Isolated mechanical aortic valve replacement in rheumatic patients in a low- to middle-income country

A Global Systematic Review of Open Heart Valvular Surgery in Resource-Limited Settings

BACKGROUND

Many obstacles challenge the establishment and expansion of cardiac surgery in low- and middle-income countries, despite the unmet cardiac surgical needs. One challenge has been providing adequate follow-up care to monitor anticoagulation, manage morbidity, and prevent mortality. This systematic review describes outcomes after valvular cardiac surgery and focuses on strategies for prolonged follow-up care in resource-constrained settings.

METHODS

Studies published between 2012 and 2022 were collected from Embase and the Cochrane Library. Article inclusion criteria were adolescent and adult patients, open heart valvular surgery, and analysis of at least 1 postoperative outcome at least 30 days postoperatively. Studies that focused on pediatric patients, pregnant patients, transcatheter procedures, in-hospital outcomes, and nonvalvular surgical procedures were excluded. Descriptive statistics were assessed, and articles were summarized after abstract screening, full-text review, and data extraction.

RESULTS

Sixty-seven relevant publications were identified after screening. The most commonly studied regions were Asia (46%), Africa (36%), and Latin America (9%). Rheumatic heart disease was the most commonly studied valvular disease (70%). Reported outcomes included mortality, surgical reintervention, and thrombotic events. Follow-up duration ranged from 30 days to 144 months; 11 studies reported a follow-up length of 12 months.

CONCLUSIONS

Addressing the unmet cardiac care needs requires a multifaceted approach that leverages telemedicine technology, enhances medical infrastructure, and aligns advocacy efforts. Learning from the cost-effective establishment of cardiac surgery in low- and middle-income countries, we can apply past innovations to foster sustainable cardiac surgical capacity.

A systematic review and meta-analysis on outcomes of valvular heart surgery in Africa

INTRODUCTION

The prevalence of valvular heart diseases remain considerably high in Africa, largely but not solely due to rheumatic heart disease. Valvular heart surgeries have emerged as the cornerstone in their management. While several studies have reported data on outcomes following heart valve surgery in many developed countries, there is a staggering paucity of data and evidence reporting the outcomes in the Africa population. The aim of this study is to report the perioperative outcomes following valvular heart surgery in Africa.

METHODS

The Preferred Reporting Items for Systematic Reviews and Meta-analysis guideline was utilized. Electronic searches were performed using PubMed, African journal online, and Research gate from inception to June 2023. The primary endpoints were overall mortality and 30-day mortality, and secondary endpoints included postoperative complications, length of hospital, and intensive care stays. The outcome data were pooled together and analyzed with the random effect model for proportions and mean for meta-analysis using the R software.

RESULTS

This systematic review identified 31 studies that fulfilled the study eligibility criteria and all were observational studies. The countries in which these studies were carried out include South Africa, Ethiopia, Egypt, Mali, Rwanda, Nigeria, Cameroon, Ghana, Senegal, Tanzania, and Kenya. Statistical analysis reported a pooled overall mortality of 10.48% and a pooled 30-day mortality of 4.59%.

CONCLUSION

Several obstacles, such as lack of financial resources and inadequate infrastructure, continue to impede valvular heart surgery practice in many parts of Africa. Future studies need to focus on identifying factors associated with this poor early mortality.

Development and testing of a transcatheter heart valve with reduced calcification potential

Introduction

Patients from developing countries who require heart valve surgery are younger and have less access to open heart surgery than those from developed countries. Transcatheter heart valves (THVs) may be an alternative but are currently unsuitable for young patients because of their inadequate durability. We developed and tested a THV utilizing two new types of decellularized bovine pericardial leaflets in an ovine model.

Methods

The two decellularized tissues [one with a very low dose (0.05%) of monomeric glutaraldehyde (GA) fixation and detoxification (DF) and the other without glutaraldehyde (DE)] were compared to an industry standard [Glycar-fixed with the standard dose (0.625%) of glutaraldehyde]. THVs were manufactured with the three tissue types and implanted in the pulmonary position of nine juvenile sheep for 180 days. Baseline and post-explantation evaluations were performed to determine the hemodynamic performance of the valves and their dynamic strength, structure, biological interaction, and calcification.

