Academic Appointments

Professional Education

  • PhD, University of Tokyo (2018)
  • MD, National Defense Medical College (2009)

All Publications

  • Loss of antibodies to hepatitis E virus in organ transplant patients with hepatitis E. Hepatology research : the official journal of the Japan Society of Hepatology Oshiro, Y., Harada, H., Hasegawa, K., Akutsu, N., Yoshizumi, T., Kawagishi, N., Nanmoku, K., Ichimaru, N., Okamura, K., Ohira, M., Itabashi, Y., Fujiyama, N., Ide, K., Okajima, H., Ogawa, K., Takagi, K., Eguchi, H., Shinoda, M., Nishida, K., Shimazaki, J., Shimoda, M., Takahashi, M., Okamoto, H., Suzuki, S. 2021; 51 (5): 538-547


    Studies regarding changes in antibodies to hepatitis E virus (HEV) after HEV infection in organ transplant patients are limited. This study aimed to clarify HEV infection trends in organ transplant patients who contracted HEV using data from a previous Japanese nationwide survey.This study was undertaken from 2012 to 2019. Among 4518 liver, heart, and kidney transplant patients, anti-HEV immunoglobulin G (IgG) antibodies were positive in 164; data were collected from 106 of these patients, who consented to participate in the study. In total, 32 liver transplant patients, seven heart transplant patients, and 67 kidney transplant patients from 16 institutions in Japan were examined for IgG, IgM, and IgM antibodies to HEV and the presence of HEV RNA in the serum. The χ2 -test was used to determine the relationship between the early and late postinfection groups in patients with anti-HEV IgG positive-to-negative conversion rates. The Mann-Whitney U-test was used to compare clinical factors.Anti-HEV IgG positive-to-negative conversion occurred in 25 (23.6%) of 106 organ transplant patients. Of eight patients with hepatitis E who tested positive for HEV RNA, one (14.0%) had anti-HEV IgG positive-to-negative conversion. Twenty-four (24.5%) of 98 patients negative for HEV RNA had anti-HEV IgG positive-to-negative conversion.This study revealed, for the first time, the changes in HEV antibodies in organ transplant patients. Loss of anti-HEV IgG could often occur unexpectedly in organ transplant patients with previous HEV infection.

    View details for DOI 10.1111/hepr.13637

    View details for PubMedID 33749100

  • Survival Outcomes of Two-Stage Intracardiac Repair in Large Ventricular Septal Defect and Trisomy 18. Pediatric cardiology Nakai, R., Fujioka, T., Okamura, K., Suzuki, T., Nakao, A., Kobayashi, J., Tsuchiya, K. 2021; 42 (4): 821-831


    Surgical management has not been encouraged in patients with trisomy 18 (T18) and congenital heart diseases due to poor survival. This study aimed to investigate (1) the appropriateness of palliative surgeries followed by intracardiac repair (ICR) (i.e., two-stage ICR) for patients with a large ventricular septal defect (VSD) and T18, and (2) its impact on their long-term outcomes.Medical charts of patients with VSD and T18 who underwent two-stage ICR at the Japanese Red Cross Medical Center between January 2005 and December 2019 were retrospectively reviewed. Demographic data, timing, and types of palliative surgeries, information related to ICR, peri- and postoperative clinical information, postoperative survival, and cause of death were collected. The long-term prognosis of patients treated with two-stage ICR was compared with that of patients treated with primary ICR and palliative surgery without ICR.Overall, 18 (2 male, 16 female) patients underwent two-stage ICR. Pulmonary artery banding was the initial palliative surgery in all patients after a median duration of 19.5 (range 6-194) days of life. The median age and the mean body weight at the time of ICR were 18.2 (7.6-50.7) months and 6.0 ± 1.0 kg, respectively. The mean pulmonary artery pressure and pulmonary vascular resistance index before ICR were 19.1 ± 7.3 mmHg and 3.4 ± 2.0 U m2, respectively. Overall, 17/18 (94%) patients were discharged after ICR. Fourteen (78%) patients were alive during data collection. None of the patients died of cardiac insufficiency, and the median duration of survival was 46.3 (14.3-186.4) months since birth. Most patients required cardiac medications rather than pulmonary vasodilators at the last follow-up. During the study period, three patients underwent primary ICR, and 46 underwent palliative surgery without ICR. Of those who underwent primary ICR, two died in the hospital on the first and 48th day following ICR, and the third died 179 days after the ICR. The Log-rank test revealed a significantly longer survival for the patients treated with two-stage ICR compared with those treated with palliative surgery without ICR (P = 0.003).Two-stage ICR improves the long-term survival of patients with VSDs and T18. This safe surgical strategy can also prevent pulmonary hypertension in such patients.

