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Biomedical subjects

C N Barnard

Publications and source records attributed to C N Barnard.

At least 73 records · Page 4Linked to original sources
PubMed1979

Controlled sequential pacing in isolated perfused auxiliary rat hearts.

An important question after clinical auxiliary heart transplantation is whether controlled pacing of both hearts is desirable in order to protect the diseased recipient heart. A comparison of the effects of spontaneous beating with three types of pacing (random, simultaneous and sequential) was undertaken in an isolated perfused working double rat heart. The two hearts were attached to each other by the atria, in a way comparable to the clinical situation. During controlled sequential pacing of both normal hearts, the peak systolic pressure fell and diastolic pressure rose, but the combined cardiac output did not changes. In contrast, during simultaneous pacing, systolic pressure rose, diastolic pressure fell and coronary flow was less than with sequential pacing, but the oxygen uptake was higher. Hence the effects of sequential pacing could be expected to be beneficial when function of one of the hearts was depressed by left main coronary artery ligation. During sequential pacing the cardiac output was significantly improved from 10 to 30 ml/min (P less than 0.001) and coronary flow rose. Myocardial oxygen consumption increased from 80 to 110 microliters/g/min (P less than 0.05). Thus sequential pacing could improve the severely depressed hemodynamics of the coronary-ligated heart in the presence of an auxiliary heart. The increased myocardial oxygen consumption is viewed as a beneficial effect of increased diastolic perfusion pressure and was not associated with increased enzyme release. It is concluded that the effects of sequential pacing warrant assessment in clinical auxiliary heart transplantation.

Animals↗
PubMed1978

Risk factors in surgical correction of congenital heart defects in early childhood.

The technique of surface-induced hypothermia, circulatory arrest and limited extracorporeal circulation was used in the surgical correction of congenital heart defects in 125 young children. Hospital mortality was 18% and no death could be attributed to the surgical technique. An analysis of risk factors demonstrated that successful corrective surgery was not significantly related to age, body weight or pulmonary vascular obstructive disease. In transposition of the great arteries, the presence of a ventricular septal defect was associated with an increased mortality. Emergency operations performed because of severe hypoxaemia carried a high mortality, especially in patients with tetralogy of Fallot.

Child↗
PubMed1978

Use of a double atrial-triggered standby pacemaker system for a patient with a biventricular bypass heterotopic cardiac homograft.

In a patient who had a biventricular bypass heterotopic cardiac homograft a double atrial-triggered standby pacemaker system was implanted to allow sequential atrial pacing of both hearts. The system design permitted either the recipient or the donor heart to dictate the rate of its fellow, depending on which heart had the faster spontaneous sinus rate at any time. Alternative methods for achieving sequential pacing are discussed.

Adult↗
PubMed1978

Evaluation of endomyocardial biopsy in the diagnosis of cardiac rejection. A study using bioptome samples of formalin-fixed tissue.

The reliability of endomyocardial bioptome samples in detecting cardiac rejection was assessed in 26 formalin-fixed previously transplanted hearts. Thirteen human donor hearts (mean postoperative survival 128 days) and 13 baboon donor hearts (mean survival 16.5 days) were studied. Twenty samples were taken under direct vision from the endomyocardium of each heart with an Olympus bioptome catheter. A total of 397 tissue samples was examined "blindly" histologically (177 human and 220 baboon). The bioptome samples were assigned a histological rejection score and then compared with the score accorded multiple tissue sections from the same heart. Sample scores agreed with tissue section scores as follows: humans 86% (samples showed more severe alterations in 5% and less severe in 9%) and baboons 57% (samples more severe in 40% and less severe in 3%). Only 2 false-negative samples were encountered among 285 tissue samples from hearts showing rejection. Changes of rejection were equally distributed between the left and right ventricles. Endomyocardial sampling proved an accurate means of detecting the presence of rejection. In the baboon hearts the endomyocardium tended to show more severe changes than the rest of the myocardium.

Animals↗
PubMed1978

Results after mitral valve replacement with cloth-covered Starr-Edwards prostheses (models 6300, 6310/6320, and 6400).

The actuarial survival and thromboembolic rates for the three types of cloth-covered Starr-Edwards mitral prostheses, models 6300, 6310/6320, and 6400 followed 6, 5, and 2 years, respectively, were not significantly different throughout the years they were followed. The combined cumulative survival and thromboembolic proportion at 5 years for these prostheses were 71 and 66 per cent, respectively. The thromboembolic rates were not different in the following two groups: (a) 238 patients receiving anticoagulants, and (b) 52 patients who had discontinued or who were not receiving anticoagulants. Four patients thrombosed their mitral prostheses. Another 8 per cent had class 3 symptoms after operation, which were attributed to myopathic or restrictive left ventricular dysfunction or other valvular disease.

Adult↗
PubMed1978

Double outlet right ventricle: clinical and anatomical spectrum.

