Biomedical subjects

H Koyanagi

Publications and source records attributed to H Koyanagi.

At least 73 records · Page 4Linked to original sources

PubMed1999

Ex vivo evaluation of a roller screw linear muscle actuator for an implantable ventricular assist device using trained and untrained latissimus dorsi muscles.

In this study, the power output and contraction length of trained and untrained canine latissimus dorsi (LD) muscles were measured using a roller screw linear muscle actuator (RSLMA). The RSLMA consisted of a roller screw-nut assembly and translation unit to convert the linear pull force of the muscle into an axial displacement of the roller screw. When a cable wound around a spool attached at each end of the roller screw nut was pulled in either direction, the nut was rotated which in turn advanced the roller screw in the axial direction. Under anesthesia, a Telectronics myostimulator (Model 7220) was implanted in the subcutaneous area of the canine left thoracic region with its bipolar intramuscular leads implanted around the thoracodorsal nerve and the distal muscle. A total of 6 dogs went through the myostimulator implantation, followed with 8 weeks of continuous stimulation. After completion of the training, the contraction lengths of the trained and untrained LD muscles were measured, and they were 4.25 and 5.5 cm, respectively, while the instantaneous power outputs were 4.24 and 8 W, respectively. Although untrained muscles could provide much higher instantaneous power immediately following the start of the stimulation, it diminished rapidly. On the other hand, the trained muscle showed prolonged fatigue resistance. The thoracolumbar and humeral approaches in attaching the actuator cable did not show a difference with respect to muscle power output. The trained LD muscle can provide sufficient power in the range of 3-4 W to drive a left heart assist device, but its long-term evaluation awaits development of an appropriate muscle-device interface for chronic in vivo application.

Animals↗

PubMed1999

Cardiac autonomic nervous function during long-term nonpulsatile left heart bypass.

We investigated the changes in cardiac autonomic nervous activities during long-term nonpulsatile left heart bypass (NLHB) by analyzing heart rate variability. A pulsatile ventricular assist device was installed in 3 goats, and pulsatile left heart bypass (PLHB) was conducted for 2 weeks. Then, NLHB was maintained for the following 4 weeks. The segmental data of the R-R intervals (R-Rs) was analyzed by maximum entropy spectral analysis. Changes in evaluated parameters from the last week of PLHB to the 4th week of NLHB were as follows: the mean R-Rs increased from 511 ms to 692 ms; the coefficient of variation of R-R increased from 10.2 to 14.1%; the power of the low frequency band (LF) increased from 747 ms2 to 2,855 ms2; the power of the high frequency band (HF) increased from 512 ms2 to 1,270 ms2; and the ratio of LF to HF increased from 2.6 to 6.5. These results indicated that the cardiac autonomic nervous activity, both sympathetic and parasympathetic, increased during long-term NLHB.

Analysis of Variance↗

PubMed1999

Long-term in vivo left ventricular assist device study for 284 days with Gyro PI pump.

A totally implantable centrifugal artificial heart has been developed. The plastic prototype, the Gyro PI 601, passed 2 day hemodynamic tests as a functional total artificial heart (TAH), 2 week screening tests for anti-thrombogenecity, and a 1 month system feasibility study. Based upon these results, a metallic prototype, the Gyro PI 700 series, was subjected to long-term in vivo left ventricular assist device (LVAD) studies of over 1 month. The Gyro PI 700 series has the same inner dimension and same characteristics of the Gyro PI 601 such as an eccentric inlet port, a double pivot bearing system, and a magnet coupling system. The PI metallic pump is also driven with the Vienna DC brushless motor actuator like the PI 601. The pump-actuator package was implanted in 3 calves in the preperitoneal space, bypassing from the left ventricular (LV) apex to the descending aorta. Case 1 achieved a 284 day survival. Case 2 was euthanized early at 72 postoperative days as a result of the functional obstruction of the inlet port due to the excessive growth of the calf. There was no blood clot inside the pumps of either case. Case 3 is on-going (22 days on July 24, 1998). During these periods, all cases showed no physiological abnormalities. In conclusion, the PI 700 series pump has excellent results as a long-term implantable LVAD.

