Challenges to Adopting Transcatheter Aortic Valve Implantation in Sub-Saharan Africa

The advent of Transcatheter aortic valve implantation (TAVI) as a treatment option to conventional heart valve surgery has revolutionized the management of patients with valvular heart disease, with an explosive growth globally over the last decade. TAVI received regulatory approval in the United States (US) for patients with symptomatic severe aortic stenosis (AS) at extremely high risk for surgical aortic valve replacement (SAVR) in late 2011. Following favorable results from multiple randomized trials, the indications for TAVI were gradually expanded in the US to high surgical risk (Society of Thoracic Surgeons [STS] Predicted Risk of Mortality score >8%) in 2012, intermediate risk (STS score: 4%–8%) in 2016, and low risk (STS score: <3%) in 2019.[¹]

The STS-American College of Cardiology (ACC) Transcatheter Valve Therapy Registry which documents the use of transcatheter aortic valve replacement in the US has demonstrated the rapid growth of TAVI, which surpassed isolated SAVR in 2015 and all SAVRs in 2018 [Figure 1].

Figure 1: Annual volumes of TAVR and SAVR in the US. TAVR: Transcatheter aortic valve replacement, SAVR: Surgical aortic valve replacement, US: United States.

Transcatheter mitral procedures have similarly gradually increased in the US [Figure 2].[¹]

Figure 2: Transcatheter mitral valve procedures in the US. US: United States.

A major consideration in decision-making between TAVI versus SAVR is finding the balance between expected patient longevity and valve durability which varies across the age spectrum, with a more durable valve preferred for patients having longer life expectancy.

The 2020 ACC/American Heart Association (AHA) clinical practice guideline states, when deciding between bioprosthetic versus mechanical AVR, that a bioprosthetic is preferred in patients of any age with contraindication to Vitamin K antagonist anticoagulant therapy and a reasonable choice in patients >65 years.[²]

The guideline also recommends SAVR for patients with severe AS and age <65 years or a life expectancy >20 years, while for patients 65–80 years of age with no contraindication to transfemoral TAVI, either SAVR or TAVI. In patients >80 years or younger patients with a life expectancy <10 years, TAVI is preferred over SAVR if no anatomic contraindications to transfemoral TAVI.

TAVI is, therefore, recommended for patients with an indication for AVR for whom a bioprosthetic valve is preferred, if valve and vascular anatomy are suitable, and for symptomatic patients of any age with a high or prohibitive surgical risk.

Although TAVI has now been used in all risk categories ranging from low- to high-risk patients, its adoption in low-to-middle-income countries remains limited for a variety of reasons, primarily financial constraints, valve pathology, gaps in imaging technology, and skilled personnel. A real-world cost analysis limited review comparing 239 SAVR versus 75 TAVI patients from South Africa, found that despite common perception of cost, SAVR was more expensive than TAVI in post hoc defined high-risk patients.[³]

Calcific AS seen mainly in patients over 65 years is the predominant pathology for aortic valve disease in the developed world compared to rheumatic heart disease (RHD) involving principally young adults in developing countries.

The WHO estimates that 50% of the approximately 2.4 million children aged 5–14 years with RHD globally live in sub-Saharan Africa and about 20% of these die within 6 years of disease onset at a mean age of 25 years mainly from chronic heart failure.[⁴] Therefore, even if TAVI was readily available and financial constraints not an impediment, most patients in sub-Saharan Africa would still not qualify with the current ACC/AHA guidelines.

Besides, the long-term durability of TAVI is still unknown, and bioprosthetic valves have a higher structural failure rate in young patients who generally have a longer life expectancy.

Nevertheless, a counter-argument is that life expectancy in sub-Saharan Africa is lower than in developed nations (Nigeria: 55.4 years, Ghana: 64.3 years, South Africa: 64.3 years, Kenya: 66.9 years, and Rwanda: 69.3 years in 2020), and additionally, patients with RHD are likely to have a shorter life expectancy compared to their age-matched general population. Therefore, TAVI could still be considered a reasonable option for aortic valve disease if available, given the increasing deployment and success of valve-in-valve TAVI for surgically implanted aortic bioprosthetic valve degeneration.

In a bid to address some of these obstacles hindering a wider adoption of TAVI in low-to-middle-income countries, Scherman et al.[⁵] from Chris Barnard Hospital, Cape Town, South Africa, following experimental animal studies showed a proof of concept for a cost-effective nonocclusive TAVI deployment system for noncalcific aortic valve disease seen in RHD. Should the device eventually prove efficacious and safe in clinical trials, it could lower cost and bridge the technologic and technical expertise gaps and offer hope for the millions of patients with RHD who may be potential candidates for percutaneous valve implantation in Africa.