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Biomedical subjects

K Miyaji

Publications and source records attributed to K Miyaji.

At least 37 records · Page 2Linked to original sources
PubMed2000

Right heart bypass for left circumflex coronary artery bypass grafting.

Displacement of the heart to expose the left circumflex artery (LCX) causes hemodynamic disturbance during off-pump coronary artery bypass grafting (CABG). We applied right heart bypass (RHB) using a heparin-coated centrifugal pump without an oxygenator in an attempt to stabilize the hemodynamics. Five mongrel dogs (15.5-20 kg) were used. Hemodynamic parameters were continuously monitored at a fixed rate of 80 beats/min. The LCX was exposed with the use of an Octopus Tissue Stabilizer. After baseline data were obtained, each dog was placed in the Trendelenburg position. Finally, RHB was established with different pump flows. LCX exposure caused a significant decrease in aortic flow (to 33.1% +/- 13.1% of the baseline value) and arterial mean pressure (to 68.3% +/- 8.5%) (P < 0.001). Trendelenburg positioning caused these values to recover to 57.1% +/- 6.7% and 72.5% +/- 7.7%, respectively. RHB with 50% flow significantly improved the hemodynamic values, although 100% flow significantly increased LAP by 134.8% +/- 19.7% (P < 0.01). Tilting of the canine heart to expose the LCX caused significant deterioration of the hemodynamic values. Trendelenburg positioning was moderately effective, and RHB very effective, in improving the hemodynamics. In a limited number of cases, an appropriate flow of RHB may provide safe hemodynamic assistance during off-pump CABG of the LCX.

Animals↗
PubMed2000

Video-assisted cardioscopy for intraventricular repair in congenital heart disease.

BACKGROUND: Video-assisted thoracoscopic surgical techniques have been widely adopted as a means to reduce surgical trauma. By adapting pediatric thoracoscopic instrumentation, we have developed a technique for video-assisted cardioscopy (VAC). We report our experience and describe the technical feasibility of VAC. METHODS: Since June 1995, 409 consecutive patients underwent 431 intracardiac procedures (ventricular septal defect, 150; tetralogy of Fallot or double outlet right ventricle, 101; atrioventricular canal, 52; subaortic stenosis, 43; valve repair, 50; Rastelli procedure, 12; Konno or Ross Konno operation, 11; and miscellaneous, 12) using VAC at Miami Children's Hospital. Using a prospective database, we tracked outcomes and operative events to delineate the usefulness and efficacy of this technique. RESULTS: VAC provided clear and precise imaging of small or remote intracardiac structures during repair of congenital heart defects without technical complications. Procedure times and aortic cross-clamp times using VAC were not prolonged. Intraoperative images were collected for every operation, documenting each patient's cardiac anatomy before and after repair. Surgery through small incisions was facilitated. Operative mortality was 1.2% (5 of 409), and no patient required reoperation before discharge. At a mean follow-up interval of 22 months, the incidence of reoperation for residual or recurrent lesions was 1.2% (5 of 404). CONCLUSIONS: Our experience demonstrates the technical feasibility and clinical utility of routine endoscopic imaging during open heart surgery for congenital heart repair.

Adolescent↗
PubMed2000

Myocardial tactile stiffness during acute reduction of coronary blood flow.

