Feasibility of a novel atrial mechanical sensing method for leadless atrioventricular synchronous pacing.

INTRODUCTION: Few studies have demonstrated a high degree of atrioventricular (AV) synchrony with a new leadless pacemaker called Micra AV. Our group previously reported a new and unique sensing method. We believe that this novel sensing method, "Simplified A3 method," might facilitate better AV synchrony than a conventional sensing method in almost all cases with Micra AV implantation. METHODS: We conducted a non-randomized retrospective study comparing the two pacing methods at two centers. From December 1, 2021 to October 31, 2022, Micra AV was implanted for 32 patients at the two centers. Twenty of the 32 patients with sinus rhythm and complete AV block were included in this study. In Group 1, the conventional setting was programmed as follows: auto A3 threshold, auto A3 window-end (WE), and auto A4 threshold turned on during hospitalization. In Group 2, the "Simplified A3 method" was programmed as follows: auto A3 threshold and auto A3WE turned off. Instead, an intentionally prolonged A3WE (850-1000 ms) and low A3 threshold (A3 signal amplitude + 0.5-1.0 m/s2) were programmed. RESULTS: Twenty patients were analyzed. In Group 2, AV synchrony (%AMVp) was significantly higher at the first outpatient clinic (63.0 ± 5.7% vs 81.0 ± 4.2%, p = .03). A3 threshold was significantly lower in Group 2 (5.9 ± 0.7 m/s2, p < .05 vs 2.3 ± 0.5 m/s2, p < .05). CONCLUSION: Our novel sensing method might be a more feasible sensing method for obtaining higher AV synchrony than the conventional algorithm.

Case report: successful termination of ventricular tachycardia by intrinsic anti-tachycardia pacing beyond conventional anti-tachycardia pacing.

Background: Anti-tachycardia pacing (ATP) is a pain-free alternative to defibrillation shock for monomorphic ventricular tachycardia (VT). Intrinsic ATP (iATP) is a novel algorithm of auto-programmed ATP. However, the advantage of iATP over conventional ATP in clinical cases is still unknown. Case summary: A 49-year-old man with no significant past medical history was transferred to our institution with sudden-onset fatigue from working on a farm. A 12-lead electrocardiogram showed monomorphic sustained wide QRS tachycardia with a right bundle branch block pattern and superior axis deviation with a cycle length (CL) of 300 ms. Sustained monomorphic VT originating from the left ventricle due to underlying vasospastic angina was diagnosed by contrast-enhanced cardiac magnetic resonance imaging, coronary angiography, and the acetylcholine stress test, and implantable cardioverter defibrillator implantation was performed. Nine months later, a clinical VT episode with a CL of 300 ms was observed, which could not be terminated by three sequences of conventional burst pacing. Ventricular tachycardia was finally terminated by a third iATP sequence without any acceleration. Discussion: Although standard burst pacing by conventional ATP reached the VT circuit, it failed to terminate the VT. Using the post-pacing interval, iATP automatically calculated the appropriate number of S1 pulses required to reach the VT circuit. In iATP, the S2 pulses are delivered with a calculated coupling interval based on the estimated effective refractory period during tachycardia. In this case, iATP might have led to less aggressive S1 stimulation, followed by aggressive S2 stimulation, which probably helped terminate the VT without any acceleration.

Analysis of Orbital Morphology and its Relationship With Eyelid Morphology.

Correct anatomical reconstruction of the orbital wall for function and cosmesis is important; however, this is difficult because of the structure's complexity. The authors aimed to analyze and classify orbital morphology from computed tomography (CT) images and examine the relationship between orbital morphology and eyelid morphology in the Japanese population. CT images of 60 men (right side, 29; left side, 31) and 44 women (each side, 22) were included. The lengths of the orbital medial wall and floor in the coronal plane at the anterior, middle, and posterior planes of the orbit; angle between them; simotic index; and the thickness of upper eyelid were measured. Additionally, the presence or absence of double eyelids was evaluated. Non-paired Student's t test and Pearson correlation coefficient test were used for analysis. Orbital morphology was symmetrical on both sides, and men had a larger orbit than women. Orbital morphology was classified into 2 groups according to the posterior angle, and there was a difference between the groups in the simotic index. The difference between groups may represent a genetic difference between the Jomon and Yayoi people and not only provide a new classification for the orbit of the population but also be useful in orbital reconstruction.

