systemic embolism in mitral valve diseasehad predominant mitral stenosis, and i02 had mitral...

British Heart Journal, 1970, 32, 26.

Systemic embolism in mitralvalve disease

N. Coulshed, E. J. Epstein, C. S. McKendrick, R. W. Galloway, and E. WalkerFrom Liverpool Regional Cardiac Centre, Sefton General Hospital, Liverpool I5

The analysis of a series of 839 cases of mitral valve disease has shown the following. (a) Systemicembolism is as common with mitral regurgitation as with mitral stenosis. (b) Atrialfibrillation, withclot formation in the atrium, is the main cause predisposing to systemic embolism. (c) Mitral valvecalcification is important only in that it predisposes to operative emboli. (d) Atrial appendage sizehas no influence on the occurrence of systemic embolism, and atrial appendagectomy has no influenceon the occurrence of post-operative embolism. (e) Only in patients with atrial fibrillation and an

operable valve, is there any reduction in the number of emboli after surgery.Certain guide-lines with regard to treatment are suggested.

Peripheral arterial embolization is a serious,sometimes fatal, complication of mitral valvedisease. Askey (I957) and Askey and Bern-stein (I960) state that a first recognizedembolus is fatal in about one in six so affec-ted, and that one-half of the survivors diewithin three years, half of these because ofrecurrent embolism. Surgical measures de-signed to improve valve function, and toremove potential sources of clot formation,have been advocated for the prevention ofthis hazard. Among the many reports arethose of Madden (I949), Belcher and Somer-ville (I955), Glover (I956), Turner andFraser (1956), Ellis, Harken, and Black(I959), Baker and Hancock (i960), andLearoyd et al. (I960). Kellogg et al. (I96I)and Taber and Lam (I960) emphasized thepossible hazards of emboli occurring atoperation, but Ellis and Harken (I96I) in afurther review of their patients reassertedtheir belief in the protective value of mitralvalvotomy against further emboli. They alsothought that where mitral stenosis waspresent, the occurrence of a systemic embo-lus was in itself an indication for operation.

SubjectsThis paper is based on 839 cases of rheumaticmitral valve disease seen at the Liverpool RegionalCardiac Centre between I952 and i965. Wherefollow-up was possible, assessments were made at6-monthly intervals by at least one of the authors.We have attempted to study the incidence ofarterial embolism, together with possible factorsin its causation; and where cardiac operation

Received I6 January i969.

has been undertaken, we have tried to evaluateits usefulness in the prevention of systemicemboli.Of the 839 patients, 28 had systemic emboli

before coming under review, but each of thesepatients was known to have had mitral valvedisease before the embolism, and in no case wasmitral valve disease recognized because of theoccurrence of an embolus. For the purpose ofthis review, those patients having had systemicembolism as a result of bacterial endocarditiswere excluded.As judged by the usual criteria, i.e. clinical,

electrocardiographic, and radiological, 737 patientshad predominant mitral stenosis, and I02 hadmitral regurgitation. This was an arbitrary divi-sion, and occasionally it was difficult to decidewhich was the dominant lesion, but stenosiswas always considered the most important lesionin those cases put forward for closed mitralvalvotomy.

In all, 74 patients (8 8°'%) had more than trivialaortic valve disease, and 17 of these had closedmitral and aortic valvotomy; 8 patients were foundto have organic tricuspid valve disease, the diag-nosis being based mainly on catheter findings,and in 3 of the 8, closed mitral and tricuspidvalvotomy was performed.

ResultsThe total incidence of embolism is shown inTable i for mitral stenosis and in Table 2 formitral regurgitation, with reference to thecardiac rhythm, the age of the patient, anddisability graded according to the classifica-tion of the New York Heart Association(I964).