Animals↗

PubMed1999

Comparative study of biocompatibility between the open circuit and closed circuit in cardiopulmonary bypass.

The theoretical benefit of a centrifugal pump or heparin coating demonstrated through in vitro or in vivo studies is not recognizable in cardiopulmonary bypass (CPB) during chemical open heart surgery. The objective of this study was to investigate the influence of the interface of air and blood in current CPB with an open circuit system and its relative significance in relationship to the heparin dose and heparin coating. Using the same oxygenator and circuit, an open circuit and closed circuit CPB with the same priming volume were prepared for a 4 h perfusion experiment using diluted and heparinized (3.6 U/ml) fresh human blood. In these experiments, both heparin-coated and noncoated circuits were examined. Blood was sampled before and 2, 30, 60, 120, and 240 min after the start of perfusion, and the platelet and white blood cell counts and beta-thromboglobulin (beta-TG) and C3a levels were measured. The amount of adsorbed protein in the hollow fibers was also measured after retrieval. Although the results demonstrated significantly better biocompatibility of the heparin-coated circuit than the noncoated circuit, the difference between the open and closed circuits was unexpectedly small and insignificant with either the heparin-coated circuit or noncoated circuit. In contrast, the C3a level was higher in the closed circuit than the open circuit. However, the amount of adsorbed protein was markedly lower in the closed circuit (0.7 microgram/cm2) than in the open circuit (11.1 micrograms/cm2). An immunoblot of the adsorbed protein showed a higher density of fibrinogen bands and conversion to fibrin in the open circuit. We speculate that the lower blood C3a level in the open circuit suggests that C3a was taken in by the adsorbed protein. In conclusion, analysis of the adsorbed protein indicates the lower biocompatibility of the open circuit. Similar experiments with less heparin use and more severe conditions will be necessary to elucidate the essential benefit of making a CPB closed circuit.

Adsorption↗

PubMed1999

An emergency balloon occlusion system for a rotary blood pump left ventricular assist system.

A fatal outcome is expected in a left ventricular assist system (LVAS) utilizing a rotary blood pump if there is no mechanism to prevent the backflow from the aorta to the heart in the case of acute pump failure. To solve this problem, a passive mechanical clamping system at the outflow graft of a rotary blood pump was developed together with Fuji Systems, Inc., Yokohama, Japan. The system consisted of an emergency clamp port and an occlusion balloon. The balloon was fixed around the outlet graft of the LVAS. In an in vitro study, a fail-safe clamping operation with 2 ml saline injection under 7 L/min flow against 140 mm Hg pressure reduced the flow to 0.5 L/min while the pressure in the system increased to 190 mm Hg. The systems were also applied to 2 in vivo LVAD studies. When the pumps were stopped, there were approximately 3.0 L/min regurgitant flows. The balloon occluder prevented this regurgitant flow effectively against a 100/80 mm Hg arterial pressure. In conclusion, this emergency balloon occlusion system is relatively easy to operate and will work efficiently in all possible clinically encountered malfunctions of the rotary blood pump LVAS.

Animals↗

PubMed1999

Sealing properties of mechanical seals for an axial flow blood pump.

A miniature intraventricular axial flow blood pump for left ventricular support is under development. One of the key technologies required for such pumps is sealing of the motor shaft. In this study, to prevent blood backflow into the motor side, mechanical seals were developed and their sealing properties investigated. In the experimental apparatus, the mechanical seal separated the bovine blood on the chamber side from the cooling water on the motor side. A leakage of the blood was measured by inductively coupled plasma (ICP) light emission analysis. The rate of hemolysis was measured by the cyanmethemoglobin method. Frictional torque acting on the shaft was measured by a torque transducer. In the experiments, the rotational speed of the shaft was changed from 1,000 to 10,000 rpm, and the contact force of the seal faces was changed from 1.96 to 4.31 N. To estimate lubrication regimes, the Stribeck curve, a diagram of the coefficient of friction against the bearing characteristic G number, was drawn. The results of the experiments showed that both the leakage of blood and the rate of hemolysis were very small. The friction loss was also very small. The mechanical seal was operated in various lubrication regimes, from a fluid lubrication regime to a mixed lubrication regime.

