Lesion Width Research Articles

Catheter contact angle influences local impedance drop during radiofrequency catheter ablation: insight from a porcine experimental study

Abstract Background Local impedance (LI) at a distal tip of the ablation catheter can indirectly measure catheter contact and tissue temperature during radiofrequency catheter ablation (RFCA). LI decreases by RFCA, and a degree of LI drop is correlated with lesion size. However, data on the effects of catheter contact angle on lesion size and LI drop were scarce. This study aimed to evaluate the influence of catheter contact angle on lesion size and LI drop in a porcine experimental study. Methods Lesions were created on porcine myocardial left ventricles by the LI-sensing ablation catheter (IntellaNav MiFi OI®). Contact force (CF) was measured using pressure to current transducer (load cell). Radiofrequency ablation was performed with a power of 30 Watt and a duration of 30 seconds. CF (0g, 5g, 10g, 20g, and 30g) and catheter angle (30°, 45°, and 90°) were changed in each set (total 120 lesions, n=8 each). LI rise, LI drop by RF application, and lesion size (maximum lesion width, maximum surface width, and maximum lesion depth) were evaluated. Results There was no angular dependence in LI rise in all CF. The values of LI rise increased as CF increased. The LI drop also increased as CF increased in all contact angles. Regarding the difference of catheter angles, LI drop with 90° was lower than those with 30° and 45°in CF 10g, 20g, and 30g, respectively. Maximum lesion width and surface width were larger in 30° and 45° than those in 90°, whereas there were no differences in maximum lesion depth. Conclusion LI drop in 90° were significantly lower than those in 45° and 30°. Although lesion depths were not different among the three angles, the absolute values of LI drop were different. Caution should be exercised to comprehend the LI drop with catheter angles. Funding Acknowledgement Type of funding sources: None.

Quantification of irrigated lesion morphology using near-infrared spectroscopy

There are currently limited means by which lesion formation can be confirmed during radiofrequency ablation procedures. The purpose of this study was to evaluate the use of NIRS-integrated RFA catheters for monitoring irrigated lesion progression, ex vivo and in vivo. Open-irrigated NIRS-ablation catheters with optical fibers were fabricated to sample tissue diffuse reflectance. Spectra from 44 irrigated lesions and 44 non-lesion sites from ex vivo swine hearts (n = 15) were used to train and evaluate a predictive model for lesion dimensions based on key spectral features. Additional studies were performed in diluted blood to assess NIRS signatures of catheter-tissue contact status. Finally, the potential of NIRS-RFA catheters for guiding lesion delivery was evaluated in a set of in vivo pilot studies conducted in healthy pigs (n = 4). Model predictions for lesion depth (R = 0.968), width (R = 0.971), and depth percentage (R = 0.924) correlated well with measured lesion dimensions. In vivo deployment in preliminary trials showed robust translational consistency of contact discrimination (P < 0.0001) and lesion depth parameters (< 3% error). NIRS empowered catheters are well suited for monitoring myocardial response to RF ablation and may provide useful intraprocedural feedback for optimizing treatment efficacy alongside current practices.

Catheter Ablation Using Half-Normal Saline and Dextrose Irrigation in an OvineVentricularModel.

This study hypothesized that catheter ablation in healthy ovine ventricular myocardium using low ionic 0.45% saline (half-normal saline [HNS]) and nonionic 5% dextrose in water (D5W) would result in larger lesions compared with use of 0.9% saline (normal saline [NS]). Limited data exist regarding the safety and efficacy of catheter ablation using low and nonionic irrigants. Open irrigated ablation was performed on 14 beating ovine hearts (NS, n=5; HNS, n=4; D5W, n=5). Ablation was delivered by using identical parameters (ie, 30W in power control mode, 60-second duration, contact force of 10-20g in the endocardial ventricles and 5-10g in the epicardium). Catheter orientation and tissue contact were optimized by using intracardiac echocardiography. Lesion width, depth, and volume and number of steam pops were compared. Overall, 196 lesions were analyzed (mean duration: 56.7 ± 8.3 seconds; mean contact force: 15.3 ± 6.1 g; and mean impedance drop: 31 ± 19.1Ω). Compared with NS, HNS and D5W resulted in larger lesion volumes (NS 349.2 ± 245.1mm3 vs HNS 645.7 ± 386.4mm3 vs D5W 633.2 ± 387.1mm3; HNS vs NS; P< 0.001; D5W vs NS; P< 0.001; D5W vs HNS; P=0.87). However, D5W was associated with higher steam pop occurrence (NS 5% vs HNS 11% vs D5W 35%; HNS vs NS; P=0.22; D5W vs NS; P< 0.001; D5W vs HNS; P=0.002). Catheter ablation with HNS and D5W resulted in larger ablation lesions compared with NS but similar lesion dimensions between HNS and D5W. The increase in lesion size with HNS and D5W was associated with a higher incidence of steam pops, especially with D5W, compared with NS.

