Bridging Knowledge Gaps in Low- and Middle-Income Countries: Valvular Heart Disease as a Model of Global Epidemiological Transition

Key Points

• Valvular heart disease (VHD) in low- and middle-income countries (LMICs) is characterized by a dual burden of rheumatic and degenerative etiologies, reflecting the global epidemiological transition.

• Despite increasing prevalence and severity, VHD remains markedly under-researched in LMICs, leading to diagnostic and therapeutic inequities.

• Local and regional disparities in healthcare access and infrastructure exacerbate this burden and must be addressed through contextualized research.

• Strategic investment in epidemiological mapping, etiological profiling, economic evaluation, and implementation science is essential to guide action.

• International and regional collaborations are crucial to support capacity-building, funding, and the integration of VHD care into broader public health strategies.

VHD is an increasingly recognized global health issue with evolving epidemiological patterns reflecting socioeconomic transitions and demographic shifts. Historically dominated by rheumatic heart disease (RHD) in LMICs, VHD now comprises a broader spectrum of etiologies, including degenerative and calcific forms, with recently evidenced links with cardiometabolic and kidney diseases.^1-3 Despite its growing relevance, VHD in LMICs remains significantly under-researched, leading to a critical gap in knowledge.

Indeed, VHD has seen a growing research interest globally over the past decade, although this interest remains unevenly distributed. A bibliometric analysis of PubMed-indexed articles from 2010 to 2024 reveals marked disparities in publication volumes between high-income countries (HICs) and LMICs, depending on the type of VHD (Figure 1). These trends highlight a growing disparity between regions. While the volume of research on degenerative valvular diseases is rapidly expanding in HICs, LMICs continue to focus on RHD, with far fewer publications overall. The global scientific visibility of LMIC-specific VHD is therefore limited, despite a significant and evolving burden of disease.

Figure 1.

Estimated Publications from PubMed on Valvular Heart Disease (VHD) by Region and Disease Type (2010–2024). AS, aortic stenosis; MR, mitral regurgitation; MS, mitral stenosis; RHD, rheumatic heart disease; AR, aortic regurgitation; TR, tricuspid regurgitation; HIC, high income countries; LMIC, low- and middle-income countries.

This paucity of locally extensive research translates into major public health and healthcare challenges. Without accurate epidemiological data, health systems struggle to implement appropriate screening programs, allocate resources effectively, or prioritize interventions. The absence of robust evidence also impedes the development of context-specific clinical guidelines and limits the ability of policymakers to respond to the increasing prevalence of degenerative valve diseases in aging LMIC populations. Ultimately, this knowledge gap contributes to screening and diagnostic delays, under-treatment, and worsened outcomes for millions of patients.

This viewpoint outlines the urgent need for research on VHD in LMICs, framed through a public health and epidemiological perspective

The burden of VHD in LMICs: Dual pathology and epidemiological transition

RHD affects more than 40 million people worldwide and is responsible for over 300,000 deaths annually, with more than 80% of the global burden concentrated in LMICs. SubSaharan Africa, South Asia, and parts of Oceania and Latin America remain the most affected regions. School-based echocardiographic screening studies have revealed prevalence rates as high as 20–30 cases per 1000 children in endemic settings. The disease predominantly strikes during childhood and adolescence but leads to progressive valvular damage, often resulting in complications in early adulthood. Despite its preventable nature, RHD remains a leading cause of cardiovascular morbidity and mortality in young populations in LMICs.^4-6

Although RHD prevalence has declined in some LMICs (eg, India, Bangladesh, Nepal, Morocco) due to improved access to antibiotics and better hygiene, persistent barriers still remain. These include limited access to primary healthcare facilities, long travel distances to medical centers, shortage of trained personnel, and financial constraints. In many rural or peri-urban areas, patients may rely on informal healthcare providers or experience diagnostic delays due to lack of echocardiography. These structural barriers contribute to the late-stage presentation of RHD and delay appropriate management. Of note, optimal care for VHD typically involves early detection through auscultation and/or echocardiography. Accurate etiological classification, severity grading, myocardial and pulmonary consequences assessment and risk stratification, may require advanced imaging modalities or biomarkers. Subsequently, timely therapeutic interventions may include secondary prophylaxis (for RHD), medical therapy to manage heart failure symptoms, and surgical or percutaneous valve interventions depending on severity and valve anatomy. In LMICs, limited access to such a continuum of care—particularly specialized cardiac imaging, surgery or interventional cardiology—exacerbates the burden and contributes to excess disability and morbid-mortality.