An All-Inside Repair for Full Radial Posterior Lateral Meniscus Tears.

There is controversy about the treatment for unstable full radial posterior lateral meniscus tears, particularly that involving the posterior root. Some surgeons have advocated repairing these types of meniscus tears using various techniques, but their methods are somewhat technical. We developed the technique for an all-inside repair for full radial posterior lateral meniscus tears using the Meniscal Viper (Arthrex, Naples, FL). A doubled thread is passed through 1 edge of the radial tear by the Meniscal Viper and is kept in place without tying the knot. The Meniscal Viper is used again to set a new thread, repeating the same procedure to another edge of the tear. At this step, 2 doubled threads are passed through each stump of the tear, and both a loop end and 2 free ends of each thread are located outside of the joint. Then, 2 doubled threads pass the third thread into its own loop, pulling it out. Finally, the third thread becomes the mattress suture over the radial tear site and is fastened by sliding knot techniques. This procedure makes it easy to strictly, smoothly, and less invasively shorten the gap by drawing each stump of the meniscus in the direction of the circumference.

Anatomic Oblong Double Bundle Anterior Cruciate Ligament Reconstruction.

Double-bundle anterior cruciate ligament (ACL) reconstruction using hamstring tendon grafts is a standard procedure for ACL injury. However, its clinical effectiveness is not always satisfactory. One cause of this was problems with the graft-tunnel healing of the posterolateral bundle (PLB) on the femur. To solve this problem, we devised a new anatomic ACL reconstruction technique to improve the graft-tunnel healing of the femoral PLB by using a single-bundle with one bone tunnel on the femoral side and a double-bundle on the tibial side. We have performed 40 procedures with excellent results and no cases of intra- or postoperative complication. This procedure can help improve the graft-tunnel healing around the femoral bone tunnel aperture for the PLB.

A Case of Acromioclavicular Joint Dislocation Associated with Coracoid Process Fracture.

Rupture of any two or more parts of the superior shoulder suspensory complex (SSSC) including the distal clavicle, acromion, coracoid process, glenoid cavity of the scapula, acromioclavicular ligament, and coracoclavicular ligament is associated with shoulder girdle instability and is an indication for surgery. Here we report a case of acromioclavicular joint dislocation associated with coracoid process fracture. A 48-year-old man sustained a hard blow to the left shoulder from a fall, and simple radiography detected a coracoid process fracture and acromioclavicular joint dislocation. The injury consisted of a rupture of two parts of the SSSC. For the coracoid process fracture, osteosynthesis was performed using hollow cancellous bone screws. For the acromioclavicular joint dislocation, hook plate fixation and the modified Neviaser's procedure were performed. The bone healed well 5 months after surgery, at which time the screws were removed. At 18 months after initial surgery, the coracoid process fracture had healed with a 10% rate of dislocation on radiography, and the patient currently has no problem performing daily activities, no range of motion limitations, and a Japanese Orthopaedic Association scale score of 93.

Regeneration of ring-shaped lateral meniscus after partial resection of discoid meniscus with anterior cruciate ligament reconstruction.