    View details for DOI 10.1007/s00246-021-02546-9

    View details for PubMedID 33515091

  • Complete resection of a giant calcifying fibrous tumor of myocardial origin. General thoracic and cardiovascular surgery Okamura, K., Nawata, K., Shimada, S., Ono, M. 2020; 68 (4): 389-391


    A calcifying fibrous tumor (CFT) is a rare, benign tumor that commonly develops in the internal viscera. It is histologically characterized by hyalinized collagenous tissue with calcifications and lymphoplasmacytic infiltrates. There have been few reports of CFTs occurring in the heart. and the therapeutic approach of such cases has not been well established; however, complete surgical resection appears to be the best treatment option for cardiac CFT, since this lesion can cause cardiac symptoms and recurrence has been recently noted. To our knowledge, this report describes the largest cardiac CFT for which complete surgical resection was successfully performed.

    View details for DOI 10.1007/s11748-019-01103-9

    View details for PubMedID 30850932

  • Therapeutic targeting of mitochondrial ROS ameliorates murine model of volume overload cardiomyopathy. Journal of pharmacological sciences Okamura, K., Nakagama, Y., Takeda, N., Soma, K., Sato, T., Isagawa, T., Kido, Y., Sakamoto, M., Manabe, I., Hirata, Y., Komuro, I., Ono, M. 2019; 141 (1): 56-63


    Concomitant heart failure is associated with poor clinical outcome in dialysis patients. The arteriovenous shunt, created as vascular access for hemodialysis, increases ventricular volume-overload, predisposing patients to developing cardiac dysfunction. The integral function of mitochondrial respiration is critically important for the heart to cope with hemodynamic overload. The involvement, however, of mitochondrial activity or reactive oxygen species (ROS) in the pathogenesis of ventricular-overload-induced heart failure has not been fully elucidated. We herein report that disorganization of mitochondrial respiration increases mitochondrial ROS production in the volume-overloaded heart, leading to ventricular dysfunction. We adopted the murine arteriovenous fistula (AVF) model, which replicates the cardinal features of volume-overload-induced ventricular dysfunction. Enzymatic assays of cardiac mitochondria revealed that the activities of citrate synthase and NADH-quinone reductase (complex Ⅰ) were preserved in the AVF heart. In contrast, the activity of NADH oxidase supercomplex was significantly compromised, resulting in elevated ROS production. Importantly, the antioxidant N-acetylcysteine prevented the development of ventricular dilatation and cardiac dysfunction, suggesting a pathogenic role for ROS in dialysis-related cardiomyopathy. A cardioprotective effect was also observed in metformin-treated mice, illuminating its potential use in the management of heart failure complicating diabetic patients on dialysis.

    View details for DOI 10.1016/j.jphs.2019.09.005

    View details for PubMedID 31611176

  • Experiences With Aggressive Cardiac Rehabilitation in Pediatric Patients Receiving Mechanical Circulatory Supports. International heart journal Amao, R., Imamura, T., Sawada, Y., Endo, S., Ozaki, S., Okamura, K., Masuzawa, A., Takaoka, T., Hirata, Y., Shindo, T., Ono, M., Haga, N. 2016; 57 (6): 769-772


    Although some patients with fulminant myocarditis can be rescued owing to the improvements in mechanical circulatory support therapy, there are few reports providing evidence of cardiac rehabilitation during mechanical circulatory supports, particularly among pediatric patients. We treated two pediatric patients who underwent aggressive cardiac rehabilitation during mechanical support. Five days after the initiation of extracorporeal membrane oxygenation therapy aggressive cardiac rehabilitation was started in a 10-year-old girl with fulminant myocarditis. After explantation of the device, she was discharged on postoperative day 23. A 6-year-old girl with fulminant myocarditis started receiving cardiac rehabilitation two days after the initiation of an extracorporeal left ventricular assist device, despite having hemiplegia due to a recent broad stroke. She achieved an exercise capacity of supported walking for 280 meters after 127 days of cardiac rehabilitation and then went abroad to undergo heart transplantation when she was in the best physical condition possible. Early initiation of cardiac rehabilitation may be safe and effective for successful pediatric mechanical circulatory support therapy; this acts as a bridge to explantation or heart transplantation.

