ECHOCARDIOGRAPHV-DOPPLER Noninvasive evaluation of pulmonary hypertension by a pulsed Doppler technique

We used a pulsed Doppler technique to examine the flow velocity pattern in the right ventricular outflow tract in 33 adults. In the patients with normal pulmonary artery pressure (mean pressure < 20 mm Hg, 16 patients), ejection flow reached a peak level at midsystole (137 + 24 msec, mean + SD), producing a domelike contour of the flow velocity pattern during systole. In contrast, the flow velocity pattern in patients with pulmonary hypertension (mean pressure ¢ 20 mm Hg, 17 patients) was demonstrated to accelerate rapidly and to reach a peak level sooner (97 + 20 msec, p < .01); in 10 of the pulmonary hypertensive patients a secondary slower rise in flow velocity was observed during a deceleration, resulting in the midsystolic notching. The time to peak flow (acceleration time, AcT) and right ventricular ejection time (RVET) were measured from the flow velocity pattern. Either AcT or AcT/RVET decreased with increase in mean pulmonary artery pressure, and a very high correlation (r = .90) was found between AcT/RVET and log,0 (mean pulmonary artery pressure). The use of this technique permitted the noninvasive estimation of the pulmonary artery pressure. Circulation 68, No. 2, 302-309, 1983. NONINVASIVE evaluation of pulmonary hypertension has been an important clinical problem for many years. The presence of pulmonary hypertension has been assessed by abnormalities in heart sounds,' in electrocardiographic tracings, or in chest x-rays,2 but to date, the accurate measurement of the pulmonary artery pressure requires the use of cardiac catheterization procedures. The development of echocardiographic techniques has allowed the investigation of pulmonic valve motion,3 which represents some characteristic abnormalities associated with pulmonary hypertension, such as rapid opening slope in systole,j5 attenuation or absence of the "a" dip,' prolongation of the ratio of right ventricular preejection period (RPEP) to right ventricular ejection time (RVET),57 and midsystolic semiclosure of pulmonic valve. )6 A recent experimental study8 emphasized that these abnormalities of the pulmonic valve motion were determined by abnormal flow changes in the pulmonary From the First Department of Internal Medicine, Osaka University Medical School, Osaka, Japan. Supported by Japan Heart Foundation Research Grant for 1979, and grant 57570349 from the Ministry of Education, Japan. Address for correspondence: Akira Kitabatake, M.D., The First Department of Internal Medicine, Osaka University Medical School, 1-150 Fukushima, Fukushima-ku, Osaka 553, Japan. Received Nov. 11, 1982: revision accepted April 14. 1983. 302 artery. However, flow characteristics with regard to pulmonary artery pressure either in the pulmonary artery or in the right ventricular outflow tract have not been successfully studied in man. Our objectives were to study the blood flow characteristics in the right ventricular outflow tract in patients with pulmonary hypertension by a pulsed Doppler technique9I and to develop an index that would permit quantitative evaluation of pulmonary hypertension by noninvasive methods. Materials and methods Patient selection. Thirty-eight patients admitted for diagnostic catheterization were examined by a pulsed Doppler technique. Five patients were excluded in whom Doppler recordings of flow velocity in the right ventricular outflow tract were not satisfactorily obtained because of poor penetration of ultrasound through the chest wall. Doppler examination was performed 18 to 24 hr before cardiac catheterization in 23 patients, within 1 week in four patients, and simultaneously with right-sided pressure recordings in six patients. The study population comprised 22 female and 11 male subjects, ranging in age from 15 to 66 years (average 44). Eighteen patients had predominant mitral valve disease, seven had atrial septal defect, five had ischemic heart disease, two had primary pulmonary hypertension, and one had predominant aortic valve disease. Twenty patients were in sinus rhythm and the remainder had atrial fibrillation. The mean pulmonary artery pressures (MPAPs) ranged from 6 to 88 mm Hg. Pulmonary hypertension CIRCULATION by gest on A uust 4, 2017 http://ciajournals.org/ D ow nladed from DIAGNOSTIC METHODS-ECHOCARDIOGRAPHY-DOPPLER was defined as MPAP greater than 20 mm Hg. There were 16 patients with MPAP in the 6 to 19 mm Hg range (the group without pulmonary