Animals↗

PubMed1999

Rotary blood pump flow spontaneously increases during exercise under constant pump speed: results of a chronic study.

Many types of rotary blood pumps and pump control methods have recently been developed with the goal of clinical use. From experiments, we know that pump flow spontaneously increases during exercise without changing pump control parameters. The purpose of this study was to determine the hemodynamics associated with the long-term observation of calves implanted with centrifugal blood pumps (EVAHEART, Sun Medical Technology Research Corporation, Nagano, Japan). Two healthy female Jersey calves were implanted with devices in the left thoracic cavity. A total of 22 treadmill exercise tests were performed after the 50th postoperative day. During exercise, the following parameters were compared with conditions at rest: heart rate, blood pressure, central venous oxygen saturation (SvO2), pump speed, and pump flow. The pump flow in a cardiac cycle was analyzed by separating the systole and diastole. Compared to the base data, statistically significant differences were found in the following interrelated parameters: the heart rate (66.8 +/- 5.2 vs. 106 +/- 9.7 bpm), mean pump flow (4.8 +/- 0.2 vs. 7.0 +/- 0.3 L/min), and volume of pump flow in diastole (26.0 +/- 1.8 vs. 13.5 +/- 2.5 ml). During exercise, the volume of pump flow in systole was 3 times larger than that measured in diastole. Blood pressure, SvO2, and pump speed did not change significantly from rest to exercise. These results suggested that the mean pump flow depends on the systolic pump flow. Therefore, the increase in the mean pump flow during exercise under constant pump speed was caused by an increase in the heart rate.

Animals↗

PubMed1999

Effects of immunosuppressants on platelet-derived growth factor-A chain mRNA expression and coronary arteriosclerosis in rat cardiac allografts.

Graft coronary arteriosclerosis (GCA) that results in proliferative and obstructive lesions limits the long-term success of cardiac transplantation. Despite extensive study, the pathogenic mechanisms underlying GCA are still unclear and therapeutic strategies for this condition have been inadequate. In this study, we compared the therapeutic effectiveness of cyclosporine A (CsA), 15-deoxyspergualin (DSG), and Multiglycosidorum tripterygii (MT) on GCA. In addition, we studied the correlation between the extent of GCA and the degree of platelet-derived growth facter (PDGF)-A chain mRNA expression in cardiac grafts. Lewis rats receiving heterotropic heart transplants from Wistar King donors were treated with 10 mg kg(-1) day(-1) of CsA (n=7), 5 mg kg(-1) day(-1) of DSG (n=7) or 30 mg kg(-1) day(-1) of MT (n=7) respectively. Histological evaluation of coronary arteriosclerosis and Northern blot analysis of cardiac allograft PDGF-A chain mRNA expression were conducted on day 60 after transplantation. Varying levels of GCA were observed in the 21 transplanted hearts. Significant differences in both the degree of PDGF-A mRNA expression and the extent of GCA were found among the 3 groups. GCA was significantly reduced in allografts treated with MT or DSG in comparison with the level seen in CsA-treated grafts. A significant correlation was found between PDGF-A chain mRNA expression and the grade of arterial intimal thickening (r=0.76, p<0.05) as well as with the incidence of diseased vessels (r=0.82, p<0.01). Our results indicate that both MT and DSG are more effective in the treatment of GCA than CsA. In our cardiac allografts, the degree of PDGF-A chain mRNA expression correlated well with the extent of GCA, suggesting that PDGF-A may play an important role in the development of transplant-related GCA.

