Approach Considerations
The diagnosis of tetralogy of Fallot (TOF) with pulmonary stenosis may be established with fetal ultrasonography. Until the early to mid 1990s, the overwhelming majority of patients with tetralogy of Fallot underwent diagnostic cardiac catheterization before surgical repair. Since the mid 1990s, most centers have surgically repaired the majority of patients with tetralogy of Fallot with preoperative echocardiography without preoperative cardiac catheterization.
Routine blood studies indicated in patients with tetralogy of Fallot with pulmonary stenosis include a complete blood cell (CBC) count, chemistry panel, and coagulation studies, such as prothrombin time (PT), activated partial thromboplastin time (aPTT), and platelet count.
Radiography
The radiographic appearance of tetralogy of Fallot (TOF) varies with whether the condition is cyanotic or acyanotic.
Cyanotic tetralogy of Fallot
The cardiac size appears normal or smaller than normal, and pulmonary vascular markings are decreased.
In tetralogy of Fallot with pulmonary atresia, black lung fields are seen.
A concave main pulmonary artery segment with an upturned cardiac apex (ie, coeur en sabot [boot-shaped heart]) is characteristic.
Right atrial enlargement (25%) and a right aortic arch (25%) may be present.
Acyanotic tetralogy of Fallot
Radiographic findings of acyanotic tetralogy of Fallot are indistinguishable from those in a small to moderate ventricular septal defect (VSD), but patients with tetralogy of Fallot have right ventricular hypertrophy (RVH) rather than left ventricular hypertrophy (LVH) on the electrocardiogram (ECG).
Electrocardiography
On electrocardiogram (ECG), right axis deviation +120 to ±150° is present in cyanotic tetralogy of Fallot (TOF). In the acyanotic form, the QRS axis is normal.
On ECG, right ventricular hypertrophy (RVH) is usually present, but the strain pattern is unusual. Combined ventricular hypertrophy (CVH) may be seen in the acyanotic form. Right atrial hypertrophy (RAH) is occasionally present.
Echocardiography
Two-dimensional (2-D) echocardiography and Doppler ultrasonographic studies are the diagnostic modalities of choice for Tetralogy of Fallot (TOF). Echocardiographic results confirm the diagnosis and help in quantitating the severity of tetralogy of Fallot.
A large, perimembranous, infundibular ventricular septal defect (VSD) and overriding of the aorta are depicted in the parasternal long-axis view.
The anatomy of the right ventricular (RV) outflow tract (RVOT), the pulmonary valve, the pulmonary annulus, and the main pulmonary artery and its branches is depicted in the parasternal short-axis view.
Doppler studies are helpful to estimate the pressure gradient across the obstruction in the RVOT.
Associated anomalies, such as atrial septal defect (ASD) and persistence of the left superior vena cava (SVC), can be imaged, and anomalous coronary artery distribution can be accurately assessed with echocardiographic studies.
Perioperative echocardiographic studies
Echocardiography is the diagnostic modality of choice for the preoperative evaluation of patients with tetralogy of Fallot. This technique is also the diagnostic modality of choice for the postoperative follow-up evaluation of patients with both palliated and repaired tetralogy of Fallot.
Transesophageal echocardiography (TEE) is used in the operating room to plan the repair and to assess the success of the repair.
Preoperative versus postoperative findings
Before surgery, tetralogy of Fallot represents a broad spectrum of VSD sizes and RVOT obstructions (RVOTOs). After surgery, residual abnormalities range from a nearly normal-appearing heart to one with substantial RV dysfunction and residual RVOTO. 2-D echocardiography and Doppler ultrasonographic techniques can be definitive means for monitoring patients with respect to their recovery of RV function and complications, such as recurrent RVOTO and residual or recurrent VSD.
Cardiac Catheterization
In the modern era, preoperative cardiac catheterization is reserved for certain high-risk patients with tetralogy of Fallot (TOF).
In patients with tetralogy of Fallot with pulmonary atresia, cardiac catheterization is used to assess the anatomy, size, and distribution of the peripheral pulmonary artery. The presence, origin, and insertion of major aortopulmonary collateral arteries (MAPCAs) should be documented.
In preoperative patients before complete repair status but after previous systemic-to-pulmonary artery shunting, cardiac catheterization allows visualization of the shunt and the pulmonary artery at the shunt insertion site.
Preoperative cardiac catheterization solely for the assessment of coronary artery anatomy is not necessary, because these data can typically be obtained with echocardiography.