    View details for DOI 10.1536/ihj.16-067

    View details for PubMedID 27829640

  • Erdheim-Chester Disease With Cardiovascular Involvement and BRAF V600E Mutation CIRCULATION JOURNAL Okamura, K., Suematsu, Y., Morizumi, S., Kawata, M., Dai, Y., Yamakawa, M., Ono, M. 2016; 80 (7): 1657-1659

    View details for DOI 10.1253/circj.CJ-16-0109

    View details for Web of Science ID 000379609200028

    View details for PubMedID 27296272

  • [Combined Open and Endovascular Repair of Multiple Aortic Aneurysms due to Syphilitic Aortitis]. Kyobu geka. The Japanese journal of thoracic surgery Shima, S., Okamura, K., Morizumi, S., Kawata, M., Suematsu, Y. 2015; 68 (6): 426-30


    The patient was a 69-year-old man who presented with low-grade fever and appetite loss. Thoracoabdominal computed tomography revealed multiple aneurysms in the distal arch and descending thoracic and infrarenal aortic regions combined with a right common iliac artery aneurysm. After endovascular stent grafting for a right iliac artery aneurysm, he underwent total arch replacement and open stent grafting for the descending thoracic aneurysms. Pathological microscopic examination revealed an inflammatory infiltrate within the adventitia and destruction of the elastic fibers in the media, which are classical features of syphilitic aortitis. Endovascular aneurysm repair is contraindicated in mycotic infected aneurysms. However, endovascular repair is useful for treating mycotic infected aneurysm, if multiple aneurysms have the possibility of rupture and a high risk of surgery.

    View details for PubMedID 26066872

  • Hybrid stenting therapy for dysphagia aortica with Rokitansky's diverticulum concomitant with thoracic aortic aneurysm EUROPEAN JOURNAL OF CARDIO-THORACIC SURGERY Okamura, K., Suematsu, Y., Morizumi, S., Kawata, M. 2015; 47 (5): E229-E231


    An 87-year old man with a past medical history of a descending aortic aneurysm for 20 years presented with progressive dysphagia and aspiration pneumonia. Computed tomography angiography demonstrated the impending rupture of the thoracic aortic aneurysm (TAA) and endoscopic examinations revealed the extrinsic compression of the middle oesophagus with Rokitansky's diverticulum proximal to the compression area. He underwent urgent thoracic endovascular aortic aneurysm repair, followed by oesophageal stenting. The patient's symptoms immediately improved, and the postoperative period was uneventful. This report is the first to describe a hybrid stenting therapy for dysphagia aortica with Rokitansky's diverticulum concomitant with a TAA.

    View details for DOI 10.1093/ejcts/ezv102

    View details for Web of Science ID 000355208200012

    View details for PubMedID 25859015

  • [DeBakey type 2 Aortic Dissection Failed to Diagnose by Enhanced Computed Tomography;Report of a Case]. Kyobu geka. The Japanese journal of thoracic surgery Numata, R., Shima, S., Okamura, K., Morizumi, S., Kawata, M., Suematsu, Y. 2015; 68 (5): 375-8


    An 81-year-old woman presented with dyspnea and chest pain. A plain chest X-ray revealed widening of the mediastinum and a contrast-enhanced chest computed tomography showed dilatation of the ascending aorta without any specific findings of aortic dissection. Transesophageal echocardiography revealed severe aortic regurgitation (AR). We planned an aortic valve replacement on the 34th day after admission because of the severe AR. During the operation, we found an entry in the intima of the ascending aorta 5 mm above the aortic valve and she was diagnosed with DeBakey type II aortic dissection. Therefore, we decided to perform Bentall's operation and the operation was successful.

