BOX 1-1 Rheumatic Heart Disease: The Unfinished Agenda
For countries in the early stages of development, rheumatic heart disease is the most common form of CVD. Indeed, it is thought to affect more than 4 million people worldwide, resulting in approximately 90,000 deaths each year (Michaud et al., 1993). It is caused by group A streptococcal pharyngitis, which if untreated will progress in about 3 percent of cases to rheumatic fever and then cause immunologic damage to heart valves and muscle. Many years later, the thickened or incompetent heart valves disrupt blood flow, which leads to congestive heart failure or death. Although rheumatic fever and rheumatic heart disease have essentially disappeared in developed countries, both remain major causes of CVD in developing countries. In Africa, Latin America, Asia (especially India), and the Pacific Islands, 1-2 percent of school children show evidence of rheumatic valvular disease (Michaud et al., 1993). A high proportion of these children will develop progressive heart failure over the next 20-40 years, then die at 25 to 44 years of age. A range of 20-35 percent of cardiac patients admitted to hospitals in Africa and Asia have rheumatic heart disease, often with heart failure or needing replacement of the heart valve. This surgery is effective at prolonging life, but where it is not available, referrals abroad are costly. For the next 20-40 years, it is likely that developing countries will experience a double burden of CVD: rheumatic heart disease will continue, while atherosclerotic CVD becomes more common.
For most developing and middle-income countries, the increased incidence of CVD adds to the continuing burden of infectious, nutritional, and perinatal diseases. It is a major setback for health care systems that are already overburdened and underfunded (WHO, 1997, Box 1-4).
Subsets of a population may be at different stages of the CVD epidemic. An ''early-adopter" community such as one with rapid social and economic development may experience an early increase in CVD and thus have a higher level than other parts of the population. The decline in CVD burden may also occur earlier for this community, as shown in Figure 1- 1. The transition of CVD from a disease of the wealthy to one of the poor has been documented in the United Kingdom and the United States (Kaplan and Keil, 1993; Marmot et al., 1991). It was relatively rare in the African-American community in the 1960s, but now its incidence equals or exceeds that in the white population of the United States (NHLBI, 1996). The pattern of disease continues to be in transition for all but the most developed countries.