Publications by authors named "Chihiro Miyagi"

8 Publications

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Left Atrial Circulatory Assistance in Simulated Diastolic Heart Failure Model: First in Vitro and in Vivo.

J Card Fail 2022 Jan 10. Epub 2022 Jan 10.

Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio.

Background: We are developing a left atrial assist device (LAAD) that is implanted at the mitral position to treat diastolic heart failure (DHF) represented by heart failure with preserved ejection fraction.

Methods: The LAAD was tested at 3 pump speeds on a pulsatile mock loop with a pneumatic pump that simulated DHF conditions by adjusting the diastolic drive. The LAAD was implanted in 6 calves, and the hemodynamics were assessed. In 3 cases, DHF conditions were induced by using a balloon inserted into the left ventricle, and in 2 cases, mitral valve replacement was also performed after the second aortic cross-clamp.

Results: DHF conditions were successfully induced in the in vitro study. With LAAD support, cardiac output, aortic pressure and left atrial pressure recovered to normal values, whereas pulsatility was maintained for both in vivo and in vitro studies. Echocardiography showed no left ventricular outflow tract obstruction, and the LAAD was successfully replaced by a mechanical prosthetic valve.

Conclusions: These initial in vitro and in vivo results support our hypothesis that use of the LAAD increases cardiac output and aortic pressure and decreases left atrial pressure, while maintaining arterial pulsatility.
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http://dx.doi.org/10.1016/j.cardfail.2021.11.024DOI Listing
January 2022

Large animal models of heart failure with preserved ejection fraction.

Heart Fail Rev 2021 Nov 9. Epub 2021 Nov 9.

Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH, 44195, USA.

Heart failure with preserved ejection fraction (HFpEF) is characterized by diastolic dysfunction and multiple comorbidities. The number of patients is continuously increasing, with no improvement in its unfavorable prognosis, and there is a strong need for novel treatments. New devices and drugs are difficult to assess at the translational preclinical step due to the lack of high-fidelity large animal models of HFpEF. In this review, we describe the summary of historical and evolving techniques for developing large animal models. The representative methods are pressure overload models, including (1) aortic banding, (2) aortic stent, (3) renal hypertension, and (4) mineralocorticoid-induced hypertension. Diet-induced metabolic syndromes are also used. A new technique with an inflatable balloon inside the left ventricle can be used during acute/chronic in vivo surgeries to simulate HFpEF-like hemodynamics for pump-based therapies. Canines and porcine are most widely used, but other non-rodent animals (sheep, non-human primates, felines, or calves) have been used. Feline models present the most well-simulated HFpEF pathology, but small size is a concern, and the information is still very limited. The rapid and reliable establishment of large animal models for HFpEF, and novel methodology based on the past experimental attempts with large animals, are needed.
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http://dx.doi.org/10.1007/s10741-021-10184-9DOI Listing
November 2021

Left atrial assist device for heart failure with preserved ejection fraction: initial results with torque control mode in diastolic heart failure model.

Heart Fail Rev 2021 May 1. Epub 2021 May 1.

Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA.

A novel pump, the left atrial assist device (LAAD), is a device specifically for the treatment of heart failure with preserved ejection fraction (HFpEF). The LAAD is a mixed-flow pump that is implanted in the mitral position and delivers blood from the left atrium to the left ventricle. During the development process, we aimed to explore whether device activation in torque control (TC) mode would improve the function of the LAAD. The TC mode causes adjustment of the pump speed automatically during each cardiac cycle in order to maintain a specified torque. In this study, we tested four different TC settings (TC modes 0.9, 1.0, 1.25, and 1.5) using an in vitro mock circulatory loop. Mild, moderate, and severe diastolic heart failure (DHF) conditions, as well as normal heart condition, were simulated with the four TC modes. Also, we evaluated the LAAD in vivo with three calves. The LAAD was implanted at the mitral position with four TC settings (TC modes 0.9, 1.0, 1.1, 1.2). With LAAD support, the in vitro cardiac output and aortic pressure recovered to normal heart levels at TC 1.25 and 1.5 even under severe DHF conditions with little pump regurgitation. The TC mode tested in vivo with three calves, and it also showed favorable result without elevating the left ventricular end-diastolic pressure. These initial in vitro and in vivo results suggest that the TC mode could be potentially effective, and the LAAD could be a treatment option for HFpEF patients.
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http://dx.doi.org/10.1007/s10741-021-10117-6DOI Listing
May 2021

Device-based treatment options for heart failure with preserved ejection fraction.

Heart Fail Rev 2021 07 12;26(4):749-762. Epub 2021 Jan 12.

Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH, 44195, USA.

Heart failure with preserved ejection fraction (HFpEF) is a syndrome with an unfavorable prognosis, and the number of the patients continues to grow. Because there is no effective therapy established as a standard, including pharmacological treatments, a movement to develop and evaluate device-based therapies is an important emerging area in the treatment of HFpEF patients. Many devices have set their target to reduce the left atrial pressure or pulmonary capillary wedge pressure because they are strongly related to the symptoms and prognosis of HFpEF, but the methodology to achieve it varies based on the devices. In this review, we summarize and categorize these devices into the following: (1) interatrial shunt devices, (2) left ventricle expander, (3) electrical therapy, (4) left ventricular assist devices, and (5) mechanical circulatory support devices under development. Here, we describe the features and specifications of device-based therapies currently under development and those at more advanced stages of preclinical testing. Advantages and limitations of these technologies, with insights on their safety and feasibility for HFpEF patients, are described.
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http://dx.doi.org/10.1007/s10741-020-10067-5DOI Listing
July 2021

A case of cardiac strangulation following epicardial pacemaker implantation.

Gen Thorac Cardiovasc Surg 2020 Dec 8;68(12):1499-1502. Epub 2020 Apr 8.

