Quadricuspid Pulmonary Valve: Case Report and the Comparison with Quadricuspid Aortic Valve

Background: Quadricuspid pulmonary valve (QPV) is a rare congenital anomaly. Simple QPV had been mainly diagnosed at the time of autopsy before 2000, and the frequency rates of QPV are approximately 0.02%–0.41%. QPV was initially diagnosed using transthoracic echocardiography (TTE) after 2000 and with contrast computed tomography (CT) or cardiac magnetic resonance imaging (CMR) after 2009. Obtaining the cross-sectional view of the pulmonary valve using TTE is difficult. We aimed to review the papers regarding the incidence, embryology, diagnosis, associated congenital heart anomalies, and prognosis in patients with QPV, and furthermore to compare with those in patients with quadricuspid aortic valve (QAV). Case Presentation: We diagnosed QPV with mild stenosis in a 12-month-old infant. With a slight angulation of the transducer superiorly from the left high parasternal short-axis view, a short-axis view of QPV was obtained. Results: In QPV cases diagnosed at autopsy, Hurwitz’s type-b with three equal cusps and one smaller cusp is dominant, whereas Hurwitz’s type-a with four equal cusps is dominant in clinically diagnosed cases. Congenital heart anomaly and valvular stenosis are more frequent in patients with QPV than in patients with QAV. Coronary artery anomalies and infectious endocarditis are more frequent in patients with QAV than in patients with QPV. The incidence of PR is more common in type-a QPV than in type-b QPV. There is no difference between type-a QAV and type-b QAV with respect to the incidence of aortic regurgitation (AR). It is assumed that QPV is a risk factor for a Ross operation. However, QPVs have been used as autografts in certain patients. Conclusion: Between QPV and QAV, various differences were found in frequency rates, diagnostic methods, valve morphology, valve function, associated congenital heart diseases, and frequencies of infectious endocarditis.