Masters Degrees (Cardiothoracic Surgery)
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Item Open Access Critical analysis of rheumatic mitral valve surgery outcomes in central South Africa(University of the Free State, 2021) De-huis, Thabo J.; Smit, F. E.; Botes, L.; Hanekom, ManieIntroduction: Rheumatic heart disease (RHD) is still an important cause of acquired heart disease affecting children and young adults from poor socio-economic backgrounds. The most common presentation of RHD is mitral valve disease requiring surgical intervention. The study aim was firstly to describe peri-operative risk factors, procedures performed and surgical outcomes after mitral valve surgery for RHD in Central South Africa. Secondly, to compare these results in patients presenting with mitral regurgitation to those presenting with mitral stenosis and mixed mitral valve disease. Methods: Patients undergoing mitral valve surgery for RHD, with or without concomitant tricuspid valve repair between January 2009 and December 2019 were identified from the departmental database. The lesions were grouped into mitral stenosis (MS), mitral regurgitation (MR), and mixed mitral (MX) disease. Statistical analyses was performed using the IBM SPSS program, version 26.0. A p-value of 0.05 or less was considered statistically significant. Results: A total of 242 patients were included in the study of which 75.2% (n=182) were female. Black patients represented 74.4% (n=180), whites 13.6% (n=33) with Asian and mixed races at 12% (n=29). The mean age of the study population was 43.7 years. Distribution of patients according to the lesions was 25.6% (n=62) for MS, 45.0% (n=109) for MR and 29.3% (n=71) for MX disease. Patients presenting in NYHA status III and IV formed 44% of the MR group and 44% of the MS group and for 28% for the MX group. Calculated EuroSCORE > 5 was 29.4% (n=18) in the MS group, 29% (n=32) in the MR group, and 9.9% (n=7) in the MR group. For the MS group, 96.7% (n=60) had mitral valve replacement and only 2.8% (n=2) were repaired (valvotomy); whilst in the MR and MX groups the replacement vs repair rate was 90.3% (n=93) and 94% (n=63) vs 9.7% (n=10) and 5.6% (n=4) respectively. The MS group had the highest number of concomitant tricuspid valve repair at 58.0% (n=36) as compared to MR (38.5%) and MX (35.2%) groups. There was no statistical difference across the groups with regards to the post-operative stroke rate (1%) as well as the rate of in-hospital complications (14%). In-hospital mortality for the entire cohort was 3.8% (n=9), with 4.8% (n=3) for the MS, 3.7% (n=4) in the MR group and 2.8% (n=2) in the MX group. Of the 242 patients in the study 82 did not have their follow up at the UAH clinic. For the 160 patients followed up at UAH clinic, the median follow-up time was 2.68 years, with 35 patients having had follow-up visits > 5 years. Conclusion: Patients received mitral valve surgery had RHD and were young females from poor socio-economic backgrounds with an average age in the 4th decade of life. MR was the most common lesion with replacement being the most performed operation in our unit. The post-operative complications rate as well as the in-hospital mortality were comparable to the published literature.Item Open Access Infective endocarditis in central South Africa in the HIV era- a surgical perspective(University of the Free State, 2021) Gwila, Taha H.; Smit, F. E.; Botes, L.; Hanekom, H. A.Introduction: Infective endocarditis (IE) remains an evolving disease with a persistently high mortality and morbidity. In Africa, it is predominantly a disease of the young in contrast to the developed world. South Africa represents a very high prevalence of HIV at 21.67% of global HIV infections. Other factors in South Africa include the high prevalence of rheumatic valvular heart disease, low socio-economic status and poverty makes the patient population completely different from the developed world. The primary aim was to determine the influence of HIV infection on infective endocarditis patients in central South Africa. The secondary aim was to compare the HIV positive patients and HIV negative patients in the context of this disease. Objectives: To determine the demographics, presentation, indication for surgery, microorganisms, and outcomes of HIV positive versus HIV negative patients presenting with Infective endocarditis. Methods: Retrospective, analytical cohort study that reviewed the records of adult patients who were tested for HIV and treated surgically for infective endocarditis between 2009 to 2019. Data was compared between the two groups using chi-square or Fisher exact tests for categorical variables. Median and interquartile ranges were used for continuous variables and frequencies and proportions for categorical variables. Significance was set as p < 0.05. Results: From the 141 IE patients who underwent surgery for IE, 105 patients were tested for HIV, 31% (n=33) tested positive. The mean age for both groups was comparable 38.87 versus 39.51 years. Eighty-eight percent (n=29) of positive patients were on HAART. In both groups, there was a male preponderance, 55% vs 46% and 56% vs 44% respectively. The majority of HIV positive (91%) and negative patients (71%) were of African descent, more than 50% of both groups presented with NYHA III&IV, both groups had a medium-high risk of developing IE (HIV (+) 72%; HIV (-) 62%). Prevention of embolization was the main indication for surgery in HIV (+) group and heart failure in the negative group. In both groups a greater proportion of patients had left sided native valve endocarditis 95% and RHD was predominantly the underlying pathology 60%, requiring mechanical prostheses mainly in the mitral 46% and aortic 33% position. Right sided endocarditis represents <5% and only 2 out 105 patients confirmed IVDA’s, Staphylococcus and Streptococcus dominated cultured organisms with staphylococcus species being more frequent, culture negative endocarditis remains high in both groups, with 47% HIV (-) group vs 