Results

Heart failure occurred in one animal due to incompetence of its Glycar valve, and the animal was euthanized at 158 days. The gradients over the Glycar valves were higher at the explant than at the implant, but the DE and DF valves maintained normal hemodynamic performance throughout the study. The DF and DE tissues performed well during the mechanical testing of explanted leaflets. Glycar tissue developed thick pannus and calcification. Compared to Glycar, the DF tissue exhibited reduced pannus overgrowth and calcification and the DE tissue exhibited no pannus formation and calcification. All tissues were endothelialized adequately. There was a striking absence of host ingrowth in the DE tissue leaflets, yet these leaflets maintained integrity and mechanical function.

Conclusion

In the juvenile sheep THV model, Glycar tissue developed significant pannus, calcification, and hemodynamic deterioration. Using a very low dose of monomeric GA to fix the decellularized bovine pericardium yielded less pannus formation, less calcification, and better hemodynamic function. We postulate that the limited pannus formation in the DF group results from GA. Bovine pericardium decellularized with our proprietary method resulted in inert tissue, which is a unique finding. These results justify further development and evaluation of the two decellularized tissue types in THVs for use in younger patients.

Simulating Subject-Specific Aortic Hemodynamic Effects of Valvular Lesions in Rheumatic Heart Disease

Rheumatic heart disease (RHD) is a neglected tropical disease despite the substantial global health burden. In this study, we aimed to develop a lower cost method of modeling aortic blood flow using subject-specific velocity profiles, aiding our understanding of RHD's consequences on the structure and function of the ascending aorta. Echocardiography and cardiovascular magnetic resonance (CMR) are often used for diagnosis, including valve dysfunction assessments. However, there is a need to further characterize aortic valve lesions to improve treatment options and timing for patients, while using accessible and affordable imaging strategies. Here, we simulated effects of RHD aortic valve lesions on the aorta using computational fluid dynamics (CFD). We hypothesized that inlet velocity distribution and wall shear stress (WSS) will differ between RHD and non-RHD individuals, as well as between subject-specific and standard Womersley velocity profiles. Phase-contrast CMR data from South Africa of six RHD subjects with aortic stenosis and/or regurgitation and six matched controls were used to estimate subject-specific velocity inlet profiles and the mean velocity for Womersley profiles. Our findings were twofold. First, we found WSS in subject-specific RHD was significantly higher (p < 0.05) than control subject simulations, while Womersley simulation groups did not differ. Second, evaluating spatial velocity differences (ΔSV) between simulation types revealed that simulations of RHD had significantly higher ΔSV than non-RHD (p < 0.05), these results highlight the need for implementing subject-specific input into RHD CFD, which we demonstrate how to accomplish through accessible methods.

Transcatheter heart valve interventions for patients with rheumatic heart disease

Rheumatic heart disease [RHD] is the most prevalent cause of valvular heart disease in the world, outstripping degenerative aortic stenosis numbers fourfold. Despite this, global resources are firmly aimed at improving the management of degenerative disease. Reasons remain complex and include lack of resources, expertise, and overall access to valve interventions in developing nations, where RHD is most prevalent. Is it time to consider less invasive alternatives to conventional valve surgery? Several anatomical and pathological differences exist between degenerative and rheumatic valves, including percutaneous valve landing zones. These are poorly documented and may require dedicated solutions when considering percutaneous intervention. Percutaneous balloon mitral valvuloplasty (PBMV) is the treatment of choice for severe mitral stenosis (MS) but is reserved for patients with suitable valve anatomy without significant mitral regurgitation (MR), the commonest lesion in RHD. Valvuloplasty also rarely offers a durable solution for patients with rheumatic aortic stenosis (AS) or aortic regurgitation (AR). MR and AR pose unique challenges to successful transcatheter valve implantation as landing zone calcification, so central in docking transcatheter aortic valves in degenerative AS, is often lacking. Surgery in young RHD patients requires mechanical prostheses for durability but morbidity and mortality from both thrombotic complications and bleeding on Warfarin remains excessively high. Also, redo surgery rates are high for progression of aortic valve disease in patients with prior mitral valve replacement (MVR). Transcatheter treatments may offer a solution to anticoagulation problems and address reoperation in patients with prior MVR or failing ventricles, but would have to be tailored to the rheumatic environment. The high prevalence of MR and AR, lack of calcification and other unique anatomical challenges remain. Improvements in tissue durability, the development of novel synthetic valve leaflet materials, dedicated delivery systems and docking stations or anchoring systems to securely land the transcatheter devices, would all require attention. We review the epidemiology of RHD and discuss anatomical differences between rheumatic valves and other pathologies with a view to transcatheter solutions. The shortcomings of current RHD management, including current transcatheter treatments, will be discussed and finally we look at future developments in the field.

