106 WILLIS: ATHEROSCLEROSIS Canad. M. A. J.

REFERENCES

1. MALLORY, G. K., WHITE, P. D. AND SALCEDO-SALGAR, J.:Am. Heart J., 18: 647, 1939.

2. MARIE, R.: L'infarctus du myocarde et ses cons&-quences. Th&se pour Doctorat en Mddecine, Facult6de Mddecine de Paris, Georges Carr6 et cie, 1896.

3. SCHLESINGER, M. J. AND REINER, L.: Am. J. Path., 31:443, 1955.

RESUMEOn ne peut pretendre que l'infarctus dans le myocarde

soit remplace par du tissu de granulation sans donnerune fausse impression de la realite. A la region peri-pherique d'un infarctus se trouve une lisiere de tissudans laquelle le stroma survit. Dans cette lisiere le musclemort est rapidement absorbe, l'absorption etant completee

vers le dixieme jour. L'endomysium qui reste se condensegraduellement en perdant son liquide d'cedeme, mais iln'y a aucune croissance de tissu conjonctif ou vasculairequi pourrait former une cicatrice. La partie centrale del'infaretus est absorbee plus lentement par les macro-phages et sa trame d'endomysium est envahie par lesfibroblastes et les cellules endoth6ldiales. Les fibres r,eticu-laires s2epaississent et deviennent hyalines avec le tempsmais conservent leur orientation et peuvent etre retraceesdans les coupes transversales. Le tout illustre la remarqua-ble capacite d'un organe a s'adapter a une infirmiteavee relativement peu de perturbation dans sa structureet aucune interruption dans sa fonction. La periode derepos devrait etre determinee beaucoup plus d'apresl'evaluation clinique de la fonction cardiaque que d'apresles alterations histologiques.

THE REVERSIBILITY OFATHEROSCLEROSIS*

G. C. WILLIS, D.T.M.&H., M.R.C.P.(Edin.),F.R.C.P. [C.], Montreal

THE QUESTION whether or not it is possible forexperimentally induced atherosclerotic plaquesto be resorbed has been investigated severaltimes. An early study by Anitschkowl indicatedthat withdrawal of cholesterol from cholesterol-fed rabbits was followed by a gradual disappear-ance of lipid from the plaques. In large plaquesit took two to three years for this to occur. Ina recent study by McMillan and his colleagues2along the same lines, histological reorganizationof plaques was noted but no decrease in arteriallipid content was detected chemically in animalskilled at intervals up to six months. Indeed, theirwork demonstrated that atherogenesis in thecholesterol-fed rabbit proceeds for some timeafter withdrawal of cholesterol from the diet.They attribute this to the persistence of hyper-lipeemia, the etiological mechanism in this ex-perimental procedure. This explanation wouldappear to be valid, as it is well recognized thatatherosclerosis of cholesterol feeding is ac-companied by extensive lipid deposits through-out the body, particularly in the reticulo-endo-thelial system. Except in such conditions asxanthomatosis, this state of cholesterol satura-tion has no counterpart in atherosclerosis inman.3 It is not etiological in human athero-sclerosis and does not offer a barrier to resorption

*Fromn the Department of Medicine and the UniversityClinic of the Montreal General Hospital.

of plaques in the way that it does in thecholesterol-fed rabbit.Any approach to the study of resorption of

atherosclerosis in experimental animals shouldthus have as its basis a method of inducingatherosclerosis without cholesterol feeding. Asthis has now become possible through themedium of scurvy in the guinea-pig,4 ascorbicacid treatment of such animals forms an idealmeans of studying the reversibility of athero-sclerosis.

MATERIALS AND METHODSA total of 77 male and female adult guinea-pigs was

rendered scorbutic in the manner described in a previouscommunication.4 After intervals of from 21 to 30 days,50 of these animals were given ascorbic acid therapyand the remaining 27 were sacrificed. Ascorbic acidtherapy consisted of a single intraperitoneal injection of75 mg. of sodium ascorbate followed by the liberaladdition of ascorbic acid powder to the basic scorbuto-genic diet. The animals in this treated group were thensacrificed at intervals of time varying from 1 to 27 days.Twelve additional animals employed as controls were

placed on the scorbutogenic diet for 42 days, withpowdered ascorbic acid liberally added from the be-ginning.

