Postgrad. med. J. (March 1969) 45, 180-185.

CURRENT SURVEY

Non-rheumatic mitral incompetence and papillary muscledysfunction

MAX ZOOBM.D., M.R.C.P.

Consultant Cardiologist, Regional Cardiac Unit,Brook Hospital, London, S.E. 18

SummaryNon-rheumatic mitral incompetence may be causedby a variety of conditions affecting the relationshipsbetween the papillary muscles, chordae tendineaeand mitral valve cusps. Among the commonest ofthese conditions are ventricular dilatation, ischaemia,congenital and familial abnormalities, senile atrophyof the muscles and spontaneous rupture. There is avery wide range of severity of the resultant clinicalsyndromes. Some patients are asymptomatic, othersare moderately or severely incapacitated, while theseverest cases may have acute pulmonary oedemawhich may be rapidly fatal. The diagnosis is stronglysuggested by a late systolic murmur which may beinitiated by a mid-systolic click while in others thereis the unusual combination of an ejection-typesystolic murmur with a quick-rising pulse. Thediagnosis can be conclusively established by cinean-giography and severe cases can be greatly helped byreplacement of the mitral valve with a prosthesis.

IntroductionIn recent years it has been realized that abnor-

malities of structure or function of the papillarymuscles and chordae tendineae can lead to importantdisturbances of mitral valve function (Sanders et al.,1965; Barlow & Bosman, 1966; Linhart & Taylor,1966; Raftery, Oakley & Goodwin, 1966; Roberts,Braunwald & Morrow, 1966; Stannard et al., 1967;Burch, de Pasquale & Phillips, 1968). The termpapillary muscle dysfunction has been used to coverthe wide variety of clinical syndromes which mayresult. It is, however, far from satisfactory becausethe function of the chordae cannot be dissociatedfrom that of the papillary muscles and the functionof both of these structures has to be considered inrelation to the valve cusps. For example chordaewhich are too long for normal valve cusps may allowincompetence, but chordae which are of normal

length may permit incompetence if the cusps areunduly voluminous. It is quite clear, therefore, thatthe valve mechanism consists of three inseparablecomponents, the papillary muscles, chordae andcusps. It is quite inappropriate to speak of a sub-valvar mechanism of mitral incompetence and theterm 'sub-valvar mitral incompetence' is even worsefor it suggests that regurgitation is occurring fromventricle to atrium through some orifice below thevalve. 'Non-rheumatic mitral incompetence', thoughclumsy, appears to be the only possible alternativebut since the term papillary muscle dysfunction hasobtained fairly widespread acceptance it is used as analternative in the sense indicated in this introduction.

The normal function of papillary muscles and chordaeThese structures have a crucial function to perform

in maintaining a suitable position of the valve cuspsthroughout ventricular systole. During the isometricphase of ventricular function sufficient tension mustbe generated in the papillary muscles to prevent pro-lapse of the cusp upward into the atrium but not somuch to pull them down into the ventricle and openthe valve. Then as the ventricular cavity shortensduring the ejection phase the papillary muscles mustshorten correspondingly to take up the slack in thechordae and prevent prolapse and regurgitation.

Situated as they are directly under the endocar-dium, the papillary muscles are as remote as ispossible from the coronary blood supply. They are,therefore, particularly susceptible to ischaemia.Normally the antero-lateral papillary muscle derivesits blood supply from the circumflex branch of theleft coronary artery but sometimes there is anaccessory supply from the anterior descendingbranch of the left coronary artery. The postero-medial muscle is supplied either from the circumflexbranch of the left coronary artery or the posteriordescending branch of the right coronary.

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Aetiology and pathologyThe main causes of non-rheumatic mitral incom-

petence and papillary muscle dysfunction are shownin Table 1. Dilatation of the left ventricular cavityalters the line of pull of the muscles which then tend

TABLE 1. Causes of non-rheumatic mitral incompetenceand papillary muscle dysfunction