hypertension), eight in the 20 to 39 mm Hg range (the group with mild pulmonary hypertension), and nine in the 40 to 88 mm Hg range (the group with severe pulmonary hypertension). Pulsed Doppler techniques. The pulsed Doppler examinations were performed with a directional pulsed Doppler flowmeter'1 (Model EUD 5; Hitachi Co, Ltd.) combined with an electronic beam sector-scanning echocardiograph (Model EUB 10-A; Hitachi Co, Ltd.), which made it possible to locatc the sample site by monitoring simultaneous display of two-dimensional echocardiograms on a cathode ray tube. The pulsed Doppler flowmeter operated with a carrier frequency of 2.5 MHz and a pulse repetition frequency of either 5 kHz or 10 kHz, with a disc-shaped sample volume I mm in depth with a radius of 3 mm. The Doppler output was analyzed by a sound spectrograph (Lion SG-07). The flow velocity away from the transducer was displayed above the baseline, and that toward the transducer was displayed below the baseline on the sound spectrogram. The technique of examination consisted of placing the transducer for the Doppler flowmeter in the second or third intercostal space along the left sternal border, with the sonar beam aimed laterally and superiorly. The sample volume was carefully positioned just below thc pulmonic cusp in the right ventricular outflow tract on the two-dimensional echocardiograms (figure 1). Analysis of data. The Doppler flow velocity pattern, obtained by the sound spectrograph, includes various Doppler frequencies simultaneously, even in a small region such as that measured in this study. Therefore the envelope of the flow velocity pattern, i.e., instantaneous maximal velocity, was used for quantitative analysis. The highest discernible frequencies were traced by hand. The RVET was defined as the time (msec) from the onset of ejection to that of zero flow. The time to peak flow velocity (acceleration time lAcT] in milliseconds) was defined as the interval between the onset of ejection and peak flow velocity. The time to peak flow velocity was also expressed as a ratio to the total duration of the systolic ejection time (AcT/RVET). All measurements from pressure recordings and flow velocity patterns are presented as the average of five to 11 (mean seven) consecutive cardiac cycles. AcT and AcT/RVET were determined in seven patients by one observer on two occasions (intraobserver variability). Another observer independently performed the determination for the same seven patients (interobserver variability). All observers were blinded to each other's results and to the results of cardiac catheterization. AcT 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 1.8% (intraobserver) and 6.1% (interobserver). Good correlations were also obtained for AcT/RVET, with a correlation coefficient of . 99 and mean absolute differences between observations of 1.5% (intraobserver) and 6.0% (interobserver). Cardiac catheterization. Cardiac catheterization was carried out with a standard technique. 12 Right-sided pressure determinations were obtained with use of fluid-filled catheters connected to a P23Db Statham strain gauge. In two patients with pulmonary hypertension, two catheter-tipped No. 5F micromanometers (Model PC-350a; Miller Instruments, Inc.) were introduced into the pulmonary arterial trunk and the right ventricle to obtain the pulmonary artery and right ventricular pressures and Doppler flow velocity simultaneously. All values were expressed as mean + SD. Comparisons among groups were performed by analysis of variance and Student's t test, and linear regression analysis was carried out by the method of least squares. Results Flow velocity patterns in the right ventricular outflow tract. A representative recording of flow velocity in the right ventricular outflow tract obtained in a patient without pulmonary hypertension is shown in figure 2. In all 16 patients without pulmonary hypertension, the pattern of ejection flow velocity exhibited a domelike contour with peak velocity in midsystole. In 17 FIGURE 1. Two-dimensional echocardiogram (left) and its schematic (right) showing the direction of ultrasonic Doppler beam (white broken line in the left panel and black broken line in the right panel) and the sample site (arrows) in the right ventricular outflow tract just below the pulmonic cusp. RA = right atrium; RV = right ventricle. PA = pulmonary artery; PV pulmonic valve. Vol. 68, No. 2, August 1983 303 by gest on A uust 4, 2017 http://ciajournals.org/ D ow nladed from