Table 2.

 Specific management considerations and pertinent pathophysiological characteristics of vulnerable adult congenital heart disease sub-cohorts

ACHD condition	Therapeutic considerations	Pathophysiological characteristics
Univentricular heart—including Fontan palliation	ARDS typically leads to mean pulmonary artery pressures of 30 → potentially devastating effect for Fontan patients   Positive pressure ventilation poorly tolerated since elevated intrathoracic pressure can adversely affect venous return   Prone to thromboembolic complications as described in COVID-19   In patients with desaturation and atrial fenestration potential for paradoxical/air embolism → venous air filters required	Physiology dependent on low PVR   Thrombophilic state   Atrial fenestration occasionally present
PAH	In stable PAH patients risk of RV failure unclear but potentially low   In patients with RV dysfunction/advanced or unstable disease potential for catastrophic RV failure   Potential for thromboembolic complications as described in COVID-19   Dependent on adequate RV preload	RV preconditioned to chronically increased afterload may be tempered to adverse changes in PVR from acute respiratory infection   Thrombophilic state
Eisenmenger physiology (shares all aspects with cyanotic conditions)	Vulnerable to ventricular dysfunction   Dependent on adequate RV preload	RV potentially preconditioned to chronically increased afterload may be tempered to adverse changes in PVR from acute respiratory infection   Fragile physiology
Cyanotic conditions	Potential for paradoxical embolism/air embolism (use of air filters on all venous canulae required)   Prone to thromboembolic complications as described in COVID-19   Maintenance of adequate haemoglobin concentrations (physiological adaptation to cyanosis) required   When considering mechanical ventilation consideration of baseline oxygen saturations (commonly below 90% at rest) required	Fragile balanced physiology   Patients adapted to cyanosis through erythrocytosis   Thrombophilic state combined with increased bleeding risk
Systemic RV	In patients with RV dysfunction/advanced or unstable disease potential for catastrophic RV failure   Diastolic dysfunction common → dependent on adequate preload	Subpulmonary LV potentially better suited to withstand acutely increased afterload during ARDS   Chronotropic incompetence common
Patients with Down syndrome	Proactive prevention and treatment of infection required   General rationing of ITU capacity for Down syndrome patients is opposed	Increased risk of pulmonary infections or ARDS
General recommendation for patients with Down syndrome, univentricular hearts, asplenia, cyanotic congenital heart disease, 22q11 syndrome and other conditions with compromised immune system	Ensure adequate immunization status (influenza/pneumococcal disease)

ACHD, adult congenital heart disease; ARDS, acute respiratory distress syndrome; COVID-19, coronavirus disease 19; ITU, intensive treatment unit; LV, left ventricle; PAH, pulmonary arterial hypertension; PVR, pulmonary vascular resistance; RV, right ventricle.