Causes of Heart Block in Young and Middle-Aged South Africans

BACKGROUND

There is a paucity of data regarding the aetiology of atrioventricular heart block (AVB) in young and middle-aged patients, particularly from low- and middle-income countries.

OBJECTIVE

To determine the aetiology of AVB in patients ≤ 55 years treated with transvenous pacemakers in a low- or middle-income country.

METHODS

We performed a retrospective review of all patients who received a transvenous pacemaker for newly diagnosed AVB from 01/01/2013 to 31/12/2020 at Groote Schuur Hospital, Cape Town, South Africa.

RESULTS

One thousand one hundred one (1101) consecutive patients received a permanent transvenous pacemaker for AVB. One hundred thirty-six patients (12.4%) were ≤ 55 years. The study patients' mean (standard deviation) age was 41 (11) years, and 48.5% were female. Third-degree AV block was diagnosed in 73.5%, 2:1 AV block in 8.1%, and Mobitz Ι second degree AV block in 5.9%. The aetiology of AVB could be determined in 97/136 (71.3%) patients. Forty-three of 136 (31.6%) patients were post-surgical, and 16/136 (11.8%) patients had developed AVB from an acute myocardial infarction. Cardiac Magnetic Resonance (CMR) imaging was performed in 26 patients: cardiac sarcoidosis was diagnosed in 7/26 patients. No pathology could be identified in 10/26 patients who had CMR. The aetiology of AVB remained unknown in 39/136 patients (28.7%).

CONCLUSION

Prior valve surgery is the leading cause of AVB treated with a transvenous pacemaker in patients ≤ 55 years in this South African referral unit. Cardiac magnetic resonance imaging identified disease processes that require further management in many cases.

The Technological Basis of a Balloon-Expandable TAVR System: Non-occlusive Deployment, Anchorage in the Absence of Calcification and Polymer Leaflets

Leaflet durability and costs restrict contemporary trans-catheter aortic valve replacement (TAVR) largely to elderly patients in affluent countries. TAVR that are easily deployable, avoid secondary procedures and are also suitable for younger patients and non-calcific aortic regurgitation (AR) would significantly expand their global reach. Recognizing the reduced need for post-implantation pacemakers in balloon-expandable (BE) TAVR and the recent advances with potentially superior leaflet materials, a trans-catheter BE-system was developed that allows tactile, non-occlusive deployment without rapid pacing, direct attachment of both bioprosthetic and polymer leaflets onto a shape-stabilized scallop and anchorage achieved by plastic deformation even in the absence of calcification. Three sizes were developed from nickel-cobalt-chromium MP35N alloy tubes: Small/23 mm, Medium/26 mm and Large/29 mm. Crimp-diameters of valves with both bioprosthetic (sandwich-crosslinked decellularized pericardium) and polymer leaflets (triblock polyurethane combining siloxane and carbonate segments) match those of modern clinically used BE TAVR. Balloon expansion favors the wing-structures of the stent thereby creating supra-annular anchors whose diameter exceeds the outer diameter at the waist level by a quarter. In the pulse duplicator, polymer and bioprosthetic TAVR showed equivalent fluid dynamics with excellent EOA, pressure gradients and regurgitation volumes. Post-deployment fatigue resistance surpassed ISO requirements. The radial force of the helical deployment balloon at different filling pressures resulted in a fully developed anchorage profile of the valves from two thirds of their maximum deployment diameter onwards. By combining a unique balloon-expandable TAVR system that also caters for non-calcific AR with polymer leaflets, a powerful, potentially disruptive technology for heart valve disease has been incorporated into a TAVR that addresses global needs. While fulfilling key prerequisites for expanding the scope of TAVR to the vast number of patients of low- to middle income countries living with rheumatic heart disease the system may eventually also bring hope to patients of high-income countries presently excluded from TAVR for being too young.

