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Biomedical subjects

E Bodnar

Publications and source records attributed to E Bodnar.

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

Heterologous antigenicity induced in human aortic homografts during preservation.

A series of rabbit experiments has been carried out to investigate the potential antigenicity of the heat-treated foetal calf serum which is commonly used to enhance viability of preserved aortic homograft valves. In all presensitised animals, the calf serum content of the nutrient medium which infiltrated the aortic wall during preservation provoked a heavy second-set reaction. It is concluded that heat-treated foetal calf serum is a potent heterologous antigen and should not be used for preserving human tissue selected for transplantation.

Animals↗
PubMed1988

Long-term performance of 555 aortic homografts in the aortic position.

Long-term results with 555 aortic homografts used for isolated aortic valve replacement (AVR) between 1964 and 1986 were analyzed to assess valve performance and the time-related onset of valve-related events. The total follow-up was 2,931 patient-years. Twenty years after operation, overall survival was 51.6 +/- 8.1%, freedom from valve-related death was 67.1 +/- 8.9%, freedom from primary tissue failure was 12.4 +/- 4.8%, freedom from infective endocarditis was 82.7 +/- 4.3%, freedom from surgical technical failure was 88.1 +/- 2.3%, and freedom from all complications including valve-related death was 9.0 +/- 3.5%. The incidence of thromboembolism was 0.034% per patient-year (one potential event). Long-term results after homograft insertion for aortic stenosis were significantly better than those after insertion for aortic incompetence. It is concluded that the good quality of life and the median life expectancy, which extends more than 20 years after operation, make the homograft an excellent choice for AVR.

Actuarial Analysis↗
PubMed1986

Damage of porcine aortic valve tissue caused by the surfactant sodiumdodecylsulphate.

The Hancock T6 treatment uses 1% sodiumdodecylsulphate (SDS) to prevent or delay calcification in porcine aortic or pericardial bioprostheses. In the current study fresh and glutaraldehyde fixed porcine aortic cusps were treated in 1% SDS. The hydrothermal stability, the histological and the electronmicroscopic appearance of the tissue were assessed and compared before and after treatment. The results suggest that the 1% SDS solution destroys the fresh material causing acellularity, extreme fragmentation and swelling of the collagen, together with a significant loss of hydrothermal stability. Glutaraldehyde fixation prior to SDS treatment seems to provide protection against the harmful effects of the 1% SDS, with only one exception on electronmicroscopic examination where foci of collagen degeneration were found.

Animals↗
PubMed1985

Long-term assessment of aortic valve replacement with autologous pulmonary valve.

Two hundred two autologous pulmonary valves were transplanted into the aortic position between 1967 and 1982 at the National Heart Hospital in London. The indication for operation was congenital or acquired aortic valve disease, and the patients were followed for periods from 1 to 4 years. The patients were not anti-coagulated, but the entire series has been completely free from thromboembolism or bleeding. The actuarial prediction of freedom from valve-related deaths was 82 +/- 6% at the end of the fourteenth year after operation; deaths were due to reoperations for technical failure and to infective endocarditis. Event-free survival of the autologous pulmonary valve in the aortic position was 73 +/- 6% after 14 years at risk. Valve failure resulted mainly from technical problems encountered during the early years of surgical experience. There was no macroscopic or histological evidence of calcification in any of the failed valves. The right ventricular outflow was reconstructed with an aortic homograft in the majority of patients; 81 +/- 5% of these homografts demonstrated event-free performance over a 12-year follow-up period. It is concluded that the long-term performance of a pulmonary autograft inserted for aortic valve disease is superior to that of any other valve substitute and that the operation offers an almost ideal means of aortic valve replacement in appropriate patients.

Adolescent↗
PubMed1982

Assessment and comparison of the performance of cardiac valves.

A statistical method is presented to assess and compare cardiac valve performances. Patient survival and valve performances have been separated, and valve function and malfunction have been described in comprehensive and comparable terms. Formulas are proposed to calculate the significance of the difference between two survival probabilities as well as to calculate the instantaneous rate of events and the median remaining lifetime.

Actuarial Analysis↗
PubMed1981

Measurement and distribution of flexibility in cardiac valve support frames.