Contrast-enhanced ultrasonography promotes differential diagnosis of ureteral neoplasms.

To compare the diagnostic value of contrast-enhanced ultrasonography (CEUS) with baseline ultrasound (B-US) in ureteral neoplasms. Retrospective analysis, comprising clinical presentation, image appearances, and diagnostic results on B-ultrasound and CEUS, considering pathological result as a gold-standard, was conducted on the clinical information of 39 patients with ureteral neoplasms. CT urography was used to detect and confirm the presence of ureteral neoplasms. Both B-ultrasound and CEUS investigations of those 39 patients under study were performed by a senior radiologist. Pathological outcomes established 27 ureteral malignancies and 12 ureteral benignancies. Ureteral malignancies were observed to occur in older patients than benignancies (p = 0.002). Only the morphological indicator of the ureteric wall on B-ultrasound was different in ureteral malignancies and benignancies (p = 0.030). Tumors with hyperenhancement, larger width, and hyperenhanced ureteric wall were easily diagnosed as malignant on CEUS, whereas iso-/hypoenhanced, narrower, and iso-/hypoenhanced ureteric wall indicated benign tumors. Moreover, the lesion widths, enhanced morphologies of the ureteric wall, and the ureteral wall's linear boundaries on CEUS were different between high- and low-stage ureteral urothelial carcinomas (p = 0.012, 0.002, 0.001, respectively). The display of microvessels in ureteral neoplasms was significantly enhanced by CEUS, thus contributing to the differential diagnosis of ureteral neoplasms while assisting the staging of ureteral urothelial carcinoma. The imaging features of different ureteral neoplasms on CEUS were analyzed in this study. The diagnostic performances of CEUS and B-ultrasound in ureteral urothelial carcinomas were also explored.

Protocolo estandarizado para la observación de la imagen tomográfica en endodoncia

Objective: Establish a standardized protocol for the observation of Cone Beam Computed Tomography (CBCT) in endodontics, to systematically determine the dimensions of chronic apical lesions. Methods: Analysis and application of the tools of the specific Cone Beam Computed Tomography software for the exploration of dental and periapical tissues, prior literature review of the subject. Subsequently, the design of standardized systematic steps of observation and measurement of the dental tomographic image in Endodontics, thus establishing the Protocol. Finally, training of 2 Endodontists in the application of the Protocol by an expert Radiologist, measuring the dimensions of chronic apical lesions (height, depth and width) in 45 high-resolution conical beam dental tomographs and checking its usefulness, through a concordance test using the Intraclass Correlation Index (ICC). Results: A written document was generated with explanatory graphic material on the steps to follow by the Standardized Protocol and a statistical concordance test was carried out that evidenced a high degree of agreement between the measurements of the trained endodontists (observers 2 and 3) against the expert radiologist (observer 1). The highest degree of agreement was found among observers 1 and 2 in the sagittal view when assessing the height of the lesion (ICC: 0.9997545), while observers 1 and 3 achieved the highest degree of agreement in axial vision (ICC 0.9996737, 95% CI) when assessing the depth of the lesion. Conclusion: The application of this simple, systematic and standardized protocol for the observation of dental tomography in clinical practice makes it possible to reliably, reproducibly and accurately assess the image of apical periodontitis, prior observer training, allowing a high degree of concordance to be achieved when apical lesions are measured.

