The role of multimodality imaging in aortic valve assessment: A review

Aortic stenosis (AS) is one of the most prevalent valvular diseases. Doppler echocardiography is the most common imaging modality for the assessment of AS severity. Cardiac catheterization is also used when there are discrepancies between clinical and echocardiographic data. However, there exist many pitfalls in the assessment of the flow rate and pressure gradient by both imaging strategies. Doppler echocardiography assumes a circular left ventricular outflow tract (LVOT) and a flat velocity profile through the LVOT and does not account for pressure recovery. While cardiac catheterization accounts for pressure recovery, the formulas used to calculate oxygen consumption needed for cardiac output are also a source of inaccuracy in assessing the aortic valve area (AVA). Therefore, less flow-dependent modalities can be used to assess AS severity. Those methods can be divided into non-invasive such as 3-dimensional and resting flow rate assessment of AVA, invasive such as valvular resistance and valvulo-arterial impedance, and surrogate markers like the degree of aortic valve calcification, the degree of cardiac damage, and the delay between left ventricular and aortic systolic pressure peaks. Multimodality imaging, specifically dobutamine stress echocardiography and non-contrast cardiac computed tomography (CT) can also be used to assess the severity of moderate AS with discordant criteria on Doppler echocardiography. Finally, cinefluoroscopy, cardiac CT, cardiac magnetic resonance, and nuclear imaging can be used to assess prosthetic aortic valves when valve dysfunction is suspected or when there is discordance between the echocardiographic assessment and the patient's clinical status.