Frequency of Doppler Measurable Pulmonary Artery Pressures

Daniel D. Borgeson, MD, James B. Seward, MD, Fletcher A. Miller, Jr., MD, Iae K. Oh, MD, and A. Jamil Tajik, MD, Rochester, Minnesota

The current literature suggests that right-sided heart pressures can be obtained noninvasively in approxi- mately 60% of patients. We hypothesized that with a focused echocardiographic Doppler examination, mea- surable tricuspid or pulmonary valve regurgitation suitable for measuring pressures could be obtained in a higher percentage of patients. The study group con- sisted of 200 consecutive patients undergoing echocar- diographic and Doppler hemodynamic evaluation. All patients were first examined by an ultrasonographer instructed t o attempt to record tricuspid and pulmo- nary regurgitant velocities. After this examination, a designated cardiologist performed a focused examina- tion with the intent of improving the signal quality

and increasing the number of measurable signals for evaluation. Tricuspid regurgitation of measurable quality was recorded in 147 (73.5%) of 200 patients by the ultrasonographer; this result was improved to 172 patients (86%) by the designated cardiologist. Pulmo- nary regurgitation was obtainable in 147 (95%) of 154 patients and was of measurable quality in 137 (89%). When results of tricuspid and pulmonary regurgitation were combined, a quantifiable signal was obtained in 194 (97%) of 200 consecutive unselected patients. This study demonstrates that a well-trained ultrasonogra- pher or echocardiologist can obtain right-sided pres- sures in at least 95% of all unselected cardiovascular patients. (J Am Soc Echocardiogr 1996;9:832-7.)

Noninvasive estimation of pulmonary pressures has been shown to have a high degree of correlation with simultaneous invasive measurements. 1'2 Approxi- mately 60% or more of normal persons have "physi- ologic" tricuspid regurgitation. 3"4 We hypothesize that with a comprehensive, focused Doppler ultra- sound hemodynamic examination, measurable tri- cuspid or pulmonary valve regurgitation suitable for measuring right-sided systolic and diastolic pressures can be obtained in a much higher percentage of unselected patients.

METHODS AND PATIENTS

The study consisted of 200 consecutive unselected patients undergoing clinically indicated comprehensive cardiac ul- trasound imaging and Doppler hemodynamic evaluation. The study was carried out prospectively, and only children with complex congenital heart disease were excluded. All examinations were initially performed by a highly trained ultrasonographer (>4 years' experience) instructed to at- tempt to record tricuspid and pulmonary regurgitant re-

From the Divisions of Cardiovascular Diseases and Internal Medi- cine, Mayo Clinic and Mayo Foundation. Keprint requests: James B. Seward, MD, Mayo Clinic, 200 First St. S.W., Rochester, MN 55905. Copyright © 1996 by the American Society of Echocardiography. 0894-7317/96 $5.00 + 0 27/1/73823

832

locity as part of a complete echocardiographic study. After this examination was completed, a designated cardiologist (J.B.S.) performed a focused examination, attempting to record tricuspid or pulmonary valve rcgurgitation with the intent of improving the signal quality and increasing the number of measurable signals for evaluation.

The patients' ages rangcd from less than 1 year to 87 years, with a mean age of 45 years. There were no exclu- sions for body weight, underlying presentation, age, sex, or cardiac rhythm. The only diagnosis excluded was complex congenital heart disease. The cross-spectrum of patients includes 7% of patients less than 20 years old, and 3% were found to have pulmonary artery pressures above 60 mm Hg. The study population was designed to represent a cross-spectrum of patients seen in an active outpatient echocardiography laboratory. The intent was not to affect the study with regard to examiner or patient sclection. The study was designed to find out how often a right-sided pressure could be obtained by detecting either a tricuspid or pulmonary regurgitant Doppler velocity signal.

Tricuspid Regurgitant Signal

Optimal Doppler signals for both tricuspid and pulmonary regurgitation were considered those recorded with a non- imaging continuous-wave Doppler transducer (2 MHz Pcdof ). All duplex Doppler signals wcrc reduplicated with thc Pedof transducer. The tricuspid regurgitant signal was recorded most consistently from a low parastcrnal long- axis view of the right ventricular inflow. Thi s view provided optimal imagcs in 98% of the study population. The re- mainder of the images were optimized with subxyphoid or apical views. The most frequently used transduccr position

