Congenital heart disease

Signs and symptoms.

Patients can present with increasing dyspnea on exertion, decreased exercise tolerance, fatigue, heart failure, palpitations, or embolic stroke. However, many patients with ASDs will remain asymptomatic for years. Smaller defects with a ratio of pulmonary to systemic blood flow (Qp:Qs ratio) of less than 1.5:1 usually remain asymptomatic and do not require further intervention. Shunt lesions with a Qp:Qs ratio greater than 1.5:1 should be considered for closure to prevent long-term sequelae. Depending on the location and size of the ASD, the lesion can be closed percutaneously using a septal occlusion device in the catheterization suite or surgically with a primary or patch closure either via sternotomy or minimally invasive thoracotomy.

Management of anesthesia.

For general management strategies, including anesthetic management, see “Balancing Pulmonary and Vascular Resistance (Qp:Qs)” later in the chapter. Management of patients undergoing ASD closure depends largely on the chosen intervention. A percutaneous ASD closure can be conducted with standard American Society of Anesthesiology (ASA) monitoring and the patient under general anesthesia or deep sedation, whereas a surgical ASD repair requires all the routine monitors, access for cardiopulmonary bypass, and the capacity to treat/manage potential postoperative heart block.

Signs and symptoms.

The severity of signs and symptoms depends on the size of the defect, the pressure difference between the ventricles, and the ratio of pulmonary to systemic vascular resistance. Small defects with a Qp:Qs ratio of 1.4:1 or less usually remain asymptomatic and do not result in major sequelae (e.g., pulmonary hypertension or heart failure). These defects are usually referred to as restrictive VSDs, as the amount of shunting is restricted by the size of the defect. Moderately restrictive VSDs with a Qp:Qs ratio of 1.4:1 to 2.2:1 or nonrestrictive VSDs with a Qp:Qs ratio greater than 2.2:1 can result in an equalization of left and right ventricular systolic pressures that causes both volume and pressure overload of the pulmonary circulation. Over time, the pulmonary vasculature starts to remodel, resulting in increased pulmonary vascular resistance and pulmonary hypertension. Eventually a decrease in the Qp:Qs ratio results, leading to shunt reversal (Eisenmenger syndrome). Consequently, patients become progressively hypoxic as blood shunts right to left across the VSD and bypasses the lungs. Such patients are no longer candidates for VSD closure, as right heart failure would inevitably ensue. Over time, even in the absence of advanced disease and Eisenmenger syndrome, patients with moderate-restrictive or unrestrictive VSDs develop left ventricular failure and pulmonary hypertension, putting them at increased perioperative risk. Therefore it is important to diagnose patients early and perform a VSD closure before pulmonary vascular resistance increases to such high levels that closure is no longer possible.

With increasing size of the defect, the ECG can demonstrate signs of left atrial and left ventricular hypertrophy, as well as right ventricular strain. Similarly, chest x-rays will show an enlarged cardiac silhouette. Echocardiography with color Doppler is most commonly used to evaluate the presence, directionality, and severity of a VSD. Other more invasive techniques include cardiac catheterization and angiography to measure the amount of intracardiac shunting, intravascular and intracavitary pressures, and pulmonary and systemic vascular resistance.

Management of anesthesia.

The most conservative summary would probably be to treat a patient with a VSD of unknown severity like a patient with congestive heart failure and pulmonary hypertension. For general management strategies and anesthetic management, refer to “Balancing Pulmonary and Vascular Resistance (Qp:Qs)” later in the chapter.

Small VSDs can occasionally be closed percutaneously in older children and adults, otherwise surgical closure is performed. Children who undergo surgical VSD closure generally tolerate it very well.

Signs and symptoms.

Most patients with a PDA have only a mild or moderate left-to-right shunt, but symptoms of pulmonary overcirculation can develop over time. When the left-to-right shunt is substantial, patients can develop pulmonary hypertension that leads to heart failure, failure to thrive, aneurysmal dilatation of the ductus, and, in longstanding disease, Eisenmenger syndrome. Diagnosis and quantification can be established with echocardiography.

