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Toshiaki Akita

Publications and source records attributed to Toshiaki Akita.

At least 19 recordsLinked to original sources
PubMed2006

Mitral valve motion assessed by high-speed video camera in isolated swine heart.

OBJECTIVE: We have recently reported our isolated and working swine heart model that examines the valve motion precisely by a high-speed digital video camera system. Using this modality, the present study aimed (1) to delineate the motion of the mitral leaflets, chords and annulus throughout the cardiac cycle, and (2) to elucidate the influence of alterations in loading conditions on leaflet excursion. METHODS: The valve motion of five isolated and working swine hearts was observed by an endoscope recording the images at 250 frames per second. Modified Krebs-Ringer solution was used as the sole perfusate. The images were obtained in hearts 30 min after reperfusion, changing the left atrial pressure as 4, 8, and 12 mmHg. RESULTS: The motion of the mitral valve in the vicinity of diastole was considered to be well understood by dividing the entire sequence into five stages: 'decoaptation,' 'E excursion,' 'diastasis,' 'A excursion,' and 'coaptation.' Initial separation occurred at both sides of the central tips of the leaflets. The leading edges always followed the mid-portion of the rough zone during opening and closing. The 'strut' second-order chords retained their tension throughout the cardiac cycle and played the role as rotary shafts of the other branching chords. The first-order chords lost their tension during opening, suggesting they mainly are involved in valve competence. Annular constriction occurred coincident with atrial contraction. An increase in preload made the isovolumic relaxation and contraction times shorter. The leaflets opened faster in the rapid-filling phase, whereas they required more time for opening and closing in the atrial-filling phase. CONCLUSIONS: The present study revealed the integrated movement of the mitral leaflets, chords and annulus, as well as the impact of altered preload.

Animals↗
PubMed2006

A vascular tube for intercostal artery reimplantation.

Paraplegia and paraparesis are major concerns in descending and thoracoabdominal aortic repair. A shorter period of spinal cord ischemia is preferred for protection. We have developed a new technique in which plural intercostal arteries are reattached in a short time. The lower descending aorta is tailored using automatic sutures, and a vascular tube is made with diameter about 2.0 cm. Blood supply of intercostal arteries including the Adamkiewicz artery is resumed by perfusing the vascular tube in not more than 20 min. This technique has been applied in four patients, and there was neither paraplegia nor paraparesis.

Aortic Dissection↗
PubMed2006

Infective endocarditis with an aortic periannular abscess extending along the right coronary artery.

A 50-year-old male underwent surgery for infective aortic valve endocarditis, which had been refractory to medical treatment. The valve was bicuspid, and involvement of the annular and subannular structures was recognized. A large suppurative discharge was obtained on incising this portion. Although there was no interventricular shunt, the abscess cavity was revealed to extend through the epicardial surface of the right atrioventricular groove. Following extensive debridement and irrigation, the defect was closed by an autologous pericardial patch. A 23 mm mechanical valve was implanted placing some of the stitches deep into the muscular interventricular septum. Infection was controlled by six-week administration of cefazolin sodium and gentamicin sulfate, and the patient survived.

Abscess↗
PubMed2006

Midterm results for endovascular stent grafts via median sternotomy for distal aortic arch aneurysm.

