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

BACKGROUND Impedance 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. METHODS A 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. RESULTS There was no statistically significant difference for the mean AVA between the two methods (0.7 ± 0.24 cm(2) using the Gorlin equation versus 0.7 ± 0.23 cm(2) using the hybrid approach, p = 0.17; r = 0.76, p < 0.001). The mean difference was 0.004 cm(2), and the limits of agreement were -0.33 to 0.37. CONCLUSION The 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.