Doppler echocardiography with mitral - heart.bmj.com · 64 The echocardiogram showed heavy echoes pro-ducedbythe valve housing, including the valve ring, moving towards the transducer

Br Heart J 1984; 51: 61-9

Doppler echocardiography in the study of patients withmitral disc valve prosthesesSIGURD NITTER-HAUGEFrom the Medical Department B, Laboratory of Cardiology, University Hospital, Rikshospitalet, Oslo, Nonvay

suMMARY A combination ofM mode and Doppler echocardiography was used to study patients withmitral disc valve prostheses. The probe used in these investigations consisted of a circular Dopplercrystal mounted around the M mode crystal in the same plane. Because of the strong echoesproduced by the prosthesis the transducer (probe) could be angled for optimum Doppler signalswithout losing the M mode echocardiographic recording of the prosthesis. With this equipmentmean and maximum blood velocities and Doppler amplitude signals could be measured simultane-ously withM mode echocardiography. A depth indication line in theM mode recording ensured thatthe Doppler signal was recorded in the region of interest. The Doppler ultrasound technique was

also used separately in both the pulsed wave and the continuous wave mode.The data show the usefulness of this technique in patients with normally functioning valve

prostheses and in three patients with valve malfunction due to thrombus formation. The data in thelatter three cases seem to indicate that the Doppler technique provides valuable information inaddition to that obtained by M mode echocardiography in recognising mitral valve prostheticmalfunction.

Since the introduction of prosthetic heart valves thesearch has continued for non-invasive methodsl 2 thatcan provide a useful technique for routine postopera-tive assessment. -A necessary prerequisite for suchmethods is that they are able to identify both normallyfunctioning prostheses as well as those with varyingdegrees of malfunction. In this respect, valve throm-bus formation is of particular interest since at presentit represents the major threat to the patient's life. Thisreport reviews experience with a technique usingDoppler ultrasound combined with M modeechocardiography in assessing patients with differenttypes of mitral disc valve prostheses. This techniquehas been used in this department for the past twoyears and appears to be of considerable diagnosticvalue.

Patients and methods

The ultrasonic Doppler instrument used3- 5 is aslightly modified version of the commercially avail-able Doppler ultrasound system (PEDOF, VingmedA/S). The ultrasonic frequency is 2 MHz. Theinstrument has a non-directional maximum frequency

Accepted for publication 23 August 1983

estimator and a mean frequency estimator that alsogives the direction of flow (positive, flow towards thetransducer; negative, away from the transducer). Theamplitude of the Doppler signal is recorded sepa-rately. The valve movements give strong reflectionsand are heard as loud clicks, whereas blood flow pro-duces a more continuous and less intense sound. Thevalve movements, therefore, show up as spikes in theamplitude of the Doppler signal. The amplitude ofthe Doppler signal is, therefore, useful for timing thevalve movements as well as for localising the samplevolume.

For a signal to pass through the instrument's highpass filter a certain velocity is required. A cutoff fre-quency of 500 Hz is most often used. When low vel-ocities are present a low frequency filter is used,whereas with high velocities a more high frequencyfilter can be used. For the best results the level of thesignal before it enters the estimator should beadjusted, so that the estimator is barely tracking themaximum signal frequency, to avoid the possibility ofthe estimator locking on to the noise. With thePEDOF system a lamp lights up when a sufficientsignal level at the estimator input is reached. A lowvalue of the gain is used initially and is then increasedso that the lamp lights up. To ensure that the

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Fig. 1 Combined pulsed Doppler ultrasound recorder (B)(modified model ofPEDOF-Vingmed AIS) and M modeechocardiograph (C) (Smith Kline ultrasonoscope) with monitor(A) and fibre optic recorder (D).

Fig. 2 Transducer (probe) with crystal for pulsed Dopplerultrasound (A) and crystal for pulsed echocardiography (B).

Nitter-Hauge

estimator is producing correct results it is necessary tocheck that the estimator output is independent ofsome increasing input gain adjustment after the lamphas lit and before the output takes off the noise.The instrument may be used either in a pulsed

mode or as a continuous wave velocity meter. Usingrepetition frequencies of 9*8 and 6-7 kHz, velocitiesup to 1*7 m/s may be measured within 7 cm and up to1 m/s within 12 cm of the transducer. When used inthe continuous wave mode, velocities up to 7 m/s maybe measured but with a loss of range resolution.