Dislocation or perigraft leakage is a major problem during the follow-up period for endovascular stent graft (EVG) implantation via median sternotomy for distal aortic arch aneurysm. Anchoring sutures have been applied for the prevention of these complications. Here, we evaluate the midterm results and the efficacy of anchoring sutures. There were 21 male and 2 female patients enrolled in the study with an average age of 70 years (59-83). Aneurysm types were 21 true aneurysms (13 fusiform, 8 saccular), 1 chronic dissection, and 1 penetrating aortic ulcer. Total arch replacement was performed in two patients and aortocoronary bypass grafting was combined in four patients. Anchoring sutures to fix the EVG via median sternotomy were applied for 11 recent patients. The average follow-up period was 44 (22-79) months. There were no operative mortalities, but one case of paraplegia, one of stroke, and two of temporary spinal cord dysfunction. Complications related to EVG via median sternotomy occurred in five patients who had not received anchoring sutures, but the 11 patients with anchoring sutures showed no EVG-related complications. A chronic type B dissection revealed impending rupture due to false lumen infection 1 year after operation and repeat surgery was performed. Stent dislocation occurred in four patients, two of whom required repeat surgery via left thoracotomy due to endoleakage 3 and 4 years after surgery. One died from aneurismal rupture 5 years after surgery. One required emergency graft replacement because of graft perforation 5 years after surgery. The proportion of patients free from EVG-related events at 5 years after surgery was 75%. Anchoring sutures (P = 0.0155) and a large aneurysm of more than 80 mm (P = 0.0190) were predictors of late EVG-related complications. There were five late deaths: two were from stroke, one from rupture, one from cancer, and one from multiple organ failure after repeat surgery. EVG shortens postoperative recovery with relatively lower mortality, but spinal cord injury is a complication occurring with a relatively high rate. Patients with large aneurysms are not good candidates for EVG implantation via median sternotomy Anchoring sutures to fix the EVG to the aortic wall should help prevent EVG-related events and improve the durability of EVG.

Aged↗
PubMed2006

Late mortality and morbidity in elderly patients with mechanical heart valves.

A retrospective study was performed in patients under and over 65 years old implanted with a mechanical valve, to compare late mortality and morbidity. Of 381 patients who underwent mechanical valve replacement at Nagoya University in the 1990s, 357 (11 hospital deaths and 13 lost to follow-up; 96.4% follow-up rate) were followed up for 7.9 +/- 3.3 years (2,811 patient-years). They were divided into two groups either side of 65 years of age at operation. The young and elderly patient groups contained 275 and 82 patients, respectively. The survival rate in the young group was 96.1% (95% confidence interval, 93.7%-98.5%) at 5 years and 92.0% (95% confidence interval, 88.3%-95.7%) at 10 years, which was significantly better than 88.0% (95% confidence interval, 80.6%-95.4%) at 5 years and 73.8% (95% confidence interval, 66.2%-85.4%) at 10 years in the elderly group. The two groups did not differ significantly in the incidence of thromboembolic events, bleeding events, endocarditis, or reoperation. We are also encouraged by the fact that mechanical valves are not a risk factor for late mortality or morbidity, even in elderly patients.

Age Factors↗
PubMed2006

Mitral valve surgery for dilated cardiomyopathy with mitral regurgitation.

Outcomes of surgery for non-ischemic non-valvular dilated cardiomyopathy with associated mitral regurgitation were assessed in 8 consecutive patients who underwent 9 mitral valve operations between 2001 and 2004. Mitral valve replacement was performed when the coaptation depth exceeded 10 mm. Two patients initially underwent mitral valvuloplasty, and 6 underwent valve replacement. One patient had valve replacement soon after valvuloplasty. Transthoracic echocardiography was performed immediately before surgery, before discharge, and during follow-up. Transesophageal echocardiography was carried out intraoperatively to assess valvular and ventricular function. Postoperative mean functional class was significantly better than the preoperative value (2.4 +/- 0.7 vs. 3.3 +/- 0.7), and the improvement was sustained during follow-up (2.0 +/- 0.7). The ejection fraction and left ventricular end-diastolic dimension did not improve. One patient died without leaving hospital and two died during follow-up. The 2- and 4-year survival rates were 75.0% and 37.5%. Mitral valve surgery improved functional class without obvious changes in ejection fraction or left ventricular end-diastolic dimension.

Adult↗
PubMed2006

Disorganization of gap junction distribution in dilated atria of patients with chronic atrial fibrillation.

