Main pulmonary artery dilation in association with congenital bicuspid aortic valve in the absence of pulmonary valve abnormality

Background: Main pulmonary artery (MPA) dilation is reported to occur in association with pulmonary valve (PV) abnormalities and in genetic diseases of connective tissue. Aim: To determine whether MPA dilation occurs with bicuspid aortic valve (BAV) in the absence of PV abnormality. Methods: MPA and aortic dimensions were investigated in 194 subjects with BAV and 178 controls matched for age, sex and body surface area (BSA) using transthoracic two-dimensional echocardiography. Using control measurements, linear regression of each parameter versus age, gender, and BSA^2/3 provided expected values. For each subject with BAV, the percentage divergence from expected value ((observed - expected value)/expected value) for each dimension was analysed. Results: MPA and aortic measurements showed normal distribution in all subjects. PV annulus and MPA were larger in BAV; 17.7% positive divergence of MPA dimension from expected was found in diastole, and 16.7% in systole. Aortic dimensions at all levels measured were larger in BAV; divergence was greater distally than proximally (10% divergence at annulus, 31% at ascending aorta). In BAV, divergence of ascending aortic dimensions from expected values increased with age (r²=0.142, p=0.02), but MPA divergence from expected values did not increase with age (r²=0.001, p=0.296). Conclusions: MPA dilation occurs in association with BAV in the absence of PV abnormality, suggesting primary vessel wall pathology predisposing to arterial dilation. A systemic abnormality of connective tissue common to both arteries may be responsible, or the dilation may result from a common developmental exposure as both originate from the embryologic conotruncus.