Radiography in Diagnosing Canine Cardiac Disease.doc (1)

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KEY FACTS

Role of SurveyRadiography inDiagnosing Canine

Cardiac DiseaseUniversity of London

Christopher R. Lamb, MA, VetMB, MRCVS, DACVR, DECVDIAdrian Boswood, MA, VetMB, MRCVS, DVC, DECVIM-CA (Cardiology)

ABSTRACT: Radiography is useful for diagnosing congestive cardiac failure because it enables

detection of pulmonary edema, a major sign of left-sided cardiac failure. In dogs that are not

in cardiac failure, survey radiography is used routinely to assess cardiac size and shape; how-

ever, radiographic measurements of cardiac size are of limited use in diagnosing cardiac dis-

ease and subjective assessments of cardiac shape are inaccurate for detecting specific cardiac

chamber enlargement. In dogs with suspected cardiac disease, it is important not to put too

much emphasis on the radiographic appearance of the cardiac silhouette.

Cardiac diseases can impose different loads on the heart depending ontheir pathophysiology, and the effect on the myocardium is variabledepending on the load.1,2 Diseases that impose a volume load, such as

mitral insufficiency, result in eccentric hypertrophy or dilation of cardiac cham-bers with a corresponding increase in the external dimensions of the heart. How-ever, diseases that impose a pressure load, such as aortic stenosis, tend to resultin concentric hypertrophy (i.e., thickening of the myocardium that encroacheson the ventricular lumen with little or no change in the external dimensions).Thus the type of cardiac disease that is present will determine what radiographicsigns will develop (Figure 1).

Structural changes affecting the heart may occur gradually, sometimes over aperiod of years, and the rate of development of a cardiac lesion also influencesthe radiographic signs. For example, the most marked left atrial enlargementoccurs in dogs with chronic mitral valve disease in which the left atrial wall andsurrounding pericardium gradually stretch in response to a chronic moderateincrease in left atrial pressure and left ventricular end-diastolic pressure. Animals

with acute mitral insufficiency (e.g., as a result of ruptured chorda tendineae)can have a sudden marked increase in left atrial pressure and develop severe pul-monary edema before significant left atrial enlargement has occurred.

CE

316 Vol. 24, No. 4 April 2002

I Radiographic signs of cardiac

disease vary according to the

prevailing pathophysiology.

I Measuring the cardiac silhouette

does not usually aid the

diagnosis of cardiac disease.

I Survey radiography is useful fordiagnosing congestive cardiac

failure.


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ASSESSMENT OF CARDIAC SIZEIn animals that are not in cardiac failure, such as

those with a murmur identified during routine physi-cal examination before vaccination, radiographic

examination of the heart is focused on evaluating car-diac size and shape. Cardiac size is usually assessed bycomparing the appearance of the cardiac silhouette ina patient with examples of normal ones retained inthe veterinarians memory; however, veterinarians(including specialists) making such a subjective assess-ment often experience difficulty deciding whether thecardiac silhouette is enlarged or misshapen.3,4 Forexample, there is a tendency to falsely assume there iscardiomegaly when examining puppies, brachy-cephalic breeds, or obese dogs because these dogs usu-ally have a relatively broad, rounded cardiac silhou-

ette. When evaluating the heart, it may be better tocompare the patient's radiographs with those of a nor-mal dog of the same breed5; however, the search forsuitable comparative radiographs can be time-con-suming and inconvenient.

Objective methods for evaluating the cardiac sil-houette involve measuring various cardiac dimensionsand cardiothoracic ratios6; however, these methodsare undermined by the marked interbreed and indi-vidual variations in thoracic conformation in dogs(Figure 2) as well as variations in the appearance ofthe heart resulting from inconsistent positioning for

radiography, phase of the respiratory or cardiac cycle,and any other concurrent thoracic diseases.3,4,7 Simi-larly, a rule of thumb such as "a normal cardiac sil-houette in the dog...usually ranges from 2.5 to 3.5times the width of intercostal spaces"8 is ineffectivebecause it is too crude to be sensitive and makes noallowance for these variations.