1. Ventricular dilatationAortic incompetenceLeft ventricular failure

2. IschaemiaLocalized, of papillary muscleInfarct± aneurysmFibrosis

3. AtrophySenileCachexia

4. Congenital anomalies5. Rupture6. Endocardial disease

EndocarditisFibro-elastosisEndomyocardial fibrosis

7. Myocardial diseaseInfiltrationCardiomyopathy

to hold the valve open during ventricular systole.Such dilatation is particularly prone to occur inaortic incompetence and the secondary mitral incom-petence which develops in this way may be so greatas to dominate the clinical picture. Any other causeof left ventricular failure and dilatation, however,will act in the same way. The papillary muscles maybe affected selectively by ischaemia or as part of acardiac infarction or ventricular aneurysm. Atrophicshrinkage of the papillary muscles is common in theelderly who often have a noisy murmur but onlyslight mitral incompetence. Atrophy also occurs incachectic conditions. Congenital abnormalities areprobably fairly common but the lack of morbidanatomical studies makes it difficult to be sure justhow often these are responsible for mild degrees ofmitral incompetence. Certainly, however, this can bedue to abnormalities of length and origin of thechordae or muscles. In some cases the abnormalitiesare familial and the clinical picture is then fairlycharacteristic and is described below. Finally, dys-function of the mechanism may be caused byrupture of the muscles or chordae either spontan-eously or following bacterial endocarditis. Theremaining possibilities shown in Table 1 are ratheruncomm n.

HaemodynamicsIn mild cases the haemodynamics are little altered

and may indeed be entirely normal. The acute de-velopment of mitral incompetence, however, causes

an extreme elevation of left atrial pressure andpulmonary venous pressure leading to pulmonaryoedema. Pulmonary vaso-constriction may resultwith extreme pulmonary hypertension. The pul-monary artery pressure in such cases is usually wellover 60mmHg and the pulmonary vascular resistanceconsiderably over 9 units (normal 1-3). In such casesthere is both left and right ventricular hypertrophy.Clinical featuresA wide range of clinical syndromes occurs in this

disorder, separable with some overlapping into fivemain groups.1. Asymptomatic non-familial casesThese patients are discovered on routine examina-

tion to have a late systolic murmur as an isolatedabnormality (Fig. 1). There are no relevant symp-toms. X-ray of the chest is normal and there is noenlargement of the left atrium. Proof of the diagnosis

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FIG. 1. A phonocardiogram showing a late systolicmurmur (SM) following a mid-systolic click (C). Theseare characteristic findings in Groups 1, 2 and 5.

has been obtained in some cases by cineangiographywhich shows slight mitral incompetence confined tothe latter half of systole. A few cases in this groupshow flattened or inverted T waves in leads 2, 3 andaVF and this links them with the next group.

2. Ischaemic fibrosis or infarction confined to thepapillary muscles

These patients do not invariably give a history ofischaemic cardiac pain and when they do, it some-times has atypical features. Occasionally, however,

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182 Current survey

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FIG. 2. The chest X-ray of a patient in Group 2. Theheart is not enlarged and the pulmonary artery pressureof 32/16 mmHg at rest was nearly normal. However, itrose abnormally to 56/30 mmHg on effort, indicating araised pulmonary vascular resistance.

the patient will describe typical central chest painlasting for I hr or so without, however, any of thesevere symptoms of cardiac infarction. Sometimesthere is transient slight breathlessness on effort. Theonly abnormal sign in these cases is a late systolicmurmur (Fig. 1). It seems that the infarcted orfibrotic papillary muscle can hold the mitral valveclosed during the early part of systole but cannotshorten sufficiently during the ejection period toprevent regurgitation in the latter half of systole.

X-ray of the chest may show a normal sized heartor there may be a slight cardiac enlargement (Figs.2 and 3). The cardiogram often shows flattening orinversion of the T waves in leads 2, 3 and aVFsometimes also in V5 and 6 (Fig. 4).

3. Cardiac infarction involving the papillary muscles(sometimes with ventricular aneurysm)These patients may present with a typical history

of cardiac infarction. This, however, is not invariableand sometimes the pain is atypical or even absent.In such cases the patient may present with acutebreathlessness due to pulmonary oedema orbreathlessness on effort. There is severe interference

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.1:..::::.: :*:....::.:::t.:.:.:.:..;::.r:::.:.....,..:.::::..;.FIG. 3. The chest X-ray of a patient in Group 2. Theheart is considerably enlarged and appreciable pulmonaryhypertension due to mitral disease is indicated by theenlarged main pulmonary arteries with attenuatedlower lobe branches and enlarged upper lobe veins.