For this study of mitral valve prostheses, the Dop-pler ultrasound equipment was combined with an Mmode echocardiograph (Smith Kline) ultrasonoscope(Fig. 1). The transducer included a circular Dopplercrystal mounted around an M mode echo crystal inthe same plane (Fig. 2). The Doppler was providedwith a depth indication line in the M mode echorecordings which ensured that the Doppler signal wasrecorded in the optimal part of the region of interest.For simultaneous measurements the Doppler systemcould be used in the pulsed mode only. When used inthe continuous mode the M mode echo was automati-cally switched off, and high velocity jets could beobtained with the Doppler.The transducer was placed in the third to fourth

intercostal space slightly medial to the apex of theheart and angled until the characteristic sound of themitral flow was detected. The direction of the trans-ducer was carefully adjusted until the maximumDoppler shift was found. As the prosthetic valve pro-duced strong echoes the transducer could be angledfor optimum Doppler signals without losing the Mmode echocardiographic record of the prosthesis,although the valve housing could be reduced in inten-sity. The maximum and mean velocities and the Mmode echocardiogram were recorded either simul-taneously or separately as described above. ThePEDOF is calibrated with an audiotone of 2-0 kHz,which is equivalent to a blood velocity of 1 m/s if theultrasound beam is in line with the flow and equival-ent to a pressure gradient of 4 mm Hg from the sim-plified Bernoulli equation.6

Results

NORMALLY FUNCTIONING PROSTHESIS

Case IA 64 year old woman with rheumatic heart diseasewas seen one year after implantation of a mitral valveprosthesis (Bjork-Shiley No 29). She was in NYHAclass I, in sinus rhythm with no systolic murmur andwith distinct prosthetic valve clicks; there were noradiographic signs of prosthetic malfunction; Fig 3shows ultrasound recordings.

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Fig. 3 Simultaneous pulsedM mode echocardiogram and pulsed Doppler recordings in a patient (case 1) with a normallyfunctioning Bjbrk-Shiley mitral disc valve prosthesis (No 29) showing sinus rhythm. Calculated AP denotes the pressure gradientacross the mitral valve prosthesis when calibrated with an audiotone of2 0 kHz which is equivalent to a blood velocity of I ms iftheultrasound beam is in line with the flow and equivalent to a pressure gradient of4 mm Hgfrom the simplified Bernoulli equation.6VO, mitral valve opening; VC, mitral valve closure; ECG, electrocardiogram.

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Fig. 4 Simultaneous pulsedM mode echocardiogram and pulsed Doppler recordings in a patient (case 2) with normalyfunctioningHall-Kaster disc valve prosthesis (No 29) showing atrial fibrillation. VO, mitral valve opening; VC, mitral valve closure; ECG,electrocardiogram; Calc AP, calculated AP (as in Fig. 3).

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The echocardiogram showed heavy echoes pro-duced by the valve housing, including the valve ring,moving towards the transducer during atrial systoleand away from the transducer during ventricular sys-tole. The patterns of motion of the disc itself consistedof abrupt separations of the disc from the baseline atthe onset of diastole, continuing as a flat line parallelto the interventricular septum. At the end of diastolethe disc echoes moved rapidly in the reverse directionand remained in this position throughout systole.Normal Doppler signals from the mitral valve

outflow tract are characterised by a peak early in dias-tole, a pronounced decrease in mid-diastole, and anincrease in late diastole with atrial contraction. Theaudible Doppler signal did not differ from the soundobtained from blood flow through normal mitralostium. In this patient, peak maximum velocity wasmeasured to 1-00 mls, which (calibrating with anaudiotone of 2 kHz, equivalent to a blood velocity of 1m/s if the ultrasound beam is in line with the flow)means a peak pressure gradient of 4 mm Hg acrossthe prosthesis in early diastole. The depth control lineindicates the distance between the probe and thestructures from which the ultrasound is reflected andensures that the Doppler signal is recorded from themitral area. The mean velocity, which is directional,is towards the tranducer (positive) in diastole. Thereis no flow from the transducer during systole, indicat-ing no regurgitation from the left ventricle to the leftatrium during ventricular systole. The amplituderecords the opening and closing of the valve.

Based on non-invasive and invasive studies of alarge number of cases, the M mode echocardiogramand Doppler ultrasound recordings described abovewere typical for normally functioning mitral disc valveprostheses in patients with sinus rhythm.