Journal of the American Society of Echocardiography Volume 9 Number 6 Borgeson et al. 833

was obtained by two-dimensional echocardiographic visu- alization of a long-axis view of the left ventricle and then tilting of the transducer medially to the tricuspid valve inflow view. Often a lower and slightly lateral precordial transducer position was required. With an optimized tri- cuspid inflow view on the video screen, the two-dimen- sional imaging transducer was exchanged at the same po- sition on the chest with the smaller, higher fidelity Pedof transducer. Visualization of the color flow jet of tricuspid regurgitation was not a prerequisite or a dependable indi- cator for obtaining measurable regurgitant signals. In ap- proximately 40% of patients, no color flow signal of tricus- pid regurgitation was visible. The continuous-wave Dopp- ler recording was scaled to accommodate at least 3 m/see, and a high wall filter was used. A good indication of proper angulation was the recording of the low-velocity continu- ous signal of inferior vena caval flow.

Pulmonary Regurgitant Signal

The pulmonary regurgitant signal was nearly always rc- corded from a mid to high left parastcrnal long-axis view of the right vcntricular outflow tract. From a long-axis view of the aortic valve, thc transducer was rotated clockwise into a long-axis view of the right vcntricular outflow. The trans- ducer beam was thcn tilted upward and optimized to a long-axis view of the right vcntricular outflow, pulmonary valve, and main pulmonary artery. A Pedof transducer was then exchanged to record the pulmonary regurgitant vc- locity. A low wall filter and velocity scale of 1 to 2 m/see were uscd. Visualization of a color flow jet of regurgitation was not a reliable predictor of a recordable regurgitant signal.

Pressure Calculations

Tricuspid valve. Peak tricuspid regurgitant signal velocity subjected to a simplified Bernoulli formula (4V ~) has been shown to be identical to the peak systolic gradient between the right ventricle and the right atrium s (Figure 1). To express the magnitude of right ventricular pressure, an estimate of simultaneous right atrial pressure is added to the gradient. Means of estimating right atrial pressure include 6 (1) clinical bedside estimate, which is inaccurate2; (2) empiric addition of 10 mm if there are no clinical features of elevated right-sided pressures~; (3) regression numbers derived from simultaneous echocardiographic catheterization studies (thus 14 is added if there is no clinical evidence of increased right-sided pressures and 20 is added if clinical or echocardiographic evidence of in- creased right-sided pressures is evident)2; and (4) a cali- brated estimate of right atrial pressure by use of phasic respiratory inferior vena caval dimensions. 7 Our clinical laboratory uses a combination of the above. If the patient is young and has absolutely no cardiovascular disease, 10 mm Hg is added. If the patient is older and has any features of cardiorespiratory disease, 14 mm Hg is added. If there is evidence of elevation of right atrial pressure by clinical or echocardiographic examination, 20 mm Hg is added. If pulmonary stenosis is absent, right ventricular systolic prcs-

sure reflects pulmonary systolic pressure. For clinical pur- poses, this technique for the determination of right ven- tricular and pulmonary pressures has been reliable.

Pu lmona ry valve. The most common technique for measurement is to record the end-diastolic regurgitant velocity, apply the simplified Bernoulli equation (4V~), and add an estimate of fight ventricular diastolic pressure (Fig- ure 2, A). Right ventricular diastolic pressure is assmned to be the same as the estimate of right atrial pressure applied to the tricuspid regurgitant signal (i.e., 10, 14, or 20 mm Hg). In our laboratory, we have also recognized that the mean pulmonary regurgitant gradient is nearly identical to the end-diastolic velocity converted to the gradient. 8 A mean regurgitant gradient is obtained by planimetcring the pulmonary regurgitant velocity envelope and using the mean diastolic gradient as the substitute for the end-dia- stolic velocity converted to gradient (Figure 2, B). This is helpful when an end-diastolic velocity is not discrete. Both techniques are used as a clinical estimate of end-diastolic pulmonary pressure. In our laboratory we have not rou- tinely applied any calculation or estimate of mean pulrno- nary pressure. Other calculations of pulmonary pressures have also been proposed, including (1) mean pulmonary artery pressures and (2) pulmonary acceleration t i m e s . 6

These techniques are not currently being used in our clinical Doppler hemodynamic laboratory. As with any hemodynamic measurement, at least three cardiac cycles are measured and averaged. If there is an arrhythmia or dynamically changing signal, five to 10 cycles are averaged. The thrust of this study was not to revalidatc Doppler measurement of pressure but to assess the incidence of measurable tricuspid or pulmonary regurgitant signals ca- pable of being used to estimate pulmonary systolic or diastolic pressure (Figure 3). The signal was graded in the following manner: (1) not recordable, (2) recordable but not measurable, (3) adequate for measurement, and (4) superior for measurement. Signals were considered mea- surable if in multiple signals a peak velocity was visible.