Management of anesthesia.

Most patients in whom the ductus fails to close spontaneously will require closure during the neonatal period, especially those born before 28 weeks of gestation. Many can be closed medically with indomethacin, which decreases the production of prostaglandins that keep the ductus open. However, side effects of the drug may preclude its use in some patients. In such cases, the ductus is closed with either a device or surgical ligation. Minimally invasive device closure is performed by interventional cardiology in the catheterization suite and usually requires only percutaneous arterial and venous access. When device closure is not feasible, surgical ligation is carried out via a left thoracotomy without cardiopulmonary bypass. When severe pulmonary hypertension is present, ductal closure may precipitate acute right heart failure, contraindicating closure.

For general management strategies and anesthetic management, see “Balancing Pulmonary and Vascular Resistance (Qp:Qs)” later in the chapter. During surgical ligation of the ductus arteriosus, single lung ventilation is rarely required; rather the surgeon gently retracts the lung out of the field. This action can lead to a temporary drop in oxygen saturation, given the high incidence of lung disease with poor lung compliance in premature infants. Often, the decrease in oxygen saturation may be minimized with ventilator adjustments. Ligation of the ductus results in an immediate increase in diastolic blood pressure. Adverse events include hoarseness (due to recurrent laryngeal nerve injury), hemidiaphragm paralysis (due to phrenic nerve injury), chylothorax (due to thoracic duct injury), and reopening of the ductus.

Aortic stenosis.

Stenosis of the left ventricular outflow tract can be due to subvalvular, valvular, or supravalvular aortic stenosis (AS). Valvular AS is frequently the result of a bicuspid aortic valve, which is present in approximately 2% of all newborns in the United States.

Patients with bicuspid aortic valves are generally not born with a stenosed valve. Rather, because the aortic valve has two (instead of the normal three) cusps, blood flow is more turbulent, leading to endothelial disruption and local inflammation that causes a predisposition for calcification. These factors all cumulate in premature AS. Severity is commonly determined by the pressure gradient across the aortic valve. A mean gradient less than 20 mm Hg is considered mild, whereas a mean gradient greater than 40 mm Hg is considered severe.

Pulmonic stenosis.

Many of the concepts for AS can be translated to pulmonary stenosis, with the main difference being that the right ventricle is much more sensitive to increases in afterload. Pulmonary stenosis is mainly valvular in origin rather than supravalvular or subvalvular. Associated lesions, especially of supravalvular pulmonic stenosis, include ASDs, VSDs, a PDA, and tetralogy of Fallot. Supravalvular pulmonic stenosis can also occur in patients with Williams syndrome (distinctive phenotype, developmental delay, hypercalcemia, and stenosis of the aorta and/or pulmonary artery). Subvalvular pulmonic stenosis is typically associated with a VSD, whereas valvular pulmonic stenosis tends to occur in isolation or sometimes in combination with a VSD. Interestingly, peak pressure gradients are frequently used for the classification of pulmonic stenosis (as opposed to mean gradients), with less than 36 mm Hg being mild and more than 64 mm Hg being considered severe.

Coarctation of the aorta.

Coarctation of the aorta consists of aortic narrowing and is often classified by its proximity to the ductus arteriosus—preductal, juxtaductal, or postductal. Depending on its location, symptoms and age at diagnosis tend to vary. The most common form, postductal coarctation, lies beyond the ductus arteriosus and is sometimes diagnosed outside the neonatal period. A preductal coarctation is located proximal to the ductus and usually manifests in the neonatal period.

Ebstein anomaly.

Ebstein anomaly is rare (<1%) and produces an acyanotic lesion if it occurs as an isolated entity. However, it can be associated with other shunting lesions that in combination with right ventricular outflow tract obstruction render those patients cyanotic. Patients with Ebstein anomaly have an atrialized right ventricle, with a malformed and caudally displaced tricuspid valve. Frequently, the anterior cusp is sail-like in structure with multiple fenestrations, resulting in tricuspid insufficiency and, in rare instances, stenosis. With the tricuspid valve displaced downward, the effective right ventricle is relatively small and inefficient.