Case 2A 59 year old man with rheumatic heart disease wasroutinely assessed one year after implantation of amitral disc valve prosthesis (Hall-Kaster size No 29).He was in NYHA class I, in atrial fibrillation, with nosystolic murmur, and with distinct prosthetic valveclicks; there were no angiographic signs of prostheticmalfunction.The M mode echo and Doppler recordings (Fig. 4)

were mainly the same as those in case 1 except for thevariations caused by the arrhythmia. The initial peakin maximum velocity after disc opening was followedby a gradual decrease in velocity, and the second peakseen in patients with sinus rhythm was absent. Thepeak maximum velocity was of the same magnitude asthat in the patient with sinus rhythm (case 1) and didnot vary with the duration of diastole. If diastole islong with ventricular rate, the initial high maximumvelocity is gradually reduced to almost zero indicating

Niuer-Haugea small flow at the end of diastole. This curve wastypical of normally functioning mitral disc valve pros-theses in patients with atrial fibrillation.

PROSTHETIC DYSFUNCTIONTo date three patients with thrombosed valves havebeen assessed.

Case 3A 70 year old woman underwent prosthetic replace-ment of the mitral valve (Bjork-Shiley No 29) in Sep-tember 1978. She progressed well until June 1981,when she gradually developed dyspnoea and cardiacfailure. On admission she had a systolic murmurgrade 2/5 apically, distinct prosthetic valve clicks, andatrial fibrillation.

Fig. 5a shows the M mode echocardiogram with aphonocardiogram and electrocardiogram. Theprosthetic valve clicks were clear. The valve echoshowed prolonged opening and closing velocities,with a reduced forward protrusion of the valve duringdiastole. The Doppler ultrasound (Fig. 5b) recordingsshowed a peak maximum velocity of 2-25 m/s corres-ponding to a fall in peak pressure of 20 mm Hg. Thuspeak maximum velocity and fall in peak pressure weregreater than those in patients with normally function-ing mitral disc valve prostheses. The mean velocityflow was towards the transducer in diastole (positive)but away from the transducer during systole (nega-tive), indicating mitral regurgitation. A left ventricu-lar angiogram recorded a few days later showedimpaired opening and closing movements of the discwith prosthetic valve regurgitation. A diagnosis ofvalve thrombus formation at the smaller orificebehind the disc was confirmed at operation.

Case 4A 64 year old man with severe mitral insufficiencyunderwent prosthetic replacement of the mitral valve(Lillehei-Kaster No 25) in January 1975. After beingwell for several years he developed severe dyspnoea in1981. On admission in July 1981 clear opening andclosing clicks of the Lillehei-Kaster valve were aud-ible. There was a faint mid-diastolic murmur at theapex but no audible pansystolic murmur. He hadatrial fibrillation.The echocardiogram (Fig. 6a) showed decreased

amplitude of excursion of the opening of the disc witha "rounded" upstroke and downstroke appearance.The audible Doppler signal was a harsh sound con-taining high frequencies from a large jet velocity andclearly differed from the sound obtained in normalblood flow. The maximum peak velocity after valveopening exceeded 1-0 m/s for the pulsed mode of theinstrument. The Doppler recordings were thereforemade in continuous wave mode (Fig. 6b). The peak

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Fig. 5 (a) Simultaneous M mode echocardiogram and phonocardiogram in a patient (case 3) with thrombotic obstruction of thesmaller orifice ofa Bjbrk-Shiley mitral disc valve prosthesis (No 29). Valve opening and closing is delayed; the delay in valvemovements is associated with abnormal forward moion of the prosthetic cage. Note the closing sound of the disc on thephonocardiogram (arrow). (b) Continuous Doppler ultrasound recordings from the same patient. The peak gradient across theprosthesis immediately after opening was 20 mm Hg. VO, mitral valve opening; VC, mitral valve closure; ECG, electrocardiogram;Calc AP, calculated AP (as in Fig. 3).

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Fig. 6 (a) M mode echocardiogram in a patient with thrombotic obstruction of the smaller orifice ofa Lillehei-Kaster mitral discvalve prosthesis (No 25) showing the same patterns asfor case 3. (b) Continuous Doppler ultrasound recordings from the same patient.The peak gradient across the prosthesis immediately after opening was 12 mm Hg. VO, mitral valve opening; VC, mitral valveclosure; ECG, electrocardiogram; Calc AlP, calculated AP (as in Fig. 3).

maximum velocity was measured to 1.72 m/s, corres-ponding to a fall in peak pressure of 12 mm Hg bet-ween the left atrium and the left ventricle. The veloc-ity decreased relatively slowly during diastole. Inbeats with a short diastole the fall in pressure acrossthe valve at the end of the period was still pro-nounced. The mean velocity was towards the trans-ducer in diastole, whereas there was no flow awayfrom the transducer during systole, indicating no reg-urgitation from the left ventricle to the left atriumduring ventricular systole. A left ventricular angiog-ram showed impaired opening and closing movementsof the disc without prosthetic valve regurgitation. Adiagnosis of valve thrombus formation at the smallerorifice of the prosthetic valve behind the disc wasconfirmed at operation.

