Spectrum of pulmonary valve morphology and its relationship to pulmonary trunk in tetralogy of Fallot

BACKGROUND Tetralogy of Fallot (TOF) is a complex congenital heart disease with anatomic variations. Although the pulmonary valve in TOF is abnormal, it has not been studied well, especially on newer imaging modalities such as multidetector computed tomography (CT), which gives excellent anatomic detail. AIMS The aim of this study was to assess the morphology of pulmonary valve in TOF on CT and evaluate its association with the degree of hypoplasia of infundibulum and pulmonary trunk. MATERIALS AND METHODS The cardiac CT scans of 30 patients with TOF were reviewed to evaluate the morphology of the pulmonary valve, infundibulum, and pulmonary arteries. Fisher's exact test was performed to examine the association between pulmonary valve morphology and degree of hypoplasia of the infundibulum and pulmonary trunk. RESULTS 16.7% of patients with TOF had pulmonary atresia. The prevalence of tricuspid, bicuspid, and absent valves were 10%, 53.3% and 6.7%, respectively. In another 13.3% of patients, although valve tissue was present, exact morphology could not be determined on CT. The commissures of 62.5% of the bicuspid valves were at 12 o'clock and 6 o'clock or slightly off the midline. There was statistically significant association between valve morphology and degree of infundibular hypoplasia (P < 0.001) and calibre of pulmonary trunk (P < 0.001). CONCLUSION Morphological abnormality of the pulmonary valve is common in TOF. The most common type of pulmonary valve in TOF patients is bicuspid valve with commissures at 12 o'clock and 6 o'clock or slightly off the midline. Fewer cusps of the pulmonary valve are associated with a more severe degree of pulmonary artery hypoplasia.