Biomedical subjects

M Komeda

Publications and source records attributed to M Komeda.

133 records · Page 8Linked to original sources

PubMedDate not supplied

Results of chronic animal experiments with a new version of a magnetically suspended centrifugal pump.

We have developed a magnetically suspended centrifugal pump (MSCP) for long-term ventricular support. This study reports results of chronic animal experiments using a new version of the MSCP. Three sheep weighing 50-70 kg were used in this study. A left heart assist system was established with cannulas into the descending aorta and the left ventricular apex. In two sheep the MSCP was positioned outside the body and in one sheep implanted on the chest wall. The pumping flow was estimated by the motor current and motor speed. The temperature of the pump and the muscle near the pump was recorded for 10 days after operation. The duration of continuous pumping was 60, 140, and 230 days+ (ongoing), respectively. The cause of termination was infection associated with thrombus formation in the first, and failure of magnetic suspension in the second sheep. No thrombus or embolus was observed after sacrifice of the second sheep. The third sheep has been going well despite skin necrosis around the pump pocket. The estimation of pumping flow was reliable even at 140 days. Temperature of the pump surface was 42 degrees C immediately after the operation and gradually reduced to 41 degrees C. The MSCP is a reliable pump for long-term circulatory assist.

Animals↗

PubMedDate not supplied

Hemodynamics on abrupt stoppage of centrifugal pumps during left ventricular assist.

A magnetically suspended centrifugal pump (MSCP), developed for long-term ventricular assist, is reliable and durable because it has no shaft or seal. However, with nonvalve pumps such as a MSCP, regurgitation occurs when they accidentally stop without cannula clamping. We investigated the hemodynamics during temporary stoppage of a MSCP being used as a left ventricular assist system (LVAS), comparing two inflow cannulation sites. In four sheep (weight, 35-45 kg), microspheres were injected into the left main coronary artery to induce heart failure. An outflow cannula was sutured onto the descending aorta, and two inflow cannulae were inserted into the left atrium and the left ventricle. The MSCP was stopped with both the left ventricular cannula and left atrial cannula clamped, and the hemodynamics and P-V loops were recorded. Each cannula was then unclamped in order, and similar parameters were recorded. LVEDP increased at unclamping of the left ventricular cannula (ULVC), and rose further at unclamping of the left atrial cannula (ULAC). Aortic pressure did not change at ULVC, but decreased at ULAC. The effective systemic flow that subtracted the regurgitant flow through the MSCP from left ventricular output was half at ULVC and almost 0 at ULAC. When stopping centrifugal pumps without circuit clamping, hemodynamic deterioration is less at ULVC than at ULAC. This finding suggests that left ventricular inflow cannulation is recommended to allow more time in emergency situations.

Animals↗

PubMedDate not supplied

How good is the radial artery as a bypass graft?

The radial artery is being used with increasing frequency to replace the saphenous vein as a coronary artery bypass graft, on the basis of the belief that it will provide improved long-term patency. Innovative techniques in assessing the ulnar collateral circulation to the hand continue to evolve, giving comfort to the surgeon. Several centres have confirmed that the early results of surgery using the radial artery are similar to those using conventional grafts. Few late graft patency results or clinical data have been reported. Unresolved issues, such as the importance of pathological changes in the radial artery, the prevention of spasm, and the hypoperfusion syndrome, lurk in the background. The role of the radial artery continues to evolve.

Coronary Artery Bypass↗

PubMedDate not supplied

PMEA coating of pump circuit and oxygenator may attenuate the early systemic inflammatory response in cardiopulmonary bypass surgery.

We investigated the effects of coating a cardiopulmonary bypass (CPB) circuit and oxygenator with poly-2-methoxy-ethyl acrylate (PMEA) on the systemic inflammatory response during and after CPB. Thirty patients undergoing elective cardiac surgery were randomized into three groups (each group n = 10): noncoated (group N), heparin coated (group H), and PMEA coated circuit and oxygenator (group X). Bradykinin (BK), complement 3 activation (C3a) and interleukin-6 (IL-6) levels were measured as early phase indicators of inflammatory response, as were maximum C reactive proteins (CRP) and white blood cell (WBC) levels. The alveolar-arterial oxygen gradient (A-a DO2) was measured as a parameter of respiratory function. IL-6 levels after CPB were significantly higher in group N than in groups H and X (p < 0.05). Serum BK and C3a levels showed similar patterns in all groups. A-a DO2 was lower at the end of and 3 hours after CPB in groups H and X than in group N (p < 0.05). Maximum CRP levels were lower in group X than in groups N (p < 0.05). This prospective study suggests that PMEA coated CPB may improve respiratory function and decrease systemic inflammatory response after cardiac surgery, possibly because this circuit is as biocompatible as heparin coated CPB circuit.