Case SIn April 1982 a 62 year old woman with rheumaticheart disease and combined aortic and mitral valvelesions was fitted with a Hall-Kaster disc valve pros-thesis No 21 in the aortic position and a No 29 in themitral position.During the interval between operation and the last

admission to hospital in November 1981, she hadthree embolic episodes and also developed increasingdyspnoea and congestive heart failure. On admission,a grade 2/6 high pitched blowing pansystolic murmurwas audible at the apex. There was no diastolic mur-mur or gallop. She had distinct prosthetic valve clicksand atrial fibrillation.The M mode echocardiogram (Fig. 7a) showed

normal echoes produced by the aortic valve and mitral

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Doppler echocardiography in the study ofpatients with mitral disc valve prostheses 67

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Fig. 7 (a) M mode echocardiogram in a patient (case 5) with a normally functioning Hall-Kaster aortic disc valve prosthesis(No 25) (left panel) and a malfunctioning Hall-Kaster mitral disc valve prosthesis (No 29) (right panel) owing to thrombusformationin the larger orifice ofthe prosthesis. Note the normal opening and closing ofprostheses. (b) Continuous Doppler ultrasound recordingsfrom the same patient takenfrom the mitral area. The peak gradient across the mitral valve prosthesis was 7 mm Hg. VO, mitral valveopening; VC, mitral valve closure; ECG, electrocardiogram; Calc AiP, calculated AP (as in Fig. 3).

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valve prostheses. The patterns of valve motion werenormal with a normal rapid opening and closingmovement of the discs. The audible Doppler signalwas more harsh than usually recorded from a normalmitral disc valve prosthesis. The maximum velocityacross the mitral prosthesis exceeded 1-0 rn/s for thepulsed mode of the instrument. The Doppler record-ings were, therefore, made in continuous mode (Fig.7b). The peak maximum velocity was 1-34 m/s aftervalve opening, corresponding to a peak pressure gra-dient of 7 mm Hg at the time when the disc hadopened. The mean velocity was towards the trans-ducer during diastole (positive) but away from thetransducer during systole, indicating mitral regurgita-tion.

Cineangiograms in different projections were per-formed to study the movement of the disc. The disc inthe Hall-Kaster prosthesis is radiopaque. The aorticas well as the mitral disc seemed to move freely withnormal opening angles. Injections of contrast materialin the aortic root showed no significant regurgitation.Retrograde catheterisation of the left ventricle wasdifferent because of serious arrhythmias occurringeach time the catheter touched the aortic valve. Leftventricular cineangiography was therefore impossible.During catheterisation the patient's conditiondeteriorated. She had an episode of ventricular fibril-lation, which was cardioverted. She was subsequentlycomatose and was taken immediately to the operatingtheatre. At surgery a mitral thrombus formation wasfound in front of the disc at the large opening. Thethrombus did not affect the disc movement butreduced the effective area of the orifice. The valve wasreplaced with a biological prosthesis.

Discussion

The present findings show that disc valve prosthesisused in the mitral position can easily be examined byM mode echocardiography and Doppler ultrasoundtechniques. In this study technically satisfactoryrecordings were obtained from the fourth intercostalspace 3-4 cm to the left of the sternal border. Fromthis position the ultrasound beam could be aimed inan appropriate direction for measuring the velocityprofile across the prosthesis. The mean velocity ismore sensitive to errors in aiming than the maximumvelocity, and furthermore interference from othervessels may reduce the mean velocity. Maximum vel-ocity is less sensitive to errors in aiming and has there-fore been used in preference to calculating changes inflow. Because the prosthetic valve produces strongechoes M mode echograms could be obtained simul-taneously from the same position. From the findingsso far the combination of the two methods seems toproduce data that can be used to distinguish between