B-AB03-03 PULSED FIELD ABLATION OF LEFT VENTRICULAR MYOCARDIUM IN A SWINE INFARCT MODEL

Pulsed field ablation (PFA) leads to cell death by irreversible electroporation. However, there is limited data about lesion characteristics in ventricular myocardium in the presence of myocardial scar. To evaluate the lesion characteristics of PFA in healthy and infarcted left ventricular (LV) myocardium. Swine (n=6) underwent 120min LAD balloon occlusion myocardial infarction (MI) and were survived 6-8 weeks. PFA was delivered to the LV endocardium of 1) healthy myocardium or 2) MI identified with electroanatomic mapping. Bipolar, biphasic PFA was delivered for 2.5secs x 4 applications/site (10secs total) using 2 different catheters: a linear quadripolar (FOCAL, 2000-2100V) or multi-spline 8-pole catheter (BASKET, 1800V) (FARAPULSE, Menlo Park, CA) (Figure). After sectioning, gross lesions were identified, measured using calipers and tissue stained for histology. 21 lesions were delivered to healthy LV and 20 to areas with MI, all without complications. Overall, there was no significant difference in lesion depth between groups (FOCAL vs. BASKET; depth: 5.6 ±1.1 mm vs. 5.5 ± 1.1 mm, P=0.740), while lesion width was greater for BASKET (10.6 ± 2.4 mm vs. 13.3 ± 3.3 mm, P=0.007). In regions of MI, histology showed ablation of surviving myocardium both within and epicardial to scar; lesion depth in MI was not significantly different between catheters (5.6 ± 1.5 mm vs. 4.6 ± 0.9 mm; P=0.235). PFA allows rapid, safe, and effective ablation of surviving islands of myocardium within and around infarcted LV substrate. This technology holds promise for treating infarct-related ventricular tachycardia in humans.

In vitro assessment of periapical lesions created in sheep mandibles by using high resolution ultrasonography and cone beam computed tomography.

Providing ultrasound images of periapical lesions may be problematic depending on the thickness of the overlying cortical bone. Clinically, it is crucial to determine the cut-off value of overlaying bone thickness in terms of interference with ultrasound imaging in conjunction with assessment of changes in periapical jaw bone lesions. Our aim was to determine the minimum amount of overlaying buccal bone thickness of artificial periapical lesions in order to be visible by ultrasound imaging and to compare width, height, depth, surface area and volume measurements of detectable periapical lesions obtained from ultrasound and CBCT images. Periapical lesions were created in 16 molar teeth of sheep mandibles. Cavities were enlarged until the borders of lesions were visible on 14 MHz hockey probe ultrasound imaging. CBCT and ultrasound images were obtained simultaneously after drilling and enlarging each size of the cavities and replacing the teeth in their sockets. two observers separately assessed images twice within 2 weeks of interval. By using CBCT and ultrasound images, buccal bone thickness, maximum width, height, depth, surface area and volume of periapical lesions were measured. Intraclass correlation coefficient (ICC) was utilized and significance level was set at p < 0.05. The mean buccal bone thickness ranged between 1.21 mm and 1.31 mm for both imaging techniques. For the measurement of buccal bone thickness, periapical lesion width, height, depth, surface area, and volume excellent ICC values were found in terms of intrarater (ranging between 0.907 and 1) and inter-rater (ranging between 0.864 and 1) reliability for both observers and their readings. There were no statistically significant differences for both observers and for their two readings between ultrasound and CBCT measurements of buccal bone thickness, and periapical lesion width and height (p > 0.05). We suggested that a buccal thickness of approximately 1.28 mm might be accepted as a cut-off value for the detection of periapical lesions with 14 MHz hockey probe ultrasound. High resolution ultrasound provided accurate information for the measurement of buccal bone thickness and lesion width and height.

Assessing the Relationship of Applied Force and Ablation Duration on Lesion Size Using a Diamond Tip Catheter Ablation System.

Background:Contact force has proven to be influential for lesion formation in power-controlled radiofrequency ablation. Lesion formation and morphology from a temperature-controlled diamond tip radiofrequency ablation catheter is not well described. We hypothesize that lesion formation from a temperature-controlled radiofrequency system is independent of applied force over short application durations.Methods:This study examined lesion depth, surface width, temperature, and ablation parameters of the DiamondTemp Ablation (Medtronic, Inc) system for ablation applications delivered with varying application duration (5, 10, and 15 s) and applied force (5, 10, and 30 g). Lesions from perpendicular radiofrequency applications were analyzed in a stepwise fashion from a computational model, thermochromic gel data (n=36), and porcine thigh preparation (n=231) experiments.Results:Varying applied force across each application duration consistently generated comparable lesion dimensions for each model. In the computational model, lesion depths from a 5 s application with 5, 10, and 30 g of applied force were similar (2.3, 2.6, and 3.0 mm, respectively). Also, the 5 s lesion depths in the gel model were consistent across applied force (5 g, 3.2±0.1 mm; 10 g, 3.5±0.1 mm; 30 g, 3.5±0.2 mm). In the thigh model, the 5, 10, and 30 g applied forces for 5 s created lesion depths of 3.1±0.5, 3.2±1.0, and 3.2±1.1 mm, respectively. For the 10 and 15 s durations, the lesion depth and width remained consistent for the 10 and 30 g applied forces. Increases in lesion depth and width, percentage of impedance reduction, minimum power, and maximum temperature were only significant when application duration increased (from 5 to 15 s).Conclusions:Lesion dimensions with the DiamondTemp Ablation temperature-controlled radiofrequency ablation system showed no marked change with increased applied force. Short application durations generated consistent lesion dimensions across computational, thermochromic gel, and thigh models.