BACKGROUND: Atrial fibrillation (AF) is an arrhythmia associated with functional and morphological remodeling of atria. We investigated the distribution and the expression of connexins in atrial tissues from patients with chronic AF and left atrial dilatation (AD). METHODS AND RESULTS: Immunohistochemistry was performed in atrial tissues obtained during cardiac surgery from patients with chronic AF + AD (n = 11), sinus rhythm (SR, n = 11) and SR + AD (n = 4). In SR patients (control), the connexin (Cx) 43 labeling of the intercalated disks seen en-face was characterized by small central spots surrounded by larger spots at the periphery. In the left atria from AF + AD patients, the area of the intercalated disk was significantly enlarged. Although peripheral Cx43 labeling was preserved, there was a striking loss of central labeling spots. The area occupied by gap junctions was slightly but significantly larger than that of the control. The left atria from patients with SR + AD showed gap junction disorganization analogous to AF + AD. The labeling patterns of Cx40 were essentially similar to those of Cx43. Conclusions In chronic AF with AD, gap junctions at the intercalated disk are disorganized, resulting most likely from AD but not from AF itself. This gap junction remodeling might be involved in altered atrial conduction properties, but its potential arrhythmogenic role remains unclear.

Adult↗
PubMed2005

Surgery for calcific aortic root stenosis in homozygous familial hypercholesterolemia.

A 35-year-old female with homozygous familial hyperlipidemia (IIa) was referred to our hospital for an operation against supravalvular and valvular aortic stenosis. She had been treated with low-density lipoprotein apheresis for 20 years, and total cholesterol ranged between 200 and 400 mg/dl under this treatment. She had undergone percutaneous coronary intervention for ostial stenosis of the right coronary artery three times since the age of 19. Unenhanced three-dimensional computed tomography showed supravalvular stenosis, funnelling and heavily calcified aorta. An operation was performed under deep hypothermic circulatory arrest without aortic cross clamping. After the ascending aorta had been replaced with a one-branched vascular graft, arterial perfusion was resumed. The stenosed ascending aorta was resected at the sinotubular junction. Because the aortic root was still extremely small, the noncoronary sinus and the commissure between left and right coronary cusp were incised, and the aortic root was enlarged with linguiform vascular-graft patches. A 21-mm mechanical valve was implanted. The postoperative course was uneventful.

Adult↗
PubMed2005

Early clinical results of St. Jude Medical Symmetry aortic connector.

An automated anastomosis device named St. Jude Medical symmetry aortic connector has been used worldwide for off-pump coronary artery bypass grafting. However, early graft obstruction was recently reported, and its predictors should be clarified. From April 2002 to March 2004, 38 patients in our institution underwent off-pump coronary artery bypass grafting using the St. Jude Medical Symmetry aortic connector for saphenous vein graft (SVG) procedures; measurement of intraoperative graft flow and postoperative coronary angiography was performed. Early SVG events occurred in 9 (24%) patients: 8 occlusion cases and 1 case of stenosis. Predictors of early SVG events were assessed from a comparative study. Univariate logistic regression identified hyperlipidemia as the only significant predictor of early SVG events (P = 0.02, odds ratio 7.78). Lower SVG flow rate and poor ejection fraction did not show statistical significance (P = 0.09, odds ratio 1.09 and P = 0.09, odds ratio 0.96). The SVG event rate was much higher for the left circumflex branch compared with other locations (31% vs. 9%, P = 0.03) and decreased with increasing aortic connector size (small, 32%; median, 14%; large, 0%). Multivariate analysis did not identify a predictor of SVG events. The aortic connector is associated with a high incidence of early SVG events. Patients should be cautiously selected and the procedure should not be used for left anterior descending coronary artery or culprit lesions.

Aged↗
PubMed2005

Arch-first technique performed under hypothermic circulatory arrest with retrograde cerebral perfusion improves neurological outcomes for total arch replacement.