Nitter-Haugenormally functioning and malfunctioning mitral discvalve prostheses.When normally functioning valve prostheses were

examined typical normal valve motion patterns whichhave been previously described in studies of disc valveprosthesis were obtained.78 The Doppler ultrasoundrecordings of normal prostheses also showed charac-teristic patterns. Flow through the prosthesis startedsimultaneously with the opening movement of thedisc and reached its maximum at the time of completeopening of the disc. In all normally functioning pros-theses examined so far, the maximum velocity at thismoment was about 1 00 n/s. If the ultrasound beam isin line with the flow, this corresponds to a fall intransprosthetic pressure of about 4 mm Hg. This cor-relates with the pressure gradients reported in post-operative "invasive" studies of patients with Bjork-Shiley or Hall-Kaster disc valve prostheses in themitral position.910 A linear fall in velocity occurredthroughout diastole. In sinus rhythm maximum veloc-ity was increased after atrial contraction. Beat to beatvariations were usually small. In patients with atrialfibrillation and slow ventricular rate, the initial highmaximum velocity was gradually reduced to nearlyzero indicating a small flow at the end of diastole.As mentioned earlier, measurement of the max-

imum velocity was preferred for calculating changesin flow. If the velocity profile across the cross sectionof a vessel is completely flat, the mean and maximumvelocities will be the same. In our experience, therelation between the mean and maximum velocities isabout 0-8 in recordings of good quality. In patientswith mitral disc valve prostheses, however, this rela-tion between mean and maximum velocities might notbe valid, as seen in Fig. 4. In addition to the fact thatthe mean velocity is more sensitive to errors in aimingthan the maximum velocity, turbulence will give largelocal velocity gradients and hence large differencesbetween mean and maximum velocity values inpatients with mitral disc valve prostheses.

Probably the most common and most serious prob-lems with prosthetic valves are clot formation andfibrin or other tissue grown into the prosthesis; thesecan reduce the effective orifice directly or indirectlyby impairing the motion of the disc. The diagnosis ofthis life threatening complication may, however, bedifficult. Clinical evidence of malfunctioning mitralvalve prostheses is limited to the occurrence of a pan-systolic murmur and missing prosthetic clicks. Thepresence or absence as well as the loudness of thepansystolic murmur is unreliable as the murmur maydiminish or disappear with increasing severity of theregurgitation, and opening and closing sounds may beheard despite thrombus formation.Thrombus formation may be detected by the pres-

ence of an echoproducing mass in the vicinity of the

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prosthetic valve without any disc or ball motion.1- 12The clot cannot always be clearly identified echocar-diographically, however, and multiple echoes fromthe valve itself or artifacts resulting from the beamtransecting both the prosthesis and the tissue besidethe valve may be misleading.

Echocardiographic alterations in excursion of thedisc have also been reported as one method of detect-ing malfunction of mitral valve prostheses due tothrombus formation.13-'6 A typical finding has areduced speed of opening and closing of the disc,resulting in a typical "rounded" appearance of theechocardiographic recordings of the prosthesis indiastole. Because of individual variation in theechocardiographic appearance of the normally func-tioning prosthesis and the importance of critical angu-lation and positioning of the transducer, it may bedifficult to use any of the measurements mentionedabove.As is evident in this study the site of the thrombus

must be taken into consideration when the sensitivityof echocardiography in detecting thrombus formationin patients with disc valve prostheses is assessed. Intwo of the three patients with valve malfunction inthis study, the thrombus was located at the smallerorifice behind the disc. The typical echocardiographicfindings of delayed opening and closing movementswere evident in these patients. In the third patient thethrombus was located at the large orifice in front ofthe disc and did not interfere with disc motion whichresulted in a normal echocardiographic pattern.The distinctive features of Doppler ultrasound in

detecting abnormal prosthetic function have beendescribed in the three cases reported. With this tech-nique all three cases of valve thrombus formationcould be differentiated from those with normallyfunctioning prostheses. Typical findings in the formerpatients were significantly higher values for peak max-

imum velocity across the malfunctioning prosthesis indiastole. The high velocities in these patients musthave been due to the jet caused by the reduction in theactual area of the valve orifice by the thrombus itself.The highest velocities were recorded in the twopatients in whom the thrombus was located at thesmaller orifice, thus interfering with the movement ofthe disc. A more moderate increase in maximum flowvelocity was found in the third patient, in whom thethrombus was located at the larger orifice in front ofthe disc.Even if the form of the velocity curves can give

information on the presence or absence of valve reg-urgitation,'7 it is my experience that quantifying thedegree of regurgitation through a malfunctioningmitral disc valve prosthesis is difficult and sometimesimpossible. In general, quantification of valvularinsufficiency is only possible if the cross section of theflow area does not change from systole to diastole.This is true in an initial assessment of the case in the

aorta or the pulmonary artery, as the arterial diametershows small changes during the heart cycle. Withinsufficient tricuspid or mitral valves the valve area isdifferent in systole and diastole. In my experience thisvariation in valve area may be of particular impor-tance in cases of regurgitation secondary to a malfunc-tioning mitral disc valve prosthesis with an abnormalbackflow pattern through the prosthesis in systole.References

1 Holen J, Nitter-Hauge S. Evaluation of obstructive characteris-tics of mitral disc valve implants with ultrasound Doppler techni-ques. Acta Med Scand 1977; 201: 429-34.