Bioprosthetic heart valve support frames of three basic designs were injection moulded in four sizes using five plastic materials and the flexibility of each individual frame post measured. There was a regular pattern of distribution of flexibility of each individual frame post measured. There was a regular pattern of distribution of flexibility in these frames in spite of the fact that within each group of frames the dimensions of each were identical. Identically produced frames of different size showed an alteration in this pattern of flexibility and even small variations in the design of the frames resulted in marked changes in both the degree and distribution of flexibility. The plastic chosen also affected the degree of flexibility obtained also affected the degree of flexibility obtained. The flexibilities of three commercially-available support frames were also measured. The Carpentier-Edwards bioprosthesis was found to have one post more flexible than the other two in a regular pattern inherent in the design of the frame. The Angell-Shiley valve frame, because of its irregular design, displayed a totally irregular pattern. There was a regular pattern of distribution of flexibility in the Hancock porcine bioprosthesis frame. It is concluded that such differences in flexibility are a consequence of frame design, variations in the crystal structure of the plastic materials during manufacture and the choice of plastic used.

Cardiac Surgical Procedures↗
PubMed1981

Bicuspid mitral bioprosthesis.

A bicuspid mitral bioprosthesis was prepared by mounting glutaraldehyde-processed porcine pericardium onto commercially available Brownlee-Yates stents. The bioprostheses were inserted into 17 dogs. Haemodynamic performance and long-term function of the valve was assessed. Of the 11 animals in the survival group, eight died within the 24-72 hour postoperative period. The clinical picture of these animals revealed progressive left ventricular failure although the bioprostheses were tested and found competent both at insertion and at necropsy. The causes of the late deaths were deterioration of the porcine pericardium in two, and cerebral embolism in another. The acute haemodynamic studies showed a significantly high closing reflux from within the tubular bioprosthesis, and this reflux was found to be inherent in the design. It was concluded that any stented bicuspid valve where the stent assumes the function of the papillary muscles, has to be tailored so that parts of the tissue can assume the function of the chordae tendineae to minimise the closing reflux.

Animals↗
PubMed1981

Semibiological left heart assist.

Previous investigations have revealed that the semibiological left heart assist gave a reasonably good performance under simulated physiological pressures, flow and rate conditions. The present study gives details of 50 animal experiments where the duration of the left ventricular-aorta bypass pumping varied between 2 and 24 hours. It was demonstrated that the device can be inserted and used without systemic or local anticoagulants and with a negligible degree of blood trauma up to 24 hours.

Animals↗
PubMed1980

Long-term performance of homograft and autograft valves.

Five hundred and eighty homograft valves have been inserted into the aortic position as isolated valve replacements, and followed up for 7--14 years. After ten years 90% of frozen homografts, 80% of autografts and 70% of freeze-dried homografts were free of valve-related death. There was only one embolism reported giving an incidence of one embolism per 143,928 patient months. Degeneration occurred in 14% of the autografts, in 30% of the freeze dried and in 60% of the frozen homografts after ten years. Eighty per cent of the fresh homografts have been free of degeneration after seven years, and 54% of freeze-dried valves have been free of degeneration after 14 years. Long-term performance of homograft and autograft valves in the aortic positon is comparable to that of any prosthetic or bioprosthetic valve. In addition, they are non-thrombogenic and excellent in terms of patient survival.

Aortic Valve↗
PubMed1980

Mitral valve replacement with dura mater bioprostheses.

Dura mater bioprostheses for cardiac valve replacement were first introduced in Brazil. They have been used since 1975 at the National Heart Hospital, London, as a mitral valve replacement instead of fascia lata valves or inverted aortic homograft valves. During this period 120 patients have had dura mater valves inserted in the mitral position; 29 also received an aortic valve replacement, 6 with dura mater, 20 with an aortic homograft, 2 with an aortic xenograft and 1 with a prosthetic valve. Perivalvular leaks occurred with seven of these mitral valves, and another seven presented with detached cusps. All but one of these 14 valves were replaced. Emboli have occurred in four of the patients, one of whom died after 35 months with thrombus on the aortic valve, but with an unaffected mitral valve. There were 15 early deaths, a hospital mortality of 12.5%, and 10 late deaths, a postoperative mortality of 9.5%. Actuarial analysis has shown a four-year postoperative survival of 78.9%.

Aortic Valve↗
PubMed1979

Long term performance of 580 homograft and autograft valves used for aortic valve replacement.

