Congenital mitral stenosis Anatomical …The diagnosis of congenital mitral stenosis can be difficult, especially in the sick neonate with associ-ated defects which may mask the signs

Br Hearty 1981; 45: 527-34

Congenital mitral stenosisAnatomical and functional assessment byechocardiography

V

JEFFREY SMALLHORN,* GIUSEPPE TOMMASINI,t JOHN DEANFIELD,JOHN DOUGLAS, DEREK GIBSON, FERGUS MACARTNEYt

From the Department of Paediatric Cardiology, The Hospital for Sick Children, Great Ormond Street,London, and Department of Cardiology, The Brompton Hospital, Fulham Road, London

SUMMARY Digitised left ventricular echocardiograms were studied in nine children with congenitalmitral stenosis to assess the severity ofinflow obstruction. In six children the two prime indices of mitralstenosis were abnormal, with a prolonged time from minimum dimension to 20 per cent dimensionchange and a reduced peak dimension change during diastole. In three, however, these values did notsuggest inflow obstruction, despite significant gradients at cardiac catheterisation.

Two-dimensional echocardiography was performed in 10 children with congenital mitral stenosisto determine the mitral annular size and the morphology of the valve and subvalvular apparatus. Theannular size and number of papillary muscles could be assessed along with the detection of combinedmitral abnormalities.

Two-dimensional studies can reliably delineate the type of mitral abnormality, and should be per-

formed in all cases with congenital heart disease having a high incidence of associated left ventricularinflow obstruction. Digitised M-mode left ventricular echocardiography is in general unreliable inassessing congenital obstruction, though it may be of some value in individual cases.

The diagnosis of congenital mitral stenosis can bedifficult, especially in the sick neonate with associ-ated defects which may mask the signs of inflowobstruction.'

Standard M-mode echocardiography is un-reliable in assessing either the severity or site ofobstruction.2 In acquired mitral stenosis digitisedleft ventricular echocardiography has proved amore reliable means of assessing severity thanmeasurements of the movement of cusps them-selves.3 4

Two-dimensional echocardiography permits amore detailed anatomical assessment of orifice sizeand valvular apparatus in acquired mitral stenosis.5 6But the anatomy of congenital mitral stenosis ismuch more complex,7 and little information isavailable as to its demonstration by two-dimensionalechocardiography.*British Heart Foundation Junior Research Fellow.tPresent address: Divisione di Cardiochirurgia Infantile, OspedaleProvinciale, Massa, Italy.IFM is supported by the British Heart and Vandervell Foundations.

Received for publication 1 September 1980

The aims of this study were to determine whethercongenital mitral stenosis could be assessed byM-mode echocardiography in the same way as theacquired form, and if, by the use of two-dimensionalechocardiography, the annular size and morphologyof the valve and subvalvular apparatus could bedetermined.

Methods

M-mode echocardiograms were performed with anEkoline 20 ultrasonoscope. Recordings were madeon ultraviolet paper from a Cambridge Multichannelrecorder at a paper speed of 100 mm/s with asimultaneous electrocardiogram and phonocardio-gram.The patients were studied in a supine position

with some slight rotation to the left side. Echo-cardiograms of the left side of the septum andposterior left ventricular wall were recorded at thelevel of the mitral valve. Only those beats whereboth the septum and posterior wall were clearcontinuous lines were used in the study.

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Smallhorn, Tommasini, Deanfield, Douglas, Gibson, Macartney

The echocardiograms were digitised as describedby Gibson and Brown3 in 1973, on a Summographicdigitising table and were processed by a Prime 300computing system. Left ventricular filling patternwas assessed from the peak rate of increase of leftventricular dimension and the time from minimumdimension to 20 per cent of the peak dimensionchange at the end of the rapid filling period. Theperiods of isovolumic relaxation (aortic closure tomitral opening) and minimum dimension to mitralopening were also studied.Two-dimensional echocardiography was per-

formed using an Advanced Technology Laboratorymechanical sector scanner with a 3-5 MHz trans-ducer. The studies were recorded in the supineposition using standard views as previously de-scribed.8 A sweep from the apex of the left ventricleto the outflow tract was performed in the short axisview, to assess valvular and subvalvular regions,including the number of papillary muscles.A subxiphoid four chambered view was used to

visualise the papillary muscles, valve, and sub-valvular apparatus. In the parasternal long axis

projection an assessment of the annular size andmitral excursion was made.The parasternal long axis cut was standardised by

ensuring that the aortic valve cusps were centrallysituated in the aortic root. Recordings of the echo-cardiogram were than made on a Sanyo video-recorder, which was subsequently replayed frameby frame until the point of maximal diastolicexcursion of the valve leaflets was recognised. Apolaroid photograph was taken of this frame, andthe annular dimension measured from the photo-

graph as the distance from a point anteriorly wherethe anterior mitral leaflet was in continuity with theposterior wall of the aortic root, to the pointposteriorly where three structures joined. Thesewere the left atrial and left ventricular free walls,and the posterior mitral leaflet.