RESULTS

Tricuspid regurgitat ion was obtainable (grade 2 or higher) in 173 (86.5%) o f 200 patients by the ultra- sonographer. This result was improved to 183 (91.5%) with a focused examination by the desig- nated cardiologist (I.B.S.). The regurgi tant signal was measurable (grade 3 or 4) in 147 patients (73.5%) by the ul trasonographer; this again was im- proved to 172 (86%) with a focused examination by the designated cardiologist. The quality o f the signals was as follows: (1) unrecordable in 28 patients (14%) by the ul t rasonographer and 17 (8.5%) by the desig- nated cardiologist; (2) recordable bu t no t measur- able (grade 2) in 26 patients (13%) by the ultra- sonographer and 12 (6%) by the designated cardiolo- gist; (3) adequate for measurement (grade 3) in 53

Journal of the American Society" of Echocardiography 8 3 4 B o r g e s o n e t al. November-December 1996

Figure 1 Tricuspid regurgitant velocity signal. From low left parasternal transducer position, with ultrasound beam in longitudinal orientation directed medially toward tricuspid orifice, ideal projection of tricuspid valve is selected and imaging transducer is carefully exchanged for stand-alone continuous-wave Doppler transducer. Velocity is set for approximately 3 m/sec, and wall filter is maximized. Peak tricuspid regurgitant signal is converted to gradient according to simplified relationship of4(v) 2, in which v is peak regurgitant velocity (e.g., 2.4 m/see or 23 mm Hg). Estimate of right atrial pressure is added to result to give determination of right ventricular or pulmonary artery systolic pressure.

patients (26.5%) as recorded by the ultrasonographer and 60 (30%) by the designated cardiologist; and (4) superior for measurement (grade 4) in 94 patients (47%) as recorded by the ultrasonographer and 112 (56%) by the designated cardiologist. During the focused examination by the designated cardiologist, pulmonary regurgitation was obtainable (grade 2 or higher) in 149 (97%) of 154 patients and was of measurable quality (grade 3 or 4) in 137 (89%) of 154 patients. This subgroup consists of only 154 patients because in the early stages of t h e study it became apparent that in a vast majority of patients noninvasive pressure measurement would be based solely on the measurement of tricuspid regurgitation. Whenever the tricuspid regurgitant signal was not measurable, the pulmonary regurgitant signal was sought vigorously. Because the objectives of the study were met with a quantifiable measurement of this signal, the pulmonary regurgitant signals were not always pursued vigorously. The quality of re- corded signals was as follows: (1) not obtainable, five patients (3.2%); (2) recordable but not measurable (grade 2), 12 patients (7.8%); (3) adequate for mea-

surement of velocity (grade 3), 53 patients (34.4%); and (4) superior for measurement of velocity (grade 4), 84 patients (54.5%). When both tricuspid regur- gitation and pulmonary regurgitation were com- bined in assessing pulmonary artery pressures, quan- tifiable signals suitable for systolic or diastolic pulmo- nary artery pressures were obtained in 194 (97%) of 200 consecutive unselected patients. There were no differences in the rate of detection on the basis of age, sex, or underlying cardiac disease.

DISCUSSION

The measurement of right-sided heart pressures has important clinical implications. The ability to obtain these measurements noninvasively in a high percent- age ofunselected cardiovascular patients is an impor- tant advance in the clinical use of ambulatory hemo- dynamics. In the echocardiographic literature, the ability to measure tricuspid and pulmonary regur- gitant velocities is reported to be high but has .not been the primary focus of any one study. Such mea-

lournal of the American Socie~ of Echocardiography Volume 9 Number 6 Borgeson et al. 83~

Figure 2 Pulmonary regurgitant velocity signal. From parasternal long-axis scan of aortic valve, imaging transducer is turned cloclcedse and tilted upward to pulmonary valve in long axis. Transducer is usually close to left sternal-costal border. Imaging transducer is carefully ex- changed for stand-alone continuous-wave Doppler transducer. Recording velocity is set for 1 to 2 m/sec with low wall filter. Pulmonary systolic velocity is helpful to confirm proper transducer direction. A, Usually end-diastolic peak regurgitant velocity is converted to pressure according to 4(v) 2, in which v is end-diastolic velocity (e.g., 1.2 m / s e c or 6 mm Hg [arrow J). B, When end-diastolic velocity is not recorded confidently, pulmonary regurgitant signal can be planime- tered and mean gradient substituted for end-diastolic gradient (e.g., in same patient 6 mm Hg is used for end-diastolic pressure).