Real-time intracardiac echocardiography validation of saline-enhanced radiofrequency needle-tip ablation: lesion characteristics and gross pathology correlation.

With the implementation of saline-enhanced radiofrequency (SERF) needle-tip ablation, real-time validation of lesion formation is needed for the controllable creation of transmural lesions. The aim of the study was to analyse the ability of two-dimensional intracardiac echocardiography (2D-ICE) to guide and validate SERF ablation in real-time. Fifty-six SERF energy deliveries at left ventricular sites of 11 dogs guided by 2D-ICE were analysed (power: 15-50 W; time: 25-120 s; irrigation saline: 60°C with 10 mL/min flow rate). Catheter tip/tissue orientation and lesion formation could be well detected by 2D-ICE in 49 (87.5%) energy deliveries. Gross pathology analysis confirmed excellent 2D-ICE lesion localization, the ability to detect transmural lesions (70% sensitivity, 47% specificity) and positive correlation between 2D-ICE and the corresponding gross pathology measurements of 'maximal lesion depth'; (repeated measures correlation: rrm = 0.43, P = 0.012) and 'depth at maximal lesion width' (D@MW; rrm = 0.51, P = 0.003). The median angle between SERF catheter tip and endocardium was 76° [interquartile range (IQR) 58-83°]. The more perpendicular the catheter tip/tissue orientation was the deeper D@MW (rrm = 0.32, P = 0.045). Grade 3 microbubbles on 2D-ICE during ablation, indicating inadequate catheter tip/tissue contact, was associated with smaller lesion volumes than with Grade 1 microbubbles (284.8 mm3 [IQR 151.3-343.1] vs. 2114.1 mm3 [IQR 1437.0-3026.3], P < 0.001). With excellent lesion localization and a 70% detection rate of transmural lesions, 2D-ICE is well suited to validate SERF ablation lesion formation in real-time. The catheter tip/tissue angle impacts the lesion formation and through perpendicular catheter positioning, deeper intramural areas of the myocardium can be reached.

Qualitative and quantitative assessments of radiographic healing of osteochondritis dissecans of the humeral capitellum.

BackgroundLittle is known about the optimal timing of early return to sports after which the osteochondritis dissecans (OCD) lesion can completely heal. The aims of this study were to investigate the clinical outcomes of nonoperative treatment and elucidate the relationship between the radiographic findings and the timing for the return to sports.MethodsWe performed a retrospective review of 32 patients who presented with stable OCD of the capitellum and were treated nonoperatively for a minimum of 3 months. The mean follow-up period was 22.1 months. OCD lesions were assessed qualitatively and quantitatively on anteroposterior radiographs of the elbow at 45° of flexion every 3 months. The width of the OCD lesion (OCDw) and lateral width of the normal capitellum were measured and were associated with return to sports activities.ResultsIn 21 patients (66%), the progression of ossification was seen at a mean period of 4.1 months. Eighteen (56%) had partial union at a mean period of 4.3 months. Twenty-nine cases (91%) returned to sports activities after a mean of 4.6 months. Nine cases (28%) achieved complete union after a mean period of 15.0 months. Fifteen (47%) required surgery after a mean period of 11.8 months. The mean OCDw (%) was 10.2 ± 3.9 mm (56%) at the initial presentation and 8.0 ± 6.0 mm (41%) at the final follow-up examination, and the decrease in OCDw was 2.2 ± 3.1 mm (15%). The mean decrease in OCDw in patients with progression of ossification during the first 3 months was significantly larger than in patients without progression of ossification (4.9 ± 4.7 mm and -0.7 ± 4.5 mm, respectively; P = .002). In patients who had both an OCDw value of <8.0 mm and a lateral width value of >2.0 mm at the time of the return to sports, the rate of successful nonoperative treatment (86%) and complete union (71%) was significantly higher in comparison with other patients (P = .03 and P = .02).ConclusionsOCD lesions showed difficult healing in the middle one-third of the capitellum. The progression of ossification during the first 3 months was a significant predictor of successful nonoperative treatment and complete union. Surgery should be considered for lesions without the progression of ossification during the first 3 months. We propose both an OCD lesion width of <8.0 mm and a lateral normal width of >2.0 mm as radiographic landmarks of the timing of the return to sports.

