According to the 2003 ESC guidelines, patients should be assigned a name for their diagnosis and classified into three groups (simple, moderate, severe), with appropriate care levels advocated for each group: (a) patients who require care exclusively in specialized ACHD centers, (b) patients in whom shared care can be established with appropriate general adult cardiac services, and (c) patients who can be managed in nonspecialized facilities (with access to specialized care if required) [3]. However, in the new 2010 version, classifications based on diagnosis were abandoned, and the guidelines emphasized that all patients should be examined once at a specialized ACHD center, where they would undergo initial evaluation and receive recommendations for long-term care [12]. To ensure that all patients are examined at specialized ACHD centers, it is important that both the patient and their attending physician (this could be a pediatric cardiologist, cardiovascular surgeon, general pediatrician, etc.) understand the importance of being examined at a specialized ACHD center and to ascertain where they are located. Therefore, it is essential that academic bodies and other such parties in each country acknowledge specialized ACHD centers and publish a list of these centers. Patient education is also vital, given that there are those who do not adequately understand the necessity of undergoing examinations starting in childhood onward and are subsequently lost to follow-up.

Specialized ACHD centers not only provide treatment but also function as an education hub. In 2012, the American Board of Internal Medicine classified ACHD as a subspecialty for basic internal medicine specialists, and the board created a formal training program [13]. The conditions for becoming a specialist include 24 months of ACHD fellowship training. It is essential that specialized ACHD centers, which treat many of the patients, also fulfill the role of a training program provider.

Specialized centers with many patients have a role in promoting research related to the treatment of ACHD. A number of guidelines have been published to date, but much of the research contained in those guidelines lacks evidence. Causes include the wide range of diseases associated with ACHD and the small number of patients in each facility. It is important that specialized ACHD centers with many patients not only promote research in their own center, but these centers should also take a leadership role in promoting research in this field, through multicenter joint research projects that include other specialized centers.

The necessity and role of specialized centers have been mentioned in many guidelines, but at present, the number of specialized centers is less than ideal [6, 8]. The number of specialized centers is inadequate because the number of patients followed up in each center is small; moreover, there is a lack of human and financial resources invested in ACHD. These factors are interrelated; if there are insufficient numbers of patients, it is not possible to adequately invest in medical resources, and if there is inadequate investment in medical resources, then it is impossible to treat many patients. We would like to introduce Japan’s example as a strategy to break out of this vicious cycle. Historically in Japan, patients with congenital heart disease were continued to be followed up by pediatricians even after they reached adulthood, and there were only a few cardiologists who were interested in treating ACHD. However, with establishment of the Japanese Society for Adult Congenital Heart Disease, the number of cardiologists interested in ACHD has slowly increased. Subsequently, cardiologists established the Japanese Network for Cardiovascular Department for ACHD, a cardiovascular medicine organization, and specialized ACHD outpatient centers were established by cardiologists throughout Japan; thus, multidisciplinary specialized ACHD centers were established in various regions around Japan [14]. This is a case in which development of human resources preceded demand.

Actions taken by patient groups are also important. Increasing the number of patients in specific centers in principle reduces the number of patients at other centers, which forces some patients to transfer between hospitals or to attend multiple medical institutions. It is essential to clarify the preferences of the patients themselves in terms of treatment systems, giving due consideration to geographical access to medical institutions; it is also important for medical personnel to support such actions, with the expectation of political action by patient associations.

It is essential that all patients with ACHD be examined once at a specialized ACHD center; however, depending on the patient’s circumstances, and access to transportation to the center, subsequent routine follow-up consultations may be conducted in related nonspecialized facilities. Depending on the country and the region, there are doctors who specialize in ACHD within related nonspecialized facilities, and there may be centers with more than 200 ACHD patients receiving regular follow-up care. However, specialized ACHD centers must be facilities that are able to consistently handle all the potential needs of ACHD patients over their lifetime, and if a center is not equipped to handle inpatient medical care functions, then that center is a nonspecialized facility. The important point is the development of a referral relationship to ensure that when patients who are receiving follow-up in nonspecialized facilities require inpatient care for surgical treatment or prenatal and postnatal care, etc., it should be possible to smoothly transfer them to specialized ACHD centers.