2 Holen J, Simonsen S, Fr6ysaker T. An ultrasound Doppler tech-nique for the non-invasive determination of the pressure gradientin the Bjork-Shiley mitral valve. Circulation 1979; 59: 436-42.

3 Angelsen BAJ. Transcutaneous measurement of aortic blood vel-ocity by ultrasound. A theoretical and experimental approach.Report 75-78-W. Norway: Division of Engineering Cybernetics,Norwegian Institute of Technology, University of Trondheim.1975.

4 Angelsen BAJ. Analog estimation of the maximum frequency ofDoppler spectra in ultrasonic blood velocity measurements.Report 76-21-W. Norway: Division of Engineering Cybernetics,Norwegian Institute of Technology, University of Trondheim,1976.

5 Brubakk AO, Angelsen BAJ, Hatle L. Diagnosis of valvular heartdisease using transcutaneous Doppler ultrasound. Cardiovasc Res1977; 11: 461-9.

6 Hatle L, Brubakk A, Tromsdal A, Angelsen B. Non-invasiveassessment of pressure drop in mitral stenosis by Dopplerultrasound. Br HeartJ 1978; 40: 13140.

7 Gibson TC, Starek PJK, Moos S, Craige E. Echocardiographicand phonocardiographic characteristics of the Lillehei-Kastermitral valve prosthesis. Circulation 1974; 49:434-40.

8 Bourdillon PDV, Sharratt GP. Malfunction of Bjork-Shiley valveprosthesis in tricuspid position. Br Heart J 1976; 38: 1149-53.

9 Nitter-Hauge S, Hall KV, Froysaker T. Mitral valve replace-ment: A comparative clinical and hemodynamic study of the newLillehei-Kaster and Bjork-Shiley prostheses. ScandJ Thorac Car-diovasc Surg 1977; 11: 111-7.

10 Nitter-Hauge S, Fr6ysaker T, Hall KV. Clinical andhaemodynamic results following replacement of the mitral valvewith the new Lillehei-Kaster pivoting disc valve prosthesis. ScandJ Thorac Cardiovasc Surg 1977; 11: 15-24.

11 Oliva PB, Johnson ML, Pomerantz M, Levene A. Dysfunction ofthe Beall mitral prosthesis and its detection by cinefluoroscopyand echocardiography. Am J Cardiol 1973; 31: 393-6.

12 Copans H, Lakier JB, Kinsley RH, Colsen PR, Fritz VU, BarlowJB. Thrombosed Bjork-Shiley mitral prostheses. Circulation1980; 61: 169-74.

13 Pfeifer J, Goldschlager N, Sweatman T, Gerbode F, Selzer A.Malfunction of mitral ball valve prosthesis due to thrombus.AmJCardiol 1972; 29: 95-9.

14 Johnson ML, Holmes JH, Paton BC. Echocardiographic deter-mination of mitral disc valve excursion. Circulation 1973; 47:1274-80.

15 Kawai N, Segal BL, Linhart JW. Delayed opening of Beall mitralprosthetic valve detected by echocardiography. Chest 1975; 67:239-41.

16 Clements SD Jr, Perkins JV. Malfunction of a Bjork-Shileyprosthetic heart valve in the mitral position producing an abnor-mal echocardiographic pattern. JCU 1978; 6: 334-6.

17 Tunstall Pedoe DS, MacPherson PC, Meldrum SJ. Absoluteintracardiac blood velocities measured with continuous waveDoppler and a new real-time spectral display. In: Lance CT, ed.Echocardiography. The Hague: Martinus Nijhoff, 1979: 77-80.

Requests for reprints to Dr Sigurd Nitter-Hauge, MedicalDepartment B, Laboratory of Cardiology, Rikshospitalet,Oslo 1, Norway.

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Doppler echocardiography with mitral - heart.bmj.com · 64 The echocardiogram showed heavy echoes pro-ducedbythe valve housing, including the valve ring, moving towards the transducer