AORTIC REGURGITATION Noninvasive evaluation of aortic regurgitation by continuous - wave Doppler echocardiography

Continuous-wave Doppler echocardiography was used to examine the aortic regurgitant flow velocity pattern in 32 patients with aortic regurgitation (AR) and 10 patients without AR. The aortic regurgitant flow velocity patterns, characterized by a rapid rise in flow velocity immediately after closure of the aortic valve, high peak flow velocity, and a gradual deceleration until the next aortic valve opening, were successfully obtained in 30 of the 32 patients with AR (sensitivity 94%, specificity 100%). The velocity decline was greater in patients with severe AR; thus, the slope of the velocity decline (deceleration) and the time to decline to half the peak velocity (half-time index) were measured from the flow velocity pattern. The deceleration became greater and the half-time index shortened in accordance with angiographic grading of AR (p < .01). The deceleration and the half-time index also correlated well with the aortic regurgitant fraction (r = .79, p < .01; r = .89, p < .01). Because the half-time index could be measured easily and independently of Doppler incident angle, it seemed a simple and accurate index of assessing the severity of AR. Thus continuous-wave Doppler echocardiography permitted the noninvasive evaluation of AR. Circulation 73, No. 3, 460-466, 1986. THE RECENT ADVENT of continuous-wave Doppler echocardiography has made it possible to measure high flow velocities that cannot be measured with conventional pulsed Doppler echocardiography.' Thus high blood flow velocity across the stenotic valve can now be obtained noninvasively for the determination of the pressure gradient across the stenotic valve and stenotic valve orifice area by means of the simplified Bernoulli equation.2-1 The usefulness of continuouswave Doppler echocardiography in evaluating valvular stenosis has been confirmed in many studies.2Recently, several investigators1' 9, 10 described that characteristic regurgitant flow velocity patterns, which could not be measured with pulsed Doppler echocardiography because of aliasing effects of high velocities, could be measured with continuous-wave Doppler echocardiography. However, the feasibility of this method for evaluating valvular regurgitation has never been studied. From the Cardiovascular Division, Osaka Police Hospital, and the First Department of Intermal Medicine. Osaka University Medical School, Osaka, Japan. Address for correspondence: Akira Kitabatake, M.D., The First Department of Internal Medicine, Osaka University School of Medicine, 1-1-50 Fukushima, Fukushima-ku, Osaka 553, Japan. Received July 29, 1985; revision accepted Nov. 7, 1985. 460 In this study, we used continuous-wave Doppler echocardiography for noninvasive evaluation of aortic regurgitation (AR). Patterns of aortic regurgitant flow velocity across the aortic valve were analyzed to develop an index that could be used for assessing the severity of AR. Methods Patient selection. The study population consisted of 32 patients with AR (22 men and 10 women, ages 37 to 71 years, mean 54) and 10 patients without AR (eight men and two women, ages 42 to 64 years, mean 55). All patients underwent diagnostic cardiac catheterization, and the presence of AR was confirmed or ruled out by aortic root angiography. Twenty-six patients had pure AR and six had combined aortic stenosis and regurgitation; 10 patients had associated mitral stenosis and I 1 patients had associated mitral regurgitation. Twenty-seven were in sinus rhythm and the remainder had atrial fibrillation. Doppler examination was performed 18 to 24 hr before cardiac catheterization in 31 patients, within 1 week in six patients, and within 4 weeks in five patients. The clinical condition of the patients did not change in the interim. Doppler examination. The Doppler examinations were performed with a duplex Doppler echocardiograph (Toshiba SDS21B with SSH-40A) equipped with a 2.4 MHz phased-array transducer. Measurements were performed in the continuouswave Doppler mode. The beam direction of the transmitted ultrasound was fixed and displayed as a bright dotted line in the two-dimensional echocardiographic image (figure 1). The beam direction of the received ultrasound was movable and displayed as a bright solid line in the two-dimensional echocardiographic CIRCULATION by gest on N ovem er 2, 2017 http://ciajournals.org/ D ow nladed from DIAGNOSTIC METHODS-AORTIC REGURGITATION FIGURE 1. Continuous-wave Doppler recording in the left ventricular outflow tract in a patient without AR. Doppler beam directions of transmitted and received ultrasound arc represented as a white dotted line and a white solid line in the twodimensional echocardiographic image (left), LA = left atrium; LV left ventricle; Ao = aorta; ECG electrocardiogram; PCG = phonocardiogram. image. In continuous-wave Doppler sampling, no specific depth gate is established, and all velocities along the lines are processed for velocity determination. Doppler