the production of experimental congestive heart...

The Production of Experimental CongestiveHeart Failure in Rabbits

By NATALIE ALEXANDER, PH.D. , HUGH A. EDMONDSON, M.D., AND DOUGLAS R. DRURY, M.D.

Observations were made on blood pressure, heart size, and physiologic state of 33 rabbits sub-jected to severe constriction of the abdominal aorta. Two-thirds of the rabbits developed symp-toms of congestive heart failure and died within two weeks. Autopsy findings revealed acute passivecongestion of liver and lungs in the majority of cases and chronic passive congestion of liver andheart failure cells in lungs in some animals which survived a month or more. Advantages of thismethod are simplicity of operative procedure and a high incidence of heart failure.

THE METHODS used to produce experi-mental heart failure fall into severalgeneral categories. They are: first, dam-

age to the myocardium of the right heartbrought about by ligation of the coronaryarteries1 or by cauterization of the myocar-dium2; second, interference with filling of theright and left heart by constriction of venousinflow tracts3 or by elevation of pericardialpressure; third, generalized damage to themyocardium,1'5 and finally, valvular lesions oneither the right or left side of the heart.6

Most of the methods cited above have beenused for acute experiments. The production ofchronic congestive heart failure, which simu-lates that seen in humans, has been difficult toinduce in animals. According to Hamilton7:

"Many attempts have been made to . . . producecongestive failure of the circulation with high venouspressure and edema. It is difficult to point to anexperiment which has been successful . . . it has notas yet been possible to produce any measurabledegree of pulmonary congestion accompanied byedema and generalized venous engorgement. Thesesigns must accompany each other before the ex-perimental situation may be said to resemble con-gestive failure of the circulation."

During the course of work on experimentalhypertension we found that severe constrictionof the aorta yielded a picture of congestive

This investigation was supported in part by aresearch grant (United States Public Health ServiceNumber H 54-C5) from the National Heart Instituteof the National Institutes of Health, Public HealthService, and the Los Angeles County and San DiegoCounty Heart Associations.

Received for publication May 27,1953.

heart failure very similar to that which occursin human hypertension.

METHODS

The rabbits (New Zealand Whites or Cali-fornians), ranging from 4 to 6 pounds in body weight,are kept in metabolism cages so that food and waterintake and urine excretion can be measured through-out the animal's survival time as well as during apreoperative control period of one week. Bloodpressures are obtained from the central ear artery bya modification of the Grant capsule technic.8 Suc-cessive readings are made until they are within 10mm. Hg of each other.

For the operation, the animal is fasted overnight.After induction of the ether anesthesia, a Goldblattclamp (0.6 cm. by 0.3 cm. by 0.5 cm.) is applied tothe aorta between the celiac artery and the superiormesenteric artery. The clamp is closed down untila resistance is felt which is due to pressing thewalls of the aorta together. Then the clamp isopened a given number of turns. The most satis-factory results have been obtained when the aorta isreduced to about one-fourth the original size, thatis, when the clamp is opened a total of one andthree-fourths to two turns.

X-ray pictures of the heart are obtained with theanimal tied down in a supine position. Special care istaken to have the animal in the same position everytime. The heart area is determined by tracing theheart shadow onto paper of uniform weight, cuttingthis out carefully and weighing it. Successive pic-tures on the same animal under constant conditionsgive values that are within 5 per cent of each other.

RESULTS

Experimental Observations. Thirty-three rab-bits have been subjected to aortic constriction.Table 1, columns A and B, shows the survivaltimes of these rabbits. About two-thirds ofthem died within two weeks and the highest

491 Circulation Research, Volume I, November 1953

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492 EXPERIMENTAL CONGESTIVE HEART FAILURE IN RABBITS

TABI.IC 1.--Survival Times and Heart Weight*/BodyWeight for Thirty] Experimental and

Seven Control Rabbits

A

Days

2-78-14

15-2122-2S29-3536-4257-6364-7091-98

Control!:Group IIGroup II§

B

No. of

1434221121

34

c

AverageHeart Wt. (Gm.)Body Wt. (Kg.)