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FIG. 4. A cardiographic pattern often seen in Groups 1,2 and 5. The T waves are inverted (or flat) in leads 2, 3,aVF, V5 and V6.

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Current survey 183

with mitral valve function and usually the infarctedpapillary muscle fails to hold the valve shut through-out systole so that a pansystolic murmur results.The patient presents signs of severe acute mitralincompetence with high left atrial pressures, pul-monary oedema and pulmonary hypertension. Thereis a small volume, sharply rising pulse. The jugularvenous pressure is considerably raised and 'a' wavesare prominent. Sinus rhythm is the rule. There isevidence of over-activity of both ventricles andcommonly there is tachycardia with gallop rhythmand some peripheral oedema. There may be ralesover the lungs.X-ray of the chest shows considerable cardiac

enlargement involving both right- and left-sidedchambers. The pulmonary artery is enlarged as areits main branches but the peripheral branches maybe attenuated (Fig. 5). The left atrium is not en-larged.The cardiogram in this particular case did not

show a typical cardiac infarction pattern but only

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FIG. 5. X-ray of a patient with an extensive anteriorcardiac infarction and ventricular aneurysm involvingthe papillary muscles. There is gross cardiac enlargementand the large main pulmonary arteries and attenuatedlower lobe branches indicate pulmonary hypertensiondue to mitral disease.

abnormal left axis deviation with S-T depression.However, the diagnosis was confirmed at operationat which the mitral valve was replaced with aprosthesis.

4. Rupture of chordae tendineaeRupture of the chordae may occur spontaneously

in apparently normal subjects or in patients knownto have a systolic murmur presumably indicatingcongenital mitral valve abnormality. It may alsocomplicate subacute bacterial endocarditis. In somepatients there is a history of sudden severe chest painon unaccustomed effort. In others, however, there isno such history and the presentation is with suddenbreathlessness on effort or in bed at night (Fig. 6).Alternatively they may present with congestive heartfailure and peripheral oedema. The physical signsresemble those of Group 3 but the murmur is notalways pansystolic. The timing depends not onlyupon the function of the papillary muscles andchordae but also upon the degree of ventriculardilatation. Quite often regurgitation is confined tomid-systole and the murmur is maximal at that timeresembling an ejection type murmur (Fig. 7). More-over, if the posterior cusp prolapses the regurgitantjet may be directed over the anterior cusp towardsthe root of the aorta so that the murmur radiates tothe base of the heart and even into the neck com-pleting the resemblance to the murmur of aorticstenosis (Fig. 8). There is, however, little difficulty indifferentiating this condition for in rupture of thechordae the ejection-type murmur is accompaniedby a small-volume, sharply rising arterial pulseinstead of the anacrotic pulse of aortic stenosis. Ifthe patient survives, signs of pulmonary hypertensiondevelop. It is noteworthy that the left atrium is notenlarged (Fig. 9).

5. Congenital and familial abnormalities of thechordae tendineaeA few of these patients rather surprisingly present

with chest pain which, however, does not usuallyhave the typical characteristics of ischaemic cardiacpain. It may be felt in the centre of the chest but maybe stabbing in quality and unrelated to effort. Inmany patients, however, there are no symptomswhatsoever and the murmur is discovered on routineexamination. As a rule there is but one physical signconsisting of a mid-systolic click followed by amurmur which continues to the second heart sound(Fig. 1). The cardiogram is usually normal butoccasionally shows the pattern described in Groups1 and 2 (Fig. 4). X-ray of the chest shows no abnor-malities but in patients submitted to cineangiographyprolapse of the posterior cusp of the mitral valvewith late systolic mitral regurgitation, has been

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184 Current survey

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FIG. 6. Chest X-rays from a patient with ruptured chordae tendineae who presented with paroxysmal nocturnaldyspnoea. (a) There is pulmonary oedema particularly involving the right middle and lower zones. (b) Followingintensive medical treatment, the pulmonary oedema has resolved but there is some cardiac enlargement and evidenceof pulmonary hypertension.

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FIG. 7. The phonocardiogram from the patient withruptured chordae tendineae shown in Fig. 6. The systolicmurmur (SM) is maximal in mid-systole and resemblesan ejection murmur (see text).