Simultaneously, demographic aging and increasingly westernized lifestyles—including reduced physical activity and higher consumption of ultra-processed foods rich in added sugars, sodium, and saturated fats^7,8—are contributing to a surge in major cardiovascular risk factors ⁹ and the growing burden of chronic noncommunicable diseases (NCDs) in LMICs. ¹⁰ These changes are shifting the epidemiological landscape toward degenerative forms of VHD, particularly calcific aortic stenosis. The adoption of such dietary and lifestyle patterns is associated with an increased prevalence of pro-atherosclerotic, pro-inflammatory, pro-thrombotic, and pro-calcifying metabolic conditions, mainly driven by central obesity, ² and mediated by elevated low-density lipoprotein cholesterol, hypertriglyceridemia, hypertension, insulin resistance, and type 2 diabetes mellitus. According to data from the Global Burden of Disease (GBD) Study, the age-standardized prevalence rate of nonrheumatic aortic valve disease in LMICs increased by more than 15% between 1990 and 2019. This trend was particularly marked among individuals aged 55 years and older, reflecting demographic aging and increasing exposure to cardiovascular risk factors. The GBD 2019 report highlighted that mortality rates associated with nonrheumatic aortic valve disease have also risen in many LMICs, underscoring the growing clinical and public health burden of degenerative valvular conditions in these regions.^11,12

This dual burden—coexistence of RHD and degenerative VHD—places immense strain on fragile health systems. Moreover, there are wide geographic disparities in the prevalence, presentation, and outcomes of VHD within and between LMICs. These disparities are influenced by urban-rural rifts, socioeconomic status, health infrastructure, and environmental conditions. Consequently, epidemiological research in these contexts must account for such heterogeneity by initiating pilot studies in diverse settings before scaling to national or multicountry surveys. This stepwise approach would help tailor study design and implementation strategies, ensuring that subsequent large-scale data collections are both context-sensitive and methodologically robust. Furthermore, it is essential to recognize that RHD and degenerative VHD differ significantly in their natural history, risk factors, and clinical pathways. RHD is primarily driven by repeated streptococcal infections and immune-mediated valvular inflammation, affecting children and young adults in overcrowded, unsanitary settings with limited access to antibiotics. In contrast, degenerative VHD, especially calcific AS and MR, emerges in older adults and is associated with traditional cardiovascular risk factors such as hypertension, diabetes, chronic kidney disease, and atherosclerosis. Screening strategies differ accordingly: RHD may benefit from school-based echocardiographic screening and secondary prophylaxis programs, while degenerative VHD requires integration into aging and chronic disease care frameworks. The management approaches also vary, from penicillin prophylaxis and early surgical repair in RHD to complex decision-making around valve replacement or transcatheter interventions in older patients, often asymptomatic, with multiple comorbidities.^13,14 In this context, LMIC health systems must urgently begin adapting to this shifting disease profile. Fortunately, the current rise in degenerative VHD remains gradual, offering a narrow but valuable window of opportunity to conduct research, develop screening strategies, and strengthen healthcare infrastructure before the burden becomes overwhelming.

Limited Data and Research Infrastructure

Epidemiological data on VHD in LMICs are extremely limited, often derived from hospital-based registries or modeled estimates with large uncertainty intervals. ¹⁵ Systematic screening is rarely implemented at the national level, and very few countries, such as India or South Africa, have established national cardiovascular disease registries. There is a lack of systematic screening, national registries, and population-based cohorts on VHD in LMICs. This paucity of data impairs the ability to understand disease dynamics, identify at-risk populations, and develop cost-effective prevention strategies. Most LMICs lack cardiovascular research infrastructure, including echocardiographic expertise and access to advanced imaging modalities. Yet national registry data are lacking even in higher-burden countries, and cardiac imaging infrastructure remains sparse: LMICs often have <1 cardiac center per 10 million inhabitants. Furthermore, international collaborations and funding opportunities remain scarce, restricting local researchers’ ability to generate and disseminate high-quality evidence.

Inequity in access to diagnosis and treatment

In most LMICs, patients present at an advanced stage of disease due to lack of awareness, suboptimal primary care systems, and limited access to diagnostics. Even when diagnosed, therapeutic options remain constrained. Valve repair or replacement procedures are often unavailable or unaffordable. Transcatheter aortic valve replacement (TAVR), which is increasingly used in HICs for older adults with AS, is rarely accessible in LMICs. . This paradox highlights a critical inequity: Populations bearing the highest burden of VHD are often those with the least access to recent therapeutic innovations.