All animals were sacrificed by stunning and thethoracic aorta was dissected out and fixed in 10%formalin. Frozen sections were then made through theaortic arch and ascending and descending portions. Asmany sections as possible were obtained from each aortaand stained with Scharlach R for lipid.The extent of deposition of stainable lipid in the

aortic intima was graded as in the previous communica-tion (i.e., + represented the earliest deposit of lipid,++++ was solid filling of the intima with lipid, and++ and +++ were intermediate). Careful note wasmade as to the morphology of the plaques under thedifferent experimental circumstances.

RESULTS

No atherosclerosis was found in the controlgroup of animals. The number of animals with

Canad. M. A. J.July 15, 1957, vol. 77

Experimer

TABLE I.-INDICATING THE NUMBER OF ANIMALS IN THE VARIOUS EXPERIMENTAL GROUPSWITH AND WITHOUT ATHEROSCLEROSIS AND THE DEGREE OF THE LESIONS IN THO.SE SHOWING THEM

Total With Without Averageawt animals atherosclerosis atherosclerosis atheros

Scorbutogenic diet 42 days with ascorbic acid addedfrom the beginning........................

Scorbutogenic diet for periods of from 21 to 30 daysScorbutogenic diet for 21 to 30 days, then ascorbic

acid for 1 to 5 days.........................Scorbutogenic diet for 21 to 30 days, then ascorbic

acid for 7 to 27 days........................

atherosclerosis in the various groups and theaverage degree of their lesions is set forth inTable I. Variations in the morphology of thelesions were as follows:

Atherosclerotic Lesions of ScturvyThe earliest lesions were characterized by a

diffuse deposit of stainable lipid along the in-ternal elastic membrane and in the immediatelyadjacent intima. This staining faded out gradu-

Fig.l.-Hiugh power view of an early atheroscleroticlesion in a scorbutic guinea-pig. The dark internal elasticmembrane and adjacent intima represents stained lipid(Scharlach R).

ally at the extremities of the' plaques, blendinginto apparently intact internal elastic membrane.A heaping up of lipid in the middle portion ofsuch early lesions eventually' extending to in-volve the whole thickness of the intima was seen

in the intermediate and advanced plaques (Fig.1). Macrophages were noted in small numbersonly. Each individual plaque appeared as a con-

fluent mass of stainable lipid with no fat-freeareas associated.

Atherosclerotic Lesions of Treated ScurvyAfter as little as two days of ascorbic acid

therapy, the early atherosclerotic plaques stainedless intensely with Scharlach R and soon losttheir diffuse lipid deposit completely. Numerous

macrophages meanwhile became apparent, some

on the intimal side of the internal elastic mem-

brane and some on the medial side (Fig. 2). Allthese macrophages stained intensely for fat.Later stages of the process were characterizedby a decrease in the bulk of lipid within macro-

phages. The end stages of lipid resorption were

not detected, as this degree of atherosclerosisappeared to heal rapidly without permanentsequele.Advanced lesions of atherosclerosis presented

quite a different pattern, being considerablymore resistant to resorption. After a period ofabout seven days, large plaques were found tobe no longer a confluent mass of lipid filling theintima. Instead, the lipid was aggregated intoseparate islands with lipid-free areas intervening(Fig. 3). Sometimes such islands had a fewmacrophages around them but often none were

noted. Sometimes there appeared to be diffusionof lipid into the inner layer of the arterial media.Even after a further period of nine days, very

little further change could be noted in suchplaques. Although animals killed as long as 27days after the initiation of ascorbic acid therapy

Fig. 2.-High power view of a plaque similar to thatshown in Fig. 1. This plaque is undergoing resolutionunder the influence of two days of ascorbic acid therapy.Note that the extracellular stainable lipid is almost allgone while several lipid-laden macrophages are seen inapposition to the internal elastic membrane both on itsintimal and medial surfaces (Scharlach R).

WILLIS: ATHEROSCLEROSIS 107

1227

25

25

>degree ofsclerosis

11

9

7.

