Tetralogy of Fallot

Essentials of Diagnosis

• Five features are characteristic:

  • Ventricular septal defect (VSD)

  • Concentric right ventricular hypertrophy (RVH)

  • Right ventricular (RV) outflow obstruction due to infundibular stenosis

  • Septal overriding aorta in half of the patients

  • A right-sided aortic arch in 25%

• Most adult patients have undergone surgical repair, usually with an RV outflow patch and VSD closure; if patch overrides the pulmonary valve, PR is common

• Physical examination may be deceptive after classic tetralogy repair, with severe pulmonary valve regurgitation difficult to detect

• Echocardiography/Doppler may underestimate significant pulmonary valve regurgitation; be wary if the RV is enlarged or enlarging

• Arrhythmias are common; periodic ambulatory monitoring is recommended

• Serious arrhythmias and sudden death may occur if the QRS complex is wide or the RV becomes quite large or both

General Considerations

• If there is an associated atrial septal defect (ASD), the complex is called pentalogy of Fallot

• The basic lesion is a large VSD and migration of the septum above the VSD upward and under the pulmonary valve

• Pulmonary valve stenosis may also be present, usually due to a bicuspid pulmonary valve or RV outflow hypoplasia

• The aorta can be enlarged and aortic regurgitation may occur

• If more than 50% of the aorta overrides the ventricular septum, the anatomy is part of the double outlet RV nomenclature

• Two vascular abnormalities are common

  • An inconsequential right-sided aortic arch (in 25%)

  • Anomalous left anterior descending coronary artery from the right cusp (7–9%)

Symptoms and Signs

• Most adult patients in whom tetralogy of Fallot has been repaired are relatively asymptomatic unless right heart failure or arrhythmias occur

• Physical examination should check both arms for any loss of pulse from a prior shunt procedure in infancy

• Jugular venous pulsations (JVP) may reveal

  • An increased a wave from poor RV compliance

  • A c-v wave due to tricuspid regurgitation (rarely)

• The precordium may be active

• P₂ may or may not be audible

• A right-sided gallop may be heard

• A residual VSD or persistent pulmonary outflow or aortic regurgitation murmur may be heard

• The insertion site of a prior Blalock or other shunt may create a stenotic area in the branch pulmonary artery (PA) causing a continuous murmur

• Pulmonary arterial stenotic bruits may best be heard on the lateral chest wall

Imaging Studies

• Chest radiograph shows

  • A classic boot-shaped heart with prominence of the RV and a concavity in the RV outflow tract

  • An enlarged and right-sided aorta

• Echocardiography/Doppler

  • Establishes the diagnosis by noting the unrestricted (large) VSD, the RV infundibular stenosis, and the enlarged aorta

  • Provides data regarding the amount of residual pulmonary valve regurgitation if a transannular patch is present, RV and LV function, and the presence of aortic regurgitation in patients who have undergone repair

• Cardiac MRI and CT

  • Can quantitate both pulmonary valve regurgitation and RV volumes

  • Can identify whether there is either a native pulmonary arterial branch stenosis or a stenosis at a distal site of a prior arterial-to-PA shunt or other anomalies such as an ASD

• Electrophysiologic studies with ventricular stimulation and potential VT ablation has been suggested by some experts for all patients who have had evidence for VT, unexplained syncope, or a wide QRS complex, or who are older or are about to undergo pulmonary valve replacement

Diagnostic Studies

• ECG reveals

  • RVH and right axis deviation

  • Right bundle branch block pattern in repaired tetralogy

• Ambulatory monitoring is recommended as well, especially if palpitations are felt

• Cardiac catheterization

  • Pulmonary angiography documents the degree of pulmonary valve regurgitation

  • RV angiography helps assess any postoperative outflow tract aneurysm

Surgery

• Systemic arterial to pulmonary artery shunt for significant RV outflow obstruction

  • Many infants undergo repair without this initial procedure

  • Most adult patients have undergone this initial palliative repair

    • Enables blood to reach the underperfused lung either by directly attaching one of the subclavian arteries to the PA (classic Blalock shunt) or by creating a conduit between the two (modified Blalock shunt)

  • Other types of systemic to pulmonary shunts no longer in use

    • A window between the right PA and the aorta (Waterston-Cooley shunt)

    • A window between the left PA and the descending aorta (Potts shunt)

• Total repair generally includes a VSD patch, an enlarging RV outflow tract patch (usually), and a take-down of the arterial-pulmonary artery shunt

  • Often the RV outflow tract patch extends through the pulmonary valve into the PA (transannular patch), and the patient is left with varying degrees of pulmonary valve regurgitation

  • Over time, volume overload from severe pulmonary valve regurgitation becomes the major hemodynamic problem seen in adults

  • Ventricular arrhythmias can also originate from the edge of the patch; they increase in frequency with the size of the RV

• Early surgical pulmonary valve replacement is favored

• A percutaneous approach to pulmonary valve regurgitation remains limited because the available percutaneous valve diameters are frequently too small for the size of the pulmonary annulus

• The Melody valve is a bovine jugular vein prosthesis with the largest size being 22 mm in diameter

• Percutaneous stented valves, particularly the Edwards SAPIEN XT, have been used successfully and can be used in patients with larger pulmonary root sizes

Follow-Up

• QRS width should be measured yearly

• Reoperation is needed in about 10–15% of patients 20 years after initial repair, both for severe pulmonary valve regurgitation and for residual infundibular stenosis

Complications

• Atrial fibrillation, reentrant atrial arrhythmias, and ventricular ectopy, especially after age 45

• Left heart disease causes these arrhythmias more often than right heart disease

• Biventricular dysfunction is not uncommon as the patient ages

Prognosis

• Most adults with stable hemodynamics can be active

• Most women can carry a pregnancy adequately if RV function is preserved

When to Refer

• All patients should be referred to a cardiologist with expertise in adult congenital heart disease