Subjects

Eleven patients whose ages ranged from 3 months to

15 years and who had congenital mitral stenosiswithout regurgitation were studied.

All patients had the diagnosis confirmed bycardiac catheterisation. In eight cases the preciseanatomy was observed, either during open heartsurgery (six cases) or at necropsy (two cases).

Five patients had previously had associatedcoarctation of the aorta which had been resected.None had systemic hypertension at the time of theexamination.Two patients had associated ventricular septal

defects both with a Qp/Qs of 1-4. All patients hadnormal-sized left ventricles, since cases of thehypoplastic left heart syndrome were excluded fromthe study, as were patients with cor triatriatum.The 11 patients yielded 10 adequate M-mode and

two-dimensional examinations. One child had onlyan M-mode study and another a two-dimensional,but not an M-mode investigation.

Forty-one normal children whose ages rangedfrom 1 year to 15 years had M-mode echocardio-grams to assess their left ventricular filling patterns.Thirty-two normal children whose ages were

between 1 month and 15 years had two-dimensional

Fig. 1 M-mode echocardiogramfrom a patient with congenitalmitral stenosis. Coarse vibrationsof both leaflets are seen andanterior movement of the posteriorleaflet during diastole. The leftventricle fills rapidly during earlydiastole. A,, aortic closure;MO, mitral opening; RV, rightventricle; MV, mitral valve;LVPW, left ventricular posteriorwall

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Echocardiography in congenital mitral stenosis

echocardiograms to assess their mitral annular size.Informed parental consent was given for all theseexaminations.The data were punched onto cards and analysed

on a Control Data Corporation 6600 computer(under NOSBE) at the University of LondonComputer Centre using the Statistical package for

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0.0 Time (s) 08Fig. 2 Digitised left ventricular echocardiogram ofFig. 1. A gradient of 15 mmHg across the mitral valvewas present and a supramitral membrane plus associatedparachute mitral valve seen at cardiac surgery. Thesolid verticle line represents minimum dimension and thebroken vertical line the time to 20 per cent peakdimension change. A2, aortic closure; MO, mitralopening; A2 to MO represents isovolumic relaxation.

the social sciences Version 7 0.9 Logarithmic trans-formations were used to produce linearity in re-gression and additivity for analysis of covariance.Multiple stepwise regression was used to predictnormal annular size from age, body weight, andbody height.

Results

M-MODEOf the 10 patients who had adequate M-modeexaminations one, aged 3 months, had a posteriorleft ventricular free wall which moved anteriorlyduring diastole, the septum moving in the normalway. Because of this paradoxical movement it wasnot possible to digitise the echocardiogram andobtain reliable information.

All, apart from the above patient, had M-modemitral valve echocardiograms suggesting thepresence of an abnormal valve. Of the nine patientsin whom the left ventricular echocardiograms weredigitised, six had both a reduced peak rate of di-mension change during diastole and a prolongedtime to 20 per cent peak dimension change (Table).Three, however, despite having significantobstruction, with gradients between 15 and 17mmHg, had valves within the normal range for age(Fig. 1 and 2). There was no specific pattern ofabnormality in the time intervals minimum di-mension to mitral opening and aortic closure tomitral opening (Table).

TWO-DIMENSIONALIn two cases of parachute mitral valve there was an

p associated supravalvular membrane; in neither wasthis displayed by two-dimensional echocardio-graphy.

In nine patients adequate parasternal long axisviews enabled an assessment of the annular sizeto be made. The simplest linear prediction ofnormal annular size was obtained by plotting thelogl0 of annular size against logl0 body weight. Thisexplained 85 per cent of the variance in annularsize. Though age could be added to the prediction

0 at a statistically significant level, the combination oflogl0 weight and age only explained a further 3 percent of the variance in annular size, so predictionwas based on logl0 weight alone. The further con-tribution of logl0 height was not statistically signi-ficant. The values of patients with mitral stenosiswere within the normal range for age in all cases(Fig. 3), confirmation being obtained at necropsyin two and at operation in five. The fact that annularsize in these patients was in the normal range wasalso apparent when logl0 annular size was plottedagainst height.