Societies of Futures Past: Examining the History and Potential of International Society Collaborations in Addressing the Burden of Rheumatic Heart Disease in the Developing World

This paper explores the role and place of national, regional, and international society collaborations in addressing the major global burden of rheumatic heart disease (RHD). On the same order of HIV, RHD affects over 40 million people worldwide. In this article, we will outline the background and current therapeutic landscape for cardiac surgery in low- and middle-income countries (LMICs) including the resource-constrained settings within which RHD surgery often occurs. This creates numerous challenges to delivering adequate surgical care and post-operative management for RHD patients, and thus provides some context for a growing movement for and applicability of structural heart approaches, innovative valve replacement technologies, and minimally invasive techniques in this setting. Intertwined and building from this context will be the remainder of the paper which elaborates how national, regional, and international societies have collaborated to address rheumatic heart disease in the past (e.g., Drakensberg Declaration, World Heart Federation Working Group on RHD) with a focus on primary and secondary prevention. We then provide the recent history and context of the growing movement for how surgery has become front and center in the discussion of addressing RHD through the passing of the Cape Town Declaration.

Short-term outcome after open-heart surgery for severe chronic rheumatic heart disease in a low-income country, with comparison with an historical control group: an observational study

Objectives

Rheumatic heart disease (RHD) is a major burden in low-income and middle-income countries (LMICs). Cardiac surgery is the only curative treatment. Little is known about patients with severe chronic RHD operated in LMICs, and challenges regarding postoperative follow-up are an important issue. At Tikur Anbessa Specialised Hospital, Addis Ababa, Ethiopia, we aimed to evaluate the course and 12-month outcome of patients with severe chronic RHD who received open-heart surgery, as compared with the natural course of controls waiting for surgery and undergoing only medical treatment.

Methods

Clinical data and outcome measures were registered in 46 patients operated during five missions from March 2016 to November 2019, and compared with the first-year course in a cohort of 49 controls from the same hospital’s waiting list for surgery. Adverse events were death or complications such as stroke, other thromboembolic events, bleeding, hospitalisation for heart failure and infectious endocarditis.

Results

Survival at 12 months was 89% and survival free from complications was 80% in the surgical group. Despite undergoing open-heart surgery, with its inherent risks, outcome measures of the surgical group were non-inferior to the natural course of the control group in the first year after inclusion on the waiting list (p≥0.45). All except six surgical patients were in New York Heart Association class I after 12 months and 84% had resumed working.

Conclusions

Cardiac surgery for severe chronic RHD is feasible in LMICs if the service is structured and planned. Rates of survival and survival free from complications were similar to those of controls at 12 months. Functional level and resumption of work were high in the surgical group. Whether the patients who underwent cardiac surgery will have better long-term prognosis, in line with what is known in high-income countries, needs to be evaluated in future studies.

A glimpse of hope: cardiac surgery in low- and middle-income countries (LMICs)

Currently, more than five times more people live in low- and middle-income countries (LMICs) than in high-income countries (HICs). As such, the downward trend in cardiac surgical needs in HICs reflects only the situation of one sixth of the world population while the vast majority living in LMICs has still no or limited access to life saving heart operations. In these countries, rheumatic heart disease (RHD) still accounts for a significant proportion of cardiac surgical needs. In low- and lower-middle income countries it remains the single most common cardiovascular disease in young adult and adolescent patients in need of heart surgery outweighing other indications such as congenital cardiac defects almost 4-fold. Compared to HICs with their predominance of calcific aortic stenosis in the elderly mitral valve surgery is required in >90% of the largely young patients with RHD in low-income countries (LICs) and still in 70% of the often middle aged patients in middle-income countries (MICs). Although recent government initiatives in LICs led to the establishment of local, independent cardiac surgical services gradually replacing fly-in missions, these centers still only cover less than 2% of the needs of their populations. In MICs, cardiac surgical needs continually grow with the emergence of degenerative diseases. As such, in spite of the concomitant growth of cardiac surgical capacity, significantly less than half the estimated patients in need have access. Capacities in LICs range from 0.5 to 7 cardiac operations/million population; 100-481/million in MICs and >1,200/million in HICs such as the USA and Germany. While a new level of awareness of the scope and magnitude of the problem has begun to emerge in LICs and the establishment of local cardiac surgical capacity has given rise to a glimpse of hope, the challenges of expanding these fledgling services to a significant proportion of the population still seem insurmountable. Challenges in MICs are on the other hand the widening gap between private cardiac medicine for the affluent few and overwhelmed public services for the many and the rural urban divide with the underappreciation of the ongoing dominance of RHD in the rural and indigent population on the other. Overshadowing all LMICs is the low level of valve-repair skills associated with insufficient cardiac surgical capacity and the unavailability of suitable replacement valves which address the young age of the patients and the difficulties of anticoagulation in a socioeconomic environment distinctly different from the elderly patients of HICs.