Need for Contextualized Research Priorities

Research on VHD in LMICs must be designed with strong contextual relevance (Figure 2). First, disparities in VHD burden—linked to geographic, socioeconomic, and healthcare access variability—call for pilot studies that precede large-scale epidemiological investigations. These pilots can help tailor study protocols to local constraints and ensure feasibility.

Figure 2.

Key Pillars to Guide Research Priorities on Valvular Heart Disease in Low- and Middle-Income Countries (LMICs). The diagram highlights four major domains: (1) epidemiological mapping, (2) etiological transition, (3) economic evaluation, and (4) implementation models. Each pillar supports a coordinated approach to addressing data gaps and guiding future healthcare planning.

Second, with a transition from RHD to degenerative etiologies underway, longitudinal data are essential to understand the evolving disease spectrum. This shift has critical implications: Degenerative VHD typically affects older patients with others chronic diseases (eg hypertension, diabetes, metabolic syndrome), involves different clinical management pathways, and imposes distinct pressures on health systems. Research must capture this evolution and support evidence-based planning.

Third, health economic studies—including cost-of-illness assessments and projections—are needed to anticipate the growing financial impact of VHD. These findings should inform strategic decisions around infrastructure, diagnostic pathways, and access to interventions.

Finally, implementation science should be employed to assess how best to deliver screening, prevention, diagnosis, and treatment services. This includes evaluating task-shifting models—such as the use of point-of-care ultrasound (POCUS) by trained noncardiologists or nonphysician health workers—to improve diagnostic capacity in settings with limited specialist access. Mobile technologies can facilitate remote monitoring and data collection, while telemedicine and tele-expertise platforms allow for timely decision-making and collaboration with regional or international experts. Integrated care within primary health systems is also critical to ensure continuity of care and early detection of VHD, particularly through linkage with chronic disease programs and maternal and child health services.

While international societies can support partnerships, capacity building, and advocacy for research funding, it is essential that local scientific societies and national stakeholders take the lead in prioritizing research agendas and models of care for VHD. Regional consortia—spanning several neighboring countries—may offer an effective framework to coordinate epidemiological studies, share data and methodologies, and adapt innovations to regional contexts. This locally driven and regionally coordinated approach ensures ownership, contextual relevance, and long-term sustainability.

Preparing for the Wave: Global Responsibility and Local Readiness

While international scientific societies can support partnerships, capacity building, and advocacy for research funding, it is essential to consider the question of financing and responsibility. Implementing VHD-focused strategies in LMICs will incur substantial costs—not only for diagnostics and interventions but also for research, training, and infrastructure. Given the limited fiscal space —ie the restricted capacity of many LMIC governments to expand health spending without jeopardizing other essential public services or economic stability—external support is imperative. In this regard, the global health community should revisit its funding priorities. Over the past decades, substantial international investments have been directed toward combating infectious diseases such as HIV/AIDS, malaria, and tuberculosis, which led to remarkable global health achievements; including a marked reduction in AIDS-related mortality, the near-eradication of polio in many regions, and large-scale access to antiretroviral therapy and insecticide-treated nets.

While these efforts remain critical, the growing burden of cardiovascular diseases, including VHD, calls for a progressive and proportional reallocation of resources. Supporting cardiovascular health, including structural heart disease, should be framed as a global responsibility. Institutions such as the World Health Organization, World Bank, Global Fund, and major philanthropic donors must recognize the epidemiological transition and act accordingly.

Simultaneously, countries and subregions must proactively prepare to absorb the rising wave of chronic cardiovascular conditions. This includes investing in the training of healthcare professionals, scaling up cardiac imaging capacity, and developing integrated care pathways within primary and secondary health systems. National health authorities must anticipate future demand and develop strategies to build resilient infrastructure capable of delivering timely and equitable care for VHD. Failure to act now risks amplifying existing disparities and overwhelming already fragile health systems in the near future. Prioritizing VHD prevention, diagnosis, and treatment aligns with the principles of equity, sustainability, and health systems strengthening, and represents an opportunity to mitigate the impending burden of NCDs in the world's most vulnerable regions.

Conclusion

VHD in LMICs exemplifies the intersection of old and new global health challenges: Lingering infectious diseases and rising noncommunicable conditions. These disorders reflect—and reveal—the broader epidemiological transition under way in many LMICs. The limited research dedicated to VHD in these settings results not only in diagnostic and therapeutic inequities but also in missed opportunities to better understand and respond to this epidemiological shift. Bridging the knowledge gap in VHD research would not only improve clinical outcomes for millions but also provide a powerful model for studying global cardiovascular transitions. Addressing this need requires targeted investment in research, surveillance infrastructure, and international collaboration.