Tetralogy of Fallot - Erler Zimmer
Clinical History
A 21-month-old boy was admitted with a history of exhaustion and exertional dyspnoea over the previous 2 to 3 months, experiencing several attacks of acute dyspnoea lasting up to two minutes each. Examination revealed central cyanosis, mild finger clubbing, and a harsh systolic bruit maximal at the left sternal edge. Cardiac catheterization led to the diagnosis of Fallot's tetralogy with severe pulmonary oedema. Surgical correction, specifically a Willis-Potts anastomosis between the aorta and the origin of the left pulmonary artery, was performed. Unfortunately, the child developed acute dyspnoea and left lobar consolidation 12 hours postoperatively and passed away despite treatment.
Pathology
The anterior aspect of the child's heart reveals an excised anterior wall of the right ventricle, displaying prominent right ventricular hypertrophy and a narrowed pulmonary outflow tract. The pulmonary valve ring is small, featuring a bicuspid stenosed valve, and there is a patch of endocardial fibrosis in the outflow tract below the pulmonary valve. The origin of the aorta overlies a high ventricular septal defect. A probe could be passed from the hypertrophied right ventricle into the aorta, and another probe passed from the narrowed pulmonary trunk into a dilated, thin-walled left pulmonary artery and through the surgical anastomosis into the descending aorta. Examination of the posterior aspect reveals an opened right atrium and left ventricle. When viewed from the right side, a large atrial septal defect (ASD) is evident at the site of the foramen ovale (large arrow), along with a tiny ASD (small arrow) posterior to the upper border of the large ASD. The left ventricle wall appears slightly thinner than the right ventricle wall.
Further Information
Tetralogy of Fallot is characterized by four features: 1. Ventricular septal defect (VSD); 2. Over-riding aorta that straddles the VSD, communicating with both ventricles; 3. Pulmonary stenosis or obstruction of the right ventricular overflow tract; 4. Right ventricular hypertrophy. Typically causing early cyanosis, the severity depends on the degree of pulmonary outflow obstruction, determining the presence of a left-to-right or right-to-left shunt. Surgical correction is now possible and desirable, although some patients may survive untreated into adulthood. In this case, additional cardiac abnormalities included an atrial septal defect (ASD). The cause of most cases is unknown, but genetic factors may play a role, with an increased incidence in conditions like Down syndrome (Trisomy 21) or DiGeorge syndrome.
