Echocardiographic Evaluation of PulmonaryHypertension

By NAVINC. NANDA, M.D., RAYMOND GRAMIAK, M.D.,

TREVOB I. ROBINSON, M.D., AND PRAXVIN M. SHAH, M.D.

SUMMARYEchocardiographic studies of the pulmonary valve were obtained in 63 adults. Patients with normal

pulmonary artery pressure (22 cases) showed an oblique position of the valve images in diastole, slow valveopening slopes (< 300 mm/see), sizable (> 2 mm) posterior displacement of the cusp echoes with atrialsystole ('a' dip), and a relatively short right ventricular pre-ejection period. In contrast, pulmonary valves inpulmonary hypertension (mean pressure > 20 mm Hg, 41 cases) appeared straight in diastole with rapidopening slopes (> 350 mm/sec) and prolonged pre-ejection periods (P < 0.001). In patients maintainingsinus rhythm (25 cases), mild to moderate pulmonary hypertension (mean pressure < 40 mm Hg) was in-dicated by small 'a' dips (< 2 mm), while absence of 'a' dips denoted more severe pulmonary hypertension(mean pressure > 40 mm Hg) when uncomplicated by severe right heart failure. In the latter instance rapidvalve opening slopes were associated with large 'a' dips. Echocardiography appears to be of value in theassessment of pulmonary hypertension.

Pulmonary stenosis"A' dip Right ventricular pre-ejection peri

THE DIAGNOSIS OF PULMONARY HYPER-TENSION and evaluation of its severity rep-

resent a common challenging clinical problem whichrequires invasive techniques for accurate assessment.Ultrasound represents a noninvasive, non-traumatic,repeatable diagnostic technique whose role is well es-

tablished in the evaluation of various conditions affect-ing the mitral valve,'-6 the aortic root,7`10 and thetricuspid valve.3'" The recent development in our

laboratory of a detection method for the pulmonicvalve12 has allowed investigation of its function in nor-

mal subjects as well as in patients with pulmonaryhypertension. 13' 1 The purpose of this report is to pre-

sent our early experiences in the recognition ofpulmonary hypertension and to describe criteria bywhich the severity of this condition can be estimated

From the Departments of Medicine (Cardiology) and Radiology,University of Rochester School of Medicine and Dentistry,Rochester, New York.

Supported in part by NIH Grant 1-RO1-HL-15186-01, HL-03966,and HL-05500. Dr. Nanda's work was carried out in part during thetenure of a Research Fellowship awarded by the Finger LakesHeart Chapter, Inc., and Dr. Shah's work was carried out duringthe tenure of an American Heart Association Teaching Scholarshipin Cardiology.

Address for reprints: Navin C. Nanda, M.D., Cardiology Unit,University of Rochester Medical School, Rochester, New York14642.

Received February 26, 1974; revision accepted for publicationApril 26, 1974.

(Circulation. Volunoe .50, September 1.974'J75

Pulmonary valve

by echocardiographic examination of the pulmonaryvalve.

Material and Methods

The clinical material consisted of 63 adult patients inwhom the pulmonic valve was recorded successfully byechocardiography 18-24 hr prior to cardiac catheterization.There were 38 males and 25 females. Their ages rangedfrom 16 to 66 years, the average being 42 years. Twenty-sixpatients had predominant mitral valve disease, 12 hadischemic heart disease, 11 had aortic valve disease, seven

had congenital heart disease, six had cardiomyopathy, andone had Barlow's syndrome. Patients with pulmonarystenosis were excluded from the study.

Standard techniques were employed to obtain right ven-

tricular and pulmonary artery pressures during cardiaccatheterization. Twenty-two patients had normal right-sided pressures (mean pulmonary artery pressure 20 mm Hgor less). All were in sinus rhythm. Forty-one patients hadpulmonary hypertension, of whom 16 were in atrial fibrilla-tion and the remainder in sinus rhythm. The diastolicgradient across the pulmonic valve was determined as thedifference between the pulmonary artery diastolic pressureand the right ventricular end-diastolic pressure.

All ultrasonic examinations were carried out using a com-

mercially available echograph (Picker) and a 2 MHzcollimated transducer. Continuous records at high recordingspeed (equivalent to 125 mm/sec on a strip chart recorder)were made on 35 mm film by means of a Fairchild os-

cilloscope record camera and a dual beam oscilloscopeoperating as a slave.

