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Biomedical subjects

E Imamura

Publications and source records attributed to E Imamura.

At least 37 records · Page 2Linked to original sources
PubMed1988

In vitro analysis of performance of porcine xenografts with inward bending of stent posts: real-time measurement of valve orifice area using an area meter.

The influence of inward bending of the stent posts on bioprosthetic valve function was assessed in a hydromechanical simulation of the left heart. A Carpentier-Edwards mitral xenograft (31 mm) and an aortic xenograft (27 mm) were used. Valve function was evaluated before and after the stent posts were bent inward 15 degrees by suture constriction of the tops of the three posts. To evaluate the effects of the stent-post deformity on valve performance, the mean transvalvular pressure drop during steady flow, the bioprosthetic valve orifice area, and the maximum valve opening and closing speeds during pulsatile flow were measured using an area meter. Steady-flow data showed identical transvalvular pressure drops, and no significant difference in valve performance was detected in the pulsatile-flow study under the two experimental conditions (i.e., normal valve and deformed valve). We conclude that a 15-degree inward bending of the stent posts does not appreciably affect valve function in vitro.

Aortic Valve↗
PubMed1988

[Long-term results of porcine bioprosthetic heterograft; a 13-years' experience].

One hundred and ninety-four patients underwent valve replacements with the glutaraldehyde-preserved porcine bioprostheses (133 Hancock valves, 39 Angell-Shiley valves, 22 Carpentier-Edwards valves and 3 other valves) from 1974 through 1979. There were 105 women and 89 men, whose age ranged 18 to 62 (mean 38.8) years. One hundred and eighty-two patients had mitral bioprosthetic valve replacement (BVR)s, of which 52 had combined aortic mechanical valve replacements, 8 had aortic BVR's, 3 had tricuspid BVR's and 3 had multi-BVR's. Operative mortality was 10.8%. Only one patient was lost to follow-up. Cumulative duration of follow-up is 1421 patient-years. Linearized rate of anticoagulant related hemorrhage, thromboembolism (TE), prosthetic valve endocarditis (PVE), primary tissue failure (PTF) and valve dysfunction (VD) were 0.07, 1.62, 0.49, 2.74 and 3.66% per patient-year. Actuarial freedom from TE, PVE, PTF and VD were 87.0 +/- 2.7%, 95.6 +/- 1.5%, 65.2 +/- 4.9% and 56.9 +/- 5.6% at 13 years. Actuarial survival rate was 67.4 +/- 4.0% at 13 years. Long term follow-up after valve replacement with porcine bioprosthetic valve confirms low thrombogenicity. But primary tissue failure was the chief cause of valve dysfunction and represent a major problem. At this time, we are going to use porcine bioprosthetic valve in the selected patients, that is in the situations in which anticoagulation is contraindicated.

Adolescent↗
PubMed1988

[Limitations and extension of surgical indications for acquired valvular heart disease; retrospective study of hospital death].

Between 1981 and 1987, valvular surgery was performed in 988 patients, 27 of which were dead before discharge. Among them, 14 patients of cardiac deaths due to low cardiac output syndrome (LOS) and arrhythmias were analyzed to withdraw factors correlated with their cause of death. There was a tendency for the patients with stenotic valvular disease to die of LOS and regurgitant valvular lesions of arrhythmias. Statistical analysis showed the cause of deaths were multifarious including pulmonary, hepatic and renal failure, so no definite factor was pointed out. Case study of typical limited and extended surgical indications revealed (1) the patients with mitral stenosis combined with organic tricuspid regurgitation and RV/LV EDVI ratio over 1.5, and (2) the patients with aortic insufficiency and LVEDVI over 400 ml/m2 or LVESVI over 300 ml/m2 were candidate for hospital death after valve replacement. Extended approach for those patients should be two staged heart transplantation using ventricular assist device.

Adult↗
PubMed1988

[Clinical study of "stent creep" in porcine bioprosthesis].

