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Biomedical subjects

D N Ross

Publications and source records attributed to D N Ross.

At least 73 records · Page 4Linked to original sources
PubMed1981

Surgical enucleation of discrete sub-aortic stenosis.

Three forms of discrete sub-aortic stenosis have been recognised and described. A long tunnel-like narrowing of the left ventricular outflow tract was the most severe form and was recognized as different from hypertrophic obstruction cardiomyopathy (HOCM). Sixty patients with discrete sub-aortic stenosis have been operated on with enucleation of the stenosis during the past 15 years at the National Heart Hospital, London, and followed-up for up to 14 years. Overall there were 4 hospital deaths (6.6%) and only one late death. Emphasis has been placed on the superiority of blunt dissection in the enucleation of the entire, discrete stenosis when contrasted with the conventional sharp dissection technique which may well lead to subsequent accretions of obstructive thickening. The surgical enucleation of the discrete sub-aortic stenosis has been an entirely satisfactory procedure from a hemodynamic viewpoint and carries a low operative risk with every possibility of a subsequent event-free follow-up.

Adolescent↗
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

Management of cardiovascular complications in Marfan syndrome.

From 1965 to 1979, 59 patients with the Marfan syndrome and cardiovascular complications underwent aortic root and aortic valve surgery. The hospital mortality was 12% (6.5% over the past 5 years). At follow-up an average of 5.1 years later, 2 patients had postoperative heart block, and late complications required reoperation in 4. There was 8 late deaths (overall mortality 25%). Survival at 6 years was 77% and improvement was noted in the functional class of 32 (74%) of the 43 survivors. 3 patients with abnormal preoperative ventricular function have continued in cardiac failure; 3 have moderate mitral regurgitation and 2 have aortic regurgitation. Aneurysms of the abdominal aorta and pulmonary artery have developed in 2 patients. Initially patients underwent surgery when their condition deteriorated despite medical treatment. Echocardiographic assessment of the aortic root has improved diagnosis and management; a large, progressively dilating aorta and evidence of ventricular dilatation were indications for surgery in 11 symptom-free patients. Although patients with Marfan syndrome are prone to other cardiovascular manifestation which affect survival, elective prophylactic surgery to the ascending aorta can be done with a low mortality and expectation of improved lifespan.

Adolescent↗
PubMed1980

The Marfan syndrome: surgical technique and follow-up in 50 patients.

Fifty patients with Marfan's syndrome underwent operation at the National Heart Hospital because of cardiovascular complications. Forty-six had an aneurysm of the ascending aorta, 13 had chronic dissection, and 6 had acute dissection of the aortic wall. Forty-three aortic valves were incompetent, and five were stenotic and incompetent. One mitral valve had minor regurgitation. The Starr-Edwards prosthesis was used in 36 patients, homograft valves in 4, fascia lata valves in 2, and xenograft valves in 6. The ascending aorta was replaced with a Dacron tube in 40 patients and with an aortic homograft in 2. Three patients required Dacron patches over the aneurysm, and 1 patient had plication of the aortic wall. Early mortality totaled 12% (6 patients). Only 1 of these patients died in the last five years. Reoperations for homograft incompetence, periprosthetic leak, and acute dissection of an unreplaced aorta resulted in 1 hospital death (33%). Forty-three patients have been followed for up to 8.5 years (mean, 3.5 years), with 7 late deaths (46.2%). The improvement in recent surgical results with decreased operative mortality supports an aggressive surgical approach to Marfan's syndrome in view of the poor prognosis for the natural history of this disease.

Adolescent↗
PubMed1980

Right ventricular outflow reconstruction with aortic homograft conduit: analysis of the long-term results.

One hundred and four patients with complex congenital heart disease were operated between 1966 and 1978 for reconstruction of the right ventricular outflow using an aortic homograft conduit. The average age was 14 years, ranging between 3 years and 28 years of age with an equal male/female ratio. Hospital mortality was 50% and there were 3 late deaths (6%) amongst the surviving 52 patients. Seventy-nine percent of the survivors are well and asymptomatic between 1 year and 12 years follow-up. Only 2 patients (4%) developed homograft conduit obstruction with a peak systolic gradient over 40 mmHg and 1 patient needed reoperation 9 years after the original primary reconstruction. Thirty-one patients underwent cardiac catheterization between 1 year and 9 years following the original operation, and a further 9 patients underwent a second cardiac catheterization at a mean of 36 months after their first cardiac catheterization. Ninety-three percent of these 31 patients had a resting peak systolic gradient across the homograft conduit of between 0 and 55 mmHg (mean 14.16 +/- 14.03). Calcification in the wall of the aortic homograft appeared within the first 2 years in about 80% of the patients but this had no correlation to the gradient across the homograft, nor did it interfere with the valve performance.

Adolescent↗
PubMed1980

Flexible bioprosthetic pericardial heart valve.

A flexible bioprosthetic pericardial heart valve has been produced as a consequence of adverse long-term clinical information about tissue heart valves on rigid frames. The concept of flexibility has been supported by a comparison between homograft valves on rigid and flexible supports used in the mitral position. Principles and methods of construction of this flexible valve are described and it is intended that this inexpensive plastic frame will provide support for a bioprosthesis which will be a useful addition to choices for cardiac valve replacements.

Acetals↗
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

Ten years' experience with pulmonary autograft replacements for aortic valve disease.

Pulmonary autograft valves have been used to replace isolated, diseased aortic valves for 10 years, with a long-term survival of 73%. The low incidence of degeneration supports the principle that the autograft valve is a potentially permanent valve replacement. Operative mortality is now less than 5%, despite the longer, more complex operation. The current use of fresh homograft valves for the pulmonary replacement has contributed to these excellent long-term results.

Adolescent↗
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↗