3.213.713.993.483.544.443.813.964.S4

2.21'2.23

D

RangeHeart Wt. (Gm.)Body Wt. (Kg.f

2.2-3.673.06-4.623.10-5.022.99-3.963.04-4.03

3.67-4.25

1.8-2.442.04-2.42

* Ventricular weight only.f Three rabbits used in this study are still living.I Animals with aortic constriction that died three

days p.o. and that did not develop hypertension.§ Normal animals; no operations or hypertension.

alterations of the heart size. Eight experimentalrabbits were studied for this and showed adefinite correlation between heart size andblood pressure level. Table 2 shows the com-plete data obtained from two experimental andtwo control rabbits subjected to a sham opera-tion. It is difficult to explain the decrease inheart size seen in the control animals two hoursafter operation, since at this time the animalswere well out of the ether anesthesia. How-ever, within 24 hours the rabbits with aorticconstriction displayed some increase in heartsize, while the controls did not. With furtherelevation in blood pressure over a period ofseveral days the heart size increases. This canprobably be attributed to dilatation up toabout 48 hours. However, as shown in columnsC and D of table 1, there is a definite hyper-trophy of ventricular musculature withinseveral days.

The food and water intake of the majorityof rabbits increases gradually day by day from

TABLE 2.—Blood Pressures and Percentage Change in Area of Heart Shadow in Two Experimental and Tivo ControlRabbits

Rabbit

ExperimentalEi % Change in Heart Area

Blood PressureE2 % Change in Heart Area

Blood PressureControl

Ci % Change in Heart AreaBlood Pressure

C2 % Change in Heart AreaBlood Pressure

-'reopera-tive

110—

100-105

9S-102—

105-110

Postoperative

2 Hours

- 1 6110-116

- 1 1100-110

- 1 2100-110

- 1 6S5-95

24 Hours

+811S-126

- 8117-120

- 392-102

- 310S-112

48 Hours

+ 15114-118

+23120-126

- 3 . 790-9S

S Days

+58131-136

+73'142-146

death rate occurred within seven days afteroperation.

As soon as the aorta is constricted there is animmediate, brief rise in blood pressure. Thisrise may last one-half hour or so and then theblood pressure drops to normal or subnormalvalues. The blood pressure remains at theselevels for one to six days and then increases andremains high until the animal dies. Varicositiesof the iris vessels accompany the rise in bloodpressure.

Blood pressure changes were reflected in

the very low level of the first postoperativeday. However, unless the animal lives beyondabout three weeks, the daily intake rarelyreaches the preoperative level. Also, postopera-tive urine output follows the same generaltrend as water intake. With the decrease inurine volume, there is an increase in urinespecific gravity which suggests that renal func-tion is adequate. In general, then, the rabbitsappear healthy and seem to be having a normalpostoperative recovery. Suddenly, however,this recovery period is interrupted. The rabbits


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ALEXANDER, EDMONDSON AND DBURY 493

TABLE 3.—Survival Time and Microscopic Findings in Liver and Lungs of Twenty-seven* Rabbits with AorticConstriction

Animal

]

2

34

5

6

7

8

9

10

11

12

13

14

SurvivalTime

(Days)

2

4

44 ^

5

5

6

6

7

7

7

7

7

8

Edema

3+Acute

2-3+Acute

2+Few neutrophils in

alveoli

1 +Early pneumonia

2+Acute

2+Acute2+Acute2+Acute

2+AcuteIntra-alveolar fibrin

& hyalin mem-branes

2+

3+

0-1 +

2+

Lung

Hemorrhage

0-1 +Patchy

Occasional areas

Many areas

0-1+1+ Atelectasis

2+Some perivascular

1 +

1 +

Intense hyperemiawith only mildhemorrhage

3+Very acuteBlood everywhere

0

0-1 +

0-1 +

1 +

Macrophages

2+

Few

3+Much erythrophago-

cytosis

2+

2+

2+Early pigmentation

3+

Few

0-1 +

2+Pigment in occasiona

macrophage1-2+

Liverf

1+ A.P.C.Widening sinusoids in

central % of lobule.2+ A.P.C. of central

]4 of lobule.2+ A.P.C.3+ A.P.C. of % of lob-

ule.Occasional round area

of complete disrup-tion of liver cord bymass of fibrin.

Occasional focal area ofnecrosis of liver cells.

1+ A.P.C. of central %of lobule.

Fibrinoid necrosis ofarteries.

Necrosis, early focal todiffuse, more mid-zonal than central.

3+ A.P.C. of % of lob-ule.

Many areas of centralnecrosis (1+)

2-3+ A.P.C. of central% of lobule.

2-3+ A.P.C. of central% of lobule.

