Initial studies on the implanting sites of high and low ventricular septa using leadless cardiac pacemakers.

OBJECTIVE: To study the safety and electrical characteristics of various implanting sites of the Micra pacemaker. METHOD: A total of 15 patients from Beijing Anzhen Hospital, Capital Medical University, were included, who were implanted with Micra leadless pacemakers and allocated to either the high ventricular septum group (eight patients) or the low ventricular septum group (seven patients) based on their individual patient factors and clinical conditions. The baseline of the patients, the implanting area, the electrocardiogram change after implantation, the implantation data, the threshold, R wave, impedance, and the date of the 1-month follow-up were then analyzed. With all of the data, the characteristics of different implantation sites of the Micra pacemaker were determined. RESULTS: Overall, the thresholds were low at implantation and remained stable over the 1-, 3-, 6-month, 1-, 2-, 3-, and 4-year follow-ups. On comparing the two groups, there was no difference in QRS duration at pacing (140.00 [40.00] ms vs. 179.00 [50.00] ms), threshold at implantation (0.38 [0.22] mV vs. 0.63 [1.00] mV), R wave at implantation ([10.85 ± 4.71] V vs. [7.26 ± 2.98] V), or impedance at implantation ([906.25 ± 162.39] Ω vs. [750.00 ± 173.40] Ω). While the difference in QRS duration between the two groups was not significant, the QRS duration of the high ventricular septum group exhibited a reduced tendency compared with that of the low ventricular group. The corrected QT interval during pacing exhibited a significant difference (440.00 [80.00] ms vs. 520.00 [100.00] ms; p < .05). For the 1-, 3-, 6-month, 1-, 2-, 3-, and 4-year follow-ups, there was no difference between the threshold of the high ventricular septum group and that of the low ventricular septum group (p > .05). CONCLUSION: High ventricular septum pacing appears to be a safe site for implantation of the Micra pacemaker. It could entail a shorter QRS duration at pacing and could be more physiological than low ventricular septum pacing.

Catheter ablation of ventricular premature depolarizations originating from the mid interventricular septum: Significance of electrocardiographic morphology for predicting origin.

BACKGROUND: Ventricular premature depolarizations (VPDs) originating from the mid interventricular septum (IVS) adjacent to the atrioventricular annulus between the His bundle and the coronary sinus ostium (mid IVS VPDs) have not been characterized. OBJECTIVE: The aim of this study was to investigate the electrophysiological characteristics of mid IVS VPDs. METHODS: Thirty-eight patients with mid IVS VPDs were enrolled. VPDs were divided into different types according to precordial transition of the electrocardiogram (ECG) and QRS morphology in lead V1. RESULTS: Four types of VPDs were divided. The precordial transition zone appeared earlier and earlier from types 1 to 4. The notch in lead V1 moved gradually backward, and its amplitude gradually became higher, resulting in the transition from left to right bundle branch block morphology in lead V1 from types 1 to 4. Based on activation and pace mapping, ablation response, and 3830 electrode pacing morphology in the mid IVS, the 4 types of ECG morphology corresponded to an origin in the right endocardial side, right/mid intramural region, left intramural region, and left endocardial side of the mid IVS, respectively. An intramural origin was identified for 50% of VPDs. Eighty-nine percent of mid IVS VPDs could be eliminated. Bilateral ablation (waiting for delayed efficacy) or bipolar ablation was sometimes needed for intramural VPDs. CONCLUSION: Mid IVS VPDs were found to have unique electrophysiological characteristics. The ECG characteristics of mid IVS VPDs were important in terms of prediction of its exact origin, the choice of ablation method, and the likelihood of treatment being successful.

Congenitally corrected transposition of the great arteries and implantation of a leadless pacemaker: a case report.

BACKGROUND: Congenitally corrected transposition of the great arteries (ccTGA) is a rare cardiac anomaly and can lead to abnormal electrical activity of the heart. The implant of a pacemaker in such patients is more complicated than conventional operations. This case report of an adult with ccTGA who had a leadless pacemaker implant will provide a reference for diagnosing and treating such patients. CASE PRESENTATION: A 50-year-old male patient was admitted to hospital having experienced intermittent vision loss for a month. An electrocardiogram and Holter monitoring showed intermittent third-degree atrioventricular block, and echocardiography, cardiac computed tomography and cardiac magnetic resonance imaging confirmed a diagnosis of ccTGA. A leadless pacemaker was successfully implanted into the patient's anatomical left ventricle, and the postoperative parameters were stable. CONCLUSION: Implanting a leadless pacemaker into a patient with a rare anatomical and electrophysiological abnormality, such as ccTGA, is feasible and efficacious, but preoperative imaging evaluation is of considerable importance.