Thirty-two patients with double outlet right ventricle (DORV) were studied between 1960 and 1976. Associated congenital defects frequently compounded the difficulty of clinical diagnosis. Cardiac catheterisation was performed in 27 patients, and the ventriculograms were studied with particular regard to the relative positions of the great vessels to each other and to the ventricular septal defect. These relationships determine which corrective operation is possible. Correction has been performed in 12 patients with a perioperative mortality of 25%. Although mitral-aortic discontinuity was demonstrated in all cases, consideration of the anatomical spectrum included in the term DORV suggests that discontinuity is not an essential feature. In common with other clinical data and in contrast with necropsy studies, none of our patients was found to show the normal relationship of the great vessels to each other, in which the aorta lies posterior and to the right of the pulmonary artery. The reason for this difference between the clinical and necropsy findings is not apparent. A similar disparity was shown with regard to pulmonary stenosis, which was demonstrated at catheterisation in 68% of the 27 patients (mean gradient 68 +/- 3 mmHg), in contrast with incidences of 18% and 25% in recent necropsy series. Patients in the necropsy studies were frequently neonates or infants, in whom death may have been the result of intractable cardiac failure secondary to excessive pulmonary blood flow. In older patients without pulmonary stenosis and with pulmonary hypertension, frequent observation is imperative so that surgical treatment can be instituted before the development of irreversible pulmonary vascular disease.

Adolescent↗
PubMed1977

Heterotopic cardiac transplantation with a xenograft for assistance of the left heart in cardiogenic shock after cardiopulmonary bypass.

One of the indications for the use of the heterotopic cardiac transplant is temporarily to support a failing heart in the anticipation of its recovery when all other measures of support have been unsuccessful. Human donors are not always available when required and we decided to use a xenograft for this purpose when the need arose. This report details our experience with a baboon and a chimpanzee cardiac xenograft transplant in the heterotopic position. We have found (a) that the operation is technically feasible; (b) that the xenograft will support the failing circulation, but that the more support required, the bigger the xenograft should be and the species chosen accordingly; (c) that severe acute rejection will occur within 4 days and the procedure should therefore only be employed where there is evidence that the patient's own heart function will recover rapidly.

Adult↗
PubMed1977

Results of valve replacement with the Lillehei-Kaster disc prosthesis.

The results of valve replacement in 150 patients with Lillehei-Kaster aortic and mitral prostheses followed for 20 to 40 months are reviewed. Actuarial analysis showed 78 per cent cummulative thromboembolic-free rate three years following mitral valve replacement and 89 per cent following aortic valve replacement. Five patients had a total of six episodes of mitral valve thrombosis despite anticoagulant therapy. Early detection of mitral valve obstruction was difficult because a mid-diastolic murmur and absence of an opening sound was frequently encountered in normally functioning prostheses. Hemodynamic results assessed clinically in patients with nonthrombosed prostheses were satisfactory.

Aortic Valve↗
PubMed1977

Myocardial fibrinolytic activity in allogenic cardiac rejection.

The relationship between alterations in myocardial fibrinolytic activity and the degree of graft tolerance or rejection was studied in 22 nonimmunosuppressed heterotopic cardiac transplants in chacma baboons. Fibrinolysis was evaluated on tissue sections and tissue extracts. Fibrinolytic activity was compared with electrocardiographic voltage alterations and multiple myocardial biopsies and terminal heart specimens were examined by light and electron microscopy. Histopathology and reduction in fibrinolytic activity proved superior to electrocardiographic voltage reductions in assessing early cardiac rejection. The two former modalities correlated well with one another. Myocardial histology showed rejection change earlier than fibrinolytic activity reduction.

Animals↗
PubMed1977

[The heterotopic heart transplantation: first clinical experiences (author's transl)].

Ten patients, all men, have been operated of heterotopic heart transplantation since the end of 1974. Ages ranged from 59 to 24 years with an average of 38 years. Six of them suffered from ischaemic heart disease, two from cardiomiopathy and two from rheumatic heart disease. All of them presented end stage cardiac disease. The first two patients underwent to left ventricular bypass only, in the remaining eight a right and left bypass was performed. At the present time, June 1977, 6 of the original 10 patients are alive all of them in functional class I. Five of them have resumed a full time job, the sixth will be soon able to do so. Four patients died. There were no deaths from acute rejection, but three died from infection, and the fourth one from a pulmonary embolus, 4 months after transplantation. There has been only one episode of acute rejection which has responded well to the treatment. The advantages of the heterotopic versus the orthotopic cardiac transplantation are discussed.

Adult↗
PubMed1977

The advantage of heterotopic cardiac transplantation over orthotopic cardiac transplantation in the management of severe acute rejection.

The major problems with organ transplantation are rejection of the allograft and the side effects of antirejection therapy. This report describes the successful treatment of a patient in whom rejection of the donor heart developed 10 months after implantation. The recipient's own heart had been left intact and was able to support the circulation during the period of rejection. Indications are that the "rest" period of 10 months was beneficial to the myopathic left ventricle of the recipient's heart.

Adult↗
PubMed1977

Fistula of the sinus of Valsalva.

Operative repair of sinus of Valsalva aneurysms and fistulas was performed in 10 patients between 1960 and 1976. Associated cardiac defects were corrected in 6 patients. There were no postoperative deaths, and the 8 patients observed to date are still alive and well. Only 2 patients required a second operation. The employment of a transchanber or a transaortic approach or both continues to be a matter of individual preference.

Adolescent↗
PubMed1976

Arrhythmias in two patients with left ventricular bypass transplants.

Two patients who underwent left ventricular bypass transplants are described. Both patients sustained postoperative rhythm disturbances of their own hearts during sinus rhythm of the donor hearts. Illustrative examples of atrial flutter, ventricular flutter, ventricular fibrillation, blocked atrial extrasystoles, and double ventricular parasystole in the recipient hearts are presented. The patients tolerated all these arrhythmias well during uninterrupted sinus rhythm in the donor heart. The problems in interpretation of arrhythmias in the presence of two hearts are discussed.

Arrhythmias, Cardiac↗