Congenital heart disease is the most common of all congenital defects. In terms of organization of care, the emphasis has always been on the impact of congenital heart disease in the first years of life: in the era before cardiac surgery, congenital heart disease was the most important cause of infant death and only a few of those born with complex congenital heart disease survived until adulthood. Since the introduction of cardiac surgery by Lillehei in 1953, a gradual improvement in survival has been achieved over the subsequent decades. This has led to a situation where the number of patients with congenital heart disease who reach adult age has gradually increased, and with the current level of healthcare it is expected that over 90% of babies born in developed countries with congenital heart disease will now survive until adulthood.

Most patients who survive into adulthood after cardiac surgery in childhood, are not ‘cured’ for life; almost all have residual abnormalities . The need for continuation of specialized care after their childhood years has been emphasized since the early 1980s . The existing healthcare networks for adult patients with cardiac problems – the regular cardiology services – are not equipped for this task, because of lack of training and exposure and therefore skills in this specific field . Awareness of this issue has led to the establishment of programmes for specialized adult congenital heart disease (ACHD) care throughout Europe. Some programmes started in the 1980s, many in the 1990s, and the number of centres is still increasing. In addition, existing centres tend to grow, many of them rapidly .

In a recent survey, Moons et al. identified 70 centres in Europe that could be labelled as centres for ACHD. Altogether, these 70 centres had some 130,000 adult patients in their care. The authors stated that this was only a fraction of the entire population of patients with ACHD, that this population is heavily under serviced in terms of available care at an adequate level and that many more centres – or much larger units – would be needed.

Establishing and running a unit for specialized ACHD care is, however, a costly affair, as these chronically ill patients with considerable morbidity , need a relatively large amount of “doctor time” and claim a fairly large proportion of health-care resources . If we want to convince health-care planners and boards (or directors of hospitals) of the necessity of investing in such a costly service, we need to answer a few basic questions. How many patients in total are involved? How many of these patients have complex ACHD, how many have ACHD of moderate severity and how many have mild ACHD? Which defects really require specialized tertiary referral ACHD care and which can be dealt with in regional hospitals by cardiologists? How many patients need no special cardiac follow-up at all? These are simple and fair questions, but are difficult to answer.

We do not know the incidence of congenital heart disease (i.e., how many patients are born per year with congenital heart disease in a specific population or country), because reports on this topic vary enormously from four per 1000 live births to 50 per 1000 live births.

We also do not know the prevalence of congenital heart disease (i.e., how many patients are alive with congenital heart disease in a population or country), because we do not know the starting point (the incidence) or how many patients have died. We are not aware of any country in which there is a population-based registry that is solid and detailed enough to answer these questions.

What should be considered as complex congenital heart disease? There is no uniformity in the definition that has been used in the various published studies, task force reports and position papers. For example, tetralogy of Fallot and atrioventricular septal defects – both fairly large diagnosis groups – are defects that are classified as severe or complex by some and as moderately severe by others. Neither is there consensus about which patient group actually needs highly specialized, tertiary referral care. There is not much discussion about really complex congenital heart disease (it is accepted that patients should be seen in a specialized centre]) and there is also a shared belief that truly simple lesions do not need specialized care. But what is the best option for the group of patients with moderately complex congenital heart disease? Regional care provided by the regular cardiology services near the patient, tertiary referral specialized care, or both options as shared care? And who should do a catheter-based intervention or a surgical procedure in a simple defect detected in adulthood? Atrial septal defect closure and aortic coarctation are the most typical examples. Should they all be referred to a tertiary referral centre?

With the major issues of incidence and prevalence largely unresolved, and no consensus about the number and category of patients that should be seen in a tertiary referral, specialized ACHD centre, it is very difficult to make plans to create adequate healthcare for these patients. This probably explains the current situation in Europe regarding ACHD care, as described by Moons et al. .

There have been some excellent attempts in recent years to tackle this issue. Although based mainly on estimations and not on actual measurements, and coming mostly from the USA, these studies might be very helpful in trying to understand the scope of the problem in Europe.