Tetralogy of Fallot

Tetralogy of Fallot is the most common form of cyanotic congenital heart disease. The defect consists of a hole between the right and left ventricle (ventricular septal defect or VSD) in conjunction with an obstruction between the right ventricle and the pulmonary artery (pulmonary stenosis). As a result of these two abnormalities, deoxygenated blood can bypass the lungs, enter the aorta and produce cyanosis.

Most patients with tetralogy of Fallot require cardiac surgery early in childhood. In severe cases, the initial operation may be a shunt procedure which improves oxygenation and allows the surgeon to delay correction until the pulmonary arteries have grown. Repair of tetralogy of Fallot involves closure of the VSD and relief of obstruction between the right ventricle and the pulmonary artery. Successful surgery eliminates cyanosis, relieves the pulmonary stenosis, and improves exercise capacity. Relief of pulmonary valve stenosis often produces a leak in the pulmonary valve, referred to as pulmonary regurgitation.

Most adults who were successfully repaired during childhood continue to do well although life-long follow-up with an adult congenital heart disease specialist is recommended to address potential long term issues such as arrhythmias, right ventricular function, and abnormalities of the pulmonary valve and pulmonary arteries. Pregnancy is generally well tolerated in patients with a satisfactory repair.

Assessment of Repair

Assessment of tetralogy of Fallot repair is an important part of the follow up during adulthood. This will ensure that residual abnormalities resulting from childhood repair are appropriately addressed in a timely fashion.

The most common problem in adults following childhood tetralogy repair concerns the pulmonary valve and function of the right ventricle. Most of the patients will have a leak in their pulmonary valve known as pulmonary insufficiency. Although this leak is usually well tolerated throughout the pediatric years, it does produce progressive enlargement of the right ventricle over time and may result in reduced stamina and diminished exercise capacity. This problem can be treated with pulmonary valve replacement which has become the most frequently performed operation in adults with congenital heart disease.

Although the optimal timing for pulmonary valve replacement continues to be debated, patients with symptoms, marked enlargement of the right ventricle, or abnormal right ventricular function are often advised to undergo valve replacement. Cardiac MRI is an important tool in the evaluation of adult tetralogy patient because it provides quantitative analysis of RV volumes and function, and pulmonary artery flows which are not feasible with echocardiography. It also provides excellent visualization of the pulmonary arteries, and can detect pulmonary artery narrowing which may require placement of a stent.

Though less common, reoperation in adult tetralogy patients may be for other indications such as residual obstruction between the right ventricle and pulmonary artery, a significant residual VSD, or an important leak in the tricuspid valve (tricuspid regurgitation). In rare instances, surgical replacement of the aortic valve and aortic root may be indicated because of a leak in the aortic valve and marked enlargement of the aorta.

In rare instances, a patient with tetralogy of Fallot may reach adulthood without repair or by means of a systemic to pulmonary artery shunt. Careful evaluation of these patients will determine whether they may still be candidates for corrective surgery.

Arrhythmias

Adults with tetralogy of Fallot may experience atrial or ventricular arrhythmias. Atrial arrhythmias arise from the upper chamber of the heart and occur in approximately 20% of adult tetralogy patients. The most common form seen in patients with tetralogy of Fallot is atrial flutter although atrial fibrillation and other forms of atrial arrhythmias also occur. These arrhythmias can result in heart racing, diminished stamina, dizziness, and fluid retention. Restoration of a normal rhythm is generally advised. Treatment modalities may include electrical cardioversion, medications, or catheter ablation.

Ventricular arrhythmias originate from the bottom chamber of the heart. They can be self-limited or sustained and in some instances can result in a dangerously rapid heart rate. Treatment depends on the type of arrhythmia but may include medications, radiofrequency ablation, and/or an implantable cardioverter defibrillator (ICD). Patients who experience these arrhythmias should be evaluated by a team with expertise in adult congenital heart disease care and arrhythmias.