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Table Digitised values from left ventricular echocardiograms

A,-MD A,-MO MD-MO Peak d-Dim/dt diastole Time to 20% PFR(ms) (ms) (ms) (cm/s) (ms)

Control 1-5 40 2 42-3 11-6 176(n=41) ±27 i13-3 ±22-3 ±2-9 ±285Mitral stenosis 12-7 32-2 45-0 9-6 281(n=9) ±21 ±12-0 ±20-3 ±4-2 ±126-7

p<05 p<08 p<08 p<0 1 p<00001

Mean values ± 1 standard deviation.A2, aortic closure; d-Dim/dt, rate of change of dimension; MD, minimum dimension; MO, mitral opening; PFR, peak filling rate.

The mitral valve excursion was reduced in all 10cases, with dense echocardiograms from the leafletsbeing seen in nine. In all examinations abnormallydense echocardiograms from the subvalvular regionwere seen in both the parasternal long axis and fourchamber view (Fig. 4 and 5). These echocardio-grams represented abnormal papillary muscles andthickened chordae, the latter being shortened withpartial obliteration of the interchordal spaces byfibrous tissue. As a result of the above abnormalitiesit was difficult, if not impossible, to differentiatebetween the various components of the subvalvularregion by two-dimensional echocardiography.

In the short axis projection, echocardiograms of amitral orifice could be visualised at a much lowerlevel than is normally seen in sequential cuts fromthe level of the upper part of the mitral valve leafletsto the region just above the papillary muscles. Insome cases this gave the appearance of a funnel typeeffect with the orifice decreasing in size towards theapex. Six children were assessed as having twopapillary muscles and four as having one (Fig. 6, 7,and 8), confirmation being obtained by surgery ornecropsy in eight cases.

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Fig. 3 Plot of the log of mitral annular size versusthe log of the patient's weight. A line of identity isshown.

Discussion

Congenital mitral stenosis is a rare conditionoccurring in 0-6 per cent of necropsied patients withcongenital heart disease.' It is usually associatedwith other cardiac defects, particularly left sided.The frequency in coarctation of the aorta may be ashigh as 19 to 21 per cent.'0 Under 1 month of age inpatients with congenital aortic stenosis the incidenceof associated mitral stenosis is as high as 30 percent." The physical signs of the obstruction areoften subtle and may go unrecognised because ofthese other lesions.The anatomy of congenital mitral stenosis is

variable, and can be the result of any or all of com-binations of a supravalvular ring,'2 annular hypo-plasia,7 13 and abnormalities of the leaflets, chordaetendineae, and papillary muscles.7 12-14By angiocardiography the detection of congenital

mitral stenosis may be difficult; even with adequatepictures a failure of diagnosis in 10 out of 21 caseshas been reported.' In particular, the chordaetendineae cannot be directly visualised, though it ispossible to deduce by indirect means some of theiranatomical abnormalities."3M-mode echocardiography has enabled earlier

diagnosis in some cases, but normal mitral valveappearances can be seen especially in the sickneonate with tachycardia. An assessment of eitherthe site or severity of the obstruction by thistechnique has been unreliable.2With the advent of digitised left ventricular

echocardiograms it has been possible to study theeffect of left sided inflow obstruction by measuringthe rate of diastolic filling and the associated timingintervals.3 This technique has provided a reliablemethod for assessing the extent of the physiologicaldisturbance, and in postoperative evaluation inadults.'5 Classically in acquired mitral stenosis thereis a reduced rate of change of dimension in diastoleand a prolonged time from minimum dimension to20 per cent peak dimension change. In addition, ithas been shown that the period aortic closure to

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Fig. 4 Parasternal long axisview from a patient withcongenital mitral stenosis. Themitral valve and subvalvularechocardiograms are dense, withreduced movement observedduring diastole. L V, leftventricle; MV, mitral valve;LA, left atrium; AO, aorta.

mitral opening is shortened and the time fromminimum dimension to mitral opening prolongedin acquired mitral stenosis.16

In the group studied only six out of the ninepatients had features suggesting inflow obstruction,with the rate of change of dimension in diastole andminimum dimension to 20 per cent peak dimensionchange being the most reliable indices. Threepatients, despite having significant obstruction, hadnormal filling patterns which suggested the stenosiswas minimal. In all of these no other significantdefects were present, which indicates that as anassessment of the severity of stenosis this techniqueis unreliable.An explanation for this is that the M-mode cut is

taken at the level of the leaflets where the inter-ventricular septum and posterior wall are seen, butis in a position proximal to the major inflowobstruction which in many cases is caused by

thickened fused chordae. If, during diastole, themitral leaflets proximal to the obstruction movedoutwards, taking the left ventricular wall withthem, this could explain the normal filling pattern.