    View details for PubMedID 25963787

  • [Vacuum-assisted Closure (VAC) Treatment for Sternal Infection in a Patient after Cardiovascular Surgery; Report of a Case]. Kyobu geka. The Japanese journal of thoracic surgery Shima, S., Okamura, K., Morizumi, S., Kanamori, T., Ichihara, T., Kawata, M., Suematsu, Y. 2015; 68 (3): 225-8


    One year ago, a 42-year-old woman underwent aortic root replacement because of a pseudoaneurysm that developed at the site of an anastomosis after ascending aortic replacement for acute aortic dissection. Six months later, she complained of fever and cough. A computed tomography revealed recurrence of the peudoaneurysm at the proximal anastomosis of the aortic root replacement. After emergency re-do aortic root replacement, she was admitted to intensive care unit (ICU) without sternal closure because of mediastinitis. The mediastinitis was managed by debridement and lavage drainage, followed by vacuum-assisted closure (VAC) treatment. The VAC treatment facilitated wound healing and active rehabilitation using a portable device. Finally, the wound was closed completely using a skin graft. VAC treatment is considered very useful in a case of post-sternotomy madiastinitis.

    View details for PubMedID 25743558

  • A rare case of axillobifemoral bypass graft infection caused by Helicobacter cinaedi JOURNAL OF VASCULAR SURGERY Suematsu, Y., Morizumi, S., Okamura, K., Kawata, M. 2015; 61 (1): 231-233


    Helicobacter cinaedi infection is rarely encountered in nonimmunocompromised patients. We report the case of an 85-year-old man who presented with axillobifemoral bypass graft infection caused by Helicobacter cinaedi. The patient was not immunocompromised. We successfully treated him by iliac stenting of the native iliac artery, with near-total removal of the infected graft. At present, 48 months later, the patient is doing well at home, with no evidence of infection. To the best of our knowledge, this is the first report of infection of a prosthetic graft caused by Helicobacter cinaedi.

    View details for DOI 10.1016/j.jvs.2013.08.048

    View details for Web of Science ID 000346637600036

    View details for PubMedID 24103408

  • Coronary artery aneurysm occurring very late after drug-eluting stent implantation INTERACTIVE CARDIOVASCULAR AND THORACIC SURGERY Okamura, K., Suematsu, Y., Morizumi, S., Kawata, M. 2014; 19 (6): 1068-1070


    An 82-year old woman presented with chest pain and was diagnosed as having acute myocardial infarction. Coronary angiography (CAG) showed 90% stenosis in the proximal left anterior descending artery (LAD). The patient underwent percutaneous coronary intervention using a sirolimus-eluting stent (SES). A repeat CAG performed 6 months after SES implantation revealed no problems. Eight years later, the patient presented with recurrent angina. CAG showed severe stenosis of the SES with a large aneurysm. We performed off-pump coronary artery bypass grafting without ligation or plication of the LAD, but with the application of fibrin glue to the coronary artery aneurysm. The postoperative course was uneventful. The mechanism responsible for the occurrence of coronary artery aneurysms occurring late after drug-eluting stent implantation remains unclear, and the treatment strategy remains controversial. Herein, we discuss a surgical treatment for this rare entity.

    View details for DOI 10.1093/icvts/ivu286

    View details for Web of Science ID 000347622300039

    View details for PubMedID 25164132

  • Conservative Therapy as a Primary Treatment for Spontaneous Isolated Dissection of the Superior Mesenteric Artery ANNALS OF VASCULAR SURGERY Okamura, K., Morizumi, S., Kawata, M., Suematsu, Y. 2014; 28 (8): 1939-1945


