Poorly suited heart valve prostheses heighten the plight of patients with rheumatic heart disease

Mechanical valve replacement for patients with rheumatic heart disease: the reality of INR control in Africa and beyond

The majority of patients requiring heart valve replacement in low- to middle-income countries (LMICs) need it for rheumatic heart disease (RHD). While the young age of such patients largely prescribes replacement with mechanical prostheses, reliable anticoagulation management is often unattainable under the prevailing socioeconomic circumstances. Cases of patients with clotted valves presenting for emergency surgery as a consequence of poor adherence to anticoagulation control are frequent. The operative mortality rates of reoperations for thrombosed mechanical valves are several times higher than those for tissue valves, and long-term results are also disappointing. Under-anticoagulation prevails in these regions that has clearly been linked to poor international normalised ratio (INR) monitoring. In industrialised countries, safe anticoagulation is defined as >60%-70% of the time in the therapeutic range (TTR). In LMICs, the TTR has been found to be in the range of twenty to forty percent. In this study, we analysed >20,000 INR test results of 552 consecutive patients receiving a mechanical valve for RHD. Only 27% of these test results were in the therapeutic range, with the vast majority (61%) being sub-therapeutic. Interestingly, the post-operative frequency of INR tests of one every 3-4 weeks in year 1 had dropped to less than 1 per year by year 7. LMICs need to use clinical judgement and assess the probability of insufficient INR monitoring prior to uncritically applying Western guidelines predominantly based on chronological age. The process of identification of high-risk subgroups in terms of non-adherence to anticoagulation control should take into account both the adherence history of >50% of patients with RHD who were in chronic atrial fibrillation prior to surgery as well as geographic and socioeconomic circumstances.

Differential Immune Response to Bioprosthetic Heart Valve Tissues in the α1,3Galactosyltransferase-Knockout Mouse Model

Structural valve deterioration (SVD) of bioprosthetic heart valves (BHVs) has great clinical and economic consequences. Notably, immunity against BHVs plays a major role in SVD, especially when implanted in young and middle-aged patients. However, the complex pathogenesis of SVD remains to be fully characterized, and analyses of commercial BHVs in standardized-preclinical settings are needed for further advancement. Here, we studied the immune response to commercial BHV tissue of bovine, porcine, and equine origin after subcutaneous implantation into adult α1,3-galactosyltransferase-knockout (Gal KO) mice. The levels of serum anti-galactose α1,3-galactose (Gal) and -non-Gal IgM and IgG antibodies were determined up to 2 months post-implantation. Based on histological analyses, all BHV tissues studied triggered distinct infiltrating cellular immune responses that related to tissue degeneration. Increased anti-Gal antibody levels were found in serum after ATS 3f and Freedom/Solo implantation but not for Crown or Hancock II grafts. Overall, there were no correlations between cellular-immunity scores and post-implantation antibodies, suggesting these are independent factors differentially affecting the outcome of distinct commercial BHVs. These findings provide further insights into the understanding of SVD immunopathogenesis and highlight the need to evaluate immune responses as a confounding factor.

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.

Expanding Valve Repair in Rheumatic Heart Disease

Rheumatic heart disease is a serious ailment with significant morbidity and mortality in endemic areas; yet, there is no agreement on indication, timing, and surgical modality for treating rheumatic valve affection. There is mounting evidence that rheumatic mitral valve repair is possible with good long-term results, less is the case with rheumatic aortic valve disease. We discuss the surgical approach for both valves emphasizing the role of multimodality imaging.

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.

Long-Term Stability and Biocompatibility of Pericardial Bioprosthetic Heart Valves

The use of bioprostheses for heart valve therapy has gradually evolved over several decades and both surgical and transcatheter devices are now highly successful. The rapid expansion of the transcatheter concept has clearly placed a significant onus on the need for improved production methods, particularly the pre-treatment of bovine pericardium. Two of the difficulties associated with the biocompatibility of bioprosthetic valves are the possibilities of immune responses and calcification, which have led to either catastrophic failure or slow dystrophic changes. These have been addressed by evolutionary trends in cross-linking and decellularization techniques and, over the last two decades, the improvements have resulted in somewhat greater durability. However, as the need to consider the use of bioprosthetic valves in younger patients has become an important clinical and sociological issue, the requirement for even greater longevity and safety is now paramount. This is especially true with respect to potential therapies for young people who are afflicted by rheumatic heart disease, mostly in low- to middle-income countries, for whom no clinically acceptable and cost-effective treatments currently exist. To extend longevity to this new level, it has been necessary to evaluate the mechanisms of pericardium biocompatibility, with special emphasis on the interplay between cross-linking, decellularization and anti-immunogenicity processes. These mechanisms are reviewed in this paper. On the basis of a better understanding of these mechanisms, a few alternative treatment protocols have been developed in the last few years. The most promising protocol here is based on a carefully designed combination of phases of tissue-protective decellularization with a finely-titrated cross-linking sequence. Such refined protocols offer considerable potential in the progress toward superior longevity of pericardial heart valves and introduce a scientific dimension beyond the largely disappointing 'anti-calcification' treatments of past decades.