33%. Morbidity was limited in both groups 12% vs 11% with no major difference. The overall mortality was higher in the HIV (+) group (39% vs 34%); however, the in-hospital mortality was higher in the HIV (-) group (17% vs 12%). Conclusion: Infective endocarditis remains a deadly disease with high short- and long-term mortality. HIV infection has minimal to no impact on perioperative and in- hospital morbidity and mortality, left heart endocarditis is the dominant disease within the HIV patients due to the rheumatic valvular heart disease as opposed to right heart endocarditis. The high prevalence of culture negative endocarditis warrants further investigation. Given the low number of patients in this cohort study, further prospective studies need to be conducted to establish a statistical significance between the HIV (+) and (-) groups.Item Open Access Processed pulmonary homografts in the right ventricle outflow tract: an experimental study in the juvenile ovine model(University of the Free State, 2020-02) Van den Heever, Johannes Jacobus; Smit, F. E.; Dohmen, P. M.The availability of pulmonary homografts with improved biomechanical properties, tissue stability, reduced calcification and improved durability for right ventricular outflow tract (RVOT) reconstruction is desired. In paediatric patients, a valve with growth potential will be advantageous. Extending the post-mortem ischaemic time will enlarge the donor pool. Cryopreservation of homografts remains the gold standard, but it damages the extracellular matrix (ECM) and reduces the cellularity, contributing to early valve degeneration. Decellularization of homografts might reduce immunogenicity, promote recellularization and tissue remodeling, maintain mechanical stability and improve clinical outcomes. The decellularization process should not compromise the durability and strength of the homograft, and alternative stabilization of the scaffold might be required. The current study evaluated the effect of the further processing of pulmonary homografts, following a 48 h cold ischaemic postmortem harvesting time, on the structural integrity and function when implanted in the RVOT position in the juvenile ovine model. Sheep pulmonary homografts (n = 30) were subjected to 48 h cold ischaemia to simulate the clinical homograft donor circumstances, and equally divided into three groups. Homografts in group 1 were cryopreserved, decellularized in group 2 and decellularized, GA-fixed and detoxified in group 3. Decellularization consists of a multi-detergent and enzymatic protocol with numerous washout steps, and additional fixation and detoxification were done with EnCap technology. The study was divided into three parts. In study 1, the histological (DAPI, H&E, von Kossa, Modified von Gieson, SEM, TEM) and mechanical (TS and YM) properties of the processed homografts (n = 15, 5 per group) were compared. Study 2 involved implantation of cryopreserved and decellularized pulmonary homografts (n = 5 per group) in the RVOT of juvenile sheep for 180 days, monitored with echocardiography and compared on histology, mechanical properties and calcification after explantation. Study 3 involved the same parameters, however, decellularized and decellularized plus EnCap treated homografts (n = 5 per group) were implanted and compared. Cryopreserved homografts demonstrated collapsed and disrupted/fractured collagen with cells and cellular remnants. Homografts in the decellularized group were acellular with large interfibrillar spaces and a loosely arranged collagen network, while decellularized plus EnCap treated homograft were acellular with a compacted collagen network. Decellularization did not reduce tensile strength and tissue stiffness, but EnCap treatment did increase tissue stiffness. Implanted cryopreserved homografts demonstrated significant regurgitation due to leaflet thickening and retraction, loss of interstitial cells, calcification and increased tissue stiffness. Decellularized homografts showed increased annulus diameter with trivial regurgitation, excellent haemodynamics, remained soft and pliable, recellularized extensively with young fibroblasts exhibiting rough endoplasmic reticulum, and mitigated calcification. Decellularized and EnCap treated homografts became rigid and stenotic, showed poor haemodynamic characteristics, development of bacterial endocarditis and premature death, no leaflet recellularization, and fibrous encapsulation. Cryopreserved homografts remain the valve of choice for RVOT reconstruction surgery, however, cryopreservation causes cell death and collagen disruption, and loss of cellularity and calcification during implantation, which will result in early valve degeneration. Our proprietary decellularization protocol proved to be effective for complete decellularization of pulmonary homografts with a post-mortem ischaemic time of 48 h, while maintaining a well-organized collagen matrix and tissue strength and stiffness. Implanted decellularized homografts repopulated extensively without signs of inflammation, maintained structural integrity and strength, calcification was mitigated, and the potential for remodeling and growth in size with somatic growth was observed. Additional fixation of the decellularized homograft scaffold will be counterproductive in growing individuals, and should only be performed on adult size homografts where valve growth is not required. GA-fixation restricts valve repopulation with host cells and tissue remodeling, and defies the purposes and advantages of decellularization. Additional fixation may not be necessary when using decellularization methods that achieve complete acellularity without altering the ECM structure and mechanical properties of homografts. Successful decellularization of donor homograft heart valves and other collagenous tissues holds exciting new prospects and possibilities for tissue processing, and can open a new era in supply of substitution valves and tissues with improved properties and advantages to medical patients in South Africa.