In all patients pulmonary valve echocardiograms were ob-tained by a method previously described.'2 The aortic root isidentified either by angling the transducer medially and

Additional Indexing Words:Ultrasound

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NANDA, GRAMIAK, ROBINSON, SHAH

Figure 1

Schematic representation of the pathway of the ultrasonic beam asit obliquely traverses the right ventricular outflow-pulmonary arteryarea during pulmonic valve detection. The upward oblique beamdirection explains why usually only a single posterior valve cusp isdetected and illustrates how elevation of the valve cusp towardopening produces a posterior deflection on the echogram.PA = pulmonary artery; RV = right ventricle; LA = left atrium;LV = left ventricle.

superiorly from the mitral valve or by directly placing thetransducer one interspace above the mitral valve positionand directing the beam medially. From this position the ul-trasonic beam is then angled superiorly and laterally towardthe left shoulder (fig. 1). As the signals from aortic walls dis-appear, an anterior sonolucent space which represents theright ventricular outflow-pulmonary root junction becomesvisible. Within this space the pulmonary cusp echoes appearas thin moving lines. Posteriorly, the pulmonary artery isseparated from the left atrium by a thick echo complexproduced by structures in the atriopulmonic sulcus.12 It ishelpful in some patients to first locate this thick echo com-plex and then by minimal angulation delineate the

P.V

ECG

Figure 2

Pulmonary valve measurement technique. A representative tracingof the pulmonary valve echo through the cardiac cycle illustratesthe parameters studied. PV = pulmonary valve echo; ECG = elec-trocardiogram; OS = maximal opening slope of the pulmonaryvalve; a = posterior displacement observed following atrial systole;qo = pre-ejection period of the right ventricle; am = amplitude ofthe valve opening movement.

pulmonary cusp echoes. An anterior and a posterior leafletcan occasionally be observed but usually only the posteriorcusp is detected. Correlation with anatomic specimens in-dicates that the posteriorly located leaflet image is derivedfrom the left pulmonary cusp.A schematic representation of the pulmonary valve cusp

image recorded through a cardiac cycle is shown in figure 2and illustrates the following determinations which weremade from the pulmonary valve echograms: 1) maximalopening rate in mm/sec. This was obtained by averagingmeasurements (to the nearest 50 mm/sec) made from anumber of pulmonary valve recordings; 2) maximalmagnitude (in mm) of the posterior motion of the valve cuspfollowing atrial systole ('a' dip); 3) pre-ejection period of theright ventricle as determined from the beginning of the QRScomplex of the electrocardiogram to the onset of the valveopening measured in msec and corrected for heart rate. Thismeasurement was not made in patients with bundle-branchblock (3 cases) or those in atrial fibrillation; 4) amplitude ofthe valve opening movement (in mm). In addition, the posi-tion of the valve cusp in diastole relative to the walls of theright ventricular outflow-pulmonary artery complex wasstudied (fig. 3).

Results

Patients with normal right-sided pressures showedan obliquely posterior position of the pulmonary cuspecho in diastole resulting in nonparallelism with themargins of the right ventricular outflow-pulmonaryartery complex in all cases but one. The pulmonaryvalve opened relatively slowly, the opening velocity inall equalling 300 mm/sec or less. A transient posteriordisplacement of the cusp signal ('a' dip) was observedfollowing atrial systole in all cases. This posteriordeflection was large (3-12 mm, average 4.4 mm) in 21of 22 patients in this group. The pre-ejection period ofthe right ventricle was relatively short (mean 85

Figure 3

Normal pulmonary valve echogram. This patient demonstrates theoblique position of the cusp echo in diastole, a slow valve openingslope and a large 'a' dip characteristic of normal pulmonary arterypressure. PV = pulmonary valve; PHONO = phonocardiogram;ECG = electrocardiogram.

