Radiofrequency Lesion in the Atrial Wall: How Variable Is It? 9.4 Tesla MRI Analysis of Radiofrequency Lesion Volume in a Swine Model.

Background/Objectives: Most data on radiofrequency (RF) effects come from ex vivo or in vitro studies that quantify lesions using width and/or depth, while electrophysiologists use manufacturers' indirect indices. The objective of this study was to evaluate RF lesion volume by high-resolution MRI of excised lesions in an in vivo porcine model, comparing a low-energy long-duration (LE) (20 W, 50 s) RF application strategy with a high-energy short-duration (HE) (50 W, 20 s) one. Methods: Eighteen piglets were divided into LE (n = 9) and HE groups (n = 9). RF applications were performed at four locations in both atria. Animals were sacrificed after 5-7 days, and RF lesion specimens were excised, fixed, and analyzed by 9.4 Tesla MRI. RF lesion volume, variability (variance), depth, and any extracardiac lesions were compared between the groups. Results: Seventy RF applications were performed (36 LE, 34 HE). MRI analyzed 26 LE and 28 HE samples. The HE group showed 35% higher volume than the LE group (100.2 mm3 (±81.2) in LE vs. 178.3 mm3 (±163.7) in HE, p = 0.033). RF volume variance was 6.6 mm3 in LE and 40.3 mm3 in HE. The HE group had more complications (seven vs. zero, p = 0.02) and extracardiac lesions (18 vs. 14, p = 0.613). Conclusions: There was large and unpredictable variability in RF injury on the atrial wall, even under controlled conditions, which could explain arrhythmia recurrences. The greatest lesion variability was found during HE applications. The dose/effect relationship of RF needs careful study for treating cardiac arrhythmias.

Feasibility of Neovessel Embolization in a Large Animal Model of Tendinopathy: Safety and Efficacy of Various Embolization Agents.

Targeting neovessels in chronic tendinopathies has emerged as a new therapeutic approach and several embolization agents have been reported. The aim of this study was to investigate the feasibility of embolization with different agents in a porcine model of patellar tendinopathy and evaluate their safety and efficacy. Eight 3-month-old male piglets underwent percutaneous injection of collagenase type I to induce patellar tendinopathies (n = 16 tendons). They were divided into four groups (2 piglets, 4 tendons/group): the control group, 50-100 µm microspheres group, 100-300 µm microspheres group, and the Imipenem/Cilastatin (IMP/CS) group. Angiography and embolization were performed for each patellar tendon on day 7 (D7). The neovessels were evaluated visually with an angiography on day 14. The pathological analysis assessed the efficacy (Bonar score, number of neovessels/mm2) and safety (off-target persistent cutaneous ischemic modifications and presence of off-target embolization agents). The technical success was 92%, with a failed embolization for one tendon due to an arterial dissection. Neoangiogenesis was significantly less important in the embolized groups compared to the control group angiographies (p = 0.04) but not with respect to histology (Bonar score p = 0.15, neovessels p = 0.07). Off-target cutaneous embolization was more frequently depicted in the histology of the 50-100 µm microspheres group (p = 0.02). Embolization of this animal model with induced patellar tendinopathy was technically feasible with different agents and allowed assessing the safety and efficacy of neovessel destruction. Particles smaller than 100 µm seemed to be associated with more complications.

Effects of Fluid Therapy on Mesenteric Microcirculation Using New Probe-Based Confocal Laser Endomicroscopy (Cellvizio®) in a Porcine Model of Endotoxic Shock.

BACKGROUND: Microcirculatory alterations have been observed at the early phase of sepsis, although macrocirculation seems preserved. The aim of this study was to analyze the effect of crystalloid fluid therapy on mesenteric microcirculation, assessed by using the confocal laser endomicroscope Cellvizio®, in an endotoxic porcine model. METHODS: It is a prospective endotoxic shock (lipopolysaccharide infusion) experimental trial. Piglets were divided into 3 groups: 6 in the sham group (no LPS injection, no fluid), 9 in the control group (LPS infusion, no fluid), and 6 in the crystalloids group (LPS infusion and fluid resuscitation with crystalloids). Fluid resuscitation consisted in a fluid bolus of 20 mL/kg 0.9% saline over 30 min followed by a 10 mL/kg/h fluid rate over 4 h. Mesenteric microcirculation was assessed using a confocal laser endomicroscope (Cellvizio®). Blood flow within capillaries was visually assessed according to the point of care microcirculation (POEM) score. RESULTS: At baseline, the 3 groups were similar regarding hemodynamic, biological, and microcirculatory parameters. At T360, the POEM score significantly decreased in the control and crystalloids groups, whereas it remained unchanged in the sham group (respectively, 1.62 ± 1.06, 1.2 ± 0.45, and 5.0 ± 0, p = 0.011). There was no significant difference in cardiac output at T360 between the sham and crystalloids groups (3.1 ± 0.8 vs. 2.3 ± 0.6, p = 0.132) or between the control and crystalloids groups (2.0 ± 0.6 vs. 2.3 ± 0.6, p = 0.90). CONCLUSION: There was no significant improvement of microcirculatory alterations after crystalloids resuscitation despite improvement in macrocirculatory parameters in early experimental sepsis.

Collagenase-Induced Patellar Tendinopathy with Neovascularization: First Results towards a Piglet Model of Musculoskeletal Embolization.

BACKGROUND: Therapeutic strategies targeting neovessels responsible for musculoskeletal chronic pain have emerged, including neovessels embolization. Our study aimed to develop a large animal model of patellar tendinopathy with neovascularization. METHODS: Nine 3-month-old male piglets (18 patellar tendons) received percutaneous injections of increasing doses of collagenase (0 to 50 mg) at day 0 (D0). Tendinopathy was evaluated by ultrasound (D7 and D14). Neovascularization was evaluated visually and on angiographies. Bonar score was used for histological analysis (D14). Correlations were evaluated using Spearman's rank (Rs) test. RESULTS: Research protocol was well tolerated. All tendons were enlarged with a median increase of 31.58% [25-40.28] at D7 (p = 0.244) at D7 and 57.52% [48.41-91.45] at D14 (p = 0.065). Tendons with collagenase injection had more hypoechoic changes, with one tendon rupture (p = 0.012). Neovascularization was reported above 5 mg collagenase (p < 0.01) at D7 and D14 with dose-related neovessels induction (Rs = 0.8, p < 0.001). The Bonar score increased above 5 mg collagenase, correlated with the dose (Rs = 0.666, p = 0.003). CONCLUSIONS: The study shows the feasibility, safety and reproducibility of this new large animal model of patellar tendinopathy with neovascularization after collagenase injection. It will allow studying new treatments on direct embolization of neovessels by endovascular approach.