Stent creep is often associated with malfunction of bioprosthesis. We measured the inward bending angle of the stent-post showing maximum bending (IBA) on 42 mitral porcine xenografts retrieved 1 to 12 yrs (mean 7.7 yrs) postoperatively at reoperation. Patients were 12 men and 28 women, ranging in age from 26 to 58 yrs. Mean +/- S.D. for IBA was 12.7 +/- 4.2 degrees(ds) in 14 valves being implanted for less than 7 yrs and 16.9 +/- 5.5 ds in 28 valves longer than 8 yrs (p less than 0.05). There was a significant difference in IBA between 36 valves of 25-29 mm size (16.3 +/- 5.1 ds) and 6 valves of 31 mm (10.3 +/- 5.5 ds) (p less than 0.05), but no significant difference between 23 Hancock valves (15.5 +/- 4.4 ds), 10 Angell-Shiley valves (16.2 +/- 8.6 ds) and 9 Carpentier-Edwards valves (14.4 +/- 3.7 ds). IBA showed a tendency to have large valve in the heart with small left ventricular end-systolic volume. The results showed that stent creeping phenomenon was not related to the material or design of stent-post, but tended to increase with passage of time in place. Furthermore, it was suggested that stent creep was induced by the mechanism of compression of the stent by the left ventricular wall.

Adult↗
PubMed1987

Cell-mediated and humoral immune response to non-viable Mycoplasma pulmonis in mice enhanced by cross-linked ricin.

The enhancing effect of cross-linked ricin (CL-ricin) on the cell-mediated and humoral immune response of mice to non-viable Mycoplasma pulmonis was studied. The cell-mediated immune response was evaluated by means of the delayed-type footpad swelling, and the humoral immune response by means of the indirect hemagglutination test. Mice pre-treated subcutaneously with non-viable M. pulmonis and CL-ricin showed significantly increased delayed-type footpad swelling when they were injected in the footpad with the same antigen 7 days later. Delayed-type footpad swelling was not detected in mice pre-treated only with non-viable M. pulmonis or CL-ricin followed by footpad injection with non-viable M. pulmonis. Injection of non-viable M. pulmonis in the footpad on Days 3, 7, 14, 21, 28, 35 and 42 after pre-treatment with non-viable M. pulmonis and CL-ricin resulted in significant footpad swelling. Delayed-type footpad swelling was transferred by intravenous injection of spleen cells from mice which had been pre-treated 7 days previously with non-viable M. pulmonis and CL-ricin into non-treated recipient mice. Intravenous injection of anti-mouse thymus cell serum into mice previously pre-treated with non-viable M. pulmonis and CL-ricin reduced the delayed-type footpad swelling significantly. Mice pre-treated subcutaneously with non-viable M. pulmonis and CL-ricin showed a marked increase in serum antibody titers compared with those that received non-viable M. pulmonis alone.

Adjuvants, Immunologic↗
PubMed1987

Six-year experience with the St. Jude Medical prosthesis: early and late results of 540 valves in 462 patients.

From July 1978 to June 1984, 540 St. Jude Medical valve prostheses were implanted in 462 adult patients. Overall operative mortality was 4.8% (22/462): 5.7% after aortic valve replacement (AVR) (8/140); 3.3% after mitral valve replacement (MVR) (8/244); and 7.7% after aortic and mitral valve replacement (DVR) (6/78). There were 16 late deaths among 440 operative survivors; six (38%) were valve related. The actuarial survival rate at six years was 94.5% in AVR and 93.5% in MVR. At five years it was 91.6% in DVR. The freedom from valve-related death at six years after AVR, MVR and at five years after DVR was 97.8%, 98.6% and 95.8%, respectively. The incidence of valve-related complications (expressed as %/patient-year (number of events] was as follows: thrombo-embolism (AVR 0.7 (2), MVR 2.0 (13), DVR 2.8 (5], valve thrombosis (AVR 0.3 (1), MVR 0.2 (1), DVR 0 (0], prosthetic valve endocarditis (AVR 0.3 (1), MVR or DVR 0 (0]. There were no cases of primary structural failure, serious anticoagulant-related hemorrhage or clinical event of hemolysis. The incidence of all valve-related complications in AVR, MVR and DVR was 1.3, 2.2 and 2.8%/pt-yr, respectively. The freedom from thrombo-embolism at six years after AVR and MVR and at five years after DVR were 91.4%, 92.4% and 88.7%, respectively. Re-operation was performed in only one patient with MVR because of valve thrombosis (0.2%/pt-yr after MVR, overall 0.1%/pt-yr). These results indicate that St. Jude Medical prosthesis has provided a satisfactory performance with acceptable risks of late complications in patients who were properly anticoagulated during six-year follow-up period.