BACKGROUND: Evaluation of regional myocardial contractile function is of clinical importance. We have developed a new tactile sensor system for accurate measurement of myocardial stiffness in situ. We found that the myocardial stiffness measured by this sensor, which we call tactile stiffness, can be a very useful index for accurate quantification of regional myocardial function. In this study, we used a coronary stenosis model to investigate regional myocardial tactile stiffness under conditions of reduced coronary blood flow. METHODS: The myocardial tactile stiffness, coronary blood flow, and ventricular pressure and volume, of five open chest mongrel dogs weighing 15 to 17 kg, were measured. After measuring the baseline myocardial stiffness, coronary arterial stenosis was induced with a balloon occluder. RESULTS: Reducing the coronary flow to 50% and 25% of the baseline level reduced the end-systolic tactile stiffness significantly from 2.20+/-0.16 g/mm2 to 2.05+/-0.20 g/mm2 (p<0.05) and from 2.21+/-0.16 g/mm2 to 1.96+/-0.18 g/mm2 (p<0.01), respectively. Reducing the flow, to 50% and 25%, increased the end-diastolic stiffness significantly from 1.29+/-0.15 g/mm2 to 1.39+/-0.14 g/mm2 (p<0.01) and from 1.30+/-0.16 g/mm2 to 1.46+/-0.14 g/mm2 (p<0.05), respectively. CONCLUSIONS: We consider that the regional myocardial tactile stiffness will be a useful index sensitive enough to detect changes in regional contractile function under conditions of reduced coronary blood flow.

Acoustics↗
PubMed2000

The Ross operation in a Jehovah's Witness: a paradigm for heart surgery in children without transfusion.

A 3-year-old 18 kg male child of the Jehovah's Witness faith presented with severe aortic regurgitation. A successful Ross procedure was performed using a pulmonary autograft, without the use of blood or blood product transfusion. Blood conservation strategy included: (1) preoperative treatment with recombinant human erythropoietin; (2) intraoperative strategies, including technical modifications to the Ross procedure, and the prophylactic use of fibrin glue; (3) utilization of a heparin-bonded cardiopulmonary bypass circuit and assisted venous drainage; and 4) the use of prebypass phlebotomy, cell-saving device and autotransfusion. The patient was discharged home on postoperative day 7 with a hemoglobin level of 11.9.

Aortic Valve Insufficiency↗
PubMed2000

Minimally invasive resection of congenital subaortic stenosis.

Fifteen consecutive patients with membranous subaortic stenosis underwent resection by a minimal-access approach through a partial upper sternotomy using a cardioscope. There were no operative deaths and no postoperative complications. Twelve patients (80%) were extubated in the operating room. The mean hospital stay was 3.1 days, and 3 patients (20%) needed blood products. Our experience demonstrates that this modified approach is a safe and effective surgical option for resection of subaortic stenosis.

Adolescent↗
PubMed2000

Right heart mini-pump bypass for coronary artery bypass grafting: experimental study.

BACKGROUND: Visualization of the left circumflex arteries during off-pump coronary artery bypass grafting (CABG) causes hemodynamic disturbance. We investigated whether right heart mini-pump bypass (RHB), using a centrifugal pump, improved the safety of this procedure by studying the influences of different heart displacement positions, the Trendelenburg maneuver and RHB on hemodynamics. METHOD: Hemodynamic parameters in eight mongrel dogs (15.5-20 kg) were continuously monitored at a fixed heart rate of 80 beats/min through a conventional median sternotomy. The posterior descending artery (PDA) and left circumflex artery (LCX) were exposed using an Octopus tissue stabilizer. After evaluating the influence of the Trendelenburg maneuver on hemodynamics, a heparin-coated centrifugal pump without an oxygenator was introduced and the impact of different pump flow volumes was investigated during RHB. RESULTS: LCX exposure caused significant decreases in aortic flow (to 35. 1+/-12.8%) and arterial mean pressure (to 66.1+/-9.3%) compared with baseline (P<0.001). In contrast to PDA exposure, values remained significantly decreased during the Trendelenburg maneuver. On the contrary, RHB significantly improved the hemodynamic impairments caused by both heart displacement procedures, especially LCX exposure, although 100% pump flow significantly increased left atrial pressure to 131.3+/-19.5% (P<0.01). CONCLUSION: Exposure of the LCX caused severe hemodynamic deterioration, which was not fully reversed by the Trendelenburg maneuver. In contrast, RHB significantly improved hemodynamics, and therefore this technique can be beneficial for CABG of LCX in the limited cases.

Animals↗
PubMed2000

Prostate cancer with multiple lung metastases in a hemodialysis patient.