Progress in methods for evaluating Schwann cell myelination and axonal growth in peripheral nerve regeneration via scaffolds.

Peripheral nerve injury (PNI) is a neurological disorder caused by trauma that is frequently induced by accidents, war, and surgical complications, which is of global significance. The severity of the injury determines the potential for lifelong disability in patients. Artificial nerve scaffolds have been investigated as a powerful tool for promoting optimal regeneration of nerve defects. Over the past few decades, bionic scaffolds have been successfully developed to provide guidance and biological cues to facilitate Schwann cell myelination and orientated axonal growth. Numerous assessment techniques have been employed to investigate the therapeutic efficacy of nerve scaffolds in promoting the growth of Schwann cells and axons upon the bioactivities of distinct scaffolds, which have encouraged a greater understanding of the biological mechanisms involved in peripheral nerve development and regeneration. However, it is still difficult to compare the results from different labs due to the diversity of protocols and the availability of innovative technologies when evaluating the effectiveness of novel artificial scaffolds. Meanwhile, due to the complicated process of peripheral nerve regeneration, several evaluation methods are usually combined in studies on peripheral nerve repair. Herein, we have provided an overview of the evaluation methods used to study the outcomes of scaffold-based therapies for PNI in experimental animal models and especially focus on Schwann cell functions and axonal growth within the regenerated nerve.

Occurrence of ventricular septal perforation in patients with permanent left bundle branch pacing followed up using echocardiographic and computed tomography images.

OBJECTIVE: To explore short-term changes after left bundle branch pacing (LBBP) using echocardiography and computed tomography (CT), especially for postoperative ventricular septal perforation. METHODS: Between January and September 2019, 33 patients with atrioventricular block underwent LBBP at Beijing Anzhen Hospital. All the patients were evaluated using electrocardiography, pacing, parameters and echocardiographic measurements, including for major complications, during the 1, 3, 6, 12 and 24-month follow-up. Interval perforations were examined during a 1-month follow-up echocardiogram and CT. RESULTS: Left bundle branch pacing was successfully performed in 100% (33/33) of patients. The mean seizure threshold was stable and unchanged postoperatively at the 1, 3, 6, 12 and 24-month follow-up. The paced QRS duration of the LBBP was 119.72 ± 2.53 ms and <130 ms in all patients. Unipolar impedance during the procedure was higher than 500 Ω (662.00 ± 181.50 Ω). No ventricular septal perforation occurred at the end of the procedure. At the 1-month follow-up, two patients reported transthoracic echocardiography, with CT revealing septal lead perforation. Through CT, two other patients were found to have septal lead perforation, and echocardiography indicated that the pacing lead had penetrated the interventricular septum and entered the left subendocardium. At the 1, 3, 6, 12 and 24-month follow-up, these four patients exhibited no significant increase in pacing threshold or impedance (p > .05). No ventricular thrombus or stroke was detected. CONCLUSION: Permanent LBBP is safe and feasible in patients with bradycardia. Echocardiography and/or CT can more accurately evaluate changes in cardiac structure and function after LBBP.

Regenerative Role of T Cells in Nerve Repair and Functional Recovery.

The immune system is essential in the process of nerve repair after injury. Successful modulation of the immune response is regarded as an effective approach to improving treatment outcomes. T cells play an important role in the immune response of the nervous system, and their beneficial roles in promoting regeneration have been increasingly recognized. However, the diversity of T-cell subsets also delivers both neuroprotective and neurodegenerative functions. Therefore, this review mainly discusses the beneficial impact of T-cell subsets in the repair of both peripheral nervous system and central nervous system injuries and introduces studies on various therapies based on T-cell regulation. Further discoveries in T-cell mechanisms and multifunctional biomaterials will provide novel strategies for nerve regeneration.

Light-Triggered Adhesive Silk-Based Film for Effective Photodynamic Antibacterial Therapy and Rapid Hemostasis.

Successful control of massive hemorrhage in deep wounds with irregular shape and low elasticity still remains great challenges in the clinic. As the wound sites are usually at risk of bacterial infection, it is necessary to design an ideal hemostatic agent with rapid hemostasis and excellent antibacterial activity. In this study, we developed a light responsive hemostatic film for effective handling of liver bleeding with promising photodynamic therapy against S. aureus onnear infrared (NIR) irradiation. Based on silk fibroin, the film exhibited desirable biocompatibility and mechanical property as a hemostat tape. Significantly, the film tape achieved excellent tissue adhesion and hemostasis in vivo within 2 min of UV exposure, which would have a great potential as a multifunctional biomedical material in the field of tissue repair such as wound healing, bone repair, and nerve regeneration.