2-3+ A.P.C.

3+ A.P.C.Central necrosis involv-

ing 3-^ of lobule.

0-1+ A.P.C.Mild fatty change in

central % of lobule.1+ A.P.C.Fibrinoid necrosis of ar-

teries (subintimal, inwalls, or perivascu-lar).

1+ A.P.C.1+ fatty change in cen-

ters of lobules.Extreme A.P.C.Acute necrosis and

atrophy of centra]Yz-y2 of lobule.

(continued)


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TABLE 3.—Continued

Animal

15

16

17

18

19

20

-9.1

?,2

23

24

25

26

27

SurvivalTime

(Days)

9

12

16

17

18

21

24

28

34

38

58

64

94

Edema

3+

2+

0-1+

0-1 +

2+

1 +

1 +

1 +

0-1 +Alveolar walls thick-

ened0-1 +Mild thickening al-

veolar wall0-1 +

2+ with pneumonia

1-2+3+ early bronchial

pneumoniaThickening of alveo-

lar walls

Lung

Hemorrhage

0

2+

1 +

1-2+

?

Occasional area

0

Good passive conges-tion of alveolarcapillaries

0-1 +

0-1 +

0±

Few recent areas notassociated withpneumonia

0±

Macrophages

i +Few with pigment

2+± Pigmentation1-2+

2+

3+1+ Pigmentation

3+

2-3+1-2+ Pigmentation

1 +Few with pigment

2+Many heart failure

cells2+ heart failure cellsPigmented

0-1 ±

3+ Heart failure cellsPigmented

1+Some heart failure

cells

Livrerf

Mild A.P.C.Dilatation central veins

and sinusoids.1+ pigment in Kupfei

cells.Widening of central

veins.1+ A.P.C. of center of

lobule.Fibrinoid necrosis of

arteries.1+ A.P.C.Fibrinoid necrosis oi

arteries.Periportal fibrosis.Central necrosis of \i

of lobule.1 artery with fibrinoid

necrosis.Chronic passive conges-

tion.Necrosis central }i of

lobule.A.P.C. central % of

lobule.Hemorrhage and necro-

sis subcapsular.Old areas of hemor-

rhage deep in liver.1+ A.P.C.1 vessel with little fi-

brinoid necrosis.1+ A.P.C.

3+ Chronic passivecongestion.

2+ Atrophy.1+ A.P.C.Early atrophy.1+ Chronic passive

congestion.

1-2+ A.P.C.1+ central necrosis.1+ fatty changes.

* Histologic sections of tissues of three rabbits were not made,f A.P.C. = acute passive congestion.

begin to take less food and the signs of heartfailure (labored breathing, hyperpnea, and

cyanosis) appear. Death follows within hoursto days after the onset of these signs.


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ALEXANDER, EDMONDSON AND DRURY 495

Ufe&VJ&V*.-/

Fici. 1 ((op /e/0- Passive congestion of vessels and acute pulmonary edema. Rabbit number 1. Sur-vival time: 3 days. X100.

FIG. 2 (top right). Pulmonary macrophages filled with hemosiderin, so-called heart failure cells.Rabbit number 24. Survival time: 38 days. X120.

Fia. 3 (middle left). Thickened alveolar walls and passive congestion. Rabbit number 23. Surviv-al time: 34days. X120.

Fia. 4 (middle right). Chronic passive congestion and atrophy of liver cords in animal with survivaltime of 38 days. Rabbit number 24. X60.

FIA. 5 (bottom). Fibrinoid necrosis of brunch of hepatic artery in animal with survival time of 5days after surgery. Rabbit number 5. X200.


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49G EXPERIMENTAL CONGESTIVE HEART FAILURE IN RABBITS

Pathologic Observations. The gross autopsyfindings are very much the same in all animalsregardless of the length of survival time. Thepostmortem examination revealed that 60 percent of the animals had at least 20 cc. of intra-pleural fluid in both sides of the chest (range,0 to 70 cc), congestion and edema of the lungs,dilated heart chambers, and hypertrophiedventricles. Fifty per cent of the cases hadascites of at least 20 cc. (range, 0 to 300 cc.)and the liver was enlarged and congested.Occasionally subcutaneous edema was found.

Sections of heart, lung, liver, and kidneywere saved for histologic study on most of theanimals. The results of these studies on thelung and liver are given in table 3. No sig-nificant changes were seen in the kidney exceptfor a mild degree of passive congestion. Theheart showed no significant histologic changes.