In hemodialysis patients, few cases of prostate cancer have been reported until recently. We present a case of prostate cancer with multiple lung metastases in a chronic hemodialysis patient. A 65-year-old Japanese man who had maintained hemodialysis for 5 years was referred to our hospital with multiple metastatic lung tumors. Serum prostate tumor markers were highly elevated although his plasma testosterone level was within the normal range. A transrectal needle prostate biopsy confirmed a histologic diagnosis of moderately differentiated adenocarcinoma. Androgen blockade therapy was very effective as evidenced by a quick decrease of serum tumor markers. The follow-up computed tomography scan of the chest performed 3 months later showed a complete disappearance of the coin lesions. The early detection of prostate cancer in hemodialysis patients is difficult because of a lack of urologic symptoms, which indicate the importance of periodic screening by serum tumor markers. Combined androgen blockade is effective even in hemodialysis patients. However, close follow up is necessary because long-term results and prognoses are still unknown.

Adenocarcinoma↗
PubMed2000

Use of tactile stiffness to detect fatigue in the latissimus dorsi muscle.

In clinical settings, no method has been established to examine the fatigue of a latissimus dorsi muscle (LDM) preconditioned for cardiomyoplasty. We examined the feasibility of measuring muscle stiffness (tactile stiffness) to evaluate muscle fatigue in situ using our tactile sensor. We stimulated canine LDM with burst pacing and monitored both stiffness and tension to determine their relationship. In both dissected LDM and LDM in situ, the decrements of these parameters during burst pacing were compared between preconditioned and unconditioned LDM. In measurement in situ, the sensor probe was placed on the LDM through a small incision. Strong statistical correlation was shown between stiffness and tension (r = 0.935). In decrements of stiffness in situ, there were statistically significant differences between preconditioned and unconditioned LDM. Our tactile sensor system can provide an efficient method for evaluating fatigue of muscles in situ without measuring muscle tension.

Analysis of Variance↗
PubMed2000

Standardized thigh muscle area measured by computed axial tomography as an alternate muscle mass index for nutritional assessment of hemodialysis patients.

BACKGROUND: Quantification of muscle mass, which represents the largest protein pool in the body, is important for nutritional assessment but is difficult to achieve with conventional methods in hemodialysis patients. OBJECTIVE: We measured the cross-sectional area of the thigh occupied by muscle by using computed tomography and compared this with other muscle mass indicators. DESIGN: Thigh muscle area (TMA) was examined and correlated with creatinine production and various nutritional indexes in 163 patients undergoing hemodialysis. Where appropriate, TMA was expressed relative to bone area in the thigh (TBA) to avoid the influence of body size. RESULTS: TMA was highly correlated with creatinine production as measured in the spent dialysate (r = 0.85, P < 0.001), indicating that TMA substantially reflects total-body muscle mass. TMA standardized for TBA was negatively correlated with age and positively correlated with other nutritional indicators including body weight, body mass index, serum albumin, serum transthyretin, and protein catabolic rate. Multiple regression analysis revealed that of these variables, age, serum albumin, and protein catabolic rate independently predicted TMA standardized for TBA. By using correlations with various nutritional indicators, we concluded that patients with a value <10.0 for TMA standardized for TBA were likely to be malnourished whereas those with a value >13.0 were likely to be well nourished. CONCLUSIONS: These results indicate that TMA standardized for TBA, measured by computed tomography, is a reliable indicator of muscle mass that could be used for nutritional assessment of hemodialysis patients.

Aged↗
PubMed2000

Energy-wasteful total Ca(2+) handling underlies increased O(2) cost of contractility in canine stunned heart.

