Successful low-energy cardioversion using a novel biodegradable gel pad: Feasibility of treating postoperative atrial fibrillation in animals

ObjectivePostoperative atrial fibrillation is one of the most frequent complications of cardiac surgery. We developed a novel biodegradable gel pad consisting of biopolymers that directly attach to the myocardium by electrostatic interaction. The present study examines the feasibility and effectiveness of low-energy internal cardioversion using these pads.MethodsThe hearts of 6 pigs were exposed through a median sternotomy under general anesthesia, and 2 monopolar pacing wires were placed on the left pulmonary veins (chest open group). Two biodegradable cardioversion gel pads were placed on the right appendage and the left atria without suturing. All wires were extruded through the skin and secured with a suture. Sustained atrial fibrillation was induced by burst-pacing from the pulmonary veins in continuous 20-ms cycles. Shock intensity started at 0.5 J, and the energy level was increased in 0.5-J increments until cardioversion occurred. This protocol was repeated 5 times per pig. In a second group of 6 pigs (chest closed group), the epicardial cardioversion electrode gel pads and pacing wire electrodes were positioned as described above. Shock intensity was started at 0.5 J. If the shock was unsuccessful, the energy level was increased in 0.5-J increments until 2 consecutive cardioversions were achieved at a single energy level. At postoperative days 1, 3, 5, and 7, the defibrillation threshold was determined with the chest closed. At postoperative day 10, the cardioversion wires were removed. At predetermined time intervals, the heart was reexposed and the extent of degradation in vivo was visually evaluated and histologically assessed after sacrifice.ResultsAll pigs with induced atrial fibrillation were cardioverted to sinus rhythm on the determined postoperative day. The mean energy and lead impedance in the chest open group were 0.65 ± 0.23 J and 97.6 ± 5.52 Ω, respectively, and the overall values of mean energy and lead impedance in the chest closed group were 1.67 ± 1.00 J and 75.9 ± 13.3Ω, respectively. No complications were observed after wire removal. The gel pads became degraded and decreased in thickness, and signs of mild inflammation were evident on the gel pad. However, the gel pads did not elicit significant severe inflammatory reactions according to both gross and histologic assessments at 1 month after the surgery.ConclusionAtrial cardioversion using novel biodegradable gel pads that are easily affixed may afford a straightforward and effective treatment for atrial fibrillation after cardiac surgery

Signet Ring Cell Gastric Cancer Occurring after Radiation Therapy for Helicobacter pylori-Uninfected Mucosa-Associated Lymphoid Tissue Lymphoma

Helicobacter pylori infection is the major cause for mucosa-associated lymphoid tissue (MALT) lymphoma and gastric cancers. On the other hand, gastric cancers are known to arise from gastric mucosal atrophy. We here report a case of signet ring cell gastric cancer that developed after radiation therapy for MALT lymphoma in H. pylori-uninfected patient whose stomach did not show gastric mucosal atrophy. A 58-year-old female was referred to our hospital for treatment of gastric MALT lymphoma. This patient was not infected with H. pylori, and upper gastrointestinal endoscopy revealed that she did not have gastric mucosal atrophy but had submucosal tumor-like MALT lymphoma lesion in the anterior wall of the upper gastric body. Since conventional eradication therapy was ineffective, her whole stomach was irradiated as a second-line therapy. The MALT lymphoma lesion turned into complete remission state after the therapy. The patient was followed every 6 months by upper gastrointestinal endoscopy for 4 years as complete remission until a newly developed decolorized depressed lesion was detected in the greater curvature of the proximal antrum, a completely different location from the MALT lymphoma lesion. A biopsy specimen from the lesion contained signet ring cell carcinoma, and she was successfully treated by endoscopic submucosal dissection. No signs of recurrence have been detected so far. The radiation therapy for MALT lymphoma might be associated with the occurrence of this signet ring cell gastric cancer, and since MALT lymphoma is indolent in nature, this case suggests that careful consideration is required when choosing the second-line therapy for MALT lymphoma patients