Hypothalamic lesions in neuromyelitis optica spectrum disorders: exploring a scoring system based on magnetic resonance imaging.

We propose a scoring system for early diagnosis of sleep abnormalities in neuromyelitis optica spectrum disorders (NMOSD) with hypothalamic lesions based on magnetic resonance imaging (MRI). We evaluated MRI features of 45 patients with hypothalamic lesions identified from two cohorts. Univariate logistic regression analysis identified factors associated with sleepiness, which were subsequently used to develop a scoring system. Interrater reliability was determined using intraclass correlation coefficient (ICC). Correlations between scores and clinical features were analyzed. In total, 48.9% of 45 patients with hypothalamic lesions exhibited sleepiness. The number of involved slices, maximum width/length of hypothalamic lesions, and boundaries extending beyond the hypothalamus were associated with sleepiness (all p < 0.05). The sensitivity and specificity of the scoring system were 68.2% and 87.0%, respectively. The ICC values for the maximum width and length measurement of hypothalamic lesions were 0.82 and 0.81, respectively. Daily sleep time and Epworth sleepiness scale scores were positively correlated with MRI-based scores (p < 0.05, 95% confidence interval (CI) 0.69-0.93 and p < 0.05, 95% CI 0.55-0.88, respectively). A scoring system based on MRI features was developed to provide diagnosis of sleepiness in NMOSD with hypothalamic lesions earlier than other measures.

Synergistic effect of platelet-rich plasma in combination with fractional carbon dioxide laser versus its combination with pulsed dye laser in striae distensae: A comparative study.

Striae distensae (SD) are very common atrophic cutaneous scarring that are therapeutically challenging. Various kinds of laser had been suggested as effective treatment modalities for SD. In addition, platelet-rich plasma (PRP) was recently recommended for its therapy. To evaluate the synergistic role of PRP injection as a combined modality to fractional CO2 laser (Fr CO2 ) versus its combination with pulsed dye laser (PDL) in SD. Thirty SD patients were included in this study and treated by intradermal injection of autologous PRP on both sides, followed by laser therapy (Fr CO2 laser on right side and PDL on left side). They received 3 treatment sessions at 6weeks interval. Both treatment sides reported significant clinical improvements of SD lesions, evidenced by significant reduction of width of striae lesions and significant improvement of skin texture. Furthermore, significantly higher degree of clinical improvements were observed in response to treatment sessions by combined PRP with Fr CO2 laser rather than combined PRP with PDL. Generally, post-inflammatory hyperpigmentation (PIH) were mild in all patients. Histopathologically, SD lesions showed improvement of epidermal thickness, and more homogenization and regular orientation of dermal collagen fibers in both treatment sides, with more significant improvement on the side treated by combined PRP with Fr CO2 laser sessions rather than the other side. PRP injection in combination with Fr CO2 laser or PDL is considered safe and effective therapeutic regimens for SD. However, its combination with Fr CO2 laser is more promising with better outcome and fewer side effects.

Circular Multielectrode Pulsed Field Ablation Catheter Lasso Pulsed Field Ablation: Lesion Characteristics, Durability, and Effect on Neighboring Structures.

Pulsed field ablation (PFA) is a nonthermal energy with potential safety advantages over radiofrequency ablation. This study investigated a novel PFA system-a circular multielectrode catheter (PFA lasso) and a multichannel generator designed to work with Carto 3 mapping system. A 7.5F bidirectional circular catheter with 10 electrodes and variable expansion was designed for PFA (biphasic, 1800 Volts). This study included a total of 16 swine used to investigate the following 3 experimental aims: Aim 1 examined the feasibility to create a right atrial ablation line of block from the superior vena cava to the inferior vena cava. Aim 2 examined the effect of PFA on lesion maturation including durability after a 30-day survival period. Aim 3 examined the effect of high-intensity PFA (10 applications) on esophageal and phrenic nerve tissue in comparison to normal intensity radiofrequency ablation (1-2 applications). Histopathologic analysis of all cardiac, esophageal, and phrenic nerve tissue was performed. Acute line of block was achieved in 12/12 swine (100%) and required a total PFA time of 14 seconds (interquartile range [IQR], 9-24.5) per line. Ablation line durability after 28±3 days was maintained in 11/12 (91.7%) swine. PFA resulted in transmural lesions in 179/183 (97.8%) sections and a median lesion width of 14.2 mm. High-intensity PFA (9 [IQR, 8-14] application) had no effect on the esophagus while standard intensity radiofrequency ablation (1.5 [IQR, 1-2] applications) resulted in deep esophageal tissue injury involving the muscularis propria and adventitia layers. High-intensity PFA (16 [IQR, 10-28] applications) has no effect on phrenic nerve function and structure while standard dose radiofrequency ablation (1.5 [IQR, 1-2] applications) resulted in acute phrenic nerve paralysis. In this preclinical model, a multielectrode circular catheter and multichannel generator produced durable atrial lesions with lower vulnerability to esophageal or phrenic nerve damage.