In both groups, there is an increasingincidence of embolic episodes with increas-ing age and with atrial fibrillation, but not

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Systemic embolism in mitral valve disease 27

TABLE I Incidence of systemic emboli in 737 cases of mitral stenosis

Diseility Sinus rhythm Atrial fibrillation and atrtalfibril-lation combined

Age 35 and below Age 36 and above Age 35 and below Age 36 and above All ages

Total Emboli Total Emboli Total Emboli Total Emboli Total Embolicases cases cases cases cases

0, 1, 2 146 6 I28 17 32 10 158 64 464 973 4I 2 52 5 12 2 83 19 I88 284 I0 I 15 0 7 2 53 I2 85 I5Totals 197 9 195 22 5I I4 294 95 737 140

TABLE 2 Incidence of systemic emboli in 102 cases of mitral regurgitation

Disability Sinus rhythmgrade Sinus rhythm Atrial fibrillation and atrial fibril-

lation combined

Age 35 and below Age 36 and above Age 35 and below Age 36 and above All ages

Total Emboli Total Emboli Total Emboli Total Emboli Total Embolicases cases cases cases cases

0, 1, 2 25 0 10 2 7 0 i6 3 58 53 I 0 I 0 5 I I6 6 23 74 I I I 0 7 2 I2 2 2I 5Totals 27 I 12 2 19 3 44 II I02 I7

with a worsening disability. With dominantmitral stenosis, emboli occurred in 31 Out of392 patients with sinus rhythm (8%), andin I09 Out of 345 with atrial fibrillation(3I 5%). With dominant mitral regurgitation,emboli occurred in 3 out of 39 patients withsinus rhythm (7 7%), and in 14 out of 63with atrial fibrillation (22%).The incidence of embolism is similar

in both groups, and when considered to-gether, the figures range from IO emboli in224 patients aged,35 or less in sinus rhythm(4 4%)°, to Io6 emboli in 338 patients aged36 or more with atrial fibrillation (3I 6%).

QX the I57 patients with emboli, 32 (20%)were in sinus rhythm when examined. Noneof these patients gave a history of paroxysmaldysrhythmia, though this diagnosis couldnot be excluded. It was not possible todetermine the rhythm at the time of em-bolization in I8 (II'5%), and I07 (68 i%)were in atrial fibrillation when examined.Nine (5 8%) had the atrial fibrillation forless than one month, and 6o (38 I%) formore than one month when embolizationoccurred. In 38 (24I%) it was not possibleto determine the duration of the atrial fibril-lation.

In all, 28 patients with known rheumatic

mitral valve disease were referred only aftera major embolus had occurred. Of the 28, 9were in sinus rhythm, and I9 in atrial fibril-lation; 24 had a disability of grade 2 or less,and 4 were aged 35 or less.

Pre-operative emboli, atrial thrombus,and atrial appendage size In most cases,embolism must be related to the formationof thrombus in the left atrium or ventricle,and certainly if clot is present it must increasethe risk of producing emboli at operation.Unfortunately, a history of embolism doesnot help in predicting the presence of clotdiscoverable at operation, since, in thispresent series, such clot was found in onlyI7 of 114 patients where emboli had occur-red (i5%), and in 75 of 44o patients withno history of embolism (i7%).

It has been thought that the size of theatrial appendage has a direct influence onthe clot formation therein, and hence therisk of embolus formation, both before andduring operation (Somerville and Cham-bers, I964). If this could be proved true,then it would be of considerable value bothprognostically and in the planning of opera-tion. We have tried to elucidate this problemby an attempted radiological assessment of



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28 Coulshed, Epstein, McKendrick, Galloway, and Walker

the left atrial appendage size in two differentgroups of patients.The radiological assessment of the left

atrial appendage from a standardized 6-footpostero-anterior x-ray was accomplished withreference to an imaginary line drawn fromthe left border of the aortic knuckle to thecardiac apex. Thus, grade o is where no

atrial appendage shadow can be seen, grade I

is where the appendage is visible on theleft cardiac border but does not extendcloser than 2 mm. to this line, grade 2 iswhere the left border of the appendage shadowlies from 2 mm. medial to 7 mm. lateral tothe line, while grade 3 is where the appen-

dage shadow extends beyond the laterallimits of grade 2, and often has a separateoutline of its own.

