Quantification of aortic regurgitant volume by a newly developed automated cardiac flow measurement method: An in vitro study

Background: Quantifying regurgitant volumes is important for treatment of patients with valvular aortic regurgitation. Simple, reliable methods to quantify aortic regurgitation have been sought both in the catheterization laboratory and the echocardiography laboratory. Objectives: The aim of our study was to investigate the applicability of a new automated cardiac flow measurement method with color Doppler velocity data for quantifying retrograde flow volumes of aortic regurgitation in an ascending aorta model. Methods and Results: A 2-chamber pulsatile flow system with a modeled ascending aorta and a regurgitant aortic valve orifice was developed. The model could generate 'aortic regurgitation-like' waveforms through the use of an electrically controlled valve. The regurgitant flows through the orifice (8.5 to 28.1 mL/beat) were measured by an ultrasound flowmeter; they were also calculated in the ascending aorta 1.0 cm above the orifice by the automated cardiac flow measurement method, which integrated spatially distributed digital flow velocity data through 'diastole.' Calculated regurgitant volumes measured with the low color Doppler filter (5.4 cm/s) agreed well with those measured with the flowmeter (r = .99, P< .001, mean difference = 2.2 ± 3.7 mL). However, the regurgitant volume was underestimated when 2 higher filter settings were used (9.6 and 10.9 cm/s). Although there was no significant difference in mean volume, higher frame rate (19 frames/s) provided more reproducible results with smaller standard deviation as compared with lower frame rate (7 frames/s). Conclusions: This new automated cardiac flow measurement method appears to be promising for semiautomatic quantification of aortic regurgitant volume. Appropriate choice of filter setting and high frame rate assists reliable data acquisition.