Ranibizumab therapy for predominantly hemorrhagic neovascular age-related macular degeneration.

Objective:Predominantly hemorrhage represents one of the possible manifestations of choroidal neovascularisation (CNV) in eyes with age-related macular degeneration (AMD). The purpose of this study is to evaluate the effecte of ranibizumab treatment in patients with predominantly hemorrhagic CNV secondary to AMD.Methods:Twenty-five patients with predominantly hemorrhagic choroidal neovascularization due to AMD with at least three ranibizumab injections and followed up for at least 12 months were included in the study. The months of follow-up were recorded (baseline, 3rd, 6th, and 12th months). The change in central macular thickness (CMT) on optical coherence tomography, visual acuity (VA) in ETDRS letters, and lesion size on fundus fluorescein angiography were evaluated.Results:The mean age of the patients was 68.1±5.7 (range: 63–82) years, the mean follow-up was 19.9±14.5 (range: 12–67) months, and the mean number of injections was 4.0±1.4 (range: 3–15). The initial VA was 39.3±17.9 (range: 1–65) letters, CMT was 272.7±104 (range: 164–587) μm, and the initial lesion width was 11.4±10.5 (range: 1.3–45.7) mm2. The VA was 41.4±20.1 (range: 5–75) and 36.9±21.8 (range: 4–80) letters (p=0.150), CMT was 270.7±110 (range: 159–570) and 230.4±108 (range: 109–667) μm (p=0.009) and the lesion width was 10.9±11.5 (range: 1.1–39.7) and 10.4±11.6 (range: 1.2–44.3) mm2 at 6th and 12th month, respectively. No factor was found to be associated with final CMT.Conclusion:Although the final visual outcome is limited by the progression of the disease, hemorrhagic lesions treated with ranibizumab have stable anatomical outcome.

Comparison of ablation characteristics of three different radiofrequency applicators in renal sympathetic denervation

Objective Renal sympathetic denervation (RDN) is an alternative treatment for resistant hypertension (RH). This study aims to compare ablation effects using three radiofrequency applicators (i.e., balloon-based four electrodes, spiral and monopolar devices). Methods An idealized three-dimensional model of the renal artery was established using COMSOL Multiphysics to mimic radiofrequency ablation (RFA). Radiofrequency (RF) energy was delivered to the tissue at the same simulation settings, i.e., 4, 6, and 8 W for 60 s, using the three abovementioned RF applicators. The temperature distribution in the tissue was calculated using the coupled electrical–thermal–fluid finite element method. Lesion borders were defined using 50 °C isotherms. The maximum lesion depth, width, area, and circumferential coverage rate were compared among the three applicators at a blood flow of 0.4 m/s. Monopolar RF ablations in a renal artery phantom model were performed to validate the reliability of the simulation method. Results The balloon-based system yields greater lesion depths and widths compared with spiral and monopolar denervation under the same power. The range of maximum lesion depth is 1.58–3.11 mm for balloon-based RDN, 0.90–1.81 mm for spiral RDN and 1.12–2.38 mm for monopolar RDN, at a power of 4–8 W. The corresponding ranges of maximum lesion width are 2.22–5.73, 1.48–3.54, and 1.93–5.31 mm, respectively, and the circumferential coverage rates of the renal artery are 41.43%–91.99%, 31.71%–66.23%, and 9.55%–23.06%, respectively. The average velocity after balloon-based, spiral, and monopolar RDN increases by 3, 5, and 1 cm/s, respectively. The validation of the computer model offered prediction errors are <5% in terms of temperature at different locations (i.e., 2, 4, and 8 mm). Conclusions In terms of lesion size, balloon-based RDN appears to be the best option for the treatment of RH. However, the change in flow velocity in the arterial flow field suggests that its hemodynamic changes must be prioritized for investigating its safety. Although spiral catheter ablation yields the smallest lesion size and a significant change in flow velocity in the flow field, its coverage rate is larger than that of monopolar RDN; compared with balloon-based RDN, it did not obstruct most of the blood flow.