Pre-operative x-rays were assessed in 104patients known to have had systemic emboli,and 53 were found to have an atrial appendagesize of grade i or less; only 2I were of grade 3.To view the problem in another way, we

also assessed the pre-operative left atrialappendage size in a different, random sampleof I04 patients known to have mitral valvedisease, where the radiological grading was

made without knowledge of the clinicalfindings. Of this second group of patients,43 had small appendages, of grade i or

less, and IO of the 43 had a history of em-

bolism (23%); 36 had large appendages(grade 3), of whom 5 gave a history of sys-temic embolism (I4%).These figures show that systemic embolism

occurs with any size of left atrial appendage,and a large appendage is not necessarilyassociated with an increased risk of embolusformation.

Pre-operative embolism and valve cal-

cification Table 3 shows the relation be-tween valve calcification (assessed atoperation), pre-operative embolism, and car-

diac rhythm in all types of cases, i.e. both

TABLE 3 Incidence of pre-operativeembolism in all cases operated upon, cor-related with valve calcification and cardiacrhythm

Rhythm I Pre-operative embolism No pre-operative embolism

Calcification Calcification Calcification Calcificationpresent absent present absent

Sinus 10 II 8i I83Atrial

fibrillation 37 56 78 98

mitral stenosis and those cases in whichexploratory cardiotomy was performed.Operation was carried out on 206 patientswith valve calcification, 47 having had pre-operative emboli (23%); 348 patients with-out valve calcification included 67 who hadsuffered pre-operative emboli (:i%). Thisdifference is not significant, but the Tableagain shows the clear relation between atrialfibrillation and systemic embolism.

Valve calcification has a much more sig-nificant effect upon the production of em-

bolism at operation, as will be shown later.

Operative embolism We have adoptedthe criterion of Ellis and Harken (I96I) thatan operative embolus is one that occurs inthe operating room or any time before thepatient is discharged from hospital afteroperation. Atrial clot, valve calcification, thetype of operation, and the severity of thepatient's disability have been considered as

factors influencing the incidence of operativeembolism.

(a) Atrial clotAs would be expected, the risk of operativeembolism is much greater in the presence ofatrial clot, occurring in I4 of the go patientswhere such clot was found (15-5%) (Table 4

TABLE 4 Relation between cardiac rhythm, valve calcification, clot,and operative embolization in dominant mitral stenosis

Operative findings(a) (b) (c) (d)

No calcification Calcification only Clot only Calcification andor clot clot

Total Emboli Total Emboli Total Emboli Total EmboliRhythm cases cases cases cases

Sinus !87 2 86 6 2 0 4 OAtrial fibrillation I03 3 66 6 40 7 44 7Totals 290 5 152 12 42 7 48 7



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cols. (c)-(d)). Only I7 of 442 patients with-out clot formation had an operative embolus(3-8%) (Table 4, cols. (a)-(b)). The problemis how to predict the presence of atrial clot.It has been shown that a history of embolismdoes not help, and indeed the incidence ofsystemic embolism at mitral valvotomy,where there was a history of pre-operativeembolism, is no higher than where no em-

bolism had occurred before operation. OfI 14 cases with pre-operative embolism, 4 hadfurther emboli at operation (3 5%), and in442 patients without a history of pre-opera-tive embolism, 27 operative emboli occurred(6 I%).The figures in Table 4 show that clot

formation is closely related to the presenceof atrial fibrillation; only 6 of 279 patientswith sinus rhythm had discoverable clot atoperation (2 2%) compared with 84 of 252patients with atrial fibrillation (33%), andfrom a total of 3I operative emboli, 23 oc-

curred in patients with atrial fibrillation.Theoretically, pre-operative anticoagulationcould reduce the incidence of atrial clot foundat operation. Among the II4 patients havinghad pre-operative emboli, 2I were in sinusrhythm, and only 3 were given anticoagu-lants before operation. None of the 2I haddiscoverable atrial clot at operation.

