What is the validity of continuous wave Doppler grading of aortic regurgitation severity? A chronic animal model study

Continuous wave Doppler methods have been widely used clinically for evaluating the severity of aortic regurgitation; however, there have been no studies comparing these continuous wave Doppler methods with a strictly quantifiable reference for regurgitant severity. The purpose of this study was to test the applicability of continuous wave Doppler methods (deceleration slope and pressure half-time) for evaluation of chronic aortic regurgitation in an animal model. Eight sheep were studied 8 to 20 weeks after surgery to create chronic aortic regurgitation. Twenty-nine hemodynamically different states were obtained pharmacologically. A Vingmed 775 system was used for recording continuous wave Doppler traces with a 5 MHz annular array transducer directly placed on the heart near the apex. The aortic regurgitation was quantified as peak and mean regurgitant flow rates, regurgitant stroke volumes and regurgitant fractions determined with pulmonary and aortic electromagnetic flow probes and meters balanced against each other. Peak regurgitant flow rates varied from 1.8 to 13.6 L/min (6.3 ± 3.2 L/min) (mean ± SD), mean regurgitant flow rates varied from 0.7 to 4.9 L/min (2.7 ± 1.3 L/min), regurgitant stroke volume varied from 7.0 to 48.0 ml/beat (26.9 ± 12.2 ml/beat), and regurgitant fraction varied from 23% to 78% (53% ± 16%). Only marginal correlations were obtained between reference indexes and continuous wave Doppler deceleration slope and pressure half- time (r = 0.55 to 0.74). A deceleration slope greater than 3 m/sec² and pressure half-time less than 400 msec did, however, provide 100% specificity for detecting severe AR (regurgitant fraction >50%). Our study shows that the continuous wave Doppler deceleration slope and pressure half-time methods have limited use for quantifying aortic regurgitation.