Compendium April 2002 Diagnosing Canine Cardiac Disease 317

Types of Cardiac Enlargement

Concentric hypertrophy Normal

Eccentrichypertrophy

Dilation

Figure 1Types of cardiac chamber enlargement that mayoccur in response to different loads imposed on the heart.Concentric hypertrophy is a likely response to increased after-

load (e.g., affecting the left ventricle as a result of aorticstenosis). Eccentric hypertrophy is a likely response toincreased preload (e.g., affecting the left ventricle as a resultof patent ductus arteriosus or mitral insufficiency). Dilationis a likely response to chronically increased preload and isassociated with cardiac failure.

Figure 2BSmall cardiac silhouette

Figure 2Example of difficulty in interpreting the size of thecardiac silhouette. Knowing the breed of dog often aids inter-pretation of cardiac size and shape; however, this assessmentmay be difficult if the breed is uncommon (these are radi-ographs of a Pharaoh hound). (A) Normal radiograph. (B)Radiograph in the same dog showing a small cardiac silhou-ette (and pulmonary vessels and caudal vena cava) thatoccurred as a result of hypovolemia following acute hemor-rhage. (Note that an optimal diagnostic workup requires aventrodorsal or dorsoventral radiograph in addition to a lat-

eral radiograph, and interpretation should be based on both.In these and other figures, orthogonal radiographs have beenomitted to save space.)

Figure 2ANormal radiograph


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The vertebral heart scale (VHS) is a method ofcardiac measurement that compares the dimensionsof the cardiac silhouette with the length of thoracicvertebral bodies9 (Figure 3). Based on analysis of100 dogs of various breeds, the generic normalrange is 8.7 to 10.7. VHS measurements tend toincrease in dogs with cardiac disease.10,11 There is afair correlation between VHS measurements and avariety of other indices of cardiac chamber enlarge-ment, including end-systolic and end-diastolic ven-

tricular diameters as well as duration of the P waveand QRS complex.11

Measuring the cardiac silhouette might be expectedto aid radiographic diagnosis of canine cardiac disease;however, this does not appear to be the case. For exam-ple, in a recent study, observers ability to correctlyidentify dogs with cardiac disease did not improve

when using the VHS method compared with subjectiveradiographic interpretation alone.10 When observerschanged their initial impression on the basis of a VHSmeasurement, it was just as likely to result in an incor-rect diagnosis as a correct diagnosis.10

Measuring the cardiac silhouette does not aid diag-nosis of cardiac disease because there is considerableoverlap in results from dogs with cardiac disease andnormal dogs (Figure 4). This overlap occurs partlybecause dogs with concentric hypertrophy and thoseexamined in the early stages of their disease may nothave any significant cardiac enlargement and partlybecause certain breeds have relatively large-appearinghearts. Normal boxers have significantly higher meanVHS measurements than normal dogs of other breeds,and Labrador retrievers have significantly higher meanVHS measurements than other breeds except the

318 Small Animal/Exotics Compendium April 2002

Figure 3Method for determining the VHS measurement ona lateral thoracic radiograph. The long axis measurement ofthe cardiac silhouette (A)encompasses 5.1 thoracic vertebrae;the short axis measurement (B) encompasses 4.4 vertebrae.Therefore, the VHS = 5.1 + 4.4 = 9.5. The generic normalVHS range is 8.7 to 10.7; therefore, this result is compatible

with normal cardiac size.

Figure 4BExpiration

Figure 4Example of difficulty in interpreting the size of the

cardiac silhouette. Dogs frequently have a larger cardiac sil-houette in expiratory radiographs. This is a real difference, notan optical illusion arising because the lung looks relativelysmaller. In these lateral radiographs of a golden retriever, theVHS measurement is 10.6 on inspiration (A) and 11.1 onexpiration (B). Using a generic normal VHS range of 8.7 to10.7 and the expiratory radiograph alone would support anerroneous conclusion that this dog has cardiomegaly. (Thisdog had no clinical signs of cardiac disease; it was radi-ographed to look for signs of pulmonary metastasis.)

Figure 4AInspiration

boxer and the cavalier King Charles spaniel12 (Table

1). There is also evidence that females have smallermean VHS measurements than males.12 Clearly, inter-breed differences, and possibly gender, should betaken into account when interpreting the significanceof a cardiac measurement.