Homograft valves have been used at the National Heart Hospital since 1964, and autograft valves since 1967. The homografts were treated either by freeze drying, by flash freezing, or by tissue maintenance in a nutrient medium (fresh). In order to compare these three groups of homograft valves with the autograft valves some long term assessment of valve function was required. In the whole group of 580 valves there have been 40 late deaths, which is a probability of only 7% over 6 to 14 years. Homografts and autografts are therefore excellent valves in terms of patient survival. Thromboembolism, haemolysis and bleeding may be regarded as complications which do not occur with homograft and autograft valves. There was one thrombogenic episode in this group, an incidence of one per 11,994 patient years and a probability of only 0.000083 patient years. Potentially fatal hazards of late complications with homoor autograft valves decrease with time and at this time is a negligible factor. The similarity in pattern of onset of late infections and degeneration probably reflects the greater susceptibility to infection of a degenerating valve. All three groups of homografts are very similar and differ only from the excellent performance of the autograft valves.

Aortic Valve↗
PubMed1979

An 11-year assessment of 93 flash-frozen homograft valves in the aortic position.

Flash-frozen homograft aortic valves were used for isolated aortic valve replacement at the National Heart Hospital between 1968 and 1971. This study of 93 patients with an average follow-up of 8.5 years complements a previous report on 30 patients but shows a higher incidence of degeneration. There was an early mortality of 4.8% and a late mortality of 15.9% over 11 years. Only five of the 15 late deaths were directly attributable to valve malfunction. There were no episodes of thromboembolism during the 11 year follow-up and only three cases of infective endocarditis. Despite the late onset of valve degeneration there is a 77% probability of patient survival at 11 years. The use of frozen valves delayed the time of onset of degenerative changes when compared over an 11-year period with the earlier use of freeze-dried valves. The evaluation of replacement cardiac valves is thus seen to be time-dependent and needs a long follow-up and an adequate number of patients in the sample for a meaningful assessment. There was no significant difference in the long-term performance between the frozen valves sterilized in ethylene oxide or sterilized with gamma irradiation.

Adult↗
PubMed1979

Semibiological left heart assist: in vitro evaluation.

A semibiological left heart assist device has been designed and built at the Cardiothoracic Institute and National Heart Hospital, London, England. This device is a Dacron/polyurethane conduit between the left ventricle and aorta in which part of the conduit assumes the function of a pumping chamber. This segment is enclosed by two biological valves and has side arm. A polyurethane balloon is inserted through this side arm, and is pumped in a synchronously counter-pulsating manner. Upon completion, the balloon can be removed without thoracotomy and with the conduit left in situ. Under simulated physiologic pressure and rate conditions, the pumping device gives reasonably good performance.

Assisted Circulation↗
PubMed1979

Comparative method for actuarial analysis of cardiac valve replacements.

The use of survival analysis in cardiac surgical reports has been widely accepted in order to characterise and compare performances of different valve prostheses. However, the analyses that have been described elsewhere may be improved in several respects. The original method proposed for prosthetic valve evalation examined follow-up related to patients rather than the valves themselves and therefore neglected the possibility of factors other than the valve itself which could affect the fate of cardiac patients. Furthermore, there has not yet been any application of life table methods to compare two different sets of data, or to estimate the average time before an event occurs. The present work defines valve function and malfunction and separates patient survival from valve performance. We define statistical indices, namely the median remaining lifetime and the instantaneous decrement rate. Both indices can be useful; the former measures the average survival time and the latter focuses attention on the intensity of risk changes. Using established statistical theory we calculate the significance level of difference between two independent survival rates. We qualify the presentation of probabilities with a statement of the associated standard errors.

Actuarial Analysis↗
PubMed1979

Observations on glutaraldehyde-treated heterologous cardiac valves.

Recent publications on commercial porcine bioprosthetic cardiac valves have stated that the endothelium disappears during the glutaraldehyde processing and that in many cases histological evidence of early tissue deterioration was found. Our experiences have shown that porcine aortic valves can be processed in glutaraldehyde without loss of the integrity of the endothelium and with the development of optimum collagen fibre structure. The valve mounted in a Dacron tube is not restricted in diameter and performs well under biological conditions up to a period of six months.

Aldehydes↗