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ECHOCARDIOGRAPHY/PULMONARY HYPERTENSION

Table 1

Pulmonary Valve Echocardiographic Findings in Pulmonary Normotensive and HypertensivePatients

Mean 'A' dip PEP/,/ Openingpulmonary artery Diastolic Opening slope mm (mean) msec (mean) amplitudepressure position mm/sec (mean) (NSR only) (NSR only) mm (mean)

<20 mm Hg Oblique 211 4.4 85.07 8.68(22 patients) SE 12.7 SE 0.46 SE 4.36 SE 0.92>20 mm Hg Straight 420 0.92 110.3 11.15(41 patients) SE 15.8 SE 0.34 SE 4.00 SE 0.47Level of significance P < 0.001 P < 0.001 P < 0.001 P < 0.05of t value*

Abbreviations: NSR = normal sinus rhythm; PEP = right ventricular pre-ejection period; R-R =square root of the interval (in sec) between two consecutive QRS complexes of the electrocardiogram; sE =standard error.

*Derived using unpaired t-test with unequal iiumber of observations."5

msec). The amplitude of the opening movement was 9mm or less in 15 of the 22 pulmonary normotensives(table 1 and fig. 3).On the other hand, patients with pulmonary

hypertension showed a general straightening of thediastolic configuration of the pulmonary cusp imagein 38 of 41 cases. The diastolic echo was observed tobe parallel to the walls of the right ventricular

90-

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100 200 300 400 500 600PV OPENING SLOPE (mm-/sec.)

Figure 4

1

700 800

Relationship of the pulmonary valve opening slope to the mean

pulmonary artery pressure. The correlation coefficient (r value) is0.74. The closed circles represent patients with normal pulmonaryartery pressure (mean pulmonary artery pressure <20 mm Hg),while the open circles denote pulmonary hypertensives.

Circuilation, Volutme 50, September 1974

outflow-pulmonary artery segment. The pulmonaryvalve in this group showed rapid opening movementsin contrast to the normotensives. Opening slopes of350 mm/sec or more were observed in 22 of 25patients in sinus rhythm and 13 of 16 patients in atrialfibrillation (fig. 4). With pulmonary hypertension, theeffect of atrial systole on the pulmonary valve motionwas minimized or absent in those maintaining sinusrhythm. Shallow 'a' dips (2 mm or less) wereassociated with mildly elevated pressures (meanpulmonary artery pressure 40 mm Hg or less). Patientswith more severe pulmonary hypertension (meanpressure over 40 mm Hg) showed total absence ofcusp motion following atrial systole (table 2 and fig.5). The only exceptions to this were two patients withsevere pulmonary hypertension complicated by severeright heart failure (right ventricular end-diastolicpressure 18 mm Hg and 28 mm Hg) who showedsizable 'a' dips (3 mm and 8 mm). However, theycould be differentiated from normotensives by theirrapid valve opening slopes (400 mm/sec and 600mm/sec) and straight diastolic cusp positions (fig. 6).'A' dips were not observed in patients with atrialfibrillation. As a rule, the opening movement of thepulmonary valve occurred late with pulmonaryhypertension resulting in an increased right ven-

Table 2

Relation of 'A' Dip to Pulmonary Artery Pressure

Mean WDipPulmonary artery 'A' Dippressure (mm Hg) > 2 mm <2 mm Absent

<20 (22 pts) 21 1 021-40 (10 pts) 1 8 1>40 (15 pts) 2* 0 13

*Severe right heart failure.

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Figure 5

Echcaardiograms in pilnmonmary hypertension. Upper panel. Thisshows a pulmonary valve echlocardiogram fronm a patient withmoderate ptulmonary hypertension (mean pressure = 40 mm Hg).Note the tiniy bhtt clearly discerntihle 'a' dip. Lower panel. Thepulmionary valve echocardliogramn is fromi a patient with severepulnionary hypertenision (mean pressure = 83 mm Hg) showingcomiplete alhsence of the 'a' dip. Both patients show. a genieralstraighteniing of the diastolic tuslp images and rapid valve openingslopes. PX = ptiulnonary valve echo tracing; PIION) = phonocar-(liograni; ELCG = elect rocardiogrami.

Py

ECG

tricular pre-ejection period. The amplitude of theopening movement of the pulmonary valve wasgenerally greater in this group when compared to thenormal pressure category, being more than 9 mm in29 of 41 cases.The diastolic gradient across the pulmonary valve

showed correlation with the magnitude of the'a' dip.With low gradients of 15 mm or less, 'a ' dips wereregularly noted while higher gradients (over 20 mm)resulted in complete absence of any deflection at-tributable to atrial systole on the pulmonary valveimage.

