Ablation catheter-induced mechanical deformation in myocardium: computer modeling and ex vivo experiments

Cardiac catheter ablation requires an adequate contact between myocardium and catheter tip. Our aim was to quantify the relationship between the contact force (CF) and the resulting mechanical deformation induced by the catheter tip using an ex vivo model and computational modeling. The catheter tip was inserted perpendicularly into porcine heart samples. CF values ranged from 10 to 80 g. The computer model was built to simulate the same experimental conditions, and it considered a 3-parameter Mooney-Rivlin model based on hyper-elastic material. We found a strong correlation between the CF and insertion depth (ID) (R2 = 0.96, P < 0.001), from 0.7 ± 0.3 mm at 10 g to 6.9 ± 0.1 mm at 80 g. Since the surface deformation was asymmetrical, two transversal diameters (minor and major) were identified. Both diameters were strongly correlated with CF (R2 ≥ 0.95), from 4.0 ± 0.4 mm at 20 g to 10.3 ± 0.0 mm at 80 g (minor), and from 6.4 ± 0.7 mm at 20 g to 16.7 ± 0.1 mm at 80 g (major). An optimal fit between computer and experimental results was achieved, with a prediction error of 0.74 and 0.86 mm for insertion depth and mean surface diameter, respectively.

Possible involvement of HSP70 in pancreatic cancer cell proliferation after heat exposure and impact on RFA postoperative patient prognosis

Purpose

As an alleviative treatment measured in patients with unresectable advanced pancreatic cancer, radiofrequency ablation (RFA) needed more clinical data to prove its advantages and to explore limitations in its utilization. This study was determined to observe the efficacy of RFA, and to explore its impact on perioperative periphery carcinoma as well as the normal pancreatic tissues.

Methods

Clinical data of 32 patients with pancreatic cancer accepted RFA surgery were collected. Followed up patients' pain degree and the changes in serum tumor markers CA19-9 and CA 242 before and after surgery. Ex vivo, gave human pancreatic cancer cell line PANC-1 heat treatment to simulate the heat exposure condition periphery carcinoma was experienced during RFA surgery, and to observe the proliferation rate and HSP70 expression change compared with control group.

Results

Of the 32 patients, 1 died of upper gastrointestinal hemorrhage, and 29 survived for more than 5 months, 2 of which for more than 16 months. The average CA19-9 and CA 242 levels of the patients were significantly decreased in 3 months after surgery (t = 9.873, 5.978, P < 0.001). During in vitro experiments, the proliferation rate of PANC-1 cells after heating was significantly increased, accompanied with the increased HSP70 expression. The addition of HSP70 inhibitor can inhibit the rise of proliferation after heat therapy.

Conclusion

Utilizing RFA treat patients with unresectable advanced pancreatic cancer, could effectively relieve the pain, decline jaundice, and deduce tumor marker levels significantly. However, it failed to extend the long-term survival rate of the patients significantly. This study found that a higher proliferative rate accompanied with a higher HSP70 expression level were observed on in vitro cultured pancreatic carcinoma cells after heat treatment, which could be altered by HSP70 inhibitor. And these findings indicated that the heat exposure might impact periphery carcinoma during RFA surgery and HSP70 might play an important role in patients' prognosis.

Local application of doxorubicin- loaded Iron oxid nanoparticles and the vascular disrupting agent via the hepatic artery: chemoembolization-photothermal ablation treatment of hepatocellular carcinoma in rats

Objectives

This study investigates the effectiveness of local application of doxorubicin(Dox)-loaded, polydopamine (PDA)- coated single crystal hematite (α- Fe₂O₃) nanocubes (Fe₂O₃-PDA-Dox) and combretastatin A-4 phosphate disodium(CA4P)in treating hepatocellular carcinoma (HCC) in rats.

Methods

The magnetic characteristics and photothermal effects of the nanoparticles were determined in vitro. Tumor-bearing Sprague–Dawley rats were divided into 3 groups of 8 according to treatment: controls, transarterial chemoembolization–photothermal ablation (pTACE) (Lipidol+Fe₂O₃-PDA-Dox + NIR), and CA4P + pTACE (CA4P+ Lipidol+Fe₂O₃-PDA-Dox + NIR). Drugs were administered through the hepatic artery, and the tumors exposed to 808-nm near-infrared radiation. The Fe content of tumors was assessed using neutron activation analysis. Treatment effectiveness was assessed using heating curves, magnetic resonance imaging, pathology results, and immunohistochemical analysis.

Results

The mean tumor Fe content was greater in rats treated with CA4P + pTACE (1 h, 23.72 ± 12.45 μg/g; 24 h, 14.61 ± 8.23 μg/g) than in those treated with pTACE alone (1 h, 5.66 ± 4.29 μg/g; 24 h, 2.76 ± 1.33 μg/g). The tumor T2 imaging signal was lower in rats treated with CA4P + pTACE. Following laser irradiation, the tumor temperature increased, with higher temperatures reached in the CA4P + pTACE group (62 °C vs 55 °C). Tumor cells exhibited necrosis, apoptosis, and proliferation inhibition, with greater effects in the CA4P + pTACE group. Transient liver and kidney toxicity were observed on day 3, with more severe effects after CA4P + pTACE.

Conclusions

Fe₂O₃-PDA-Dox nanoparticles are effective for TACE–PTA. Pretreatment with CA4P increases nanoparticle uptake by tumors, increasing the treatment effectiveness without increasing hepatorenal toxicity.

Safety and Efficacy of Radiofrequency Ablation of the Medial Branch Nerves with Preexisting Spinal Hardware. A Case Series and Review of Literature

PURPOSE OF REVIEW

To explore the efficacy of radio frequency ablation in treating pain in patients with hardware at site of the procedure.

RECENT FINDINGS

There is very limited data in literature about this topic. One study performed in 2016 indicated no complications when performing RFA close to hardware in patients with chronic pain conditions. Radiofrequency ablation can be safely and effectively performed close to hardware. While heating of the hardware can happen which can theoretically lead to tissue injury or decreased heat going to target nerve, this does not seem to be of clinical significance. More studies are needed to confirm this finding.