surements have been shown to correlate accurately with simultaneous catheter measurements of pres- sure. 2 In these studies, investigators found the occur- rence of Doppler-detectable tricuspid regurgitation to be in the range of 60% to 70%. 9 In this study, recordable tricuspid regurgitant velocities were ob- tained in 92% of the patients and measurable veloci- ties in 86%. Pulmonary regurgitation was recordable in 96% of patients and measurable in 89% of the patients studied. When both tricuspid and pulmo-

nary regurgitant velocities are considered, a nonin- vasive estimation of right-sided systolic or diastolic pressure was obtainable in 194 (97%) of 200 con- secutivc unselected patients. The ability to obtain measurable velocities capable of clinical estimation of pulmonary systolic or diastolic pressures has not been appreciated adequately. This study demon- strates that with a focused Doppler examination a mcasurable tricuspid or pulmonary regurgitant ve- locity can be obtained consistently in most patients.

Journal of the American Society of Echocardiography 8 3 6 B o r g e s o n e t al. November-December 1996

Figure 3 Paticnt with mild pulmonary hypertcnsion. Systolic pulmonary pressure is calcu- lated from tricuspid regurgitation (e.g., 2.96 m/sec or 35 mm Hg, to which estimate of right atrial pressure is added). Diastolic pulmonary artery pressure is obtained from pulmonary regurgitant signal (e.g., 1.62 m/scc or 10.5 mm Hg [middle panel] or 11.8 mm Hg [rig/at panel by planimetry], to which estimate of right atrial pressure is added).

Routine recording of pulmonary systolic or diastolic pressure should be incorporated into a complete noninvasive hemodynamic examination. The ability to measure pulmonary artery pressure has many clinical implications. These hemodynamic param- eters have prognostic value in patients with condi- tions such as mitral valve dysfunction, aortic steno- sis, 1°'11 and chronic lung disease. Noninvasive mea- surement of pulmonary artery pressure has been shown to predict both morbidity and death in pa- tients with ischemic and dilated cardiomyopathy. 12 For patients with pulmonary hypertension, the pul- monary artery pressure is superior to both clinical and radiographic features in predicting survival. 1~ Cooper et a l l 4 investigated pulmonary artery pres- sure as an independent predictor of death in patients with known cardiac disease. Pulmonary artery pres- sure appeared to be the strongest predictor of death, independent of the severity of coronary atherosclero- sis, ejection fraction, or left ventricular hypertrophy.

Limitat ions

The incidence of normal tricuspid and pulmonary valve regurgitation is very high ~a6 and, with more sensitive technology and a focused examination, the velocities of the signals can be recorded and mea- sured. This study did not test the utility of echocar- diographic contrast-enhanced Doppler signals or the

utility of transesophageal or intracardiac Doppler echocardiography. 17a8 This study was focused solely on the ability to record a tricuspid or pulmonary regurgitant velocity suitable for calculation of pul- monary systolic or diastolic pressure.

C o n c l u s i o n

Doppler-detectable tricuspid or pulmonary regur- gitant velocities allow right ventricular and pulmo- nary artery pressures to be measured noninvasively. Data presented herein demonstrate that a well- trained ultrasonographer or echocardiologist can ob- tain right-sided pressure in at least 95% of all unse- lected cardiovascular patients. This information should be provided routinely as part of a complete echocardiographic hemodynamic examination. It should be reemphasized that lack of color flow signal does not imply the absence of a measurable tricuspid or pulmonary regurgitant signal. During the past few years, the echocardiographic laboratory has evolved into a combined hemodynamic and imaging labora- tory. 19 A comprehensive examination now routinely includes functional and hemodynamic information that can obviate invasive catheterization. No longer is it acceptable to perform hemodynamic catheteriza- tion routinely to obtain data on valve area, ventricu- lar function, gradient, or valve regurgitation. This clinical study shows the feasibility of measuring pul-

Journal of the American Societ T of Echocardiography Volume 9 Number 6 Borgeson et al. 837

m o n a r y systolic o r diastol ic pressures non invas ive ly

in m o s t pa t ien ts . These m e a s u r e m e n t s are n o w con-

s idered an in tegra l c o m p o n e n t o f any c o m p l e t e ul-

t r a s o u n d h e m o d y n a m i c a n d i m a g i n g study. 2°m

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