Mitophagy is required for brown adipose tissue mitochondrial homeostasis during cold challenge.

Brown adipose tissue (BAT) is a specialized thermogenic organ in mammals. The ability of BAT mitochondria to generate heat in response to cold-challenge to maintain core body temperature is essential for organismal survival. While cold activated BAT mitochondrial biogenesis is recognized as critical for thermogenic adaptation, the contribution of mitochondrial quality control to this process remains unclear. Here, we show mitophagy is required for brown adipocyte mitochondrial homeostasis during thermogenic adaptation. Mitophagy is significantly increased in BAT from cold-challenged mice (4 °C) and in ß-agonist treated brown adipocytes. Blockade of mitophagy compromises brown adipocytes mitochondrial oxidative phosphorylation (OX-PHOS) capacity, as well as BAT mitochondrial integrity. Mechanistically, cold-challenge induction of BAT mitophagy is UCP1-dependent. Furthermore, our results indicate that mitophagy coordinates with mitochondrial biogenesis, maintaining activated BAT mitochondrial homeostasis. Collectively, our in vivo and in vitro findings identify mitophagy as critical for brown adipocyte mitochondrial homeostasis during cold adaptation.

Patterning Poly(dimethylsiloxane) Microspheres via Combination of Oxygen Plasma Exposure and Solvent Treatment.

Here a simple low-cost yet robust route has been developed to prepare poly(dimethylsiloxane) (PDMS) microspheres with various surface wrinkle patterns. First, the aqueous-phase-synthesized PDMS microspheres are exposed to oxygen plasma (OP), yielding the oxidized SiOx layer and the corresponding stiff shell/compliant core system. The subsequent solvent swelling and solvent evaporation induce the spontaneous formation of a series of curvature and overstress-sensitive spherical wrinkles such as dimples, short rodlike depressions, and herringbone and labyrinth patterns. The effects of the experimental parameters, including the radius and Young's modulus of the microspheres, the OP exposure duration, and the nature of the solvents, on these tunable spherical wrinkles have been systematically studied. The experimental results reveal that a power-law dependence of the wrinkling wavelength on the microsphere radius exists. Furthermore, the induced wrinkling patterns are inherently characteristic of a memory effect and good reversibility. Meanwhile, the corresponding phase diagram of the wrinkle morphologies on the spherical surfaces vs the normalized radius of curvature and the excess swelling degree has been demonstrated. It is envisioned that the introduced strategy in principle could be applied to other curved surfaces for expeditious generation of well-defined wrinkle morphologies, which not only enables the fabrication of solids with multifunctional surface properties, but also provides important implications for the morphogenesis in soft materials and tissues.

Swelling/deswelling-induced reversible surface wrinkling on layer-by-layer multilayers.

Layer-by-layer (LbL) multilayer film is incorporated in the fabrication of a film/substrate system for the investigation of swelling/deswelling-induced wrinkle evolution for the first time. As one typical example, hydrogen-bonded (PAA/PEG)n (PAA, poly(acrylic acid); PEG, poly(ethylene glycol)) is deposited on a poly(dimethylsiloxane) (PDMS) substrate via the LbL technique. Heating treatment causes the covalent cross-linking reaction to occur in the H-bonded multilayers with simultaneously spontaneous formation of labyrinth wrinkles. Subsequent water immersion leads to the evolution of a series of the swelling-sensitive wrinkles in the thermally cross-linked (PAA/PEG)n/PDMS bilayer, ranging from initial labyrinth wrinkles (a) to an intermediate smooth wrinkle-free state (b), hexagonally arranged dimples (c), and the later-segmented labyrinth patterns (d). Upon deswelling by reheating of the swollen bilayer, the reverse wrinkle evolution happens via the process of d → b, or d → b → a, or c → b, or c → b → a, which is dependent on the reheating temperature and the swelling-induced pattern. We investigate the influences of experimental conditions on the swelling kinetics and the resulting wrinkle evolution, which include the thickness of (PAA/PEG)n, the additionally deposited outermost layer (e.g., Pt and polystyrene), and the swelling solution pH. The involved mechanism has been discussed from the viewpoint of the relation between the wrinkling behavior and the swelling/deswelling-induced stress state. The results indicate that the combined strategy of LbL assembly with the introduction of additional layers endows us with considerable freedom to fabricate multifunctional film/substrate systems and to tune the instability-driven patterns for advanced properties and extended applications.