Anticoagulants were given to 47 patientswith atrial fibrillation and a history of sys-temic embolism before operation, and atrialclot was found in 6 (I2-8%). Anticoagulantswere not given to 46 similar patients withatrial fibrillation and a history of systemic

embolism, and atrial clot was found in II

(24%), but this apparent difference is notstatistically significant.

(b) Valve calcification and type of operationWith both digital and instrumental valvo-tomy, the presence of valve calcificationclearly increases the risk of operative em-

bolism. Table 4 shows that operative embolioccurred in I9 of 200 patients with valvecalcification (95°%), compared with I2emboli in 332 patients without valve calcifica-tion (3 6%).

In I35 finger-split operations 5 emboli occur-

red (3-7%), 2 of which were in the 39 withcalcified valves (5%). In 397 instrumentalvalvotomies, 26 embolic episodes were pro-duced (6-5%), but I7 occurred in the I62patients with valve calcification, a frequencyof Io05 per cent (Table 4). It is probable thatthe greater force used with instrumentalvalvotomy accounts for the higher incidenceofembolic episodes with this type ofoperation.There is evidence in these figures, there-

fore, to suggest that valve calcification andinstrumental valvotomy both increase therisk of operative embolism, as does thepresence of atrial clot.

(c) Grade of disabilityIt might be expected that increasing dis-ability, associated often with increasing age,

atrial fibrillation, and valve calcification,would be associated with an increased inci-dence of operative embolism, but this is notso, though the operative mortality increases.

TABLE 5 Systemic emboli in follow-up: incidence per patient-year

Group of patients Cases Total No. of Average No. of No. of emboli Incidence offollowed up patient-years patient-years in follow-up emboli as

in follow-up in follow-up per cent perpatient-year

Finger-split without 6i 431 7 4 0-92appendagectomy (i:io8)

Finger-split with 65 388 6 7 i-8appendagectomy (I: 56)

Instrumental split with 318 io88 3-4 14 1.3appendagectomy (I:78)

For mitral regurgitation(a) Appendagectomy only 9 57 4 3 5-3

(I:1I9)(b) Appendagectomy and

Glover's operation* 5Mitral stenosis, no operation I66 646 3-9 24 3-7

(1:27)Mitral regurgitation, no 68 256 3-8 5 -29

operation (1:51)

*Glover's operation consisted of an attempt to reduce the circumference of the mitral annulus by tighteninga ligature passed around the annulus from the outside.



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Of 326 patients with grade 2 disability orless, i8 had operative emboli (5 5%), countingboth types ofoperation, and of the I3 operativedeaths in this group (4%), only one was attri-butable to an embolus. With the more severelydisabled patients in grades 3 and 4, 13 embolioccurred when operating upon 206 patients(6-3%), and of 27 operative deaths (I3 2%),5 were embolic in nature.

Emboli occurring during follow-up ob-servations (Table 5) The period of follow-up of these patients varied from less than ayear to over I3 years. The earlier finger-splitvalvotomies were not combined with atrialappendagectomy, unlike the later finger-split operations and the instrumental valvo-tomies.The figures for the different types of valvo-

tomy do not confirm the view thatappendagectomy plays any part in the pre-vention of systemic embolism, since thoseoperations without appendagectomy do notshow a greater incidence of post-operativeembolism (o092% per patient year) thaneither the finger-split (i 8% per patient year)or the instrumental valvotomies (I 3% perpatient year) where appendagectomy wasperformed. In addition to this evidence, itcan be seen from Table 5 that where opera-tion was predominantly exploratory, i.e.where mitral regurgitation was found, andatrial appendagectomy was performed butthe state of the mitral valve was not funda-mentally changed, the incidence of post-operative embolism was higher still (5 3%per patient year). In all cases where it wasperformed, appendagectomy was complete.In no case where Glover's operation wasperformed was there any evidence that theregurgitation had been modified.

