A hybrid approach for quantifying aortic valve stenosis using impedance cardiography and echocardiography.

Abstract

BackgroundImpedance cardiography (IC) is a noninvasive modality that utilizes changes in impedance across the thorax to assess hemodynamic parameters, including stroke volume (SV).This study compared aortic valve area (AVA) as assessed by a hybrid approach of transthoracic echocardiography (TTE) and impedance cardiography (IC) to AVA determined at cardiac catheterization using the Gorlin equation.MethodsA total of 30 patients with moderate to severe aortic stenosis underwent AVA measurement using two different approaches: using the continuity equation (CE) in a hybrid method combining IC and TTE (AVA = stroke by volume impedance cardiography/trans-aortic-VTI) and using the Gorlin equation. Patient age ranged from 37 to 82 years (mean 48); there were 21 men and 9 women. Twenty-five patients were in sinus rhythm, and five had atrial fibrillation.ResultsThere was no statistically significant difference for the mean AVA between the two methods (0.7 ± 0.24 cm2 using the Gorlin equation versus 0.7 ± 0.23 cm2 using the hybrid approach, p = 0.17; r = 0.76, p < 0.001). The mean difference was 0.004 cm2, and the limits of agreement were −0.33 to 0.37.ConclusionThe hybrid method using impedance cardiography and TTE is a reasonable, clinically applicable approach to evaluate AVA and has significant correlation to invasive measurement using the Gorlin equation.