Department of Cardiovascular Surgery, Japan Community Health Care Organization (JCHO), Kyushu Hospital, 1-8-1, Kishinoura, Yahatanishi-ku, Kitakyushu, 806-8501, Japan.

An 8-year-old boy had undergone permanent epicardial pacemaker implantation with a Y-shaped bipolar ventricular lead on day 6 after birth for treatment of congenital complete atrioventricular block. He was found to have pulmonary stenosis and mitral stenosis by follow-up echocardiography. Further studies including computed tomography and cardiac catheterization revealed that the pacemaker lead had completely encircled the cardiac silhouette and was in a state of "cardiac strangulation". We removed the previous pacing leads and generator and implanted a new epicardial dual-chamber pacing system in the right atrium and right ventricle. Additionally, an expanded polytetrafluoroethylene sheet was placed between the new leads and the heart to prevent recurrence of cardiac strangulation.
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http://dx.doi.org/10.1007/s11748-020-01337-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7680322PMC
December 2020

Endovascular Repair for Ruptured Axillary Artery Aneurysm Proximal to Hemodialysis Access.

Vasc Endovascular Surg 2019 Jul 22;53(5):429-432. Epub 2019 Apr 22.

1 Department of Cardiovascular Surgery, Japan Community Health Care Organization Kyushu Hospital, Kitakyushu, Fukuoka, Japan.

Axillary artery aneurysms are uncommon and potentially high-risk lesions threatening the upper extremities. In hemodialysis patients, arteriovenous fistulae creation rarely triggers aneurysmal degeneration and arterial aneurysms in inflow arteries. These aneurysms are usually treated by surgical repair. However, this may lead to complications because of the anatomical complexity surrounding aneurysms of axillary arteries. We report a patient undergoing hemodialysis who had a ruptured ipsilateral axillary artery aneurysm proximal to vascular access. We successfully treated it by endovascular repair with the GORE Excluder AAA contralateral leg endoprosthesis, approaching from the left brachial artery proximal to the shunt. No complications occurred during 15 months after the endovascular repair.
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http://dx.doi.org/10.1177/1538574419844072DOI Listing
July 2019

Size and Stiffness of the Pulmonary Autograft after the Ross Procedure in Children.

Pediatr Cardiol 2019 Apr 7;40(4):776-783. Epub 2019 Feb 7.

Department of Cardiovascular Surgery, Japan Community Health Care Organization Kyushu Hospital, 1-8-1 Kishinoura, Yahatanishi-ku, Kitakyushu, 806-8501, Japan.

Progressive dilatation of the pulmonary autograft is one of the greatest concerns after the Ross procedure. Increased stress in the arterial wall may cause changes in the elastic properties of the pulmonary autograft, and thus lead to pathological dilatation. The present study aimed to investigate the changes in the autograft diameter and stiffness during follow-up after the Ross procedure. A total of ten patients underwent the Ross procedure at our institution between 2003 and 2011. Echocardiography was used to measure the diameters of the pulmonary autograft at the level of the annulus, sinus of Valsalva, and sinotubular junction. The stiffness index was calculated from the angiographic data, and compared with that of 16 age-matched control children. The diameters of the pulmonary autograft increased throughout the follow-up period, particularly at the level of the sinus of Valsalva and at the sinotubular junction. The aortic root was stiffer in Ross patients compared with control children (7.9 ± 1.8 vs. 3.9 ± 0.7 immediately postoperatively, p < 0.01; 10.1 ± 2.8 vs. 4.2 ± 1.4 at 5 years postoperatively, p < 0.01). Although no significant relationship was found between the stiffness index and the autograft diameter, the stiffness index tended to increase over time. Dilatation of the pulmonary autograft was accompanied by progressive change in aortic stiffness. Longer follow-up is warranted to clarify the impact of this change in aortic stiffness on autograft failure.
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http://dx.doi.org/10.1007/s00246-019-02064-9DOI Listing
April 2019

Development of a rapid diagnostic method for identification of Staphylococcus aureus and antimicrobial resistance in positive blood culture bottles using a PCR-DNA-chromatography method.

J Infect Chemother 2016 Jun 4;22(6):372-6. Epub 2016 Apr 4.

Department of Microbiology, Graduate School of Medicine Gifu University, Gifu, Japan.

Blood culturing and the rapid reporting of results are essential for infectious disease clinics to obtain bacterial information that can affect patient prognosis. When gram-positive coccoid cells are observed in blood culture bottles, it is important to determine whether the strain is Staphylococcus aureus and whether the strain has resistance genes, such as mecA and blaZ, for proper antibiotic selection. Previous work led to the development of a PCR method that is useful for rapid identification of bacterial species and antimicrobial susceptibility. However, that method has not yet been adopted in community hospitals due to the high cost and methodological complexity. We report here the development of a quick PCR and DNA-chromatography test, based on single-tag hybridization chromatography, that permits detection of S. aureus and the mecA and blaZ genes; results can be obtained within 1 h for positive blood culture bottles. We evaluated this method using 42 clinical isolates. Detection of S. aureus and the resistance genes by the PCR-DNA-chromatography method was compared with that obtained via the conventional identification method and actual antimicrobial susceptibility testing. Our method had a sensitivity of 97.0% and a specificity of 100% for the identification of the bacterial species. For the detection of the mecA gene of S. aureus, the sensitivity was 100% and the specificity was 95.2%. For the detection of the blaZ gene of S. aureus, the sensitivity was 100% and the specificity was 88.9%. The speed and simplicity of this PCR-DNA-chromatography method suggest that our method will facilitate rapid diagnoses.
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http://dx.doi.org/10.1016/j.jiac.2016.02.013DOI Listing
June 2016
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