Acrylates↗

PubMedDate not supplied

A rat model of dilated cardiomyopathy to investigate partial left ventriculectomy.

BACKGROUND: This study is the first to assess a small animal model of dilated cardiomyopathy (DCM) for evaluation of partial left ventriculectomy. METHOD: Eighteen Dahl salt-sensitive (DS) rats were divided into three groups. Six rats were fed an 8% high-salt diet from the age of 7 weeks (Group 1), and similarly six rats from 8 weeks (Group 2) and six from 9 weeks (Group 3). Blood pressure (BP) was measured by the tail-cuff method and left ventricular (LV) dimensions by echocardiography. RESULTS: In Groups 1 and 2, systolic BP rose and reached 200 mmHg by the 10th to 11th week, when all rats died within a week without signs of heart failure. However, in Group 3, systolic BP gradually rose to 196+/-15 mmHg (mean +/- SD) at the age of 14 weeks, when LV end-diastolic diameter (EDD) was 6.2+/-0.4 mm (control 5.1+/-0.7 mm) and LV fractional shortening (FS) was 77+/-3% (control 68+/-3%). At the age of 25 to 30 weeks, all rats in Group 3 showed signs of congestive heart failure, systolic BP remained high, EDD markedly increased (8.7+/-0.6 mm), and LVFS decreased (38.9+/-8.1%). From this stage, rats survived for 13.7+/-5.9 days. We employed the Group 3 model for our pilot PLV study. Eight rats had PLV with a beating heart by plicating the LV area between the papillary muscle bases. Two rats died perioperatively but the rest survived (60% survival 3 weeks after PLV). Postoperatively, the rats' LVEDD decreased and FS improved significantly. CONCLUSIONS: Using DS rats, we developed a DCM model for investigating PLV. The model may contribute to scientific investigation of PLV.

Animals↗

PubMedDate not supplied

Repair of intracardiac defects associated with congenitally corrected transposition of the great arteries.

From October 1976 to June 1986, 12 patients with corrected transposition of the great arteries (c-TGA) underwent repair of associated intracardiac defects. Ventricular septal defect (VSD) was closed by the method of de Leval in 7 patients, pulmonary outflow tract obstruction was relieved by valvotomy in 2, and bypassed by an external valved conduit in 6. The systemic atrioventricular (A-V) valve was replaced in 2. There was one operative death, giving a mortality rate of 8%. None of the patients developed complete heart block. The ejection fraction of the systemic ventricle was impaired (29-38%), particularly after ventriculotomy of this chamber. Surgical repair of intracardiac defects associated with c-TGA currently can be performed with acceptable risk, and de Leval's method for VSD closure is recommended; but the possibility of the postoperative development of systemic ventricular dysfunction and A-V valve regurgitation necessitates careful follow-up.

Adolescent↗

PubMedDate not supplied

Sinus of Valsalva repair for annulo-aortic ectasia and aortic insufficiency.

OBJECTIVE: The standard treatment of ascending aortic aneurysms (AsAAs) with annulo-aortic ectasia and aortic insufficiency has been composite graft replacement of the valve and ascending aorta. The authors propose a method of repair which preserves the native aortic valve and correct the aneurysmal dilation of the sinus of Valsalva yet preserves its normal shape. PATIENTS/INTERVENTIONS: Two patients with large AsAAs and severe aortic insufficiency had operative repair by plication of the sinuses of Valsalva which maintained the normal sinus shape and restored coaptation of the aortic leaflets. MAIN RESULTS: Late postoperative echocardiography revealed only mild aortic insufficiency in both patients and no evidence of further sinus dilation. CONCLUSIONS: Repair of the sinus of Valsalva preserves the aortic valve and native coronary ostia, can correct existing aortic insufficiency and can provide a good functional result without the need for anticoagulation.

Adult↗