Tetralogy of Fallot – treatment options and sequelae

Tetralogy of Fallot – treatment options and sequelae

The four cardinal features of tetralogy of Fallot (TOF) are malalignment ventricular septal defect (VSD) with an overriding aorta, infundibular pulmonary stenosis and right ventricular hypertrophy. The variability in clinical presentation of TOF correlates with degree of right ventricular outflow tract (RVOT) obstruction and the size/anatomy of pulmonary artery and its branches.

Surgical approaches to TOF would include palliative systemic – pulmonary shunts like Blalock-Taussig shunt, Waterston shunt and Potts shunt. Complete repair is accomplished by patch VSD closure, resection of subpulmonic obstruction, a transannular patch around the pulmonary valve annulus if necessary and take down of prior shunt. Placement of a transannular patch for widening of the RVOT usually leads to severe pulmonary regurgitation.

Systemic-pulmonary shunt leads to high flow through pulmonary artery, elevated pulmonary vascular resistance and branch pulmonary artery distortion. Survival after repair is worse in patients with prior central shunts (Waterston or Potts) possibly due to the higher unrestricted pulmonary blood flow. Some patients with Blalock-Taussig shunts may survive unrepaired into adulthood. These patients should be evaluated for pulmonary artery stenosis and pulmonary hypertension.

Those who had pulmonary valve atresia or anomalous left anterior descending coronary artery may have had prosthetic or homograft conduits with or without a valve placed between the right ventricle and pulmonary artery. Endothelial overgrowth can occur within the conduits and cause obstruction of the right ventricular outflow tract. This can be treated with balloon dilatation or surgical replacement of the conduit.

The risk of sudden cardiac death in operated tetralogy of Fallot is 25-100 fold than in the general population and it can occur decades after correction. The risk is related to QRS duration more than 180 milliseconds. The QRS widening is related to pulmonary regurgitation, right ventricular dilatation and conduction defect. Atrial arrhythmias are also common after TOF repair. Hemodynamic effects of pulmonary regurgitation include chronic right ventricular volume overload, right ventricular dysfunction and exercise intolerance. Pulmonary valve replacement can decrease QRS duration and stabilise right ventricular function, though the timing is unclear; but earlier would be better than later. Right ventricular function can be evaluated by echo or magnetic resonance imaging (MRI).