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

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Cardiac output during cardiac catheterization is often estimated using the modified Fick method (CO(Fick)). In this proof-of-concept, prospective non-randomized study carried out in a single academic healthcare centre, we examined whether replacing CO(Fick) in the Gorlin formula with Cheetah-NICOM monitor cardiac output (CO(Cheetah)) could produce an accurate and precise estimate of aortic valve area in patients with severe aortic stenosis. In twenty-six subjects, CO(Fick) and CO(Cheetah) were obtained concurrently. A spot and 3-minute running average of CO(Cheetah) 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(Cheetah) (average) and AVA(Fick) was 0.11 cm(2) and the 95% LOA were ±0.42 cm(2). The 95% CI of the bias was 0.02-0.2 cm(2). The bias and 95% LOA of AVA(Cheetah) (spot value) were 0.14 ± 0.42cm(2), with a 95% CI of 0.06-0.23 cm(2). No proportional bias was present. AVA(Cheetah) thus appears to be a reasonably accurate measure of AVA in patients with severe aortic stenosis compared to AVA(Fick) measured using a modified Fick CO. However, the limits of agreement were not narrow enough to consider AVA(Cheetah) and AVA(Fick) interchangeable.