SummaryThe quadricuspid aortic valve (QAV) is a rare congenital malformation that usually presents with aortic regurgitation (AR). The first case was reported in 1862. Most cases were diagnosed at the time of surgery or postmortem examination. With advances in imaging techniques, more cases have been diagnosed before surgery. We describe a 59-year-old man whose QAV had not been noted until the current admission. Transthoracic echocardiography revealed dilation of the left ventricle, severe AR, and suspected QAV. The QAV was confirmed by transesophageal echocardiography and 64-slice multidetector computed tomography. This case was a QAV with three equal cusps and one smaller cusp (type B in Hurwitz and Roberts classification). Because the ca...