OBJECTIVE: From 1998, we have adopted the arch first technique (reconstruction of arch vessels first and distal anastomosis second) instead of the distal anastomosis first technique for total arch replacement. The aim is to reduce the period of deep hypothermic circulatory arrest and the retrograde cerebral perfusion time. We evaluate the surgical results of the arch first technique. METHODS: The arch first technique was used in 50 cases (38 male and 12 female), of average age 68 years, from 1998 to 2003. There were 33 true aneurysms and 10 chronic and seven acute type A dissections. Clinical results were evaluated and compared with the distal first technique used in 24 cases operated on between 1992 and 1998. These were 14 males and 10 females, with an average age of 68 years. There were 16 true aneurysms, and three chronic and five acute aortic dissections. RESULTS: For the arch first technique there is a significantly shorter circulatory arrest time (32 vs. 72min, P<0.0001), but similar body ischemic times (76 vs. 72min, N.S.). With the arch first technique, all but two patients awoke within 24h, with an average delay of 9.3h. In the distal first technique, two patients did not awaken and three patients showed delayed awakening, with an average awakening time of 24h. The arch first technique led to one hospital death (2%), due to residual aneurysm rupture. Reversible ischemic neurological deficit (RIND) was complicated in three cases (6%), but no stroke occurred during operation. In the distal first technique there were four strokes, one RIND and three hospital deaths (12.5%). The arch first technique gave a significantly lower intra-operative stroke rate (P=0.0030) and smaller hospital mortality (P=0.0615). The arch first technique led to five late deaths, with an 84.5% 3 year survival rate, and the distal first technique led to six late deaths with a 59.1% 3-year survival rate. CONCLUSIONS: The arch first technique is clearly superior to the conventional distal first technique in surgical mortality and morbidity regarding neurological outcome, and provides a higher survival rate and better quality of life. The arch first technique is an excellent method for total arch replacement.

Adult↗
PubMed2005

Pressure-volume relationship in isolated working heart with crystalloid perfusate in swine and imaging the valve motion.

OBJECTIVE: It is widely accepted that both valve and cardiac functions are closely correlated. In order to investigate the relationship between the valve and cardiac functions, we developed a model of an isolated working heart with crystalloid perfusate in swine. We investigated the feasibility of this model to evaluate the precise left ventricular function using the pressure-volume relationship and metabolic measurement. Another objective was as a trial for the imaging and analysis of valvular interventions with a high-speed digital camera on this model. METHODS: Six isolated working hearts were subjected in the pressure-volume study, and additional three hearts were used in the valve imaging study. Measurement of the pressure-volume relationship was undertaken in situ before the heart was removed, and on the working heart mode during the initial 30 min as the baseline, and at every 60 min. Lactate levels were measured at every stage in the working heart mode. Mitral valve interventions were performed in three hearts, and valve motions were observed by a high-speed digital camera via the left ventricle. RESULTS: The end-systolic elastance maintained a baseline level (5.17+/-2.25) until 180 min and decreased at 240 min (3.97+/-1.97, NS) and 300 min (2.85+/-1.29, P<0.01) of the working heart mode as compared with baseline. The Tau maintained a constant level until 180 min and increased at 240 min (62.2+/-13.3, NS) and 300 min (85.5+/-43.4, P<0.05) as compared with baseline (50.3+/-13.6). The slope of the end-diastolic pressure-volume relationship gradually increased with no significance until 180 min and increased significantly (0.147+/-0.066, P<0.01 vs 0.067+/-0.041 at baseline). Lactate increased accumulatively. The total heart energy was reduced from the initial phase of the working heart mode. The valves were well captured by the high-speed digital camera. CONCLUSIONS: The systolic and diastolic functions of an isolated heart were preserved at an acceptable level for 180 min. The practical reliability of the swine working heart model was demonstrated. This model will be used reliably for the investigation of the interaction of valve and cardiac functions.