The most pronounced changes were seen inthe lungs and liver. In the lungs, congestion ofcapillaries, edema fluid in the alveoli, hemor-rhage, and finally the appearance of heartfailure cells and thickening of the alveolarwalls was the sequence of events. Pulmonaryedema (fig. 1) was more prominent in theanimals that died within five days of theoperation. After this time it was occasionallysevere, but more often only moderate inamount. Likewise, hemorrhage was morelikely to be severe in the animals dying withinthe first week. After this time it was not souniformly seen. Occasionally perivascular hem-orrhages were seen. The appearance of macro-phages began within four days, and theiractivity was evidenced throughout the series.In many instances their number did not seemto parallel the amount of hemorrhage. Edemaand infection may also be factors in theirmobilization. The actual demonstration ofunquestionable hemosiderin containing macro-phages was noted at 34 days and later (fig. 2).Much earlier, at about seven days, questionableintracellular pigment was seen, but formalinpigment clue to formalin fixative made diag-nosis difficult. Thickening of alveolar walls asseen in chronic congestive failure in humanswas noted by the thirty-fourth day (fig. 3).

In the liver the more extreme acute passive

congestion was seen in animals dying in thefirst week. Apparently the picture of acutepassive congestion might intervene much later,as was seen in one animal after 94 days. Chronicpassive congestion with atrophy of the livercells in the central portion of the lobules wasseen by the thirty-eighth day (fig. 4). Necros'sof liver cells varying from focal to irregularareas usually in the central one-third to one-half of the lobule was present in 10 rabbits.This had no relation to the survival time ofthe animal. This type of necrosis is commonlyseen in humans dying of acute coronary throm-bosis and is apparently due to sudden and pro-longed anoxia of the liver cells.

An unexpected finding was that of acutearteritis, or fibrinoid necrosis, of branches ofthe hepatic artery (fig. 5). These might be onlyoccasionally seen or in some cases nearly halfthe small arteries were affected. They were ob-served in six animals from the fifth to thetwenty-seventh day. The necrosis involvedmostly the outer layer of the media and adven-titia and did not result in thrombosis oraneurysm.

DISCUSSION

Our results indicate that hypertensive con-gestive heart failure can be induced in rabbitsby severe constriction of the abdominal aorta.This method has two important advantages:the simplicity of operative procedure, and thefact that no thoracic surgery is involved. Inaddition a high incidence of heart failure isrealized. This permits institution of pertinentexperimental procedures which could influencethe course of events. For example, a group ofrabbits could be subjected to low environ-mental temperatures, or to low salt diets, bothbefore and after surgeiy. Such procedures arenot feasible unless they can be repeated in astandardized animal preparation.

We suggest that the events leading to deathoccur in the following way. When the clamp isapplied to the aorta, there is a reduction inblood flow to the kidneys and hindquarters.The circulatory system attempts to overcomethis by elevating the blood pressure. However,before this occurs there is a time, one to six


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ALEXANDER, EDMONDSON AND DRURY 497

•days, during which the tissues distal to theclamp will have an Inadequate blood supply.Nevertheless, the general condition of the ani-mal, which depends largely upon those organsproximal to the stricture (brain, heart, lungs,liver, stomach, and duodenum) seems to im-prove. If the animal is unable to cope with therapidly rising blood pressure by sufficient leftventricular hypertrophy, the congestion and•edema of the lungs will cause death. Thoseanimals which survive for the longer periods•of time develop sufficient cardiac hypertrophyto meet the rapidly rising blood pressure. The•exact time of death of these rabbits which livefor more than two weeks will be determined inpart by intercurrent diseases and by the abilityof the blood supply to nourish the rapidlygrowing heart muscle.

It should be emphasized that severe aortic•constriction causes an exceptionally fast rise inblood pressure as compared with other methodsof inducing experimental hypertension. When•constriction of the aorta is less severe than the•degree used here, hypertension develops withinone week to a month and death is usually notthat of congestive heart failure. It is doubtfulif heart failure ever develops in animals whichhave experimental hypertension induced byrenal artery constriction. Goldblatt in hisrecent monograph does not mention it.9 It hasnot been seen in any member of an extensiveseries of renal hypertensive rabbits studied inthis laboratory.10 Yet these animals may livefor years with a higher blood pressure thanoccurs in the animals cited in this paper.

