EVALUATION OF AORTIC REGURGITATION WITH DIGITALLY DETERMINED COLOR DOPPLER-IMAGED FLOW CONVERGENCE ACCELERATION - A QUANTITATIVE STUDY IN SHEEP

Objectires. The aim of the present study was to validate a digital col or Doppler-based centerline velocity/distance acceleration profile met hod for evaluating the severity of aortic regurgitation. Background. C linical and in vivo experimental applications of the Bow convergence a xial centerline velocity/distance profile method have recently been us ed to estimate regurgitant Bow rates and regurgitant volumes in the pr esence of mitral regurgitation. Methods. In six sheep, a total of 19 h emodynamic states were obtained pharmacologically 14 weeks after the o riginal operation in which a portion of the aortic noncoronary (n = 3) or right coronary (n = 3) leaflet was excised to produce aortic regur gitation. Echocardiographic studies were performed to obtain complete proximal axial flow acceleration velocity/distance profiles during the time of peak regurgitant flow (usually early in diastole) for each he modynamic state. For each steady state, the severity of aortic regurgi tation was assessed by measurement of the magni tude of the regurgitan t flow volume/beat, regurgitant fraction and instantaneous regurgitant Bow rates determined by using both aortic and pulmonary artery electr omagnetic flow probes. Results. Grade I regurgitation (regurgitant vol ume/beat <15 ml, six conditions), grade II regurgitation (regurgitant volume/ beat between 16 ml and 30 ml, five conditions) and grade III-I V regurgitation (regurgitant volume/beat >30 ml, eight conditions) wer e clearly separated by using the color Doppler centerline velicity/dis tance profile domain technique. Additionally, an equation for correlat ing ''a'' (the coefficient from the multiplicative curve fit for the v elocity/distance relation) with the peak regurgitant flow rates (Q [li ters/min]) was derived showing a high correlation between calculated p eak flow rates by the color Doppler method and the actual peak how rat es (Q = 13a + 1.0, r = 0.95, p < 0.0001, SEE = 0.76 liters/min). Concl usions. This study, using quantified aortic regurgitation, demonstrate s that the flow convergence axial centerline velocity/ distance accele ration profile method can be used to evaluate the severity of aortic r egurgitation.