title: A hybrid approach for quantifying aortic valve stenosis using impedance cardiography and echocardiography.
abstract: 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Cardiology, Department of Cardiology, Al Najah National University Hospital, Nablus, Palestine. yunis.daralammouri.@najah.edu.
authors.forename: Yunis
authors.initials: Y
authors.lastname: Daralammouri
authors.affiliation: Department of Cardiology, Department of Cardiology, Al Najah National University Hospital, Nablus, Palestine.
authors.forename: Khubaib
authors.initials: K
authors.lastname: Ayoub
authors.affiliation: Al-Quds University, Beit Hanina, Palestine.
authors.forename: Najwan
authors.initials: N
authors.lastname: Badrieh
authors.affiliation: Department of Cardiology, Zentralklinik Bad Berka, Robert-Koch-Allee 9, 99437, Bad Berka, Germany.
authors.forename: Bernward
authors.initials: B
authors.lastname: Lauer
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001024:Aortic Valve Stenosis / Q000175:diagnosis* / Q000503:physiopathology; D006328:Cardiac Catheterization / Q000379:methods; D002307:Cardiography, Impedance / Q000379:methods*; D004452:Echocardiography / Q000379:methods*; D005260:Female; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D012720:Severity of Illness Index; D013318:Stroke Volume / Q000502:physiology