INTRODUCTION: The ring-shaped lateral meniscus is very rare. Although it is essentially known as a congenital anomaly, a central tear in an incomplete discoid meniscus or an old bucket-handle tear in a meniscus may be easily mistaken for a ring-shaped meniscus. We experienced a ring-shaped lateral meniscus that regenerated after partial resection of a discoid meniscus together with anterior cruciate ligament (ACL) reconstruction. PRESENTATION OF CASE: A 37-year-old female patient still experienced unrelenting knee pain 6 months after ACL reconstruction and partial meniscectomy of a discoid lateral meniscus. A repeat arthroscopy was performed. The lateral tibial plateau was covered in the form of a ring by meniscus-like tissue. The meniscus-like tissue appeared to have regenerated inward toward the center from the stump after the partial meniscectomy and was connected from the anterior to posterior horn, forming an interhorn bridge. Partial meniscectomy was repeated. Histologically, the regenerated tissue was not meniscal, but comprised mature fibrocartilage; macroscopically; however, it was very similar to meniscal tissue. Two years after the initial operation, the patient had no complaints and experienced full return of function. DISCUSSION: The reason for such regeneration is unknown, but may have been attributed to the specific intra-articular environment that developed after the ACL reconstruction. CONCLUSION: This is the first report of regenerative development of a ring-shaped lateral meniscus. When a ring-shaped lateral meniscus is diagnosed, we must accurately determine whether it is a true congenital anomaly in consideration of the present case.

Inducement of semitendinosus tendon regeneration to the pes anserinus after its harvest for anterior cruciate ligament reconstruction-A new inducer grafting technique.

PURPOSE: To investigate the usefulness of the "inducer grafting" technique for regeneration of the semitendinosus (ST) tendon after its harvest for anterior cruciate ligament (ACL) reconstruction. METHODS: Twenty knees of 20 patients (mean age at the time of surgery, 23.1 years) underwent ACL reconstruction with a double bundle autograft using the ST tendon (7 patients) and the ST + the gracilis (G) tendons (13 patients)."Inducer grafting" techniqueAfter harvesting the ST tendon, a passing pin with a loop thread is inserted along with the tendon stripper. The passing pin is pulled out from the medial thigh and the loop thread retained. As an inducer graft, the ST tendon branch is used. After the ACL graft has been secured, the inducer graft is sutured to the pes anserinus and the proximal end passed through by pulling the thread out. Then the inducer graft is placed within the tendon canal. The mean follow-up period was 15 months. The presence and morphology of the regenerated ST tendon were examined by MRI. And the isometric hamstring strength was examined at 45°, 90° and 120° of knee flexion. RESULTS: One month after the operation in all the patients, MRI demonstrated a low-intensity structure at the anatomical location of the ST, at the level of the superior pole of the patella and the joint line, apparently representing the regenerated ST tendon. Four months after the operation, the distal portion of the regenerated ST tendon had reached the pes anserinus in all patients. Twelve months after the operation, the regenerated ST tendon was hypertrophic in 19 of the 20 patients (95%). The isometric knee flexion torque of the ACL-reconstructed limb was significantly lower at 90° and 120° compared with the contralateral limb. CONCLUSION: These results suggest that the "inducer grafting" technique is able to improve the regeneration rate of the harvested ST tendon and promote hypertrophy of the regenerated ST tendon, extending all the way to the pes anserinus. However, this technique couldn't improve the deficits in knee flexion torque after ACL reconstruction.

Regulatory natural killer cells in murine liver and their immunosuppressive capacity.

