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............................................................................................................................................................................. 4.14.4 Follow-up recommendations Regular follow-up in a specialized ACHD centre at least every year is recommended. Special attention should be given to exercise capacity (CPET), RVSP (conduit gradient), RV function, TR, and arrhythmias.

4.14.5 Additional considerations

• Exercise/sports: no restrictions are required in asymptomatic patients with mild obstruction. High-risk patients with high RV pressure must limit themselves to low-intensity activity/sports and avoid isometric exercise. Other patients should limit themselves according to symptoms. • Pregnancy: maternal and foetal risks are driven by the underlying congenital heart defect and severity of RVOTO, arrhythmia, and heart failure (see section 3.5.7). • IE prophylaxis: recommended in all patients (see section 3.4.6).

4.15 Univentricular heart

This section deals with unoperated and palliated univentricular heart (UVH). For patients after Fontan operation see section 4.16.

4.15.1 Introduction and background The term ‘UVH’ summarizes a variety of malformations where either the RV or LV is missing or, if present, is hypoplastic and thus not amenable for biventricular repair, such as: • Tricuspid atresia. • Hypoplastic right heart syndrome variants, e.g. pulmonary atresia with intact ventricular septum variants. • Hypoplastic left heart syndrome (HLHS) variants, including mitral atresia. • Double-inlet LV. • Double-inlet RV. • Extreme forms of unbalanced complete AV septal defects. • Single ventricle with undefined morphology. These malformations are always associated with additional intraand/or extracardiac lesions such as: • ASD, VSD, AVSD, PDA. • AS (valvular, subvalvular). • Aortic arch anomalies: hypoplasia, interruption, coarctation. • PS (valvular, subvalvular), pulmonary atresia. • PA anomalies: peripheral stenosis, hypoplasia, one-sided absence. • Discordant connections, malposition of the great arteries. • AV valve stenosis, regurgitation, overriding, straddling. • LA or RA isomerism, abnormal systemic or pulmonary venous connections. • Left SVC, absent innominate vein, absent right SVC, absent infrahepatic IVC with azygos or hemiazygos continuity. • Aortic-to-pulmonary collateral arteries. • Polysplenia or asplenia. Detailed anatomic description is beyond the scope of these guidelines and can be found in textbooks. Owing to the lack of data, recommendations are mainly based on expert consensus.296300 When presenting as adults, the vast majority of patients with these conditions will have undergone previous palliation with some type of systemic-to-PA shunt, cavopulmonary connection (Glenn), or now preferably a Fontan operation or one of its modifications; the latter is covered in section 4.16.

Two different haemodynamic situations can be identified: • No anatomic restriction to pulmonary blood flow: if pulmonary circulation remains unmodified (i.e. no surgery), many patients will die in childhood due to intractable heart failure. Those who survive this period will have developed severe PVD. This will be a main determinant of long-term outcome. Many will have had pulmonary banding to restrict pulmonary blood flow in early childhood. An effective banding will protect against PVD, while allowing enough pulmonary blood flow to limit the degree of cyanosis. A banding that is too loose will result in pulmonary overflow and PVD despite the banding. If the banding is too tight, pulmonary blood flow will be extremely limited, resulting in severe cyanosis. • Obstruction to pulmonary blood flow (frequently valvular and/or subvalvular PS or atresia): sometimes the obstruction is such that the pulmonary circulation is adequate (not excessive, thus avoiding development of PH, and not too restricted, thus without extreme cyanosis). These balanced situations are the exception but allow survival into adulthood without having surgery. Most patients have a very restricted pulmonary blood flow, necessitating a systemic-to-PA shunt operation in childhood  most commonly BlalockTaussig (subclavian to PA), rarely Waterston or Potts (ascending or descending aorta to PA, respectively). If a systemic-to-PA shunt is too large, pulmonary overflow will result in PVD at adult age. If the shunt is too small, patients will be extremely cyanotic. Beyond infancy, an anastomosis between the SVC and PA is a possibility: the classical Glenn anastomosis to the right PA (historical) or an end-to-side anastomosis with the PA, creating a bidirectional cavopulmonary anastomosis. An adequate shunt will lead to a balanced situation.

4.15.2 Clinical presentation and natural history Depending on the extent of pulmonary blood flow, presence or absence of PVD, and ventricular function, patients may present with various degrees of cyanosis and congestive heart failure. Exercise ability is generally substantially reduced (with exceptions); complete AV block, arrhythmias (supraventricular, but also ventricular, SCD not unusual), stroke, brain abscess, and thromboembolism can occur. Endocarditis is relatively common in this population. For more details, see section 3.4.8. Cyanosis is typically present in patients with UVH without a Fontan operation. Arterial oxygen saturation commonly ranges from 7585% but may, in exceptional cases with ideally balanced circulations, reach values >90%. Patients may present with progressive obstruction towards the aorta. This will lead to ventricular hypertrophy and, eventually, to reduced cardiac output. Progressive obstruction towards the PA will cause progressive cyanosis. In Glenn patients, worsening cyanosis may also be due to development of pulmonary arteriovenous malformations or IVC-to-SVC collaterals. The UVH has to accommodate both systemic and pulmonary venous return. This chronic volume overload will lead to a high likelihood of ventricular failure relatively early in life. AV valve regurgitation may develop or progress, if present previously. The already Downloaded from academic.oup.com/eurheartj/article/42/6/563/5898606 by guest on 07 October 2026