Statistical comparison of the pulmonary valve open-ing slopes, the magnitude of the 'a' dip and the pre-ejection period of the right ventricle in the pulmonarynormotensive and hypertensive groups revealed ahighlv significant difference (P < 0.001). Less signifi-cant (P < 0.05) was the comparison of the amplitudesof the opening movements which, standing alone,failed to separate the pulmonary normotensives fromthose vith hypertension.

Discussion

Detection of the pulmonary valve using ultrasoundis a relatively new technique. A previous study fromthis laboratory described the detection method andobtained anatomic validation of cusp echoes using in-docyanine green injection during cardiac catheteriza-

r . 'm ..-.:,%ej- +

ECG

Figure 6

Right heait failure and ptulnmonary hypertension. The pulorr.nonary valve echo is fronm a patient with severe pultnonarnhypertension complicated hy severe right heart failure. A large 'a dip is observed. Thc valve opens rapidly anid thcailpitude of the opening niovemelt is large. The representation of the right ventricular and pulmonary artery pressuretra(cinlgs was ohtained at cardiac catheterization in this patient. The high right ventrictular ernd-diastolic pressure (38 nmnm)results in1 a low gradient (4 mm) across the pulnionary valve in diastole (shiaded). PV = ptulmonary valve echo tracing;ECG = electrocardiogram; PA = pulmonary artery pressure tracing; RV = right venitricular pressure tracing. The scalerepresents pressures in mni Hg.

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ECHOCARDIOGRAPHY/PULMONARY HYPERTENSION

tion. 12 Pulmonary valve detection has already proveduseful in the identification of patients with dextro-transposition of the great vessels"6 and in the differen-tial diagnosis of truncus arteriosus. 17The initial over-all detection rate of the pulmonic

valve was approximately 35%. With additional ex-perience this has improved and a recent review showsthat it is now possible to obtain satisfactory echogramsof the pulmonary valve in about 55% of the adultsreferred to our service. Detection rate in patients withpulmonary hypertension is even higher (70%),probably a result of pulmonary artery dilatation andpossibly a more vertical orientation to the ultrasonicbeam (fig. 1). Although it is difficult to obtain com-plete tracings throughout the cardiac cycle, it isrelatively easy to record the mid and late diastolicpositions together with the opening movements of thepulmonary valve. Clinically useful echograms canthus be obtained in a high proportion of patients.The 'a' dip of the pulmonary valve echogram

represents a movement of the cusp towards the openposition and has been noted to follow the P wave ofthe electrocardiogram in normal patients as well as inthose with various degrees of atrioventricular block.Its disappearance in the presence of atrial fibrillationfurther identifies it as a response to the low pressureevents in the right ventricle associated with atrial

systole. A non-tense pulmonic valve cusp, therefore,can respond to this stimulus. On the other hand, whenthe valve cusp is tense, as occurs in pulmonaryhypertension, deflection due to atrial systole will bereduced or eliminated depending on the degree ofhypertension. Furthermore, abnormally elevatedright ventricular pressures, as were recorded in two ofour patients, can result in the production of 'a' dipsdespite the presence of significant pulmonaryhypertension. Thus, it is clear that the diastolicgradient across the pulmonary valve is the single mostsignificant parameter which governs the generation ofthe 'a' dip. Transient decrease of this gradient can oc-cur with normal pulmonary artery pressures duringpeak inspiration and produces very large 'a' dipswhich move the valve to a position close to that seenduring opening. This is also a well-documentedphenomenon in pulmonic stenosis'8 '9 and produces asimilar echocardiographic pattern (fig. 7). Recently,echocardiographic assessment of the effect of atrialsystole on the pulmonary valve motion in diastole hasbeen found helpful in the clinical evaluation ofpulmonic stenosis.20

In pulmonary hypertensives, the increasedpulmonary artery pressure results in pulmonary valveopening in a relatively high portion of the right ven-tricular pressure curve where the pressure is rising

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Figure 7

Pulmonary valve opening with atrial systole, In both illustrations the ptulmonary valve makes a strong miovement towuardopening following atrial systole and before the onset of the QRS complex. The cutsp rebountids toward closuci.e and thlenreopens with ventricular systole. Left pan el. This was obtained from7 a patient with valvidilar uIlmonary sstenosis (gradiett40 mm lIg). Right panel. This was obtained fron a pulmonary normotent siv;e sus ebject (nmean pulmn ionary artery pressuire 20nun HIg) and at peak inspiration. PV = pulmonary valve echo tracing; PHONO = phonocardiogram; ECIG electrocat-diograini.