Computer simulations of an irrigated radiofrequency cardiac ablation catheter and experimental validation by infrared imaging

Purpose To develop and validate a three-dimensional (3-D) computer model based on accurate geometry of an irrigated cardiac radiofrequency (RF) ablation catheter with microwave radiometry capability, and to test catheter performance. Methods A computer model was developed based on CAD geometry of a RF cardiac ablation catheter prototype to simulate electromagnetic heating, heat transfer, and computational fluid dynamics (blood flow, open irrigation, and natural convection). Parametric studies were performed; blood flow velocity (0–25 cm/s) and irrigation flow (0–40 ml/min) varied, both with perpendicular (PE) and parallel (PA) catheter orientations relative to tissue. Tissue Agar phantom studies were performed under similar conditions, and temperature maps were recorded via infrared camera. Computer model simulations were performed with constant voltage and with voltage adjusted to achieve maximum tissue temperatures of 95–105 °C. Results Model predicted thermal lesion width at 5 W power was 5.8–6.4 mm (PE)/6.5–6.6 mm (PA), and lesion depth was 4.0–4.3 mm (PE)/4.0–4.1 mm (PA). Compared to phantom studies, the mean errors of the computer model were as follows: 6.2 °C(PE)/4.3 °C (PA) for maximum gel temperature, 0.7 mm (10.9%) (PE)/0.1 mm (0.8%) (PA) for lesion width, and 0.3 mm (7.7%)(PE)/0.7 mm (19.1%) (PA) for lesion depth. For temperature-controlled ablation, model predicted thermal lesion width was 7–9.2 mm (PE)/8.6–9.2 mm (PA), and lesion depth was 4.3–5.5 mm (PE)/3.4–5.4 mm (PA). Conclusions Computer models were able to reproduce device performance and to enable device evaluation under varying conditions. Temperature controlled ablation of irrigated catheters enables optimal tissue temperatures independent of patient-specific conditions such as blood flow.

Impact of Catheter Contact Angle on Lesion Formation and Durability of Pulmonary Vein Isolation

Objectives: This study aimed to evaluate the impact of catheter contact angle on lesion formation and durability of pulmonary vein isolation (PVI). Background: Little is known on the effect of catheter contact angle on lesion formation and durability of PVI. Methods: Both in vitro experiment and retrospective observational study were conducted. For in vitro experiment, radiofrequency lesions were created on explanted swine hearts in three different catheter contact angles (0{degree sign}, 45{degree sign}, and 90{degree sign}). In the retrospective observational study, we assessed patients who had undergone repeat catheter ablation due to atrial fibrillation recurrence after initial PVI. When pulmonary vein (PV) reconnection was observed, we analyzed the previous ablation points within and without the gap area. The gap areas were where ablation had changed the PV activation sequence or eliminated the PV potential in the repeat session. Results: In the in vitro experiment, lesion width was the smallest (5.3 {plus minus} 0.4 mm) in perpendicular contact compared to 0{degree sign} (vs 5.8 {plus minus} 0.5 mm, p=0.040) and 45{degree sign} (vs 6.4 {plus minus} 0.4 mm, p<0.001). In the retrospective observational study, we assessed 666 tags of 16 patients with PV reconnections, and 60 tags were in the gap area. Tags in the gap area had longer interlesion distance (odds ratio [OR] 1.49, p < 0.001), greater contact force variability (OR 1.03, p = 0.008), and higher rate of perpendicular contact (OR 3.26, p < 0.001) on multivariate analysis. Conclusion:Perpendicular contact was associated with a smaller lesion and higher rate of PV reconnection

Optimizing Impedance Change Measurement During Radiofrequency Ablation Enables More Accurate Characterization of Lesion Formation.