1216

16

18

02.5+

2.5+

2.5+

108 WILLIS: ATHEROSCLEROSIS

Fig. 3.-A low power photomicrograph of an advancedlesion of atherosclerosis in a formely scorbutic guinea-pig. This animal received ascorbic acid therapy for 16days. The lipid is now collected in pools with areas oflipid-free intima intervening.

showed no lesions, the number of such animalswas too small to warrant the conclusion that alllesions are reversed in this time. It was true,however, that there was a steady decline in theincidence of lesions in direct proportion to theduration of therapy.

DIscussION

The obstacle of hyperlipaemia, which hasthwarted the studies of resorption of lipid fromatherosclerotic plaques of the cholesterol-fedrabbit, was avoided in this study and some in-sight was gained into the reversibility of athero-sclerosis comparable to the human type.The results of this investigation indicate that

early lesions of atherosclerosis are quickly re-

sorbed. The stages in this process are first a

fading of lipid staining in the region of theinternal elastic membrane with later a disappear-ance of all extracellular fat. Active phagocytosisof lipid by macrophages occurs, and when thesemacrophages finally disappear no evidence ofthe lesion remains.More advanced lesions are considerably more

resistant to reversal. Extensive lipid depositsclear in some parts of a plaque but i'slands ofintensely staining lipid persist in other parts.The macrophage response to such areas is onlyslight.

Assembling all these various phases of re-

versal of the atherosclerotic plaque, a certainimpression is gained as to the mechanism in-volved. It would appear that lipid diffusely de-posited in the intimal ground substance is easilyresorbed. Such resorption is rapid, and as it isassociated with a macrophage response of onlymoderate degree, it may well be that a portion

Canad. M. A. J.July 15, 1957, vol. 77

of the lipid is dealt with in some other way. Theindependent islands of lipid observed in thehealing of advanced plaques appear to be nolonger in a stratum of ground substance nor arethey intracellular. Rather they seem to be inertpools of fat similar to the "cholesterol abscesses"described in human atherosclerosis. Only thesurface area of such pools is in contact with*resorptive processes and this may account fortheir resistance to healing.The reversibility of human atherosclerosis is,

of course, a vital question. Following the ob-servation that total ascorbic acid depletion iscommon in human arteries5 and that ascorbicacid therapy is able to replace this deficit,5 itwas possible to make some correlation of humanatherosclerosis with that observed in thescorbutic guinea-pig. On this basis, humanatherosclerosis was studied by serial arteri-ography in 16 cases.6 Ten of these cases receivedascorbic acid therapy and six were untreated.Of the 10 treated cases, the plaques visualizedradiologically became larger in three, remainedunchanged in one and became smaller in six.There was no diminution in the size of theplaques in any of the six untreated cases whilein three of them they became bigger.

It seems likely that the histological changesassociated with resorption of atherosclerosis inthe human would be along the lines observedin this present study with guinea-pigs.

SUMMARY

Former studies into the reversibility of experi-mentally induced atherosclerosis had beenseriously hampered by the persistence of thehypercholesterolemia essential for the produc-tion of the lesions. This hypercholesterolkemiaactually causes atherogenesis to proceed evenwhen cholesterol feeding is stopped.

In the present study this difficulty is avoidedby employing scorbutic guinea-pigs in which ithad previously been shown that atherosclerosisdevelops rapidly without cholesterol feeding.When ascorbic acid is given to scorbutic guinea-pigs, the early atherosclerotic lesions resorbquickly. The advanced lesions are considerablymore resistant to reversal, apparently because ofthe islands of lipid whose only contact with theresorbing process is at the surface.A correlation is made between the athero-

sclerosis of the scorbutic guinea-pig and that

Canad. M. A. J. LERICHE AND STIVER: TONSILLECTOMY 109July 15, 1957, vol. 77 LRCEADcTVR

observed in man., and the results of a previousstudy of ascorbic acid therapy in human athero-sclerosis are quoted.

The author would like to thank Dr. J. E. Pritchardand Dr. W. H. Mathews of the Department of Pathology,The Montreal General Hospital, for their kind adviceand frequent help and the unstinted use of the facilitiesof their department.He would also like to express his appreciation to Miss

Dorean Slessor of the Department of Pathology, whokindly made the histological preparations.

This study was supported by the Cooper ResearchFund of McGill University.