Even when using breed-specific normal VHSranges, there is still significant overlap between nor-mal dogs and dogs with cardiac disease.12At the opti-mal VHS value for separation of cardiac from noncar-diac diseased dogs of each breed, the accuracy isrelatively low (range, 58% to 83%; Table 1). VHSmeasurement is an inaccurate method for diagnosing


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cardiac disease in boxers because of their high inci-dence of aortic stenosis, which tends to result in con-

centric hypertrophy of the left ventricle with no visi-ble increase in the external cardiac dimension untilthe condition is advanced. VHS measurement is moreaccurate for cardiac diagnosis in small breeds of dogsthat are affected frequently by mitral insufficiency,

which is more likely to be recognized radiographicallybecause it leads to eccentric hypertrophy or cardiacdilation, both of which increase the external cardiacdimensions.12

ASSESSMENT OF CARDIAC SHAPEVeterinarians usually reach their conclusions about

the shape of the cardiac silhouette based on a subjectiveassessment, just as described for assessment of cardiacsize. There is limited potential for use of measurements

when assessing cardiac shape, although attempts havebeen made to distinguish left- and right-sided chamberenlargement using measurements.6

Each of the cardiac chambers and great vessels con-tributes to the cardiac silhouette (Figure 5), thusenlargement of one or more of these structures maychange the shape of the cardiac silhouette, sometimesbeing visible as a localized bulge. For example, leftatrial dilation frequently results in a bulge in the car-

diac silhouette that is visible on both lateral anddorsoventral radiographs (Figure 6). However, indogs with right or left ventricular enlargement, thereis only fair agreement between the degree of chamberenlargement as assessed subjectively by radiographyand measurements made by echocardiography. 13,14

This lack of agreement reflects inaccuracy in radi-ographic interpretation that occurs because of variousfactors3,4,7,15:

Individual and interbreed variations in cardiac con-formation


Table 1. VHS Measurements on Lateral Thoracic Radiographs of Six Canine Breeds12,a

AccuracyBreed Normal Range VHS Cutoff at Cutoff

Boxer (n= 33) 10.312.6b,c,d,e,f 11.6 58%

Labrador retriever (n= 45) 9.711.7b,g,h,i,j 10.9 66%German shepherd (n= 39) 8.711.2c,g,k 10.2 75%

Doberman pinscher (n= 32) 9.010.8d,h,l 10.5 68%

Cavalier King Charles spaniel (n= 27) 9.911.7e,i,k,l,m 11.1 79%

Yorkshire terrier (n= 29) 9.010.5f,j,m 10.4 83%

aNormal ranges encompass the 5th to 95th percentiles.bmRanges with the same superscript are significantly different; P< .03).

Figure 5BCardiac silhouette (left recumbent view)

Figure 5Example of difficulty in interpreting the shape ofthe cardiac silhouette. Right (A) and left (B) recumbent lat-eral radiographs of a healthy English springer spaniel in

which there is a marked difference in the shape of the cardiacsilhouette. In the left lateral view, the heart appears morerounded, which could be misinterpreted as a sign of cardiacdilation or pericardial effusion.

Figure 5ACardiac silhouette (right recumbent view)


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to avoid biasing their interpretations.24

Under these conditions, the observersreached the correct diagnosis in less than40% of cases.24 This poor result reflects thedifficulty observers had identifying shape

changes that can occur in radiographs ofdogs with enlarged cardiac chambers (Fig-ure 8). Radiographic signs of specific car-diac chamber enlargement (or pulmonaryvascular abnormalities) were recognized byboth observers in only 20% of the instancesin which they might be expected.24Abnor-mal cardiac shape was recognized more fre-quently in dogs with anomalies that vol-ume-loaded the heart than in dogs withanomalies that induced a pressure load on acardiac chamber,24 again emphasizing the

influence of pathophysiology on the radi-ographic appearance of the heart.

RADIOGRAPHIC SIGNS OFCARDIAC FAILURE

Cardiac failure may be divided into for-ward and backward (congestive) failure.2

Forward cardiac failure may be defined asinsufficient cardiac output to maintainnormal physiologic functions, including

ambulation and perfusion of vital organs (e.g., brain,kidneys). Diagnosis of forward failure is not based on

radiography. Backward (congestive) cardiac failure maybe defined as increased end-diastolic filling pressure,which leads to congestion of the pulmonary and sys-temic veins and ultimately results in pulmonary edemaand ascites. Cardiac failure may be diagnosed based onphysical examination findings or increased plasma lev-els of atrial natriuretic peptide,25 but thoracic radiogra-phy is the most widely used diagnostic method for left-sided congestive heart failure because it enablesnoninvasive assessment of the pulmonary veins andmay be used to distinguish pulmonary edema fromother conditions that can cause similar clinical signs,

such as bronchopneumonia.3,4

In each pulmonary lobe, the lobar arteries andveins are normally equal in diameter and slightlysmaller than their accompanying bronchus in aninspiratory radiograph. In a lateral radiograph, pul-monary veins are ventral to their corresponding lobarartery; in dorsoventral or ventrodorsal radiographs,pulmonary veins are medial to the correspondinglobar artery. Pulmonary congestion may be recog-nized radiographically when the pulmonary veinsappear larger than either the corresponding lobarartery or the bronchus (Figure 9). In any particular