Animals↗
PubMed2005

Natural history of a dilated ascending aorta after aortic valve replacement.

BACKGROUND: Little information is available regarding the incidence of aortic dissection or rupture in patients with a dilated ascending aorta after aortic valve replacement (AVR). The present clinical study aimed to demonstrate the incidence of aortic complications after AVR in patients with a dilated ascending aorta and to clarify those risk factors associated with the progression of a dilated ascending aorta or late aortic events. METHODS AND RESULTS: A total of 35 patients with a dilated ascending aorta at the time of AVR were enrolled. A dilated ascending aorta was defined as 40 mm or greater in diameter by preoperative computed tomography or operative findings. The baseline ascending aorta diameter ranged from 40 to 55 mm with a mean of 44.8+/-4.4 mm. There was a high frequency of bicuspid valve disease in patients with a dilated ascending aorta (57%). The mean follow-up interval was 8.1+/-3.5 years (range: 2.3-13). Aortic events occurred in 5 patients (aortic dissection in 1, rupture in 2, reoperation in 2) during the follow-up. One aortic dissection developed at a baseline aortic size of 42 mm, whereas 2 aortic ruptures occurred at baseline aortic sizes of 47 mm and 50 mm. There was no statistically significant univariate association between any of the patient clinical characteristics and late aortic events or ascending aortic progression. CONCLUSION: Although the clinical course of patients with a dilated ascending aorta is unpredictable, aortic events may occur even in patients with a baseline aortic diameter of <50 mm. Therefore, preventive aortic surgery at the time of AVR should be considered to prevent aortic dissection or rupture in patients with an even slightly dilated ascending aorta with a diameter of 40 to 50 mm, unless the patient has a high operative risk or older age.

Adolescent↗
PubMed2004

Real time 3-D echocardiography in cardiac surgery.

OBJECTIVE: Real time 3-D echocardiography provides real time live images of intracardiac anatomy. We evaluate its clinical application for intraoperative echocardiography. METHOD: The "xStream"3-D architecture designed with "xMatrix array" using approximately 3,000 transducer elements achieves live digital volume imaging in real time 3-D echocardiography (SONOS 7500, Philips Medical Systems, Inc.). Intraoperative echocardiography was performed in mitral (n = 14) and aortic valve diseases (n = 6), 4 heart anomaly, 4 aortic diseases and 15 normal anatomies. RESULTS: Heart valves were depicted via enface view. Simultaneous movement of leaflets and subvalvular apparatus can be observed. Prolapsed leaflets are easily detected and regurgitated jets are detected as 3-D color images. The four cardiac chambers were observed in their real shape and size. Septum defects were also depicted in real shape, size and position. Precise intracardiac anatomy was observed in cardiac anomalies. Information on the endothelium, intimal flap, entry, reentry and aortic wall character was provided and allowed for planning in aortic surgery. CONCLUSION: Live 3-D echocardiography provides excellent depiction of any cardiac and aortic anatomy in any direction and greatly enhances efficiencies in planning appropriate surgical procedures.

Cardiac Surgical Procedures↗
PubMed2004

Mid-term structural change in the radial artery grafts after coronary artery bypass grafting.