REFERENCES

1. ANITSCHKOW, N.: In: Arteriosclerosis, edited by E. V.Cowdry, The Macmillan Company, New York, 1933,p. 291.

2. MCMILLAN, G. C., HORLICK, L. AND DUFF, G. L.:A.M.A. Arch. Path., 59: 285, 1955.

3. DUFF, G. L.: Arch. Path., 20: 81, 257, 1935.4. WILLIs, G. C.: Canad. M. A. J., 69: 17, 1953.

5. WILLIs, G. C. AND FISHMAN, S.: Ibid., 72: 500, 1955.6. WILLIS, G. C., LIGHT, A. W. AND Gow, W. S.: Ibid.,

71: 562, 1954.

RESUMELes r6sultats des travaux faits jusqu'a present sur la

rxversibilite de l'ath6rome experimental peuvent etre misen doute a cause de la persistance del'hypercholes-terolemie necessaire a la production de ces lesions. Cettehypercholesterolemie stimule l'ath6rogenese meme unefois que l'apport de cholesterol dans le diete est supprime.Cette difficulte a ete contournee dans le present travailpar 1'emploi de cobayes scorbutiques chez qui iI a dejaete demontr6 que I'atherome apparait rapidement me&mesans apport particulier de cholesterol dans la diete. Lors-que I'on administre de l'acide ascorbique A ces animauxles lesions atheromateuses d'origine recente se resorbentrapidement. Les lesions avancees sont beaucoup plustenaces apparemment A cause des ilots de lipide aont leseul contact avec le processtus de reabsorption est par lasurface. L'auteur compare les lesions d'art&riosclerosechez le cobaye et chez l'home; il se refere a des donneesobtenues pr6cedemment dans le traitement de I'arterio-sclerose humaine par I'acide ascorbique.

1000 CASES OF TONSILLECTOMYIN A PREPAYMENT PLAN:PREOPERATIVE ANDPOSTOPERATIVE HISTORY*

HARDING leRICHE, B.Sc., M.D.,Ch.B., M.P.H., F.S.S.t and

W. B. STIVER, M.D., D.P.H., Toronto

PRESENT STUDY

TBE MATERIAL of the present study was ex-tracted from the records of Physicians' ServicesIncorporated, Ontario. The assumption was madethat physicians would list all tonsillectomiesand that they would note all claims made for dis-eases connected with tonsillectomy. Since physi-cians are paid on a fee-for-service basis, it is im-probable that they would omit to send details ofthe work they have done.

In order to obtain a picture of the prevalenceof tonsillectomies in the various counties and dis-tricts of Ontario, a record was made of all tonsil-lectomies carried out under the comprehensiveP.S.I. Plan-that is, the Medical, Surgical andObstetrical Plan-during the period February toJuly 1955.

*Read at the Annual Meeting of the Ontario Medical As-sociaition, Toronto, May 7-11, 1956.tResearch Medical Offlcer, Physicians' Services Inc., To-ronto.$Medical Director, Physicians' Services Inc., Toronto.

The number of tonsillectomies during the sixmonths was 4281, giving an annual rate in 1955of 19.8 per thousand. As on May 1, 1955, theP.S.I. comprehensive plan covered 449,131 par-ticipants in Ontario and 21,980 outside the prov-ince. Table I gives the annual tonsillectomy rateper thousand participants in those 12 countiesand districts in Ontario which had more than10,(00 participants.

TABLE I.-ANNUAL TONSILLECTOMY RATES BASED ON ASIX-MONTHS' STUDY (FEBRUARY TO JULY 1955) OF THEP.S.I. COMPREHENSIVE PLAN. TWELVE COUNTIES OFONTARIO EACH HAVING MORE THAN 10,000 PARTICIPANTS

Annualtonsillectomy

rate perRank 1000order County or district participants

1 Thunder Bay .29.02 Lambton .24.23 Lincoln .24.04 Sudbury .23.65 Ontario ....................... 20.76 Wentworth .18.67 Welland .17.48 Cochrane .13.89 York .13.610 Carleton .6.111 Halton .5.012 Kenora. 3.5

All Counties in Ontario .19.8

Because of the large numbers involved, theserates are stable and reliable. This table indicatesthe wide variation in the tonsillectomy rate inOntario. Thunder Bay leads with a rate of 29per thousand, and Kenora is the lowest with a