Lateral Dorsoventral

Figure 6Drawings (based on cardiac angiograms) showing normal anatomy ofthe cardiac chambers as seen on lateral (left)and dorsoventral (right) thoracicradiographs. The cardiac silhouette has a smooth outline; there are no bulges ordepressions. Note the degree of overlap of the right (RV) and left (LV) ventri-cles when viewed from the lateral aspect and that the right atrium (RA) isalmost completely superimposed by other structures on each view. Compared

with a clock face, the positions of the aortic arch, pulmonary artery (PA), andleft atrial (LA) appendage on the dorsoventral view may be described as 1, 2,and 3 oclock, respectively. (Ao= aorta; RAA= right atrial appendage; CdVC=caudal vena cava; CrVC= cranial vena cava)

Variations in positioning for radiography (Figure 7)

Phase of the respiratory and cardiac cycles

Lack of change in external cardiac dimensions as aresult of concentric thickening of the myocardium

Tendency of the pericardium to smooth over anybulge on the surface of the heart

As a result, it is unlikely that radiographic attemptsto identify enlargement of these cardiac chambersare reliable.

Despite these limitations, many textbooks and arti-cles on the subject of canine congenital cardiac anom-alies describe their radiographic features with little

emphasis on the difficulties of assessment. Retrospec-tive studies have described abnormal cardiac shape as asign of enlarged cardiac chambers or great vessels in themajority of dogs with various congenital anomalies,1621

suggesting that it should be possible to diagnose manycongenital cardiac anomalies by survey radiography. Anexception to this appears to be aortic stenosis, in whichthe majority of affected dogs have no abnormalities onsurvey radiographs.22,23

In a recent study, two experienced observers examinedthe radiographs of 57 dogs with common congenital car-diac anomalies without access to any clinical information


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Figure 7BMarked LA enlargement (lateral view) Figure 7CMarked LA enlargement (dorsoventral view)

Figure 7Example of specific cardiac chamber enlargement resulting in a recognizable bulge in the cardiac silhouette.(A) Drawings showing a change in the shape of the caudal cardiac border on a lateral view(small arrow)and a shallow bulge at

the 3 oclock position on the dorsoventral view(large arrow). There is also dorsal displacement of the trachea and the left cau-dal lobar bronchus on the lateral view(open arrow). This combination of signs is typical of left atrial (LA) enlargement. Lateral(B) and dorsoventral (C) thoracic radiographs of a dog with marked LA enlargement in which similar signs may be observed.

Figure 7ACardiac border changes with LA enlargement

Lateral Dorsoventral

appearance may mimic bronchial wall thickening.There is a tendency for edema to collect first at thehilum, although this may be difficult to recognizeradiographically because the hilar region may alreadyhave an increased opacity as a result of superimposi-tion of enlarged vessels and the left atrium. Edemafluid then accumulates in the alveolar septa, whichbecome thicker, producing a hazy, diffuse interstitial

pattern. Finally, fluid leaks through the epitheliumof the alveolar ducts and floods the alveoli. If suffi-cient alveoli are flooded, the lung appears consoli-dated (sometimes with air bronchograms) and there-fore is classified radiographically as an alveolarpattern (Figure 10). In dogs, pulmonary edema isusually most marked radiographically in the caudallobes but may affect the entire lung in individuals

with severe cases. Pulmonary edema tends to obscurethe heart and pulmonary vessels, making their evalu-ation more difficult.

Note that if an animal with cardiac failure becomes

thoracic radiograph, there may be few points atwh ich the lobar ve ss el s can be vi sual iz ed cl ea rlyenough for comparison or measurements. Whenexamining animals with suspected cardiac disease, thedorsoventral radiograph may be preferred to the ven-trodorsal because it usually provides a clearer view ofthe caudal lobar vessels.15Alternatively, the left lateralrecumbent radiograph usually provides a good view

of the right cranial lobar vessels.26

The right craniallobar vessels are normally thinner than the thinnestpart of the right fourth rib, and it has been suggestedthat measurement of these structures aids recognitionof pulmonary congestion.26 In some animals withpulmonary congestion, pulmonary vessels appear tobe more numerous than normal, which probablyreflects enlargement of vessels that are normally toosmall to be clearly visualized.

