Editorial: Univentricular Heart

Decades ago, the surgeons were asking themselves if it was possible to improve the natural history of patients with “functionally” univentricular heart (1). In order to facilitate the understanding and the subsequent decision making, for the first time, the patients with “functionally” univentricular heart were divided into two groups: (1) restricted pulmonary blood flow and (2) unrestricted pulmonary blood flow, with or without obstruction to the systemic blood flow (1). Since the first stage in both groups is a palliative approach, over the years, the progress with the available materials and technology facilitated the surgical palliations to increase the pulmonary blood flow with systemic-to-pulmonary shunt (modified Blalock–Taussig shunt) (2, 3) as well as the control of distal pulmonary artery pressure and flow with adjustable pulmonary artery banding (4, 5). The introduction of the use of the end-to-side anastomosis of the transected main pulmonary artery to the ascending aorta (Damus–Kaye–Stansel), as source of systemic blood flow, facilitated themanagement of patientswith “functionally” univentricular heartwith obstruction to the systemic blood flow (6). The results of the surgical management have been substantially improved by the introduction of the bidirectional Glenn (end-to-side anastomosis of the superior vena cava to the right pulmonary artery) as second stage between the first palliation to control the pulmonary blood flow and the final stage of dividing the systemic and the pulmonary venous returns (7). The introduction of the extracardiac modified Fontan procedure as third surgical stage contributed to provide adequate early (8) and late (9) results, with better survival and lower incidence of complications. The improved knowledge of the appropriate timing of indication and the adequate preparation for the third stagewith Fontan circulation (10) together with progress in the intraoperativemanagement (11) provided a further improvement in the surgical outcomes. The availability of adequate research laboratories allowed the performance of sophisticated experimental studies on animals to improve the available knowledge on the mechanisms of chronic hypoxia (12, 13) and pulmonary hypertension (14, 15), characterizing respectively the two groups of patients, with “functionally” univentricular heart and restrictive or unrestrictive pulmonary blood flow. Finally, the combination of experimental research with computational fluid dynamic studies prompted to evaluate the feasibility of themechanical assistance for patients at high risk formodified Fontan procedure or with failure of the Fontan circulation (16).