(irculation, \vlnntr.50 September 1974-

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NANDA, GRAMIAK, ROBINSON, SHAH

rapidly and this may explain the accelerated openingrate of the pulmonic valve observed in this group.Rapid valve opening slopes were also found in the twopatients with severe right ventricular failure andpulmonary hypertension, providing a diagnostic clueto the nature of the underlying problem.

For similar hemodynamic reasons, the isovolumiccontraction time of the right ventricle is increasedwith pulmonary hypertension2` and explains the delayin the onset of the opening movement of thepulmonary valve observed in this group in the presentstudy.An upwardly oblique direction of the ultrasonic

beam is required for recording movements of the pul-monary valve because of the proximity of lung tissue.This angling technique views the right ventricularoutflow-pulmonary artery junction obliquely and ex-amines the left cusp of the pulmonic valve from itsright ventricular surface (fig. 1). Thus, upward oropening movements of the pulmonic valve arerecorded as posterior deflections. Those which followatrial and ventricular systole produce transient, cir-cumscribed displacements of the cusp signal whichcan be correlated with a simultaneously recorded elec-trocardiogram. The generalized posterior diastolicmovement of the echo trace, characteristic of nor-motensive subjects, is more difficult to explain. It ispossible that the pulmonic valve is displaced upwardas the right ventricle fills during diastole and results ina diastolic echogram which traces an obliquelyposterior path. In the present study, three patientswith large atrial septal defects, who had roentgeno-logic evidence of pulmonary artery enlargement butnormal mean pulmonary artery pressures, did notshow straightening of the pulmonic valve images inearly and mid-diastole. Thus, the absence of posteriormovement of the pulmonary valve prior to atrialsystole, observed with pulmonary hypertension, can-not be adequately explained on the basis of dilatationof the pulmonary artery alone.The most useful information regarding the severity

of pulmonary hypertension is derived from thepulmonary valve echogram when both the 'a' dip andthe pulmonary valve opening slope are taken into ac-count. Absence of pulmonary hypertension is in-dicated by the presence of a large 'a' dip and a slowopening slope of the pulmonary valve. A rapid open-ing slope generally indicates pulmonary hyper-tension. Associated persistence of minimal posteriordisplacement of the cusp echo during atrial systole isconsistent with mild to moderate elevation ofpulmonary artery pressure (mean pressure 40 mm Hgor less), while absence of any influence of atrial systoleon the pulmonary cusp motion indicates a more severedegree of pulmonary hypertension (mean pressure >

40 mm Hg). A large 'a' dip in the presence of a rapidvalve opening slope may indicate co-existent severeright heart failure. With atrial fibrillation it is less easyto assess the degree of pulmonary hypertension sincethese patients do not show 'a' dips and reliance has tobe placed on other criteria, chiefly the valve openingslope determinations.Other criteria are also of value in detecting

pulmonary hypertension, but are less useful in theassessment of its severity. Determination of the rightventricular pre-ejection period is of limited value. Itrequires correction for heart rate and is not useful inpatients with intraventricular conduction defects. Thediastolic position of the pulmonary valve is aqualitative determination which, although very usefulin identifying pulmonary hypertensives, does not helpin the evaluation of its severity. The amplitude ofvalve opening movement is the least useful criterionin separating pulmonary normotensives fromhypertensives, as there is a considerable overlap ofvalues in the two groups.

Recognition and quantitation of the severity ofpulmonary hypertension by a noninvasive, nonioniz-ing technique like echocardiography has potential ad-vantages. It can be used to carry out repeated ex-aminations without any side-effects, as well as followstages in the development of pulmonary hypertensioncomplicating certain disease processes. Also, it wouldmake it feasible to undertake longitudinal studies toevaluate the long-term effects of surgery where reduc-tion of pulmonary hypertension is a desired goal.The present study indicates that ultrasound is a

useful tool in the diagnosis and evaluation ofpulmonary hypertension. In addition to differen-tiating patients with elevated pulmonary arterypressures from those with normal right heartpressures, an estimate of the severity of pulmonaryhypertension is obtained. Use of this technique in theevaluation of pulmonary hypertension representsanother extension of the capability of echocar-diography.