BACKGROUND: Abundant amounts of natural killer (NK) cells are present in the liver, most of which are endowed with direct cytotoxic and inflammatory cytokine production capacities. However, the control of compromised immunity in the liver may be accomplished by a population of regulatory NK cells possessing suppressive or tolerogenic functions. AIMS: To identify and characterize regulatory NK cells in murine liver. METHODS: NK cells were isolated from the liver of C57BL/6 mice by magnetic-activated cells sorting (MACS). NK cells were stimulated with different agents and those cells that produced interleukin (IL)-10 were detected by flow cytometry and isolated by MACS. IL-10-producing NK cells were regarded as regulatory NK cells and the functional capacities of liver-derived regulatory NK cells were assessed in vitro. RESULTS: The frequencies of regulatory NK cells in the liver were 4.1 +/- 0.3% of hepatic NK cells and 0.45 +/- 0.02% of liver nonparenchymal cells. Regulatory NK cells produced abundant amounts of IL-10 in culture. These cells also suppressed the proliferative capacities of T cells and B cells in vitro. However, another population of NK cells that did not produce IL-10 (immunogenic NK cells) could not suppress lymphocyte proliferation. CONCLUSIONS: The presence of regulatory NK cells in the liver and their immunosuppressive capacities endowed these cells with the critical function of maintaining homeostasis under normal conditions. Exaggerated or impaired functions of these cells may also contribute to different pathological processes.

Cartilage change after arthroscopic repair for an isolated meniscal tear.

To investigate the direct effect to the cartilage caused by the meniscal repair, we examined patients who underwent an isolated meniscal repair without any other abnormalities by arthroscopic examination. A total of 17 patients were examined by second-look arthroscopy after an average interval of 9 months from the meniscal repair, and have been evaluated the status of the repaired meniscus and of the relative femoral condylar cartilage. Changes in the severity of the cartilage lesion between at the time of meniscal repair and the time of the second-look arthroscopy were considered based on the status of the repaired meniscus. Regardless of the healing status of the repair site, it was possible to prevent degeneration in the cartilage in 9 of the 10 patients who demonstrated no degeneration in the meniscal body. Of the 7 patients who demonstrated degeneration in the meniscal body, progression in cartilage degeneration was noted as 1 grade in 2 patients and 2 grades in another 3 patients. Even in those in which stable fusion of the repair site was achieved, the condition of the inner meniscal body was not necessarily maintained favorably in all cases, indicating that degeneration in the meniscal body was a risk factor for cartilage degeneration. It was concluded that recovery could not be expected even at 9 months after the repair if the lesion had already demonstrated degeneration in the meniscal body at the time of repair.

A long-term follow-up study of four cases who underwent curettage and autogenous bone grafting for steroid-related osteonecrosis of the femoral condyle.

We performed curettage followed by autogenous bone grafting in several cases of steroid-related osteonecrosis of the femoral condyle, and reviewed the outcome of this procedure after a mean follow-up of 9.5 years. The number of patients was 4; the mean age at the time of the operation was 30.5 years. The mean Knee Society Objective Score was 52.5 before the operation and had increased to 87.5 at the time of the review. The pre-operative radiographic stages were stage 2 in 2 patients and stage 3 in the other 2 patients. Progression in the disease stage was observed in 3 patients. MRI revealed survival of the grafted bone in only one case, and collapse of the articular surface in all cases. In conclusion, though the clinical results showed improvement, the autogenous bone graft failed to answer the purpose of preventing the progression in disease stage.

Fasciitis-like proliferation in the knee joint.

We describe the case of fasciitis-like proliferation in the knee joint in a 52-year-old man. The polypoid lesion developed from the synovial joint capsule around the quadriceps tendon and was impinging on the patellofemoral joint. Histologic and immunohistochemical studies revealed a myofibroblastic proliferation similar to nodular fasciitis. Until now, only 3 other cases have been reported in the English and Japanese language literature.

Anteromedial meniscofemoral ligament.

We have experienced 3 cases of comparatively rare anteromedial meniscofemoral ligament in which the anterior horn of the medial meniscus was attached to the posterolateral wall of the femoral intercondylar fossa. In 2 of these cases, there was no attachment to the tibia, whereas in the other, it was connected to the lateral meniscus and also firmly to the tibia. In the 2 with no attachment to the tibia, abnormal mobility in the medial meniscus accompanied by flexion and extension of the knee was observed. Degeneration of the intermediate posterior segment and injury of the anterior horn were also observed. This anomaly induces a future meniscus injury, depending on the attachment state to the tibia.