signals derived from structures were minimized by a high-pass filter, and all signals were analyzed in real time by fast-Fourier transform. Doppler flow velocity pattern, simultaneous lead 11 electrocardiogram, and phonocardiogram were displayed on a monitor and recorded on videotape or on a strip-chart recorder at a paper speed of 50 to 100 mm/sec. The directions of the Doppler beams could be verified frequently during the examination by briefly switching to the imaging mode. Each patient was asked to rest in a supine position or in a left lateral decubitus position and to breath in a relaxed way during Doppler examination. The transducer was placed on the cardiac apex and angulated medially to depict the left ventricular outflow tract and the ascending aorta in a left anterior oblique equivalent view. The crossing point of transmitted and received ultrasound beam lines was advanced to the level of the aortic orfice. The transducer was tilted slowly until the highest Doppler frequency shifts could be obtained with the aid of the audio signals. In four patients, additional recordings were obtained with the transducer in the lower left sternal border. Data analysis. The envelope of the flow velocity pattern in diastole, i.e., instantaneous maximal velocity, was used for quantitative analysis. The highest discernible frequencies were traced by hand, and three indexes were determined with continuous-wave Doppler echocardiographic measurements: (I) peak flow velocity, (2) deceleration, and (3) half-time index. Peak velocity was calculated from the Doppler equation as velocity = c A F/2 fo cos 0 where c = sound velocity in tissue or 1540 m/sec, A F = Doppler shift frequency, fo = carrier frequency, and 0 = Doppler incident angle. 0 was assumed to be zero in this study (cos of 0 = 1.0) because the direction of aortic regurgitation flow could not be predicted from the anatomy of the surrounding structures. The deceleration was determined as the slope of a straight line drawn between the peak velocity and the shoulder at end-diastole. Half-time index was defined as the interval between the peak velocity and one-half of the peak velocity with reference to the straight line drawn in determining the deceleration. All measurements from flow velocity patterns are presented as the average of at least five cardiac cycles. Vol. 73, No. 3, March 1986 Peak velocity and half-time index were determined in seven patients by one observer on two occasions (intraobserver varability). Another observer independently performed the determination for the same seven patients (interobserver variability). All observers were blinded to each others results and to the results of cardiac catheterization. Peak velocity correlated well between intraobserver and interobserver determinations, with a correlation coefficient of .99 and mean absolute differences between observations (expressed as a percentage of the first observer's first observation) of 2.6% (intraobserver) and 5.6% (interobserver). Good correlations were also obtained for halftime index, with a correlation coefficient of .99 and mean absolute differences between observations of 2.8% (intraobserver) and 6.4% (interobserver). Cardiac catheterization. All patients underwent cardiac catheterization. Aortic root angiography was performed with injection of 50 to 60 ml of meglumine/sodium diatrizoate (Urografin). The degree of AR was graded independently from the echocardiographic findings on a three-point scale from angiography as follows: (1) mild (nine patients), minimal dye in the upper part of the left ventricle clearing in the next systole; (2) moderate (13 patients), dye in the left ventricle not clearing in the next systole, with slow opacification of the left ventricle, which remained fainter than that of the aorta; (3) severe (10 patients), dye producing a rapid opacification of the left ventricle equal to or denser than that of the aorta. In addition to semiquantitative angiographic grading, AR was quantitated by aortic regurgitant fraction, which was determined during cardiac catheterization. Since the regurgitant output is the difference of the total cardiac output and the effective cardiac output, the regurgitant fraction is calculated as the difference divided by the total cardiac output. In this study, the effective forward cardiac output was measured with the indicator dilution procedure. The total cardiac output was measured with left ventriculography and standard area-length methods.1' 12 Statistical analysis. All values were expressed as mean + SD. Significance of differences between the mean values of peak flow velocity, decelerations, and half-time index in patients with and without AR were assessed with analysis of variance and a multiple comparison method. The diagnostic value of aortic regurgitant peak flow velocity was assessed by calculating sensitivity and specificity. Doppler indexes were also compared with the regurgitant fraction by linear regression analyses. 461 by gest on N ovem er 2, 2017 http://ciajournals.org/ D ow nladed from