Post-operative emboli and adequacy ofvalvotomy It is possible that systemicembolism after mitral valve surgery isrelated to the adequacy of the operation.This of course will depend upon the mobilityof the valve and chordae, a heavily fibrosedand calcified valve with shortened chordaebeing most likely to give an unsatisfactoryresult, but our records have not been clearenough for these detailed factors to be as-sessed. We have regarded a satisfactoryvalvotomy as one where the valve orificemeasured more than 3-o cm. in diameter atthe end of the operation, and where no morethan a minor degree of regurgitation wasproduced. A valvotomy was judged unsatis-factory where the diameter of the valveorifice was left at 3*0 cm. or less, or where the

surgeon assessed regurgitation at the end ofthe operation as moderate or severe. Becauseofthe lack ofinformation about valve mobility,these assessments are incomplete, and it couldbe that the different groups of operationshave not been composed of the same typesof valve.Of 6i finger-split valvotomies without

appendagectomy, 52 were unsatisfactoryoperations, and 4 emboli occurred in thefollow-up years in this group; there were noemboli in the 9 patients with a satisfactoryoperation. Of 65 finger-split operations withappendagectomy, 33 were unsatisfactoryvalvotomies, and 5 of these 33 had emboli;2 emboli occurred in the 32 patients withsatisfactory valvotomies. Of 3I8 instrumentalvalvotomies, 32 were unsatisfactory, and onehad a post-operative embolus; I3 embolioccurred in the 286 patients following satis-factory operations.

Taking the three groups as a whole, therewere 117 patients with unsatisfactory valvo-tomies, and I0 emboli occurred in this group,or i per 68 patient-years, an incidence ofI-5 per cent per patient-year. Of the 327with a satisfactory operation, i5 had post-operative emboli, or i per 82 patient-years,an incidence of I-22 per cent per patient-year.

Allowing for the methods of assessmentused, therefore, we cannot say that the inci-dence of post-operative emboli is influencedby the adequacy of the operation, of what-ever type.

Emboli in non-surgical cases Follow-upassessments were available on i66 patientswith dominant mitral stenosis, and 68 withdominant regurgitation, and the figures areshown in Table 5.

(a) Mitral stenosisThe i66 patients in this group were observedfor a total of 646 patient-years, and 24 em-boli occurred, I per 27 patient-years, or 3.7per cent per patient-year. They were aselected group, being either too ill to be con-sidered for operation, or too well, that is theyhad mitral stenosis but little or no disability.A small number in this group had refusedthe offer of operation. In all, 52 patients aged35 or less were followed for a total of 252patient-years, and no emboli occurred in thisgroup, 40 of them still being in sinus rhythm.Of the remaining II4 patients, only 30 werestill in sinus rhythm; 24 emboli occurred inthis group of 114 aged 36 and over, 2I inpatients with atrial fibrillation. The totalfollow-up was 403 patient-years, and the



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emboli occurred at a rate of 6 per cent perpatient-year. Altogether 44 patients died, 7deaths being directly caused by systemicembolism.

(b) Mitral regurgitationThe 68 patients with mitral regurgitationwere observed for a total of 256 patient-years;34 were aged 35 or less, and over a total ofI64 patient-years no emboli occurred, 24of the 34 being in sinus rhythm. Over theage of 35, there were 34 patients, followedfor a total of I02 patient-years, with 5embolic episodes, i.e. a rate of almost 5 percent per patient-year. There were 2I deaths,3 being the result of systemic embolism, andatrial fibrillation was present in 28 of the 34cases.Taking together the patients with mitral

stenosis and mitral regurgitation, who weretreated medically, no emboli occurred in the86 aged 35 or below, whatever the cardiacrhythm, for a total follow-up of 4I6 patient-years. In the I48 patients aged 36 or over

who were observed for a total of 505 patient-years, 29 emboli occurred, 26 in patientswith atrial fibrillation, a rate of almost 6per cent per patient-year; I0 of these emboliwere fatal.