Postischemic myocardial stunning halved left ventricular contractility [end-systolic maximum elastance (E(max))] and doubled the O(2) cost of E(max) in excised cross-circulated canine heart. We hypothesized that this increased O(2) cost derived from energy-wasteful myocardial Ca(2+) handling consisting of a decreased internal Ca(2+) recirculation, some futile Ca(2+) cycling, and a depressed Ca(2+) reactivity of E(max). We first calculated the internal Ca(2+) recirculation fraction (RF) from the exponential decay component of postextrasystolic potentiation. Stunning significantly accelerated the decay and decreased RF from 0.63 to 0. 43 on average. We then combined the decreased RF with the halved E(max) and its doubled O(2) cost and analyzed total Ca(2+) handling using our recently developed integrative method. We found a decreased total Ca(2+) transport and a considerable shift of the relation between futile Ca(2+) cycling and Ca(2+) reactivity in an energy-wasteful direction in the stunned heart. These changes in total Ca(2+) handling reasonably account for the doubled O(2) cost of E(max) in stunning, supporting the hypothesis.

Animals↗
PubMed2000

Atrial ablation using an IRK-151 infrared coagulator in canine model.

BACKGROUND: A method of atrial ablation was developed with the aim of shortening the aortic cross-clamp time during MAZE surgery. The IRK-151 infrared coagulator (Infrarot-Kontaktkoagulator: MBB: Messerschmidt-Bolkow-Blohn, Germany) was employed. Our aim was to electrophysiologically confirm the efficacy of this device. METHODS: The MAZE-III procedure was performed in four mongrel dogs. Instead of a pulmonary vein-encircling incision, IRK-151 was applied several times to create a continuously overlapping circular lesion. After aortic declamping, the potentials of both atria were recorded using 18 bipolar electrodes implanted in the atrial wall. The recording conditions were: 1) sinus rhythm, 2) overdrive pacing from outside the encircling coagulation, and 3) overdrive pacing from inside the encircling coagulation. RESULTS: 1) There was no detectable potential within the pulmonary vein-encircling coagulation. 2) There was no conduction of paced atrial potential inside the encircling coagulation. 3) Only the area within the encircling coagulation was activated by the stimulus. Other parts of the atrium showed sinus rhythm simultaneously. CONCLUSIONS: The left atrium within the pulmonary vein-encircling coagulation was isolated electrophysiologically.

Animals↗
PubMed1999

Total Ca handling in canine mild Ca overload failing heart.

We analyzed total Ca handling of the left ventricle (LV) in the mildly failing heart preparation induced by a temporary intracoronary Ca overloading intervention in eight excised and cross-circulated canine hearts. This Ca intervention consisted of interruption of coronary blood perfusion by Ca-free oxygenated Tyrode perfusion for 10 min followed by high-Ca (16mmol/l) oxygenated Tyrode perfusion for 5 min. This intervention decreased the LV contractility index, Emax (end-systolic maximum elastance), by 40% after restoration of the blood cross-circulation. We expected a Ca overload or paradox failing heart resembling the postischemic stunned heart and being characterized by an increased O2 cost of Emax. However, LV O2 consumption under mechanically unloading conditions decreased by 30% from control without increasing the O2 cost of Emax. To obtain a mechanistic view of this failing heart, we investigated cardiac total Ca handling by our integrative analysis method. In this method, we obtained the internal Ca recirculation fraction (RF) from the decay beat constant of the postextrasystolic potentiation following each sporadic spontaneous extrasystole in these failing LVs. We combined the RF with the decreased Emax and the unchanged O2 cost of Emax in our recently developed formula of total Ca handling. We found that these failing LVs had a slightly but significantly increased RF accompanied by either a slightly increased futile Ca cycling or a slightly decreased Ca reactivity of Emax, or both. Any of these three possible changes can account for the unchanged O2 cost of Emax. This result indicates that the present mildly failing heart has not yet fallen into a typical Ca overload or paradox by the temporary Ca overloading intervention.

Animals↗
PubMed1999

Surgical results of video-assisted minimally invasive direct coronary artery bypass.