BACKGROUND: Currently, excellent patency rates of radial artery grafts for coronary artery bypass grafting in the early period have been reported. However, the long-term result of radial artery grafts remains unclear. We investigated the midterm structural change in radial artery grafts using intravascular ultrasound imaging (IVUS). METHODS: IVUS studies were performed on 15 radial artery grafts in the early phase and 11 in the midterm phase (20.3 +/- 13.7 days and 37.6 +/- 7.2 months after surgery, respectively). The radial artery grafts were observed throughout the entire length and 10 cross-sectional images were selected from each graft for measurement of the thickness of the intima (IN) and intima-plus-media (IN + MD). Grafts having palpable arteriosclerosis at the time of harvesting were excluded. IN and IN + MD were compared between the early and midterm phases using repeated measures analysis of variance. The coefficient of variation of IN and IN + MD was calculated as an index of irregularity and compared between the phases. RESULTS: IVUS revealed uniform and thin intima and media in the early and midterm groups and IVUS images were similar between the groups. There was no significant difference in both IN and IN + MD between the groups (IN, p = 0.83; IN + MD, p = 0.55). The median of coefficient of variation of IN and IN + MD was 8.5% and 8.1% in the early group and 8.7% and 9.3% in the midterm group. Again, there was no significant difference between the groups (IN, p = 0.87; IN + MD, p = 0.27). CONCLUSIONS: The present study suggested that structural changes rarely developed in radial artery grafts over several years after surgery.

Coronary Artery Bypass↗
PubMed2002

Repetitive atrial flutter as a complication of the left-sided simple maze procedure.

BACKGROUND: Of 41 patients who had undergone a left-sided simple maze procedure, 4 (9.8%) developed repetitive tachycardia due to atrial flutter, and required radiofrequency catheter ablation. Linear ablation of the right atrial isthmus was effective to treat atrial flutter. METHODS: We conducted an electrophysiologic study of atrial flutter and determined its reentry circuit on the atrium. We consider how to reduce atrial flutter after the left-sided simple maze procedure. RESULTS: Common atrial flutter through the right atrial isthmus was induced in all 4 patients, and linear ablation on the right atrial isthmus was effective in 3 of these. An incisional atrial flutter around the right atriotomy was also induced in 2 of 4 patients; both were successfully treated by linear ablation between the right atriotomy and the inferior vena cava. CONCLUSIONS: Common atrial flutter through the right atrial isthmus is a risk after the left-sided simple maze procedure. When a left-sided simple maze procedure is performed, sufficient cryoablation on the right atrial isthmus of the arrested heart should be administered to prevent postoperative atrial flutter.

Adult↗
PubMed2002

Cerebrospinal dysfunction after endovascular stent-grafting via a median sternotomy: the frozen elephant trunk procedure.

BACKGROUND: Endovascular stent grafting through a median sternotomy for a distal arch aneurysm (the frozen elephant trunk procedure) is an alternative to synthetic graft replacement. But spinal cord dysfunction can easily occur as a complication after surgery. Although its cause is uncertain, some attempts at prevention have been instituted. We address the mechanism of spinal cord dysfunction and evaluate the efficacy of our preventive measures. METHODS: There were 22 men and 2 women with an average age of 71 (59 to 83) years. There were 22 true aneurysms (13 fusiform, nine saccular), one chronic dissection, and one penetrating aortic ulcer. The following strategies for prevention of spinal cord dysfunction were utilized: low flow perfusion through both axillary arteries (n = 10); pigtail catheter guidance (n = 19); use of a shorter graft with anchoring sutures (n = 12); flooding of the operative field with carbon dioxide (n = 7); aortic unclamping (n = 7), and use of ultra-thin woven Dacron grafts (n = 15). RESULTS: There was no operative mortality, but cerebrospinal dysfunction complicated four cases (17%): one paraplegia, one stroke along the basilar artery, and two cases of temporary spinal cord dysfunction (paresthesia of the right leg and urinary disturbance). Cerebrospinal dysfunction tended to occur in fusiform aneurysms (31%, p = 0.044). Except when low flow antegrade perfusion through both the axillary arteries was utilized, which resulted in no cases of paraplegia or paraparesis (p = 0.064), the methods used for prevention of cerebrospinal dysfunction appeared to have little efficacy. CONCLUSIONS: Cerebrospinal dysfunction is a serious complication of the frozen elephant trunk procedure. Its cause has not been clarified, but it tends to occur in fusiform-type aneurysms. Antegrade perfusion through both axillary arteries while the aorta is open may be helpful in its prevention.

Aged↗