Animals↗

PubMed1999

[A case report of a coronary fistula from left coronary artery to left ventricle].

The patient is a 44-year-old man. He has had chest pain on effort since 1994, diagnosed as unstable angina in 1996. He was found to have three vessel disease on coronary angiography and was sent to TWMC for operation. CABG was performed for the right and left anterior descending arteries, and TMLR for the posteroinferior region because the left circumflex artery was fine and ungraftable. Both the grafts were patent and there was improved LV function. Interestingly, we found a coronary fistula running from the left coronary artery to the left ventricle. As far as we can tell from our literature searches, this is the first time that a coronary fistula has been found after TMLR.

Adult↗

PubMed1999

[Mitral valve replacement under cardiopulmonary bypass which complicated by multiple sclerosis: a case report].

The 60-year-old women who complicated by multiple sclerosis was referred to our hospital under diagnosis of mitral valve stenosis and tricuspid valve regurgitation. The mitral valve replacement and the tricuspid valve annuloplasty were performed under cardiopulmonary bypass. In the state of multiple sclerosis, even an operation by general anesthesia could become a cause of abrupt change, but by appropriate management during and after surgery, the post operative course was uneventful without any complications, and the patient discharged on the 35th post operative day.

Cardiopulmonary Bypass↗

PubMed1999

[Complete arterial revascularization in emergency CABG].

Between August 1987 and November 1998, 137 patients underwent emergency CABG within 24 hours from the notification of cardiologist. Among them, 37 patients (27%) (34 men, 3 women) with a mean age of 59.9 (range, 39-76) underwent multiple CABG with exclusive use of arterial conduits. Preoperative diagnosis was acute myocardial infarction in 20 patients and unstable angina in 17 patients. Twenty-nine patients (78%) had either triple vessel or left main disease. There were 3 redo CABG and 3 patients were on hemodialysis. Postoperative follow-up averaged 44 months. Twenty-nine patients (78%) were under IABP support preoperatively. The mean number of anastomoses was 2.65 (range, 2-5). One patient (2.7%) died of persistent heart failure 54 days postoperatively. The patency was confirmed angiographically in 33 patients 3-4 weeks after surgery. Overall patency was 90.6% (LITA: 93.0%, RGEA: 76.2%, RITA, radial: 100%). There were no late deaths or redo CABG, and 2 patients sustained myocardial infarction and 3 patients underwent PTCA during follow-up. Five-year actuarial survival rate was 97.1% and cardiac event-free rate was 75.7%. These excellent early and long-term results suggest that complete arterial grafting for emergency CABG should be considered as a primary treatment in patients who have multivessel or left main disease, and no ongoing profound cardiogenic shock or rapid deterioration.

Adult↗

PubMed1999

[Efficacy of terminal warm blood cardioplegia in combination with Bretschneider-HTK solution for myocardial protection].

Many reports indicated that terminal warm blood cardioplegia (TWBC) was useful for reduction of the reperfusion injury in cardiac operations. We introduced Bretschneider-HTK solution (B-HTK) from April 1992, and combined use of the TWBC and the B-HTK was performed from May 1996. The purpose of this study was to evaluate clinical efficacy of the TWBC in combination with B-HTK for myocardial protection. In patient with valve operations from May 1995 to May 1997, clinical results were compared between the B-HTK with TWBC group (34 patients) and the B-HTK alone group (37 patients). Between two groups, there was no significant difference in patient characteristics, preoperative NYHA class, cardiopulmonary bypass time, aortic cross clamp time, minimum rectal temperature, rewarming and circulatory support time, incidence of IABP and blood concentration of max CPK, max GOT. Furthermore, the cardiac index in 1 postoperative day showed some trend to be higher in the combined TWBC group than that in the B-HTK alone group. But there was no significant difference between two groups in the LV shortening fraction at 14 postoperative day. Incidence of DC defibrillation was significantly lower in the combined TWBC group than that in the B-HTK alone group. These results suggested that combination of the TWBC might be useful for reduction of the reperfusion injury following myocardial protection with B-HTK solution.