    Spontaneous isolated dissection of the superior mesenteric artery (SIDSMA) is a rare and potentially fatal disease. Several therapeutic options are available, including conservative therapy, endovascular repair, and open surgery. Herein, we report our experiences in the treatment of SIDSMA.Between February 2009 and June 2013, 17 patients were diagnosed as having SIDSMA. We retrospectively reviewed and analyzed their clinical characteristics, medical history, risk factors, symptoms, diagnostic imaging modality, treatment, and outcome. The lesions were categorized according to the modified Sakamoto's classification. If no evidence of bowel necrosis or arterial rupture was present in the patients with symptomatic SIDSMA, we first performed conservative therapy, even if the patients had abdominal pain.The subjects included 15 men and 2 women, with a median age of 62.8 years. Eight patients were symptomatic and 9 were asymptomatic. Conservative therapy included the use of antithrombotic agents in 3 patients but not in 5 patients. During the follow-up period (mean, 21.1 months), all the patients were discharged without any significant complications, and none of the patients showed the progression of the dissection on follow-up computed tomography angiography examinations.Conservative therapy without antithrombotic agents should be the primary treatment for SIDSMA. Endovascular repair for SIDSMA is associated with several risks, thus the procedure might occasionally be useful and necessary.

    View details for DOI 10.1016/j.avsg.2014.06.062

    View details for Web of Science ID 000344484100046

    View details for PubMedID 25048807

  • [Bridge to recovery with ventricular assist device support for eosinophilic myocarditis]. Kyobu geka. The Japanese journal of thoracic surgery Suematsu, Y., Morizumi, S., Okamura, K., Gon, S., Shimizu, T., Kawata, M. 2014; 67 (7): 587-91


    A 39-year-old man initially presented with cough, fever, and shortness of breath. His symptom got worse gradually, and he was admitted to a nearby hospital. Echocardiography revealed a dilated left ventricle and severe left ventricular dysfunction. Despite inotropic and intra-aortic balloon pumping (IABP) support, the patient developed cardiogenic shock with fever of unknown origin, followed by multi-organ failure. A left-ventricular assist device (LVAD) was implanted. Pathologic evaluation showed an extensive eosinophil-rich inflammatory infiltrate, and consistent with the diagnosis of eosinophilic myocarditis. After high-dose steroid administration, the cardiac function improved and explantation of the LVAD was successfully performed. The patient was discharged and remains well at the 24-month follow-up.

    View details for PubMedID 25137336

  • Stanford type A aortic dissection after urgent prosthetic valve replacement: case reports JOURNAL OF CARDIOTHORACIC SURGERY Suematsu, Y., Morizumi, S., Okamura, K., Kawata, M. 2014; 9: 9


    Occurrence of acute aortic dissection after aortic valve replacement is rare, however, it is associated with high mortality and morbidity rates. We report two Asian cases in which acute aortic dissection occurred after urgent aortic valve replacement for infective endocarditis. Successful graft replacement was carried out with preservation of the prosthetic valves in both cases. Our experience with these cases suggests that, even in urgent or emergent situations, surgical intervention for associated aortic dilatation should be considered when aortic valve replacement is performed.

    View details for DOI 10.1186/1749-8090-9-9

    View details for Web of Science ID 000331887600003

    View details for PubMedID 24397918

    View details for PubMedCentralID PMC3892088

  • [Concomitant off-pump coronary artery bypass and left lower lobectomy for lung cancer;report of a case]. Kyobu geka. The Japanese journal of thoracic surgery Okamura, K., Kamiyama, K., Kimura, M., Morizumi, S., Kawata, M., Suematsu, Y. 2013; 66 (12): 1101-4


    A 58-year-old man had an abnormal shadow in the left lower lobe on his computed tomography, and also had stenosis of the coronary arteries. Preoperative coronary angiography revealed severe stenosis of right coronary artery (RCA), left anterior descending artery (LAD), and left circumflex branch(LCx). The diagnosis of lung cancer was made by transbronchial lung biopsy. Initially, we scheduled to undergo surgery of both the heart and lung in 2stage operation. However, before surgery, the infection of cavity was caused by tumor growing, so we performed the surgery in 1stage operation. Off-pump coronary artery bypass and left lower lobectomy with lymph node dissection was concomitantly performed. The postoperative course was uneventful. He was discharged after confirming the patent bypass grafting on the 13th postoperative day. Histopathological diagnosis was squamous cell carcinoma without lymph node metastasis. Lung cancer and ischemic heart disease can be surgically treated simultaneously, benefitting selected patients.

    View details for PubMedID 24322321