Multiple emboli occurring before follow-up There were 79 patients who had more

than one recognizable embolus, 24 of themhaving more than one recurrence, the mostbeing in one patient who had in all 7 pre-

operative embolic incidents. Seven of thepatients were in sinus rhythm throughout,and in this small group only one of therecurrences was within 6 months of theoriginal embolism. Three patients had sinusrhythm when examined after the first em-

bolus and atrial fibrillation with the sub-sequent incidents.At the time of the first embolus 69 patients

had atrial fibrillation, 59 having had atrialfibrillation for at least 6 months, one for lessthan a month, and in 9 the duration of thearrhythmia was not known. However, thetendency of emboli to recur over a shortperiod was shown by 23 patients with atrialfibrillation, who had two or more emboliwithin a month of each other.

Recurrence of emboli during follow-upOperations were carried out on I00 patientswho had a systemic embolus, 97 having a

mitral valvotomy and 3 an exploratory opera-

tion with atrial appendagectomy only. Intheir follow-up, II had a recurrence of theembolism (II%).

Of the 97 patients who had a mitral valvo-tomy following systemic embolism, 9 hadfurther emboli in the follow-up period,which represented a total of 359 patient-years. Of these patients, 86 had atrial fibril-lation, and in this group 7 emboli occurredin 319 patient-years, a rate of 2v2 per centper patient-year. The ii patients with sinusrhythm had a total follow-up of 40 patient-years and 2 emboli, a rate of 5 per cent perpatient-year.The other 3 patients with an atrial ap-

pendagectomy only had 2 emboli in a follow-up of i2 patient-years, a rate of I7 per centper patient-year.By comparison, 27 patients with recurrent

emboli were not operated upon. Of these,20 with atrial fibrillation had 6 further emboliin a total follow-up of 54 patient years, arate of i i per cent per patient-year; and ofthe 7 still in sinus rhythm, one had a furtherembolus in a follow-up total of 32 patient-years, a rate of 3 per cent per patient-year.

DiscussionSystemic embolism in mitral valve disease isa major problem. Our figures, combined formitral stenosis and regurgitation at all ages,show an incidence of I8'7 per cent, comparedwith the figures of Wood (I954) who quotedan incidence of 13 per cent, Askey and Bern-stein (I960) who referred to 25-30 per centof all patients with chronic rheumatic heartdisease having fatal results from systemicembolism, and Szekely (I964) who reportedan incidence of I0 per cent in a large seriesof patients.The figures for mitral stenosis alone have

varied from the 13 per cent given by Stephen-son (I966), to 35 per cent quoted by Taberand Lam (I960). Between these extremesare figures given by Ellis et al. (I959), Ban-nister (I960), Kellogg et al. (I96I), Casella,Abelmann, and Ellis (I964), Somerville andChambers (I964), Parker et al. (I965), andBakoulas and Mullard (I966).There is a higher incidence of embolism

with increasing age, a point also broughtout by Bannister (I960), and with valvecalcification, but the latter is probably amanifestation of the length of time the dis-ease process has been established. It is madeclear by our figures that atrial fibrillation isthe main factor in the production of sys-temic embolism, and since the incidence ofatrial fibrillation increases with the lengthof time the valve pathology has been present,it follows that increasing age and atrialfibrillation make systemic embolism a com-mon feature of mitral valve disease. Thus,



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mitral stenosis with sinus rhythm gives anembolic incidence of 8 per cent over-all,4-4 per cent below the age of 35, while atrialfibrillation is accompanied by systemicembolism in 3I-5 per cent of cases over-all,the figures being much the same when con-fined to patients aged 36 and over. Thesefigures again broadly agree with those of theauthors quoted above, plus Daley et al.(I95 I), Jordan, Scheifley, and Edwards,(I9si), and Turner and Fraser (1956).

Atrial fibrillation is associated with sys-temic embolism because it predisposes toclot formation in the atrium; 83 of the gopatients in this series with atrial clot hadatrial fibrillation. Turner and Fraser (I956)showed similar results, since 46 of their 48patients, with discoverable atrial clot atoperation were also in atrial fibrillation, andLowther and Turner (I962) quoted an inci-dence of atrial clot at operation in 48 per centof their patients who had atrial fibrillation.

