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 e valuating the severity of aortic regurgitation; however, there have be en no studies comparing these continuous wave Doppler methods with a s trictly quantifiable reference for regurgitant severity. The purpose o f 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 stud ied 8 to 20 weeks after surgery to create chronic aortic regurgitation . Twenty-nine hemodynamically different states were obtained pharmacol ogically. A Vingmed 775 system was used for recording continuous wave Doppler traces with a 5 MHz annular array transducer directly placed o n the heart near the apex. The aortic regurgitation was quantified as peak and mean regurgitant flow rates, regurgitant stroke volumes and r egurgitant fractions determined with pulmonary and aortic electromagne tic flow probes and meters balanced against each other. Peak regurgita nt how rates varied from 1.8 to 13.6 L/min (6.3 +/- 3.2 L/min) (mean a 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/bea t (26.9 +/- 12.2 ml/beat), and regurgitant fraction varied from 23% to 78% (53% +/- 16%). Only marginal correlations were obtained between r eference indexes and continuous wave Doppler deceleration slope and pr essure half-time (I = 0.55 to 0.74). A deceleration slope greater than 3 m/sec(2) and pressure half-time less than 400 msec did, however, pr ovide 100% specificity for detecting severe AR (regurgitant fraction > 50%). Our study shows that the continuous wave Doppler deceleration sl ope and pressure half-time methods have limited use for quantifying ao rtic regurgitation.