Two-dimensional echocardiography has playedan important role in the assessment of acquiredmitral stenosis.5 8 In congenital mitral stenosis thereis little information regarding the two-dimensionalechocardiographic features."7 The use of severalstandard views is essential for the accurate diagnosisand assessment of combined lesions. The presenceof a supramitral ring has been shown by two-dimensional echocardiography,17 but close proxi-mity of the membrane to the mitral valve leafletsand annulus in two of our cases prevented itsrecognition. The parasternal long axis view waschosen for measuring the mitral annulus as it iseasily reproducible in most cases and constantlandmarks are identifiable. Though the view only

Fig. 5 Subxiphoid fourchambered view in a child withcongenital mitral stenosis havinga dominant posteromedialpapillary muscle and rudimentaryanterolateral one. This was alsoseen in the short axis projection.The posterior leaflet is firmly

1- _ attached to the anterolateralmuscle with no normal movementseen during the cardiac cycle in

.... real time. LA, left atrium; LV,left ventricle; RA, right atrium;RV, right ventricle; MV, mitralvalve.

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Fig. 6 Short view of the leftventricle with two papillarymuscles in a child with congenitalmitral stenosis. The view isslightly more oblique than usual.RV, right ventricle; LV, leftventricle; PM, papillarymuscles.

represents a segment of the true annulus, post-mortem and intraoperative observations suggestthat if the annulus is small then its dimension shouldbe reduced in all diameters. Furthermore, in twoof these cases where the annular dimension wasjudged to be normal by two-dimensional echo-cardiography in life, confirmation of this normalitywas obtained at necropsy. In each of these cases themajor obstruction was at the valve and subvalvularlevel. In five other cases surgical confirmation of thenormal annular size was made.A thin rim of supramitral tissue, not seen by the

two-dimensional echocardiogram, obscured intra-operative assessment of the true annulus in onepatient and gave the appearance of a small ringcaused by the associated mitral valve abnormality.Preoperative assessment by two-dimensional echo-cardiography, however, showed that the annularsize was normal and that the abnormality was the

Fig. 7 Short axis view of theleft ventricle in a child with asingle papillary muscle. RV, rightventricle; PM, papillary muscle;LV, left ventricle; IVS, ___interventricular septum.

result of a parachute mitral valve.In acquired mitral stenosis the short axis view

has been reliable in detecting the effective orificesize and correlates well with that seen at operationor necropsy.6 But in many children with congenitalmitral stenosis the effective orifice is not thatvisualised in the short axis, since it may be asym-metrically situated.7 This is a result of the thickenedvalve leaflets and chordae forming a tunnel ofmitral valve tissue, which then inserts into thepapillary muscles. The effective orifice lies betweenthe papillary muscles and chordae and cannot bevisualised by two-dimensional echocardiography.The dense echocardiograms in the region of the

valve and subvalvular apparatus seen in the fourchamber and parasternal long axis view representthe above findings and also provide the explanationfor the reduced mitral valve excursion observed inour cases.

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Fig. 8 Subxiphoid fourchambered view in a child with aparachute mitral valve having anabsent posteromedial papillarymuscle. LA, left atrium; LV,left ventricle; MV, mitral valve;RA, right atrium; RV. rightventricle.

In the normal heart the anterolateral papillarymuscle is slightly larger than the posteromedial,with a great variation between different hearts. Thebase to apex length of the papillary muscles and thenumber of major muscle groups also vary con-siderably.18 The short axis and subxiphoid fourchamber view are the most reliable for determiningthe number of muscles, as both groups can bedisplayed. 8 The subxiphoid is preferred to an apicalfour chamber view as in the latter only the postero-medial muscles can be seen.

In congenital mitral stenosis a wide spectrum ofpapillary muscle abnormalities can exist. They maybe underdeveloped (Fig. 5) with a reduced inter-papillary distance, in some cases the muscles beingvery close or fused.7 14 A single papillary muscle isoften seen, the anterolateral one being absent inmany cases, but a variable array is possible. In somecases where two papillary muscles are present, thechordae from the mitral leaflets insert totally intoonly one. Many of the above cases are associatedwith thickened and short chordae which play amajor role in the pathogenesis of the stenosis. Tothe surgeon the presence of one or two papillarymuscles is of great importance in determining thetype of surgical procedure possible and the eventualprognosis.14 In the past it has been difficult todetect reliably the presence of one or two papillarymuscles by angiocardiography, with a detection rateof less than 50 per cent even in those without con-genital mitral valve abnormalities or left ventricularoutflow tract obstruction.19 In congenital mitralstenosis the figure has been reported to be as low as20 per cent of cases.' With two-dimensional echo-cardiography accurate detection is possible in all

cases where an adequate picture can be obtained.Since two-dimensional echocardiography ap-

pears to be the most reliable detector of congenitalmitral stenosis, we recommend its use not only whencongenital mitral stenosis is suspected on clinicalgrounds, but also as a screening test in patients atrisk of having masked mitral stenosis, particularlyinfants with coarctation of the aorta and aorticstenosis.

