Quantitative assessment of stenotic aortic valve area by using intracardiac echocardiography: In vitro validation and initial in vivo illustration

Quantitative assessment of aortic stenosis (AS) is subject to the limitations of all current noninvasive and invasive methods. The ability to obtain a direct measure of aortic valve area with high resolution by intracardiac echocardiography (ICE) could be of great benefit to catheterized patients. To provide a fixed AS area as an ideal standard for comparison, we performed ICE in 12 sheep hearts with experimentally created AS and five human AS hearts from autopsies. ICE catheters were passed retrograde across the aortic valve, and the minimal orifice area on pullback was planimetered and compared with calibrated video imaging. The entire orifice circumference could be successfully recorded in 16 (94%) hearts. Orifice area from ICE correlated well with actual values (r = 0.98; standard error of the estimate [SEE] = 0.06 cm2). To illustrate the applicability in vivo, two canine models and 10 patients with AS were studied. The limiting orifice could be imaged in both animals and in 8 of 10 patients, in whom values agreed well with invasive data (r = 0.95; SEE = 0.04 cm2). ICE can therefore accurately measure AS orifice area in vitro; it can be applied in vivo as well. These validation studies laid the foundation for subsequent clinical studies and applications.