Congenital Heart Disease Epidemiology in the United States: Blindly Feeling for the Charging Elephant.

Congenital heart disease (CHD) is the most common of all congenital defects, affecting nearly 1% of live births. Creative operative and catheter-based interventions have facilitated survival to adulthood with nearly all defects, setting the stage for a rapidly growing population of adolescents and adults with CHD. Although the field of adult CHD (ACHD) remains in its infancy, it is important to acknowledge the tremendous achievements in the United States and abroad over the last decades. ACHD publications have increased almost exponentially (Figure). The first American College of Cardiology/ American Heart Association joint guidelines on the diagnosis and management of ACHD were published in 20081 with a revision anticipated soon; subspecialty status in cardiology was granted by the American Board of Medical Specialties in 2012 with the first qualifying examination offered in the fall of 2015, and the first class of American Council for Graduate Medical Education–approved fellowship training begins July 2016. Multicenter and multinational research collaborations have formed, including the Alliance for Adult Research in Congenital Cardiology, as have patient/provider collaborative organizations such as the Adult Congenital Heart Association and the International Society of Adult Congenital Heart Disease. Funding for research has also improved, led by the US Department of Defense, the American Heart Association, and the National Heart, Lung, and Blood Institute. Despite tremendous progress, obstacles to the appropriate and sustained growth of this field remain numerous in the United States. Gilboa and colleagues2 remind us of one of these major limitations in this issue of Circulation. Our current estimate of the number of patients with CHD in the United States continues to be based on extrapolations from the population of Quebec, Canada. Although Marelli and colleagues3-5 have published several seminal papers using the data from this well-characterized cohort of patients, it remains uncertain just how closely Canadian data parallel our own population. Canada has a lower infant mortality rate and a smaller population of obese patients, and the United States has 5.7-fold more blacks and 17.4-fold more Hispanics.6 Socioeconomic conditions, genetic backgrounds, and environmental exposures can all affect maternal and fetal health, thus influencing birth rates of CHD.7 Canadians enjoy universal access to health care, whereas access in the United States is too often based on socioeconomic conditions. Changes to our healthcare system have recently improved access for the indigent population, although evidence suggests that not everyone has benefited.8 Patients with CHD in the United States are particularly likely to experience a loss to follow-up in their late teens to early 20s,9 which appears to coincide with loss of insurance coverage and its potentially detrimental effects on overall health.10 Healthcare system changes may help curtail this problem, but the United States is poorly equipped to handle the number of ACHD patients who need care. Certain parts of the United States have also experienced dramatic Congenital Heart Disease Epidemiology in the United States