In necropsy studies, Jordan et al. (I95I)reported 5I cases of mitral stenosis with atrialclot and systemic embolism, over 8o percent of which had atrial fibrillation.

Using radiological techniques involvingleft atrial angiography, Fisher et al. (I965),Lewis, Criley, and Ross (I965), and Parkeret al. (I965) were all able to show the closerelation between left atrial clot and atrialfibrillation.

Accepting that left atrial clot formationis common with atrial fibrillation, it is im-portant to show, if possible, the site wherethe clot formation is likely to be, first to aidthe surgeon in the prevention of operativeembolus formation, and secondly to decidewhether or not atrial appendagectomy is aworth-while procedure. We were unable toanalyse our operative findings from thisviewpoint, but in necropsy studies Daleyet al. (195I) showed that clot formation was

equally common in the body and the ap-

pendage of the left atrium, and Jordan et al.(I95i) noted the same. Wallach, Lukash,and Angrist (I953) found left atrial clot in36 per cent of patients with severe mitralstenosis. It was confined to the appendagein 20 per cent of the patients where clot wasfound, to the body in 23 per cent, and presentin both body and appendage in the rest.The left atrial angiography performed by

Fisher et al. (I965) on 482 patients showedthat clot was present as commonly in thebody of the left atrium as in the appendage,and Parker et al. (I965), also using leftatrial angiography, found I0 patients withatrial thrombi, in only 2 of whom was clotconfined to the appendage.

The findings of Somerville and Chambers(I964), that large left atrial appendages wereassociated with systemic embolism, have notbeen confirmed by our results which showthat systemic embolism is as common withsmall as with large appendages, a finding inagreement with Wood's observations (1954).

So far, we have shown that systemic em-bolism in mitral valve disease is as commonwith mitral regurgitation as with stenosis,and that it becomes commoner with in-creasing age and with atrial fibrillation, pre-sumably because of atrial stasis leading toclot formation in the atrium. We have notbeen able to predict the site of clot formation,and have not been able to show that atrialappendage size, as assessed radiologically,has any influence on the presence of clottherein. It seems probable that only atrialangiography will solve this problem, andcertainly there could be justification forroutine left atrial angiography in all patientswith mitral valve disease, who have atrialfibrillation, and in whom mitral valve surgeryis contemplated.

Pre-operative embolism does not increasethe probability that left atrial clot will bepresent at operation, and hence that the riskof operative embolism will be increased, ourfindings being similar to those of Wood(I954). Turner and Fraser (1956) and Askeyand Bernstein (I960) disagreed with Wood'sfindings, and thought that patients havinghad a systematic embolism were exposed toincreased risk at operation.Removal of the atrial appendage will re-

duce the possible sites of thrombus forma-tion, but the earlier cases in our series, wheremitral valvotomy was performed withoutatrial appendagectomy, have shown nogreater tendency to post-operative embolism,than the later cases, where appendagectomywas routine. It is possible, of course, that theatrial suture line itself, after appendagec-tomy, may be a source of further thrombusformation, as described by Stewart and Glenn(I959). The value of atrial appendagectomyin the prevention of systemic emboli hasbeen overestimated, and it should never beundertaken as an isolated procedure. Oursmall series of patients who had lone atrialappendagectomy had a higher incidence ofembolism in follow-up than any other groupof our patients, surgically or medicallytreated.There is a danger of producing emboli at

operation, either from left atrial clot, or fromfragments of calcium when this is present.Figures quoted for operative embolism in-clude those of Wood (I954) in 1o per cent



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of all mitral valvotomies, Kellogg et al.(I96I) in 6z2 per cent of all valvotomies, andLowther and Turner (I962) in io per cent ofall cases with atrial fibrillation.

Valve calcification, while not related to theincidence of emboli before operation, in-creases the incidence during operation, ourseries showing an over-all increase from 3 6to 9-5 per cent, when non-calcified valvesare compared to those that are calcified.With instrumental valvotomy the incidenceof operative emboli in calcified valves ex-

ceeded IO per cent, suggesting that fragmentsof calcium may be more easily broken offby the metal dilator. Fraser and Kerr (I96I)did not hold this view, and found operativeemboli commoner with finger-split operationsthan with instrumental valvotomies.