Adolescent↗
PubMed1987

A comparative analysis of left ventriculography and root aortography for estimating aortic annular size.

This study was undertaken to compare the usefulness of left ventriculography versus root aortography as a means of assessing the aortic annular size in 75 patients with a narrow aortic anulus. These patients were divided into two groups: Group I consisted of 57 patients undergoing standard aortic valve replacement with a 21 mm prosthesis and Group II consisted of 18 patients undergoing modified aortic valve replacement with the aid of an anulus-enlarging procedure or an apico-aortic conduit. In Group I, left ventriculography gave 23.2 +/- 1.8 mm (mean +/- standard deviation), whereas the aortography method showed 22.4 +/- 2.7 mm (p less than 0.05). Those values of 20 mm or less were regarded as imperfect measurements; inaccurate results were more frequent in the aortography method (16 cases; 28%) than in the left ventriculography method (only two cases; 3.5%), with significant difference (p less than 0.025%). In Group II, there was no significant difference in respective values determined by the two different methods; 18.7 +/- 3.0 mm, with a range from 13 to 23 mm in the left ventriculography method, and 19.9 +/- 3.1 mm, with a range from 14 to 24 mm, in the aortography method (p greater than 0.2). Imperfect measurement by the aortography method tended to occur when the cusp base was severely deformed. The results indicated that left ventriculography was more reliable than root aortography for estimating the size of the aortic anulus.

Adolescent↗
PubMed1986

A new method of conduction system staining.

Visualization of the conduction bundle is advantageous in the prevention of surgical trauma to the conduction system during open-heart surgery. Because vital staining using an iodine starch complex has been known to result in tissue damage, we have evaluated the effects of iodine gas on the specialized conduction system. The conduction bundle was stained, well enough to be identified, with iodine tincture, with Lugol's solution, and with iodine gas. However, all these agents except for iodine gas caused marked electrophysiological changes. Similar changes occurred with the use of ethanol and of 10% potassium iodine solution, which are the solvents of iodine tincture and Lugol's solution, respectively. Microscopic examination showed that iodine tincture, Lugol's solution, and their solvents caused marked histological changes in the conduction tissue. However, no significant changes in the conduction tissue were noted from iodine gas spraying. Therefore, tissue damage caused by iodine tincture and Lugol's solution was thought to be due not to a reaction to the iodine starch complex itself, but to their solvents. In a long-term experimental study of 10 dogs, we found that iodine gas caused no electrophysiological disturbances or damage of microscopic tissue. Of the agents we tested, only iodine gas is free from harmful effects and can be used clinically.

Animals↗
PubMed1986

Present status of thromboembolic complications in patients with prosthetic heart valves.

When the incidence of thromboembolism (TE) as a complication was investigated in 171 patients with prosthetic heart valves using pyrolytic carbon, 10 cases were identified in a mean follow-up period of 2.43 years. Of these 10, two patients had died. The incidence of TE as a percentage per patient--year was 2.41 on the whole, 2.15 in patients with aortic valve replacement (AVR), 2.48 in patients with mitral valve replacement (MVR) and 2.52 in patients with double valve replacement (DVR). It is evident that TE is still an important complication following prosthetic heart valve surgery and the patient's return to society. TE tended to occur somewhat more often in cases of MVR and DVR than in those of AVR. TE was apt to appear early in the postoperative period, often within a year, and was often seen in the brain. To prevent TE, it is necessary to carefully control blood coagulation by the administration of anticoagulants.

Adult↗