3D transthoracic echocardiography to assess pulmonary valve morphology and annulus size in patients with Tetralogy of Fallot.

Background: Accurate evaluation of the pulmonary valve (PV) is crucial before surgical repair of Tetralogy of Fallot (TOF).

Aims: To assess PV and pulmonary annulus (PA) morphology using three-dimensional (3D) transthoracic echocardiography (TTE) in infants referred for surgical repair of TOF. Also, to compare PA measurements obtained by 3D TTE with those from other imaging modalities, including two-dimensional (2D) TTE and computed tomography (CT), with reference to surgical measurements.

Methods: 3D zoom mode was used to assess PV morphology. 2D TTE and CT PA diameters were compared to both vertical and horizontal diameters obtained from 3D datasets. Surgical PA diameters were measured using Hegar's dilators.

Results: A total of 29 patients with TOF (median [range] age 6 [3-24] months) were included and all successfully underwent 2D and 3D TTE; 22 also underwent CT. The number of pulmonary leaflets could be visualized in 24 patients (82.8%), with complete concordance with surgical findings. Vertical diameter was significantly longer than horizontal diameter (P<0.001)-underlying PA eccentricity-and was more important in bicuspid than tricuspid valves. Correlations between 2D and 3D TTE diameters were good. Surgical diameter was better correlated with 2D and 3D diameters than with CT diameter. 3D minimum, 2D and CT diameters were significantly lower than surgical diameters, but 3D mean and maximum diameters were not.

Conclusion: 3D TTE is accurate to assess PV morphology and PA size in patients with TOF. 2D TTE and CT underestimate PA diameter with reference to surgical diameter, however 3D mean and maximum diameters did not differ significantly.