Anatomical variations on a univentricular circulation. a) Double inlet left ventricle (LV) with ventriculoarterial discordance and no pulmonary stenosis; b) tricuspid atresia with hypoplastic right ventricle (RV), ventriculoarterial concordance and hypoplastic pulmonary artery (PA); and c) hypoplastic left heart syndrome with atrioventricular and ventriculoarterial concordance, hypoplastic left ventricle, aorta and aortic arch. Many classification systems have been proposed for univentricular hearts. The physician treating adult congenital heart disease needs an understanding of atrial arrangement, atrioventricular valve morphology and the morphology of the dominant ventricle, in addition to the surgical procedures that the patient has undergone, as all of these features will contribute to problems that may be faced in adult life. RPA: right pulmonary artery; LPA: left pulmonary artery; SVC: superior vena cava; RA: right atrium; LA: left atrium; PV: pulmonary vein; IVC: inferior vena cava; TV: tricuspid valve; MV: mitral valve.
Fontan circulation. a) Modified atriopulmonary connection Fontan in which the systemic venous atrium is directly connected to the pulmonary arteries; b) inferior vena cava flow streamed directly to the pulmonary arteries in a right atrium lateral tunnel Fontan; and c) extracardiac conduit connecting the inferior vena cava to the pulmonary arteries. The latter two operations (b and c) are forms of total cavopulmonary connection (TCPC) Fontan, and show a fenestration between the total cavopulmonary connection pathway and the right atrium, a common surgical modification performed to relieve pressure in the pathway. RPA: right pulmonary artery; LPA: left pulmonary artery; SVC: superior vena cava; RA: right atrium; LA: left atrium; IVC: inferior vena cava; RV: right ventricle; LV: left ventricle.
Schematic of challenges and management strategies in the Fontan circulation. LPA: left pulmonary artery; PA: pulmonary artery; AVV: atrioventricular valve; ACE: angiotensin-converting enzyme; TCPC: total cavopulmonary connection.
Conceptual model of the ageing Fontan circulation. a) Schematic of i) normal and ii) Fontan circulation; b) relationship between circulatory output at rest and pulmonary vascular resistance (PVR) modulated by ventricular function for a normal subject and patients with a univentricular heart (UVH) and depressed ventricular function; c) relationship between circulatory output at rest and ventricular function modulated by PVR for a normal subject and patients with a UVH and depressed ventricular function; d) relationship between cardiac output, PVR and ventricular function during exercise for normal subjects and patients with Fontan circulation. LV: left ventricle; LA: left atrium; Ao: aorta; S: systemic circulation; RV: right ventricle; RA: right atrium; PA: pulmonary artery; P: pulmonary circulation; V: single ventricle; CV: caval veins; EF: ejection fraction. a) Reproduced from  with permission from the publisher.
Haemodynamic response to exercise in a) normal subjects and b) Fontan patients. In the normal circulation, exercise leads to a rise in aortic (Ao) pressure and a modest rise in systemic (S) venous pressure; right ventricular (RV) pressure increases, as does pulmonary artery (PA) pressure, leading to an increase in pulmonary (P) venous pressure and an increase in preload to the left ventricle (LV). In the Fontan circulation, systemic venous pressure is already high and must remain higher than pulmonary venous pressure to allow transpulmonary blood flow. The result is that, during exercise, there is little if any augmentation of ventricular preload. RA: right atrium; CPB: cavopulmonary bypass; LA: left atrium. Reproduced from  with permission from the publisher.