A Pilot Study Comparing Aortic Valve Area Estimates Derived from Fick Cardiac Output with Estimates Based on Cheetah-NICOM Cardiac Output.

Cardiac output during cardiac catheterization is often estimated using the modified Fick method (CO). In this proof-of-concept, prospective non-randomized study carried out in a single academic healthcare centre, we examined whether replacing CO in the Gorlin formula with Cheetah-NICOM monitor cardiac output (CO) could produce an accurate and precise estimate of aortic valve area in patients with severe aortic stenosis. In twenty-six subjects, CO and CO were obtained concurrently. A spot and 3-minute running average of CO was used. Bland and Altman analysis was used to derive bias, 95% limits of agreement (LOA) and confidence intervals (CI). The mean difference (bias) between AVA (average) and AVA was 0.11 cm and the 95% LOA were ±0.42 cm. The 95% CI of the bias was 0.02-0.2 cm. The bias and 95% LOA of AVA (spot value) were 0.14 ± 0.42cm, with a 95% CI of 0.06-0.23 cm. No proportional bias was present. AVA thus appears to be a reasonably accurate measure of AVA in patients with severe aortic stenosis compared to AVA measured using a modified Fick CO. However, the limits of agreement were not narrow enough to consider AVA and AVA interchangeable.