References

1 Collins-Nakai RL, Rosenthal A, Castaneda AR,Bernhard WF, Nadas AS. Congenital mitral stenosis.A review of 20 years' experience. Circulation 1977;56: 1039-46.

2 Driscoll DJ, Gutgesell HP, MaNamara DG. Echo-cardiographic features of congenital mitral stenosis.AmJ Cardiol 1978; 42: 259-66.

3 Gibson DG, Brown D. Measurement of instan-taneous left ventricular dimension and filling rate inman, using echocardiography. Br Heart Jf 1973; 35:1141-9.

4 Upton MT, Gibson DG. The study of left ven-tricular function from digitized echocardiograms.Prog Cardiovasc Dis 1978; 20: 359-84.

5 Henry WL, Griffith JM, Michaelis LL, McIntoshCL, Morrow AG, Epstein SE. Measurement ofmitral orifice area in patients with mitral valvedisease by real time, two-dimensional echocardio-graphy. Circulation 1975; 51: 827-31.

6 Nichol PM, Gilbert BW, Kisslo JA. Two-dimen-sional echocardiographic assessment of mitralstenosis. Circulation 1977; 55: 120-8.

7 Ruckman RN, VanPraagh R. Anatomic types ofcongenital mitral stenosis: report of 49 autopsy caseswith consideration of diagnosis and surgical implica-tions. Am J Cardiol 1978; 42: 592-601.

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8 Tajik AJ, Seward JB, Hagler DJ, Mair DD, Lie JT.Two-dimensional real-time ultrasonic imaging ofthe heart and great vessels. Mayo Clin Proc 1978;53: 271-303.

9 Nie NH, Hull CH, Jenkins JG, Steinbrenner K,Bent DH. Statistical package for the social sciences.2nd ed. New York: McGraw-Hill, 1975.

10 Van Der Horst RL, Hastreiter AR. Congenitalmitral stenosis. Am J Cardiol 1967; 20: 773-83.

11 Trusler GA, Freedom RM, Williams WG. Ex-perience with aortic valvotomy in neonates. In:Godman MJ, Marquis RM, eds. Paediatric cardiologyII. Heart disease in the newborn. Edinburgh &London: Churchill Livingstone, 1979: 237-42.

12 Davachi F, Moller JH, Edwards JE. Diseases of themitral valve in infancy. An anatomic analysis of 55cases. Circulation 1971; 43: 565-79.

13 Macartney FJ, Bain HH, Ionescu MI, Deverall PB,Scott 0. Angiocardiographic pathologic correlationsin congenital mitral valve anomalies. Eur J Cardiol1976; 4: 191-211.

14 Carpentier A, Branchini B, Cour JC, et al. Congenitalmalformations of the mitral valve in children.Pathology and surgical treatment. Jf Thorac Cardio-vasc Surg 1976; 72: 854-66.

15 Sutton MG St J, Traill TA, Ghafour AS, BrownDJ, Gibson DG. Echocardiographic assessment ofleft ventricular filling after mitral valve surgery.Br HeartJ 1977; 39: 1283-91.

16 Chen W, Gibson D. Relation of isovolumic relaxationto left ventricular wall movement in man. Br Heart Jf1979; 42: 51-6.

17 Snider AR, Roge CL, Schiller NB, Silverman NH.Congenital left ventricular inflow obstructionevaluated by two-dimensional echocardiography.Circulation 1980; 61: 848-55.

18 Roberts WC, Cohen LS. Left ventricular papillarymuscles. Description of the normal and a survey ofconditions causing them to be abnormal. Circulation1972; 46: 138-54.

19 Macartney FJ, Scott 0, Ionescu MI, Deverall PB.Diagnosis and management of parachute mitralvalve and supravalvar mitral ring. Br Heart Jf 1974;36: 641-52.

Requests for reprints to Professor F J Macartney,The Hospital for Sick Children, Great OrmondStreet, London WC1N 3JH.

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Congenital mitral stenosis Anatomical …The diagnosis of congenital mitral stenosis can be difficult, especially in the sick neonate with associ-ated defects which may mask the signs