The developmental origins of chronic rheumatic heart disease

Abstract

Programming is the phenomenon whereby the body's structures and functions are permanently set by nutrition and other influences during early development. There is increasing evidence that programming in utero initiates cardiovascular disease. We hypothesized that susceptibility to developing chronic rheumatic heart disease on exposure to Streptococcus pyogenes is programmed. We studied hospital admissions and deaths from chronic rheumatic heart disease in 20,431 people born in Helsinki, Finland, during 1924-1944. One hundred and one people, 56 men, and 45 women, had chronic rheumatic heart disease. The disease was not associated with body or placental size at birth. It was, however, associated with a long umbilical cord so that the hazard ratio for the disease was 1.23 (95% CI 1.04-1.45, P = 0.02) for every 10 cm increase in cord length. This association was present in people with mitral valve disease, hazard ratio 1.5 (1.20-1.89, P < 0.0001), but not in people with aortic valve disease, hazard ratio 1.0 (0.76-1.33, P = 0.97). Growing up in large households increased the risk of rheumatic heart disease. Longer umbilical cords have more spirals and a greater density of spirals per unit of length. Increased spiraling will increase the resistance to flow and the pressure load on the fetal heart. This could affect the development of the heart's valves and make them more vulnerable to the autoimmune process initiated by Streptococcus pyogenes. The mitral valve may be more vulnerable than the aortic valve because the valve leaflets are larger and therefore have greater wall stress.