Imaging Sciences Interesting Cases

Case 515

Keith Forrest Dockery, MD, MS

Clinical Presentation: Patient is an 18-year-old female with congenital heart disease, diagnosed in the neonatal period. She has a history of progressively worsening exercise intolerance over the past ten years, periodic severe cyanosis, and recent pulmonary hypertension. Four years ago, the patient experienced an episode of large volume hemoptysis, which was treated conservatively. She was recently treated for endocarditis and now presents with cough and chest pain for question of pneumonia versus pulmonary congestion.

Imaging Findings: See figure legends.

Figure 1A&B: Chest radiographs. Right image (A) at age 14 shows bilateral hazy opacification compatible with hemorrhage in the clinical setting of hemoptysis. Note the prominent right lung vascularity, especially a large right lower lung vessel. Left image (B) at age 18 shows expanded lung volume, clear lungs, and persistent asymmetric vascularity (right > left). Thoracic scoliosis appears to have progressed. Both images demonstrate right aortic arch. Vascular asymmetry was similarly described on radiograph reports from age 3 months.

Figure 2: Coronal reformats of chest CT at age 14. Right image demonstrates right-sided descending aorta and the prominent right lower lobe pulmonary artery that is evident on prior radiograph. Left image demonstrates the right-sided aortic arch. A ventricular septal defect was also noted (not shown).

Figure 3: MR angiogram maximum intensity image (MIP) at age 14 demonstrates asymmetric vascularity (right > left), as suggested on prior radiograph. Additional findings include aberrant pulmonary arterial supply with non-visualization of the main pulmonary artery. Cardiac outflow occurs solely via the aorta with underlying congenital heart disease classified as uncorrected Tetralogy of Fallot with pulmonary atresia. A ventricular septal defect (not shown) is also noted. Findings are not significantly changed from MR angiogram 28 months prior.

Figure 4A&B: MR angiogram coronal reformat at age 14. Selected vascular findings include: A) right upper lobe pulmonary artery branch from the aorta (large arrow); left-sided collateral arteries supplying the left upper lung (arrowhead); right pulmonary venous return (smaller arrow). B) Left lower lobe pulmonary artery branch from the aorta extends superiorly before arching downward to supply collateralized lower lobe circulation (arrowhead).

Diagnosis: Uncorrected Tetralogy of Fallot with pulmonary atresia

Discussion: Tetralogy of Fallot with pulmonary atresia (TOF-PA) is a congenital heart defect, that is usually corrected with a 90% survival into adulthood. Uncorrected TOF-PA has a 5% survival. TOF-PA is an uncommon variant in the spectrum of TOF, accounting for 20% of TOFs and 1.5% of congenital heart disease overall. Two major classifications of TOF-PA are considered: those with confluent pulmonary arteries and those with multiple aortopulmonary collaterals.

Multiple disorders/syndromes are associated to varying degrees, with one example being CATCH22. In TOF-PA of the aortopulmonary collateral type, there is a 41% increase in CATCH22 (cardiac defect, abnormal face, thymic hypoplasia, cleft palate, hypocalcemia, microdeletion of band 22q11); by comparison, with TOF-PA of the confluent pulmonary artery type, the increase is 16%. Genetic counseling is recommended, especially if there are siblings.

Maternal causative factors include diabetes mellitus, among others.

TOF-PA requires a ventricular septal defect (VSD) and an aberrant pulmonary arterial supply to survive. Viability stems from the following scheme: 1) systemic venous return (de-oxygenated blood) enters the right ventricle via tricuspid valve inflow; 2) the systemic venous blood then traverses a VSD to the left ventricle; 3) within the left ventricle systemic venous blood mixes with pulmonary venous return (oxygenated blood via mitral valve inflow from the left atrium); 4) mixed blood is pumped out via a single outflow tract to the aorta; and 5) mixed aortic blood re-enters pulmonary circulation via aortopulmonary branch arteries and/or collateral vessels.

Pulmonary blood flow depends on the size of the arterial vessels. In this case, pulmonary arterial supply is asymmetric (right > left), which reflects the more normal caliber right-sided aortic branch vessels versus the small caliber left sided collateral network.

TOF-PA can usually be corrected in the neonatal or infant period, though a small number of children remain relatively asymptomatic, resulting in delayed correction. The current patient and family have refused surgical correction to date, despite symptom progression, including worsening extertional dyspnea, hemoptysis, periodic cyanosis, and more recent pulmonary hypertension. Follow-up has involved chest radiographs, computed tomography of the chest, and magnetic resonance imaging with gadolinium enhanced angiography of the chest. Echocardiography may also be utilized, but a suspicion of aortopulmonary collaterals warrants MR angiography and/or conventional cardiac angiography.

The patient did undergo invasive cardiac angiography, which confirmed suspected pulmonary hypertension in the setting of uncorrected Tetralogy of Fallot with pulmonary atresia and multiple aortopulmonary collaterals.

References:

1. Gaca AM, Jaggers JJ, Dudley LT, Bisset GS 3rd. Repair of congenital heart disease: a primer--Part 2. Radiology. 2008 Jul;248(1):44-60. PMID: 18458241 [PubMed]
2. Pettersen M, Kulkarni A. Tetralogy of fallot with pulmonary atresia. Emedicine. Updated: Jul 9, 2010. http://emedicine.medscape.com/article/899368-overview