Background: The bicuspid aortic valve (BAV) is the most frequent congenital malformation of the heart, whereas unicuspid (UAV) and quadricuspid aortic valves (QAV) are very rare. Prevalence and associated lesions in patients undergoing TEE have not been well described.

    Methods and Results: Over a 10-year period, 4827 adult patients were studied by TEE and prior TTE. QAV was present in 3 patients (0.06%). 1 patient (age 32) with associated ventricular septal defect had 4 equal valve cusps and showed normal QAV function. The second patient (age 59) with associated fibromuscular subaortic stenosis had 1 small and 3 large cusps with grade IV aortic regurgitation. A third patient (age 46) with isolated QAV had 4 unequal cusps with grade II aortic regurgitation. No QAV had evidence of stenosis or  endocarditis. BAV was diagnosed in 38 patients (0.8%, 8f, 30m, mean age 48 y) and was regurgitant (n=17), stenotic (n=2), both stenotic and regurgitant (n=12) or showed normal BAV function (n=7). Associated lesions were: aortic valve (n=5) or mitral valve prolapse (n=1), aortic aneurysm/ dissection (n=3), mitral valve aneurysm (n=5), and subvalvular aortic stenosis, sinus of Valsalva aneurysm, aortic coarctation or aortic arch atresia (1 patient each). Infective endocarditis was present in 11 patients (active n=9, remote n=2, only BAV n=5, BAV and/ or mitral valve n=6). Diagnosis of UAV was made in 1 patient (age 45) with pure aortic regurgitation of grade IV caused by high leaflet redundancy with leaflet prolapse and associated endocarditis. There was no stenosis in this unicommissural valve. 1 UAV, 1 QAV and 19  BAV patients underwent aortic valve replacement with surgical confirmation of the valve morphology and associated lesions. The prevalence of congenitally abnormal valves in TEE patients compares well with the figures reported in the literature for autopsy series.