This study sought to determine whether a novel impedance thermal imaging system (ITIS) provides an impedance measurement that is better correlated with lesion dimensions than circuit impedance during radiofrequency (RF) ablation. A 5- to 10-Ω impedance drop is clinically used to corroborate an effective RF ablation lesion. However, the contribution of local tissue heating to circuit impedance change is small and dependent on the local environment of the catheter and placement of the grounding patch. ITIS uses ablation catheter and skin electrodes to perform 4-terminal impedance measurements with separate voltage sensing and current injection electrode pairs. Seven sheep underwent endocardial ventricular irrigated RF ablation at 40W for 60 s. ITIS impedance and circuit impedance were both measured throughout ablation. When the sheep were sacrificed, ablation lesions were cut along their long axis; the depth, width, and surface area of the cut surface were measured. A total of 68 RF ablations were performed, with a median depth of 3.5mm (interquartile range [IQR]: 2.1 to 4.9mm), width of 8.3mm (IQR: 5.7 to 10.8mm), and surface area of 23.8mm2 (IQR: 9.3 to 43.0mm2). ITIS impedance change had good correlation with lesion depth, width, and surface area (R=0.76, R=0.87, and R=0.87, respectively); and superior to circuit impedance for lesion depth, width, and surface area (p=0.0018, p=0.0004, and p=0.0001, respectively). By optimizing the current path and using 4-terminal impedance measurement during RF ablation, the contribution of tissue temperature changes to measured impedance is better standardized to provide a more reliable measure than conventional ablation circuit impedance.

Efficacy of multi-electrode linear irreversible electroporation.

We investigated the efficacy of linear multi-electrode irreversible electroporation (IRE) ablation in a porcine model. The study was performed in six pigs (weight 60-75kg). After median sternotomy and opening of the pericardium, a pericardial cradle was formed and filled with blood. A linear seven polar 7-Fr electrode catheter with 2.5 mm electrodes and 2.5 mm inter-electrode spacing was placed in good contact with epicardial tissue. A single IRE application was delivered using 50 J at one site and 100 J at two other sites, in random sequence, using a standard monophasic defibrillator connected to all seven electrodes connected in parallel. The pericardium and thorax were closed and after 3 weeks survival animals were euthanized. A total of 82 histological sections from all 18 electroporation lesions were analysed. A total of seven 50 J and fourteen 100 J epicardial IRE applications were performed. Mean peak voltages at 50 and 100 J were 1079.2 V ± 81.1 and 1609.5 V ± 56.8, with a mean peak current of 15.4 A ± 2.3 and 20.2 A ± 1.7, respectively. Median depth of the 50 and 100 J lesions were 3.2 mm [interquartile range (IQR) 3.1-3.6] and 5.5 mm (IQR 4.6-6.6) (P < 0.001), respectively. Median lesion width of the 50 and 100 J lesions was 3.9 mm (IQR 3.7-4.8) and 5.4 mm (IQR 5.0-6.3), respectively (P < 0.001). Longitudinal sections showed continuous lesions for 100 J applications. Epicardial multi-electrode linear application of IRE pulses is effective in creating continuous deep lesions.

Impact of myocardial fiber orientation on lesions created by a novel heated saline-enhanced radiofrequency needle-tip catheter: An MRI lesion validation study

Irrigated needle catheter ablation is efficacious for creation of transmural lesions in the left ventricle (LV). However, interdependence of needle orientation and myocardial fiber orientation and the resulting influence on lesion creation remain unclear. The purpose of this study was to investigate the impact of myocardial fiber orientation on reproducibility and controllability of lesion creation in LV myocardium using a heated saline-enhanced radiofrequency (SERF) needle-tip catheter system. Eleven dogs underwent catheter ablation using this novel catheter. Ablative lesions were created using different power and ablation times (15-50 W; application 25-120 seconds; 60°C irrigation saline at 10 mL/min). Hearts were explanted, and lesions were evaluated using 3-T cardiac magnetic resonance (CMR), gross pathologic, and histologic investigations. Forty-three of 57 lesions (75.4%) were transmural, and lesion depth reached approximately 90% of LV wall thickness. Lesion volume in both gross pathology and exvivo CMR showed a positive linear correlation with power × radiofrequency (RF) time index (r = 0.637, P <.001; and r = 0.786, P <.001, respectively). Maximum width (circumferential direction of LV) and maximum length (long-axis direction) of all lesions were distributed in the middle layer of LV where myocardium runs circumferentially. Paired-sample t-test showed maximum lesion width was significantly greater than maximum lesion length by both CMR and gross pathologic evaluation (26.1 ± 9.6 mm vs 17.2 ± 6.7 mm, P <.001; and 22.5 ± 7.7 mm vs 18.6 ± 5.9 mm, P <.001, respectively). This catheter showed feasibility in creating transmural LV lesions. Power × RF time index was strongly correlated with lesion volume and predicted lesion size. More importantly, SERF lesions extended along the myocardial fiber orientation.