Acute Hemodynamic Effects of Sildenafil in Patients With Severe Aortic Stenosis

Inclusion Criteria: * Severe aortic stenosis (AVA \< 1.0 cm2) * Referred for a clinically ordered right and left heart catheterization * 18 years of age and older * Able and willing to comply with all requirements of the study Exclusion Criteria: * Nitrate use within 24 hours * SBP \< 110 mmHg or MAP \< 75 mmHg * Severe mitral regurgitation * Severe aortic regurgitation * Increased risk of priapism * Retinal or optic nerve problems or unexplained visual disturbance * Alpha antagonists or cytochrome P450 3A4 inhibitors use within 24 hours * Current or recent (≤ 30 days) acute coronary syndrome * O2 sat \< 90% on room air * Females that are pregnant or believe they may be pregnant * Any condition which the PI determines will place the subject at increased risk or is likely to yield unreliable hemodynamic data * Unwilling to provide informed consent