Pulmonary edema develops in stages.2729 Initially,edema fluid leaks into the loose tissue around pul-monary vessels and bronchi, and its radiographic


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Figure 8Example of difficulty in correctly recognizing signsof congenital cardiac anomalies in dogs. (A) Dorsoventralview of a young German shepherd with pulmonic stenosis.There is radiographic evidence of an enlarged pulmonaryartery(large arrow)and enlarged right ventricle (smallarrows). (B) Dorsoventral view of a young schnauzer withpulmonic stenosis. There is no radiographic sign of pul-monary artery enlargement. The position of the cardiac apex

well to the left of midline suggests possible enlargement ofthe right ventricle; however, this appearance could also reflectan expiratory exposure, thus there is little radiographic evi-dence to suggest the diagnosis. (C) Dorsoventral view of ayoung weimaraner with a systolic murmur. There is a focalbulge at the 2 oclock position compatible with an enlargedpulmonary artery, and there is a sharply curved right cardiacborder, possibly suggesting an enlarged right ventricle. Thiscombination of signs is compatible with pulmonic stenosis;however, a comprehensive Doppler echocardiographic exami-nation found mild aortic stenosis (and no sign of pulmonicstenosis or right ventricular enlargement or hypertrophy).The radiographic appearance reflects a normal variant. (Fig-

ure 8C is reproduced from Lamb CR, Boswood A, VolkmanA, Connolly D: Assessment of survey radiography as amethod for diagnosis of congenital cardiac diseases in dogs.JSmall Anim Pract42:541545, 2001; with permission.)

Figure 8APulmonic stenosis in a German shepherd Figure 8BPulmonic stenosis in a schnauzer

Figure 8CAortic stenosis in a weimaraner

hypovolemic (e.g., because of concurrent disease), thereduction in circulating blood volume may mask signsof cardiac enlargement and pulmonary congestion andits radiographs may appear normal. In such a case,rehydration may result in rapid development of pul-monary congestion and edema.

Radiographic signs that may be observed in dogswith right-sided cardiac failure include an enlarged cau-dal vena cava, hepatomegaly, and pleural and/or peri-toneal fluid. It is generally accepted that radiography ismore sensitive for detecting peritoneal fluid than physi-cal examination, but peritoneal fluid may occur for a


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variety of reasons; therefore, it is not a specific sign ofcongestive cardiac failure.

CONCLUSIONSSurvey radiography is used routinely as part of the

diagnostic workup in animals with suspected cardiacdisease; however, clinicians should be cautious wheninterpreting radiographs, particularly in dogs that arenot in cardiac failure, because survey radiography isnot an accurate method for assessing cardiac size or


Figure 10BPulmonary edema (dorsoventral view)

Figure 10Lateral (A) and dorsoventral (B) thoracic radi-ographs of a dog with marked pulmonary edema, which isvisible as an alveolar infiltrate that is most marked in the cau-dal lobes. Dorsal displacement of the trachea on the lateralview suggests cardiac enlargement; however, the pulmonaryinfiltrate obscures the caudal cardiac border, hindering assess-

ment of cardiac size and chamber bulges.

Figure 10APulmonary edema (lateral view)

Figure 9BLeft cranial lobar vein enlargement

Figure 9Radiographic signs of pulmonary congestion. (A)Enlargement of pulmonary veins, which may be recognizedby comparing veins (V)with arteries (A)in radiographs thatshow them either side-on (top)or end-on (bottom; B =bronchus). In lateral radiographs, pulmonary veins are ventralto their corresponding lobar artery; in dorsoventral or ven-trodorsal radiographs, pulmonary veins are medial to the cor-responding lobar artery. (B) Detail of a lateral thoracic radi-ograph in which enlargement of the left cranial lobar vein isvisible just ventral to the bronchus in a dog with mitralstenosis.