Pre-operative anticoagulation may reducethe number of cases where clot is found atoperation, but will not prevent emboli causedby fragmented calcium, a point not made bySmith et al. (I965) when discussing the placeof anticoagulation in mitral valve surgery.

Mitral valve surgery reduces the incidenceof systemic embolism, whether or not ap-pendagectomy is performed, and this satis-factory result does not appear to dependupon the adequacy of the valvotomy, atleast so far as our criteria of 'adequacy' are

concerned. This suggests that neither stasisnor appendagectomy are the sole factorsinvolved. Mitral valvotomy, however in-adequate, will reduce stasis to some extent,since none of the other factors involved,including left atrial wall injury and abnormalblood clotting mechanisms, are affected byoperation. It is also possible that the lengthof follow-up in this series is still too shortto estimate the embolic incidence after opera-

tion, and that mitral valvotomy may haveno influence at all on the production of em-boli.However, the total incidence of post-

operative embolism in our series, comparedwith medically treated patients, as shown in

Table 5, suggests that mitral valvotomy withor without appendagectomy, at least in theshort term, will diminish but not abolishthe occurrence of systemic embolism. If theresults are further subdivided, the incidenceof emboli when atrial fibrillation is presentwill be reduced from II to 2 2 per cent per

patient year by mitral valvotomy. Whensinus rhythm is present, valvotomy has no

influence on the production of emboli.Owren (I963), using figures from a small

medically treated series, and Casella et al.(I964) have suggested long-term anticoagula-tion as a method of preventing systemic em-

bolism. Our limited experience supports thisview, the recurrence rate in those patientswho have had systemic emboli and are beingtreated with anticoagulants, being 2-3 percent per patient year, a figure very close tothat of the surgical series. The problem ishow long to continue the treatment; Woodand Conn (I954) offered no advice on this,but Szekely (I964) found that 66 per centof recurrences were present within a year ofthe original embolus, so that anticoagulationfor i8 to 24 months appears a reasonablecourse.From the evidence provided in this series

of patients, we think it possible to offercertain guiding principles of treatment withregard to the embolic risks in mitral valvedisease.i When atrial fibrillation is present, therisk of systemic embolism is high. If the valveis operable, surgery will lessen this risk con-siderably, and should be considered even ifthere are few other symptoms. If embolismhas occurred, then an operation is clearlyindicated, and we have not been able to showthat pre-operative anticoagulation reducesthe number of cases where atrial clot isfound at operation.2 When sinus rhythm is present, when thereis a disability of grade 2 or less, and when thepatient is aged less than 35, mitral valvotomydoes not lessen the risk of embolism, and'prophylactic' valvotomy cannot be recom-mended on these grounds in these patients.Above the age of 35, still with sinus rhythm,and even if embolism has already occurred,valvotomy does not significantly lower theincidence of further emboli, and here theembolic risk cannot be used alone as anargument for operative intervention. In thesecases long-term anticoagulation is probablythe treatment of choice.3 Instrumental valvotomy produces opera-tive emboli in IO per cent of patients withcalcified valves, and while not an absolutecontraindication to closed mitral valve sur-gery, the presence of calcification visible onthe x-ray is certainly an indication not toproceed with operation if this is to be donemainly to prevent emboli in the future.

We would like to thank our colleagues, at theLiverpool Regional Cardiac Centre, for theirhelp with these patients. In particular we wouldlike to thank our surgical colleagues, Mr. L. J.Temple, Mr. I. M. Morrison, Mr. P. J. Molloy,and Mr. W. L. Turner, for their careful record-ing of their operative findings.Wewould also like to thank the Nursing, Radio-

graphic, and Cardiographic staff for their assist-ance.



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34 Couilshed, Epstein, McKendrick, Galloway, and Walker

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