Transcatheter Valve-in-Valve Procedures for Bioprosthetic Valve Dysfunction in Patients With Rheumatic vs. Non-Rheumatic Valvular Heart Disease

Background: Bioprosthetic heart valve has limited durability and lower long-term performance especially in rheumatic heart disease (RHD) patients that are often subject to multiple redo operations. Minimally invasive procedures, such as transcatheter valve-in-valve (ViV) implantation, may offer an attractive alternative, although data is lacking. The aim of this study was to evaluate the baseline characteristics and clinical outcomes in rheumatic vs. non-rheumatic patients undergoing ViV procedures for severe bioprosthetic valve dysfunction.

Methods: Single center, prospective study, including consecutive patients undergoing transcatheter ViV implantation in aortic, mitral and tricuspid position, from May 2015 to September 2020. RHD was defined according to clinical history, previous echocardiographic and surgical findings.

Results: Among 106 patients included, 69 had rheumatic etiology and 37 were non-rheumatic. Rheumatic patients had higher incidence of female sex (73.9 vs. 43.2%, respectively; p = 0.004), atrial fibrillation (82.6 vs. 45.9%, respectively; p < 0.001), and 2 or more prior surgeries (68.1 vs. 32.4%, respectively; p = 0.001). Although, device success was similar between groups (75.4 vs. 89.2% in rheumatic vs. non-rheumatic, respectively; p = 0.148), there was a trend toward higher 30-day mortality rates in the rheumatic patients (21.7 vs. 5.4%, respectively; p = 0.057). Still, at median follow-up of 20.7 [5.1–30.4] months, cumulative mortality was similar between both groups (p = 0.779).

Conclusion: Transcatheter ViV implantation is an acceptable alternative to redo operations in the treatment of patients with RHD and severe bioprosthetic valve dysfunction. Despite similar device success rates, rheumatic patients present higher 30-day mortality rates with good mid-term clinical outcomes. Future studies with a larger number of patients and follow-up are still warranted, to firmly conclude on the role transcatheter ViV procedures in the RHD population.

The "Cairo Accord"- Towards the Eradication of RHD: An Update

Rheumatic heart disease (RHD) is the most common cause of acquired heart disease in children and young adults. It continues to be prevalent in many low- and middle-income countries where it causes significant morbidity and mortality. Following the 2017 Cairo conference "Rheumatic Heart Disease: from Molecules to the Global Community," experts from 21 countries formulated an approach for addressing the problem of RHD: "The Cairo Accord on Rheumatic Heart Disease." The Accord attempts to set policy priorities for the eradication of acute rheumatic fever (ARF) and RHD and builds on a recent series of policy initiatives and calls to action. We present an update on the recommendations of the Cairo Accord and discuss recent progress toward the eradication of RHD, including contributions from our own Aswan Rheumatic Heart Disease Registry (ARGI).

United in earnest: First pilot sites for increased surgical capacity for rheumatic heart disease announced by Cardiac Surgery Intersociety Alliance

BACKGROUND

Rheumatic heart disease affects more than 33,000,000 individuals, mostly from low- and middle-income countries. The Cape Town Declaration on Access to Cardiac Surgery in the Developing World was published in August 2018, signaling the commitment of the global cardiac surgery and cardiology communities to improving care for rheumatic heart disease patients.

METHODS

As the Cape Town Declaration formed the basis for which the Cardiac Surgery Intersociety Alliance was formed, the purpose of this article is to describe the history of the Cardiac Surgery Intersociety Alliance, its formation, ongoing activities, and future directions, including the announcement of selected pilot sites.

RESULTS

The Cardiac Surgery Intersociety Alliance is an international alliance consisting of representatives from major cardiothoracic surgical societies and the World Heart Federation. Activities have included meetings at annual conferences, exhibit hall participation for advertisement and recruitment, and publication of selection criteria for cardiac surgery centers to apply for Cardiac Surgery Intersociety Alliance support. Criteria focused on local operating capacity, local championing, governmental and facility support, appropriate identification of a specific gap in care and desire to engage in future research. Eleven applications were received for which three finalist sites were selected and site visits conducted. The two selected sites were Hospital Central Maputo (Mozambique) and King Faisal Hospital Kigali (Rwanda).

CONCLUSIONS

Substantial progress has been made since the passing of the Cape Town Declaration and the formation of the Cardiac Surgery Intersociety Alliance, but ongoing efforts with collaboration of all committed parties-cardiac surgery, cardiology, industry, and government-will be necessary to improve access to life-saving cardiac surgery for rheumatic heart disease patients.