudied using CARTO epicardial and endocardial voltage mapping and hemodynamic testing. Results: The ablation lines created by a virtual electrode energy delivery made in the antero-lateral wall showed mean length of 4.4±1.4 cm. The mean area of ablation per lesion in the endocardium, mid myocardium and epicardium was 1.1±1.0, 2.6±1.3 and 1.9±1.3 cm 2 (p<0.05) respectively, with a mean ablation depth of 1.5±0.5 cm. Sixty-four percent of the length of lesions were transmural and in non-transmural areas had an average depth of 90±16% of wall thickness. The mean number of gaps/line was 0.5±0.7 with a length of 0.6 cm. Ejection fraction was 50±14, 52±17 and 52±13% before, after and 1 week post ablation respectively. At one week the epicardial and endocardial areas of low bipolar voltage < 1.5mV and dense scar < 0.5mV in the Carto map were 11.4±1.2 and 7.9±6.1cm 2 respectively which measurements were confirmed at necropsy by macroscopic scar in the epicardium and endocardium of 11.8±4.3 and 6.6±4.1 cm 2 respectively. Conclusion: This new novel saline-injection needle catheter effectively creates continuous long transmural lines in the infarcted LV. These data also confirm that the macroscopic ablation lesions can be consistently and accurately monitored by 3D electroanatomical mapping in both endocardium and epicardium.

Background: Although pulmonary vein (PV) isolation has been used to treat AF, complications create important limitations. New energy sources, including cryothermal, have been developed to minimize these complications. The purpose of this study was to evaluate the effect of PV cryoablation on esophageal (ESO) temperatures acutely and correlate them with chronic effects on the esophageal wall. Methods: A 23 mm cryoballoon was placed in the LA of 10 dogs through a 12 Fr deflectable sheath. PV and ESO temperatures (TEMP) were recorded using 7–9 thermocouples (TC) outside the PVs and on the external and internal ESO surfaces during 2 cryoablations of 4 min duration. Results : Cryoablation of 15 PV (10 RIPV and 5 LIPV) during 1.7±0.6 ablations yielded a total of 168 TC time-TEMP profiles (6.4±2.4/PV). Minimum tissue TEMP was inversely dependent on the distance of the TC from the balloon surface (Table 1 ). All PVs were isolated acutely and 14/15 (93%) chronically. Minimum TEMP achieved at the PV surface and external ESO were similar (−32±8 and −37±9 at targets within 2.5 mm from the balloon respectively [P=NS]). A TEMP decrease at the internal ESO was seen during 15 of 25 (60%) ablations, but was significantly less pronounced than the external TEMP (17.9°C±13.3 and 6.1°C±24.8 [p<0.05]) resulting in a minimum recorded internal TEMP of −6.2°C. The ESO histological examination in 5 dogs showed very limited external lesions in these dogs (depth= 2.2±1.1, width3 18.6±7.4 and length= 12±5.7 mm), but no transmural or internal ulceration, fibrosis or scarring seen. Conclusion: Although PV cryoablation decreases external ESO temperature and produces minor lesions, significant chronic disruptive tissue damage was not seen. Esophageal injury is an unlikely, but potential complication of cryoablation, with internal temperature proving unhelpful in predict negative outcome.

Background— Multiple factors create discrepancies between electroanatomic maps and merged, preacquired computed tomographic images used in guiding atrial fibrillation ablation. Therefore, a Carto-based 3D ultrasound image system (Biosense Webster Inc) was validated in an animal model and tested in 15 atrial fibrillation patients. Methods and Results— Twelve dogs underwent evaluation using a newly developed Carto-based 3D ultrasound system. After fiducial clip markers were percutaneously implanted at critical locations in each cardiac chamber, 3D ultrasound geometries, derived from a family of 2D intracardiac echocardiographic images, were constructed. Point-source error of 3D ultrasound-derived geometries, assessed by actual real-time 2D intracardiac echocardiographic clip sites, was 2.1�1.1 mm for atrial and 2.4�1.2 mm for ventricular sites. These errors were significantly less than the variance on CartoMerge computed tomographic images (atria: 3.3�1.6 mm; ventricles: 4.8�2.0 mm; P< 0.001 for both). Target ablation at each clip, guided only by 3D ultrasound-derived geometry, resulted in lesions within 1.1�1.1 mm of the actual clips. Pulmonary vein ablation guided by 3D ultrasound-derived geometry resulted in circumferential ablative lesions. Mapping in 15 patients produced modestly smaller 3D ultrasound versus electroanatomic map left atrial volumes (98�24 cm 3 versus 109�25 cm 3 , P< 0.05). Three-dimensional ultrasound-guided pulmonary vein isolation and linear ablation in these patients were successfully performed with confirmation of pulmonary vein entrance/exit block. Conclusions— These data demonstrate that 3D ultrasound images seamlessly yield anatomically accurate chamber geometries. Image volumes from the ultrasound system are more accurate than possible with CartoMerge computed tomographic imaging. This clinical study also demonstrates the initial feasibility of this guidance system for ablation in patients with atrial fibrillation.