Another factor contributing to death is thepresence of right heart failure. Right heartfailure supervenes in this type of experimentalheart failure in both the short and long livedrabbits as evidenced by the pathologic changesin the liver. Microscopic sections showed thatgenerally lung edema was most severe (3 plus)at from five to seven days with acute passivecongestion of the liver. However, in animalswhich lived for more than two weeks the gradeof lung edema generally fell to 0 to 1 plus, withthe liver showing the results of chronic passivecongestion after one month. I t would seemthat when the animal survives with right-

sided heart failure for more than two weeksthe lung edema is relieved. Thus death will bepostponed until one of the other factors inter-feres, as mentioned above.

Fibrinoid necrosis or acute arteritis has beennoted by other authors in the liver of hyper-tensive rabbits, but only in connection witharteritis elsewhere." Six of our animals dis-played isolated necrosis of arteries in the liver.Although all organs in our animals were notexamined for arterial necrosis, those whichwere examined histologically, including heart,lung, kidney, and adrenals, had no evidence ofthe lesion.

SUMMARY

1. Constriction of the abdominal aorta inrabbits is a simple operative procedure whichelicits a high incidence of congestive heartfailure.

2. Seventeen of 33 animals died within twoweeks. Death is preceded by a persistent arte-rial hypertension and signs of congestive heartfailure.

3. Both autopsy findings and microscopicsections of tissues from animals which diedwithin a month revealed predominantly thepicture of acute passive congestion in liver andlungs. After this period of survival, evidence ofchronic passive congestion was often seen inboth liver and lung tissue. This was evidencedby heart failure cells in the lungs and atrophyof central portions of lobules of liver.

4. Fibrinoid necrosis confined to branches ofthe hepatic artery was noted in 6 of 27 animals.

REFERENCES

1 STARK, I., JEFFERS, W. A., AND MEADE, R. H.,JR.: Absence of conspicuous increments of ve-nous pressure after severe damage to the rightventricle of dogs. Am. Heart J. 26: 291, 1943.

2 LANDIS, E. H., BROWN, E., FANTEUX, M., ANDWISE, C.: Central venous pressure in relation tocardiac "competence", blood volume, and ex-ercise. J. Clin. Investigation 25: 237, 1946.

3 BOTJCEK, R. J., GRINDLAY, J. H., AND BURCHELL,H. B.: Experimental constiictive pericarditis:Analysis of induced circulatory failure. Am. J.Physiol. 169:434, 1952.


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4 Roos, A., AND SMITH, J. R.: Production of experi-mental heart failure in dogs with intact cir-culation. Am. J. Physiol. 153: 558, 194S.

5 ARMSTRONG, T. G.: Experimental heart failuie in

rabbits. Quart. J. Exper. Physiol. 30: 263, .1940.0 BARGER, A. C, ROE, B. B., AND RICHARDSON,

G. S.: Relation of valvular lesions and of ex-ercise to auricular pressure, work tolerance, andto development of chronic, congestive failurein dogs. Am. J. Physiol. 169: 384, 1952.

7 HAMILTON, W. F.: Textbook of Human Physi-

ology. Philadelphia, F. A. Davis, 1949.8 GRANT, R. T., AND ROTHCHILD, L. A.: A device

for estimating blood pressure in the rabbit.J. Physiol. 81: 265, 1934.

9 GOLDBLATT, H.: The Renal Origin of Hyperten-

sion. Springfield, 111., Charles C Thomas, 194S.10

DRURY, D. R.: The production of a new method ofrenal insufficiency and hypertension in the rab-bit. J. Exper. Med. 68:" 693, 1938.

TAGGABT, J., AND DRURY, D. R.: The action ofrenin on rabbits with renal hypertension. J.Exper. Med. 71: 857, 1940.

11 WILSON, C., AND PICKEBING, G. W.: Acute arterial

lesions in rabbits with experimental renal hy-pertension. Clin. Sc. 3: 343, 193S.


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NATALIE ALEXANDER, HUGH A. EDMONDSON and DOUGLAS R. DRURYThe Production of Experimental Congestive Heart Failure in Rabbits

Print ISSN: 0009-7330. Online ISSN: 1524-4571 Copyright © 1953 American Heart Association, Inc. All rights reserved.is published by the American Heart Association, 7272 Greenville Avenue, Dallas, TX 75231Circulation Research

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