Pulmonary Vascular Anatomy

Normal

B

Congested

V

A

B

V

A

Figure 9APulmonary vein enlargement

Bronchus

Vein

shape. Radiography should be considered only onepart of the workup, and an attempt should routinelybe made to integrate the clinical and radiographicsigns to avoid placing unwarranted emphasis on theperceived size or shape of the cardiac silhouette alone.Survey radiography is a useful method for diagnosingcongestive cardiac failure because it enables examina-tion of pulmonary vessels and detection of pul-monary edema, which is a major sign of left-sided


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cardiac failure. Survey radiography also aids differen-tiation of cardiac failure from various other pul-monary or pleural conditions that may produce simi-lar clinical signs.

REFERENCES1. Hamlin RL: Pathophysiology of the failing heart, in Fox PR,

Sisson D, Moise NS (eds): Textbook of Canine and Feline Cardi-ology. Philadelphia, WB Saunders Co, 1999, pp 205215.

2. Katz AM: Physiology of the Heart, ed 3. Philadelphia, Lippincott,Williams and Wilkins, 2001, pp 658673.

3. Kittleson MD: Radiology, in Kittleson MD, Kienle RD (eds):Small Animal Cardiovascular Medicine. St. Louis, Mosby, 1998,pp 4771.

4. Lord PF, Suter PF: Radiology, in Fox PR, Sisson D, Moise NS(eds): Textbook of Canine and Feline Cardiology. Philadelphia,

WB Saunders Co, 1999, pp 107129.

5. Lord PF: Cardiac mensuration, in Kirk RW (ed): Current Veteri-nary Therapy, ed 5. Philadelphia, WB Saunders Co, 1974, pp339340.

6. Hamlin RL: Analysis of the cardiac silhouette in dorsoventralradiographs from dogs with heart disease. JAV MA 153:14461460, 1968.

7. Silverman S, Suter PF: Influence of inspiration and expirationon canine thoracic radiographs.JAVMA166:502510, 1975.

8. Owens JM, Biery DN: Radiographic Interpretation for the SmallAnimal Clinician, ed 2. Baltimore, Williams and Wilkins, 1999,pp 185216.

9. Buchanan JW, Bcheler J: Vertebral scale system to measurecanine heart size in radiographs.JAVMA206:194199, 1995.

10. Lamb CR, Tyler M, Boswood A, et al: Assessment of the valueof the vertebral heart scale in the radiographic diagnosis of car-diac disease in dogs. Vet Rec146:687690, 2000.

11. Nakayama H, Nakayama T, Hamlin RL: Correlation of cardiacenlargement as assessed by vertebral heart size and echocardio-graphic and electrocardiographic findings in dogs with evolvingcardiomegaly due to rapid ventricular pacing. J Vet Intern Med15:217221, 2001.

12. Lamb CR, Wikeley H, Boswood A, Pfeiffer DU: Use of breed-specific ranges for vertebral heart scale in dogs as an aid to radi-ographic diagnosis of cardiac disease. Vet Rec148:707711, 2001.

13. Lombard CW, Ackerman N: Right heart enlargement in heart-worm-infected dogs: A radiographic, electrocardiographic, andechocardiographic correlation. Vet Radiol25:210217, 1984.

14. Lombard CW, Spencer CP: Correlation between radiographic,

echocardiographic, and electrocardiographic signs of left heartenlargement in dogs with mitral regurgitation. Vet Radiol26:8997, 1985.

15. Ruehl WW, Thrall DE: The effect of dorsal versus ventralrecumbency on the radiographic appearance of the canine tho-rax. Vet Radiol22:1016, 1981.

16. Suter PF, Lord PF: A critical evaluation of the radiographic find-ings in canine cardiovascular diseases. JAVMA158:358371,1970.

17. Ackerman N, Burk R, Hahn AW, Hayes HM: Patent ductusarteriosus in the dog: A retrospective study of radiographic, epi-demiologic, and clinical findings. Am J Vet Res 39:18051810,1978.

18. Fingland RB, Bonagura JD, Myer CW: Pulmonic stenosis in thedog: 29 cases (19751984).JAVMA189:218226, 1986.

19. Ringwald RJ, Bonagura JD: Tetralogy of Fallot in the dog: Clin-ical findings in 13 cases.JAAHA24:3343, 1988.

20. Sisson D, Luethy M, Thomas WP: Ventricular septal defectaccompanied by aortic regurgitation in five dogs. JAAHA

27:441448, 1991.21. Lehmkuhl LB, Ware WA, Bonagura JD: Mitral stenosis in 15

dogs.J Vet Intern Med8:217, 1994.