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FIG. 8. Prolapse of the posterior cusp may allow theregurgitant jet to impinge on the root of the aorta. Themurmur is then transmitted to the base of the heart andeven to the neck (after Burch et al., 1968).

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Current survey 185

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FIG. 9. Right oblique X-ray with barium swallow froma patient with ruptured chordae. As usual in non-rheumatic mitral incompetence the left atrium is notenlarged. This is probably because in Groups 1 and 5the condition is insufficiently severe and in the othersit is of short duration and the left atrium is uncompliant.

demonstrated. Some of these patients developsubacute bacterial endocarditis and Barlow &Bosman (1966) have pointed out that sudden deathoccurred unexpectedly frequently in their large seriesof cases of this kind.

Differential diagnosisIn cases with a late systolic murmur, whether or

not this is preceded by a mid-systolic click, thediagnosis presents little difficulty although it may behard to be sure whether the aetiology is congenital orischaemic. In patients with an ejection-type systolicmurmur differentiation from aortic stenosis is easyon the basis of the character of the arterial pulse asalready mentioned. There may, however, be somedifficulty in differentiating an obstructive cardio-myopathy. In this condition, there is usually somemitral incompetence which may in fact be due topapillary muscle dysfunction. A similar mid-systolicmurmur with quick-rising small volume pulse isfound, but a fourth heart sound is common ratherthan the third sound found in ruptured chordae orprimary papillary muscle dysfunction. Amyl nitrateinhalation intensifies the murmur of obstructivecardiomyopathy by diminishing the ventricular

diastolic volume and therefore increasing theobstruction. By contrast it softens the murmur ofother types of mitral incompetence by reducing theperipheral resistance and so encouraging forwardflow.

Cineangiography is the most reliable method ofestablishing the diagnosis for it is usually possible todemonstrate prolapse of a cusp if this is the correctdiagnosis. Moreover, it will then be seen that theventricular cavity is large and not small and deformedas in the obstructive cardiomyopathies. Gradients inthe outflow tract of the ventricle are much lessdependable signs because they may be detected inventricular hypertrophy of any cause and can easilybe simulated by artefacts. Some patients in whomthe disorder is due to cardiac infarction may presentdifficulty in diagnosis if the cardiogram does notconclusively reveal this. These patients would thenpresent as cases of unexplained mitral incompetencepresumably of rheumatic origin. In male subjects,however, this would be expected to be accompaniedby severe calcification of the valve which would atonce suggest the correct diagnosis. There would alsobe considerable left atrial enlargement and atrialfibrillation would be expected.

PrognosisThis largely depends upon the severity of the

mitral incompetence. If this is mild the patient has anearly normal expectation of life but is liable to therisk of subacute bacterial endocarditis and a fewpatients die suddenly and inexplicably.Acute mitral incompetence due to papillary mitral

dysfunction can be rapidly fatal, but many patientsrespond remarkably to medical treatment withdigoxin and diuretics (Fig. 6). If they respond onlypartially or not at all, they can be dramatically helpedby replacement of their mitral valve with a prosthesis.

ReferencesBARLOW, J.B. & BOSMAN, C.K. (1966) Aneurysmal protrusion

of the posterior leaflet of the mitral valve. Amer. Heart J.71, 166.

BURCH, G.E., DE PASQUALE, N.P. & PHILLIPS, J.H. (1968)The syndrome of papillary muscle dysfunction. Amer.Heart J. 75, 399.

LINHART, J.W. & TAYLOR, W.J. (1966) The late apicalsystolic murmur. Amer. J. Cardiol. 18, 164.

RAFTERY, E.B., OAKLEY, C.M. & GOODWIN, J.F. (1966)Acute subvalvar mitral incompetence. Lancet, ii, 360.

ROBERTS, W.C., BRAUNWALD, E. & MORROW, A.G. (1966)Acute severe mitral regurgitation secondary to rupturedchordae tendineae. Circulation, 33, 58.

SANDERS, C.A., SCANNELL, J.G., HARTHORNE, J.W. &AUSTEN, W.G. (1965) Severe mitral regurgitation secondaryto ruptured chordae tendineae. Circulation, 31, 506.

STANNARD, M., SLOMAN, J.G., HARE, W.S.C. & GOBLE, A.J.(1967) Prolapse of the posterior leaflet of the mitral valve.Brit. med. J. 3, 71.

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