Aged↗

PubMed1999

New graft holder for coronary artery bypass using arterial conduits.

An arterial graft holder was designed to facilitate coronary artery bypass surgery. It can be used to open the heel of arterial conduits and it immobilizes the graft with a spring clamp. The tip of the holder is made from flexible, silicon-coated vinyl chloride tubing, so that it can be inserted into the arterial lumen without causing endothelial injury.

Anastomosis, Surgical↗

PubMed1999

[A case report of total aortic reconstruction and choice of staged operation in Marfan syndrome].

A 37-year-old man with Marfan syndrome underwent four operations for extensive cardiovascular disease. He was diagnosed as having AAE, AR and DeBakey type I aortic dissection. First, Bentall operation using Piehler procedure and total aortic arch replacement using retrograde cerebral perfusion and profound hypothermia at 18 degrees C were performed on May 11, 1994. Second, repair of leakage of the right coronary artery anastomosis and grafting for the descending thoracic aortic aneurysm were performed on December 3, 1994. Y-type grafting for the AAA was performed on December 21, 1996. Last, grafting for TAAA was performed under hypothermia at a rectal temperature of 20 degrees C on November 17, 1997. This surgical strategy of staged operation for extensive cardiovascular disease in Marfan syndrome is an effective method. Regular follow-up by CT is necessary for deciding the time and method of reoperation.

Adult↗

PubMed1999

[Optimum anticoagulation control after bileaflet mechanical valve replacement: a prospective multi-institutional study].

This study was undertaken to assess optimum anticoagulation control after bileaflet mechanical valve replacement by using the international normalized ratio of prothrombin time (PT-INR). From January to December 1995, 261 patients (pts) underwent mechanical valve replacement in the aortic (n = 95), mitral (n = 126), aortomitral (n = 39) or isolated tricuspid (n = 1) valve position in 8 medical centers in Tokyo, Japan. The St. Jude Medical valves were implanted in 184 pts and the Carbomedics valves in 77. There were 17 valve-related events as follows: 11 thromboembolic events (3.62%/pt-yr) including 10 transient ischemic attacks. 5 non-fatal bleeding events (1.65%/pt-yr), 2 reoperations (0.66%/pt-yr). At 18 postoperative months, free rates from all deaths (actuarial survival) thromboembolism, reoperation and all valve-related events were 95.3%, 95.7%, 98.7% and 88.9%, respectively. Under anticoagulant therapy, thrombin-antithrombin III complex and D-dimmer remained in high levels at 1 month after operation, and both values decreased to the control level at 6 months. In patients with thromboembolic events, PT-INR tended to be less than 2.0. The patients with bleeding events showed some increase of PT-INP or received anti-platelet agents. The 5 to 95 percentile of PT-INR at 6 months was 1.2 to 3.0 in the patients without valve-related events. These results suggested that optimum range of PT-INR might be between 1.2 and 3.0 after bileaflet mechanical valve replacement in patients without high risk of thromboembolism and between 2.0 and 3.0 in patients with the high risk.

Adolescent↗

PubMed1999

[A successful surgical case of billowing mitral leaflet syndrome (Barlow syndrome) combined with severe mitral regurgitation].