22. Levitt L, Fowler JD, Schuh JCL: Aortic stenosis in the dog: Areview of 12 cases.JAAHA25:357362, 1989.

23. OGrady MR, Holmberg DL, Miller CW, Cockshutt JR:Canine congenital aortic stenosis: A review of the literature andcommentary. Can Vet J30:811815, 1989.

24. Lamb CR, Boswood A, Volkman A, Connolly D: Assessment ofsurvey radiography as a method for diagnosis of congenital car-diac diseases in dogs.J Small Anim Pract42:541545, 2001.

25. Boswood A, Attree S, Page K: Clinical validation of a Pro-ANP31-67 fragment ELISA in the diagnosis of naturally occurring

canine heart failure [abstract].J Small Anim Pract42:365, 2001.26. Thrall DE, Losonsky JM: A method for evaluating canine pul-

monary circulatory hemodynamics from survey radiographs.JAAHA12:457462, 1976.

27. Staub NC, Nagano H, Pearce ML: Pulmonary edema in dogs,especially the sequence of fluid accumulation in lungs. J ApplPhysiol22:227240, 1967.

28. Conhaim RL: Airway level at which edema fluid enters the airspace of isolated dog lungs.J Appl Physiol67:22342242, 1989.

29. Forster BB, Muller NL, Mayo JR, et al: High-resolution com-puted tomography of experimental hydrostatic pulmonaryedema. Chest101:14341437, 1992.

1. Which of the following morphologic changes is least

likely to be visible radiographically as an increase insize of the cardiac silhouette?a. concentric hypertrophyb. eccentric hypertrophyc. dilationd. pericardial effusion

2. Which of the following factors may influence theappearance of the cardiac silhouette?a. left versus right recumbencyb. phase of respirationc. breed of dogd. all of the above


CEARTICLE #4 CE TEST

The article you have read qualifies for 1.5 con-tact hours of Continuing Education Credit fromthe Auburn University College of Veterinary Med-icine. Choose the best answerto each of the follow-ing questions; then mark your answers on thepostage-paid envelope inserted in Compendium.

(continues on page 352)


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3. Which of the following canine breeds has the highestnormal VHS range?a. boxer

b. Labrador retrieverc. German shepherdd. cavalier King Charles spaniel

4. What is the generic normal VHS range?a. 8.2 to 10.2b. 8.5 to 10.5c. 8.7 to 10.7d. 8.9 to 10.9

5. What cardiac structure normally occupies the 2 oclockposition on the cardiac silhouette on a dorsoventralradiograph?

a. aortic archb. pulmonary arteryc. left atrial appendaged. right atrial appendage

6. Which of the following congenital cardiac anomalies isleast likely to result in abnormal cardiac size or shape?a. pulmonic stenosisb. aortic stenosisc. patent ductus arteriosusd. mitral stenosis

7. Survey radiographic signs in dogs with congenital car-

diac anomalies area. seen most frequently in dogs with pressure-loadinganomalies such as aortic or pulmonic stenosis.

b. seen most frequently in dogs with volume-loadinganomalies such as patent ductus arteriosus.

c. present in the majority of dogs.d. the basis for prognosis.

8. Which of the following statements about radiographicsigns of pulmonary congestion is correct?a. The right lateral recumbent radiograph is preferred

for assessing the right cranial lobar vessels.b. The left lateral recumbent radiograph is preferred

for assessing the right cranial lobar vessels.c. The thickness of congested veins usually exceedsthe thickness of the ribs.

d. Diagnosis of congestion depends on precise meas-urements of affected vessels.

9. The usual radiographic sequence showing develop-ment of pulmonary edema in dogs with congestivecardiac failure isa. alveolar, interstitial, hilar.b. hilar, alveolar.c. peribronchial, interstitial, alveolar.d. interstitial, peribronchial, alveolar.

10. Which of the following statements regarding the use ofsurvey radiography for diagnosing cardiac disease iscorrect?

a. Radiographic signs of cardiac disease are unrelatedto the prevailing pathophysiology.b. Quantitative assessment of the cardiac silhouette is

the key to optimal diagnostic accuracy.c. Survey radiography is an accurate method for iden-

tifying cardiac chamber enlargement.d. Survey radiography is useful for diagnosing cardiac

failure.


Canine Cardiac Disease (continued from page 326)

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