Patients with cyanotic CHD have arterial oxygen desaturation resulting from the shunting of systemic venous blood to the arterial circulation, or from cardiac anatomy that mandates mixing of systemic and pulmonary venous blood. The shunting can occur at the level of the atrium (ASD), the ventricle (VSD), or the great vessels (PDA or aortopulmonary window), or in the lungs (pulmonary arteriovenous malformations or venovenous collaterals). If a right-to-left shunt is present, it implies a right-sided obstruction distal to that level or the presence of pulmonary vascular obstructive disease causing reversal of flow through a previously left-to-right shunting lesion.

There are many specific congenital cardiac lesions that cause cyanosis, and each of the specific diagnoses may have its own variations, making memorization of a comprehensive list of diagnoses difficult. However, the spectrum of basic cyanotic congenital lesions can be remembered as the “5 Ts”: TOF, (complete) transposition of the great vessels, total anomalous pulmonary venous return, tricuspid atresia, and truncus arteriosus communis. The many remaining lesions can generally be thought of as variants of these basic diagnoses. The pathophysiology of each of these lesions is discussed in the respective section. Untreated cyanotic heart disease carries an extremely high mortality rate in the infant and child; therefore, most patients reaching adulthood have had reparative or palliative surgery. Those who reach adulthood without surgery are usually those with TOF or irreversible pulmonary vascular disease (eg, Eisenmenger syndrome) from underlying congenital cardiac lesions.

The importance of recognizing cyanotic heart disease in the adult lies not only in the potential for possible surgical or nonsurgical intervention but is also important for appropriate management of the extracardiac manifestations of long-standing cyanosis. The systemic complications of cyanotic heart disease include the development of hematologic and metabolic disorders. Neurologic abnormalities include infectious, hemorrhagic, and hypoxic disorders.

Hematologic disorders in adults with cyanotic CHD can significantly influence morbidity and mortality rates. Secondary erythrocytosis has been classified as either compensated or decompensated. Patients with compensated erythrocytosis are in equilibrium with stable hematocrits, no evidence of iron depletion, and few (if any) symptoms of hyperviscosity. Even with hematocrits above 70%, they do not appear to be at increased risk for cerebrovascular accidents and do not require phlebotomy. Patients with decompensated erythrocytosis have increased hematocrits (> 65%) with symptoms. Because iron deficiency and dehydration may also produce hyperviscosity, these conditions should be excluded and, if present, treated before phlebotomy is undertaken. Generally, phlebotomy is not recommended for patients with hematocrits of less than 65%. A bleeding diathesis is also associated with cyanotic heart disease; it is usually mild and requires no specific therapy except for the avoidance of heparin and aspirin. Because severe life-threatening bleeding can occur during surgical procedures, preoperative phlebotomy to attain a hematocrit just below 65% is recommended. Associated abnormalities include thrombocytopenia and hyperuricemia secondary to increased red cell turnover. Urolithiasis and urate nephropathy rarely occur, but gout is common. The last problem can be managed with conventional therapy, taking care to avoid the antiplatelet properties of anti-inflammatory agents. In managing CHF in cyanotic patients, diuretics must be used judiciously to avoid dehydration, which may exacerbate hyperviscosity, and thrombotic risk. These patients may also be more susceptible to digoxin toxicity.

Counseling of the young adult with reference to contraception, pregnancy, and exercise is especially important in this group of patients.

Palliative surgical procedures for complex cyanotic CHD performed during infancy or childhood in the early years of pediatric cardiothoracic surgery were associated with unique physical findings and specific complications. These procedures, such as aortopulmonary anastomoses (Waterston, Potts, Blalock-Taussig) and atrial switches (Senning and Mustard), are still commonly encountered in adult patients. These procedures may produce unique physical findings and specific complications, which are discussed later (see Palliative Surgical Procedures). Most of these procedures are no longer performed in children, since surgical techniques that optimize physiology and reduce complications have evolved over the years.