We report a successful surgical case of billowing mitral leaflet syndrome combined with severe mitral regurgitation. A 45-year-old man suffered from congestive heart failure and admitted our institution for precise examination. A heart murmur was pointed out by a medical examination at his high school, and mitral valve prolapse was detected by echocardiography at 23 year of age. No medication was applied because he showed no symptom. From 44 year of age, he noted palpitation on exercise. Holter monitor showed blocked PAC and Wenckebach A-V block, and transesophageal echocardiography indicated severe mitral regurgitation due to the billowing of voluminous both leaflets. At his operation, we recognized the billowing of both leaflets with torn chordae, and size of the mitral valve orifice was 8.5 x 5 cm. The huge mitral valve was replaced with a CarboMedics 31M prosthetic valve by plicating mattress stitches of native mitral annulus. Histopathologic findings showed accumulation of acid mucopolysaccharide. Postoperative echocardiography showed reduction of the left ventricular volume and preservation of the left ventricular function. Relatively slow progression of the billowing mitral leaflet syndrome did not cause apparent symptoms of heart failure in this patient. Therefore, proper selection of the procedure and timing of surgical treatments might be important for successful long-term results after operation of the billowing mitral leaflet syndrome.

Cardiac Surgical Procedures↗

PubMed1999

Two new drainage tubes for minimally invasive cardiac surgery.

BACKGROUND: The limited exposure typical of new minimally invasive surgical approaches to cardiac surgery makes it difficult to utilize traditional equipment such as temporary pacing electrodes or the placement of drainage tubes into the lateral pleural space. To overcome these difficulties, we have developed specialized drainage tubes just for limited access cardiac surgery. METHODS: The first device is a drainage tube with temporary pacing function. It has three fixed electrodes and one free pacing wire incorporated into an elliptical, angled 28 Fr silicone drainage tube. This tube is placed in the space between the heart and the diaphragm. The two fixed electrodes provide epicardial contact for ventricular pacing. The third fixed electrode and one free pacing wire are for the purpose of atrial pacing (Japanese patent #2,701,135). The second device is a Y-shaped drainage tube. Frequently, the pleural space is opened during harvesting of an internal mammary graft and then insertion of a chest tube in the thoracic cavity becomes necessary. We developed a new Y-shaped tube where one segment is placed in the retrosternal space and one segment is placed in the pleural cavity. (Japanese Association of Intellectual Copyright #130,591) RESULTS: The drainage-pacing device was used in 48 coronary artery bypass grafting (CABG) patients. Drainage function and pacing function were excellent in all patients. The bifurcated drainage device was used in 34 patients achieving effective drainage of both cavities without complication during or after removal. CONCLUSIONS: Due to the limited surgical exposure provided by the newer minimally invasive procedures in cardiac surgery, specialized equipment that can be inserted through small incisions needs to be developed. We report the development of a new drainage-pacing device as well as a bifurcated drain for simultaneous drainage of the mediastinal and pleural cavities. These devices have facilitated minimally invasive cases and were free of complications.

Coronary Artery Bypass↗

PubMed1998

Inhibitory effect of Multiglycosidorum tripterygii on coronary arteriosclerosis after heart transplantation.

BACKGROUND: Graft coronary arteriosclerosis (GCA) is the major limiting factor for long-term survival after heart transplantation. In this study, we investigated the effect of Multiglycosidorum tripterygii (MT) on GCA and platelet-derived growth factor A (PDGF-A) mRNA expression of transplanted hearts. METHODS: Two groups of Lewis rats (n=7/group) underwent heterotopic heart transplantation from Wistar-King donors and were treated with either cyclosporine (CsA;10 mg/kg/day) or MT (30 mg/kg/ day). Histological evaluations of rejection and coronary arteriosclerosis, as well as Northern blot analysis on graft PDGF-A mRNA expression were made 60 days after transplantation. RESULTS: Morphometric results indicated no significant difference in rejection between the CsA- and MT-treated groups. However, the extent of GCA in the MT-treated group was significantly less than that seen in the CsA-treated group (P<0.01). The expression of PDGF-A mRNA of cardiac allograft was also significantly suppressed in the MT-treated group when compared with the CsA-treated group (P<0.01). CONCLUSION: MT is superior to CsA in preventing graft coronary arteriosclerosis, and this efficacy is probably associated with the depressed expression of graft PDGF-A mRNA in the MT-treated group.

Animals↗