BACKGROUND: A video-assisted minimally invasive direct coronary artery bypass procedure is defined as a combination of video thoracoscopic internal mammary artery harvest and direct coronary bypass grafting through a minithoracotomy without cardiopulmonary bypass. We reviewed our experience with this procedure and examined its efficacy. METHODS: Since November 1995, 110 patients have undergone a minimally invasive direct coronary artery bypass procedure in our institution. Seventy (64%) of them underwent a video-assisted minimally invasive operation (group 1). As a control group (group 2), we reviewed the results in 37 patients who underwent conventional single or double coronary artery bypass grafting using an internal mammary artery graft between 1993 and 1995 and could have been candidates for minimally invasive direct coronary artery bypass grafting. RESULTS: There were two hospital deaths (2.9%) in group 1 and one hospital death (2.7%) in group 2. There were no significant differences in mortality or morbidity between the two groups. The number of patients who needed postoperative positive inotropic agents was significantly greater in group 2, and this group also had a significantly longer mean postoperative intubation time and mean hospital stay than group 1. CONCLUSIONS: The surgical results of video-assisted direct coronary artery bypass procedures were better than those of conventional coronary artery bypass grafting in this review. A long-term follow-up for graft patency is needed.

Adult↗
PubMed1999

Minimally invasive direct coronary artery bypass for redo patients.

BACKGROUND: The minimally invasive direct coronary artery bypass (MIDCAB) procedure, using a small anterolateral thoracotomy without cardiopulmonary bypass, has been recommended for high-risk patients because it is less traumatic than conventional coronary artery bypass grafting. For redo patients who have patent grafts and pericardial adhesions, the MIDCAB may be preferable to the conventional operation because manipulation of the graft and dissection of adhesions may be minimized. METHODS: Since November 1995, 120 patients underwent the MIDCAB procedure in our institution. Among these patients, there were 25 redo cases (20.8%). We reviewed these redo cases and studied their surgical results (mortality, morbidity, hospital stay, operation time, and postoperative inotropic support). To clarify the usefulness of this procedure, we compared the results of redo operations with those of the first-time operations. RESULTS: For redo MIDCAB, there was one operative death (4%) because of intestinal infarction. The mean hospital stay was 4.3 days and the number of patients who needed postoperative positive inotropic agents was 3 (12%). There was no significant differences between redo and first-time operation patients in mortality, morbidity, hospital stay, operation time, and postoperative inotropic support. CONCLUSIONS: Results of the MIDCAB procedure for redo patients were comparable to those for primary MIDCAB operations.

Adult↗
PubMed1999

Minimally invasive direct coronary artery bypass using H graft for pleural symphysis.

In November 1995, video-assisted minimally invasive direct coronary artery bypass procedure, which is defined as a combination of the thoracoscopic internal mammary artery (IMA) harvest and direct coronary bypass grafting, was introduced for patients who need minimally invasive direct coronary artery bypass (MIDCAB) using IMA. In the thoracoscopic IMA harvest, the pleural adhesions or symphysis present an obstacle. We present a case where a redo patient who had complete pleural symphysis of left chest cavity precluded the thoracoscopic IMA harvest, and MIDCAB with the H graft procedure was performed.

Aged↗
PubMed1999

Thoracoscopic mammary artery mobilization in redo minimally invasive coronary bypass operations.

BACKGROUND: It has been stated that thoracoscopic internal thoracic artery (ITA) mobilization is not recommended in the redo minimally invasive direct coronary artery bypass (MIDCAB) situation, presumably because adhesions from the previous coronary artery bypass grafting operation may preclude a thoracoscopic approach. However, there are advantages to thoracoscopic ITA mobilization in MIDCAB that could also be realized in the redo situation. METHODS: In 200 MIDCAB procedures over the last 3 and a half years, 11 patients, ages 49-83 (mean 69), were identified as having undergone an attempted ITA mobilization in a redo situation. RESULTS: Thoracoscopic ITA mobilization was successful in 9 out of 11 patients (81%). One patient had complete pleural symphysis precluding this approach, and 1 patient had poor mammary flow after harvest and this conduit was not used. Both failures were in female octogenarians. CONCLUSIONS: To realize the advantages of a thoracoscopic ITA mobilization MIDCAB, both right and left thoracoscopic ITA mobilization can safely be performed in the redo situation. Thoracic adhesions precluding a thoracoscopic approach were encountered in only 1 of 11 redo coronary artery bypass grafting patients.

Aged↗