Multisystem Disease

Congenital heart disease does not involve only the cardiovascular system; it also causes multisystem disease. It is common for patients to undergo repeated thoracic surgeries, and they are at risk for developing scoliosis, which can lead to pulmonary restriction. Renal impairment is common because of the effects of previous cardiac surgery, nephrotoxic drugs (particularly radiographic contrast agents used during cardiac catheter studies), and associated congenital kidney abnormalities, such as renal dysplasia and hydronephrosis. High systemic venous pressure, such as that which occurs after Fontan-type operations and with right ventricular dysfunction, can lead to pleural effusions, ascites, hepatic congestion, and even cirrhosis. Hepatic dysfunction can also occur due to hepatitis C infection acquired from exposure to infected blood products.

Children who have undergone repair or palliation for congenital heart disease have, on average, lower IQs than their peers and are more likely to have developmental disabilities.^3,4 Many adults with congenital heart disease were cyanotic for long periods of time during their childhoods; they may have experienced periods of circulatory compromise and may have undergone cardiopulmonary bypass during the formative years of that technology. In addition, some patients have syndromes in which congenital heart disease and mental disability are associated (e.g., Down syndrome). Anxiety and depression are also relatively common and may be exacerbated by admission to the ICU.

Cyanotic Heart Disease

Chronic cyanosis leads to polycythemia, plethora, and finger clubbing. Patients with cyanosis have a tendency toward increased bleeding due to thrombocytopenia, platelet dysfunction, and reduced levels of certain clotting factors (including protein C and protein S). Spontaneous bleeding is usually mucocutaneous and mild, but life-threatening hemorrhage, particularly pulmonary hemorrhage, can occur occasionally.

The presence of right-to-left intracardiac shunting increases the risk for cerebral embolic events. Until recently, it was accepted that polycythemia itself was a risk factor for stroke. This belief led to the widespread use of phlebotomy to control hematocrit, typically to less than 55%. More recently, the detrimental effects of phlebotomy on oxygen delivery and iron stores have been appreciated,⁵ and many centers now reserve phlebotomy for patients with symptomatic polycythemia. The increased red cell turnover associated with polycythemia predisposes to the development of gallstones and gout. The risk for gout is increased by concomitant renal dysfunction and the use of diuretics.

General Perioperative Considerations

In addition to a thorough cardiac assessment, preoperative evaluation must include consideration of other organ systems (see earlier discussion, Multisystem Disease). Respiratory function tests may be indicated for patients who have undergone multiple previous cardiac operations. Patients who are older than 40 or have risk factors for coronary artery disease should undergo coronary angiography. For patients who have cyanosis with thrombocytopenia, careful preoperative phlebotomy can promote hemostasis by initiating a temporary increase in platelet numbers. When the hematocrit exceeds 55%, increased citrate must be added to the tubes that are used for coagulation testing.

Patients have usually undergone multiple arterial and venous catheterizations. Thus, vascular access may be difficult, and there may be thrombosis and occlusion of central veins and arteries. Prior exposure to blood products may have led to antibody formation, creating difficulties in cross-matching blood for transfusion. For patients with right-to-left shunts it is essential to avoid all air bubbles in venous lines because they can embolize systemically.

Most surgeries performed for congenital heart disease in adults are reoperations, and in many cases cardiopulmonary bypass times are long. Conduits from previous operations may be located directly behind the sternum and can be damaged during sternotomy. Postoperative problems involving excessive bleeding, coagulopathy, myocardial stunning, and pulmonary hypertension are not uncommon. Chronic volume and pressure overload of the cardiac chambers, along with scarring from previous surgeries, predispose to the development of ventricular dysfunction and arrhythmias. Poor nutritional state, chronic hypoxemia, and low cardiac output contribute to poor wound healing and the occurrence of nosocomial infection. Adults with congenital heart disease are at increased risk for developing endocarditis (see Table 10-7) and require antibiotic prophylaxis prior to certain invasive procedures (see Endocarditis Prophylaxis in Chapter 10). If these patients become febrile it is essential to draw blood cultures prior to commencing antibiotic treatment.

Tetralogy of Fallot

The essence of the tetralogy of Fallot (Fig. 15-1) is anterior displacement of the conal septum. This results in obstruction of the right ventricular outflow tract (RVOT) and a ventricular septal defect (VSD) and causes the aorta to override the crest of the ventricular septum. RVOT obstruction and right ventricular volume loading cause right ventricular hypertrophy, which is the fourth feature of the tetralogy. RVOT obstruction in the presence of a VSD causes a variable degree of right-to-left shunting and hypoxemia. Patients usually present in infancy with a murmur. If right ventricular outflow obstruction is severe, patients become cyanotic and may experience hypercyanotic “spells.”

Figure 15.1 Tetralogy of Fallot. The ventricular septal defect, aortic override, right ventricular outflow tract obstruction, and right ventricular hypertrophy together constitute the tetralogy of Fallot. Ao, aorta; IVC, inferior vena cava; LV, left ventricle; PA, pulmonary artery; RV, right ventricle; SVC, superior vena cava.

A tetralogy of Fallot was first palliated in 1944 by the classical Blalock-Taussig shunt. In this procedure, the subclavian artery is transected and anastomosed directly onto the pulmonary artery. Additional palliative strategies have included the Waterston and Potts shunts, in which the aorta (ascending or descending, respectively) is anastomosed side-to-side to a branch pulmonary artery. A modified version of the Blalock-Taussig shunt, in which a tube graft is used to connect the right subclavian artery to the right pulmonary artery (Fig. 15-2), is still performed to palliate lesions in which pulmonary blood flow is inadequate.

Figure 15.2 Modified Blalock-Taussig shunt for tetralogy of Fallot. A Gore-Tex shunt is inserted between the right subclavian artery and the right pulmonary artery. This improves blood flow to the pulmonary vascular bed. Ao, aorta; IVC, inferior vena cava; LV, left ventricle; PA, pulmonary artery; RV, right ventricle; SVC, superior vena cava.

In the 1950s a more complete repair of the tetralogy of Fallot was developed. Repair involves patch closure of the VSD and reconstruction of the obstructed RVOT (Fig. 15-3); the latter is commonly achieved by placing a patch across the annulus of the pulmonary valve, rendering it incompetent. Patients usually undergo surgical correction in early childhood; depending on institutional practice and the presence and severity of cyanosis, it may have been preceded by a Blalock-Taussig shunt in infancy. Long-term survival rates are excellent. However, free pulmonary regurgitation causes right ventricular overload, which can eventually lead to right ventricular failure and ventricular arrhythmias. Patients who have undergone repair of a tetralogy of Fallot are at increased risk for sudden death, and those with ventricular tachyarrhythmias should be considered for internal cardiac defibrillators. Pulmonary valve replacement can prevent these problems, although there is disagreement about the optimal timing of surgery. Most centers use a combination of symptoms, measured exercise tolerance, and quantitative assessment of right ventricular function (usually by means of a magnetic resonance imaging scan) to establish the need for pulmonary valve replacement.

Figure 15.3 Tetralogy of Fallot after repair. This operation consists of patch repair of the ventricular septal defect (VSD) and relief of the right ventricular outflow tract obstruction, often with a transannular patch. Ao, aorta; IVC, inferior vena cava; LA, left atrium; LV, left ventricle; PA, pulmonary artery; RA, right atrium; RV, right ventricle; SVC, superior vena cava.