Mpiko Ntsekhe
University of Cape Town/Groote Schuur Hospital, Cape Town, South Africa
This section of the book aims to provide a broad overview and current understanding of infectious heart diseases as experienced by adults living in sub-Saharan Africa. By highlighting three key research areas, it explores aspects of the epidemiology, pathogenesis, clinical manifestations, and potential prevention and management strategies for the main causes of infectious heart disease in African adults. This is achieved by providing simple but concise analyses of the available information from major contemporary observational studies and randomized trials conducted on the African continent. Data from around the world suggest that HIV predisposes to heart muscle and pericardial disease, causing PH and large vessel aneurysms. It also increases the risk of acute coronary syndrome (ACS) (in the absence of significant atherosclerosis) and may accelerate progression of chronic coronary atherosclerosis in those with traditional risk factors who are receiving HAART (see Chapter 10). The extent to which this holds true in the African setting, where the HIV burden is highest and the profile of people with HIV differs significantly from most of the rest of the world, is not clear. Chapter 9 helps to unpack some of these issues by providing an analysis of data from the Heart of Soweto Study that sets out to (a) explore the clinical presentation and cardiac disease profile of HIV-infected patients presenting to one of the largest referral hospitals in Africa and (b) quantify the burden of HIV-related cardiac disease relative to other forms of CVD in a community known to have a high background prevalence of HIV infection. TB remains endemic in most of sub-Saharan Africa and can affect all organs of the body, including the heart. In immune-competent hosts, the spread of TB to the heart occurs predominantly via the multiple major lymph glands that surround the heart (mediastinal, peritracheal, and peribronchial). Alternatively, in those who are immunocompromised, the spread of TB is predominantly via the hematogenous route. Cardiac involvement is localized to the pericardium in the majority of people with TB-related heart disease, where it presents as sub-acute effusive pericarditis with or without cardiac tamponade or constrictive pericarditis with or without HF. Although not common, TB can also involve the myocardium and endocardium. In this context, Chapter 8 provides an update and summary of recent randomized controlled outcome data designed to explore the potential efficacy of adjunctive immunotherapy for the treatment of effusive TB pericarditis in those with and without HIV.
Finally, in the setting of overcrowding and poverty, both of which are highly prevalent across the African continent, the immune response to Group B Streptococcus pharyngitis can lead to both acute and chronic RHD with devastating effects. The pathogenic interrelationship between poverty, overcrowding, genetic predisposition, and the immune response in this condition is yet to be elucidated, although promising research, which will be crucial to seeing the disease eventually eradicated, is underway. Sadly, rates of cardiovascular morbidity and premature mortality related to rheumatic valvular disease across the continent have been underestimated for decades, with more recent observational data revealing that the burden remains unacceptably high. In Africa, RHD remains an important contributor to the high levels of cardiac-related maternal morbidity and mortality, accounts for a significant proportion of AF and stroke, and is the major predisposing cardiac risk factor for infective endocarditis and its devastating outcomes. The absence of the ability to provide cardiac surgery in most of sub-Saharan Africa is an important consideration that adds to the impetus and calls to implement aggressive primary and secondary preventive strategies such as wider use of empiric penicillin for pharyngitis in susceptible populations. Chapter 7 provides fairly robust data from the Heart of Soweto Study that challenges the previously held myths of RHD as a vanishing disease of bygone eras that affected mainly children and contributed little to the burden of HF in adults.
In summary, sub-Saharan Africa is currently in the midst of a quadruple burden of disease that is characterized by high levels of trauma, a growing epidemic of chronic diseases of lifestyle (see Section 3), poor maternal and child health (see Sections 1 and 2, respectively), and a persistently high burden of communicable disease. In this section we focus on the latter by examining the interrelationship between infectious diseases and CVD in Africa and exploring their contribution to the high burden of structural heart disease. Three organisms and their sequelae account for the vast majority of the cardiac disease that is attributable to infections in sub-Saharan Africa—HIV, TB, and group B streptococcus. Accordingly, it is these infectious pathways to heart disease that feature heavily in the three chapters that compose this section of the book.
In Section 4, the urban area of Soweto in South Africa provides the setting for Chapters 7 and 9 (see Section 1 for profiles of Soweto and South Africa). Chapter 8 offers a contrasting geographical backdrop, featuring a multicenter trial representing eight African countries across diverse regions of the continent.