AcknowledgmentWe wish to thank Mrs. Frances Cook and Mrs. Bonnie Hadden

for secretarial assistance, Mrs. Margaret Mecredy for help with thestatistical analysis and Mr. David Tuttle for assistance in thepreparation of illustrations.

References1. ED FIL I: Ultrasound cardiography. Atrioventricular valve

motility in the living human heart recorded by ultrasound.Acta Med Scand 170 (suppl 370): 83, 1961

2. WINTERS WL JR, HAEBo j JJR SOLOFF LA: Abnormal mitralvalve motion as demonstrated by the ultrasound techniquein apparent pure mitral insufficiency. Am Heart J 77: 196,1969

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3. Gii.nx1 \K R, SHAH PM: Cardiac ultrasonography: A review ofcurrent applications. Radiol Clin North Am 9: 469, 1971

4. N.Nxo\)' NC, GHANIIAAK R, SHAH PM, LIPCHIK EO: Ultrasoundevaluation of mitral valve calcification. Circulation 46 (supplII): II-20, 1972

5. FFIGFNA3A xI H: Echocardiography. Philadelphia, Lea &Febiger, 1972, pp 43-72

6. Nx\Ni.x NC, GRANIIAK R, SHAH PM, DEWEESE JA, MAHON'EI'EB: Echocardiographic assessment of left ventricular out-flow width in the selection of mitral prosthesis. Circulation48: 1208, 1973

7. GCi.,\IIAK R, SHAH PM: Echocardiography of the normal anddiseased aortic valve. Radiology 96: 1, 1970

8. WINSBEw; F, MERCEER E: Echocardiography in combined valvedisease. Radiology 105: 405, 1972

9. N.-xNDA NC, GRANIIAK R, SHAH PM: Diagnosis of aortic root

dissection by echocardiography. Circulation 48: 506, 197310. FEI(;ENO'~L3A I H: Clinical applications of echocardiography.

Prog Cardiovasc Dis 14: 531, 197211. JOY NE1 CR, HEyZ EB, JOHNsONT J, REID JM: Reflected ultrasound

in the diagnosis of tricuspid stenosis. Am J Cardiol 19: 66,1967

12. GCR.\NIIAK R, NANDA NC, SHAH PM: Echocardiographicdetection of the pulmonary valve. Radiology 102: 153, 1972

13. N. \.\i) NC, GRANIIAK R, SIAH PM, ROlBINSoN T:Echocardiographic diagnosis of pulmonary hypertension.Excerpta Medica 277: 12, 1973

14. NA.N>-DA NC, GRANIIAK R, ROBIN\soN\ T, SHAH PM: Evaluation ofpulmonary hypertension by echocardiography. J ClinUltrasound 1: 255, 1973

15. SNFi)F(:oi1 GW, COCHBAN WG: Statistical Methods, ed 6.Ames, Iowa State University Press, 1967, pp 104-106

16. Gii.xI\1AK R, CHI NL KJ, NANDA NC, MANNING J:Echocardiographic diagnosis of transposition of the greatvessels. Radiology 106: 187, 1973

17. CDium KJ, ALEN.SON CG, MANNING JA, GHAAMIAK R:Echocardiography in truncus arteriosus. The value ofpulmonary valve detection. Circulation 48: 281, 1973

18. REIE R: Variations of the ejection click in the valvularpulmonic stenosis. Clin Res 14: 129, 1966

19. HUIAGIREN\ HN, REExE R, COHEN K, McLEoD R: The ejectionclick of valvular pulmonic stenosis. Circulation 40: 631, 1969

20. WEYMx\.N AE, DILLON JC, FEIGENBALuI H, CHANG S:Echocardiographic patterns of pulmonic valve motion inpulmonic stenosis. Am J Cardiol 33: 178, 1974

21. T.x\ FEI ME: Clinical Phonocardiography and External PulseRecording, ed 2. Chicago, Year Book Medical PublishersInc, 1972, pp 70-75

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SHAHNAVIN C. NANDA, RAYMOND GRAMIAK, TREVOR I. ROBINSON and PRAVIN M.

Echocardiographic Evaluation of Pulmonary Hypertension

Print ISSN: 0009-7322. Online ISSN: 1524-4539 Copyright © 1974 American Heart Association, Inc. All rights reserved.

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