How might one differentiate among valvular aortic stenosis, idiopathic hypertrophic subaortic stenosis, hypertrophic obstructive cardiomyopathy, subaortic membrane, and supra-aortic membrane?

Pulsed-wave Doppler can be used to precisely locate the high-velocity jet. 2DE can be used to search for asymmetric septal hypertrophy or a subaortic or supra-aortic membrane.

Normal-appearing aortic leaflets argue against valvular aortic stenosis.

Associated aortic regurgitation may be seen with a subaortic membrane, although this finding is not specific because mixed aortic valve disease is quite common. TEE may be necessary to further evaluate the aortic valve.