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Pericardial Effusion in the Cat
Symposium on Feline Cardiology
Pericardial Effusion in the Cat Jerry M. Owens, D.V.M.*
With the increased recognition of heart disea~e in cats, diseases of the pericardium are now being found. Congenital absence of the pericardia! sac and restrictive pericarditis have been seen; 5 •6 however, pericardia! effusion accounts for the majority of recognized pericardia! disease. 5 • 9 The purpose of this article is to discuss the diagnostic methods as well as the differential diagnosis of pericardia! effusion. Physical examination, auscultation, electrocardiography, and thoracic radiography are all vital diagnostic modalities. All of these methods are easily employed in private practice. Through pericardiocentesis, cytologic analysis, and special radiographic contrast procedures, an etiologic diagnosis can often be made. Causes
Many causes of pericardia! effusion have been recognized. Infectious processes incl~ding feline infectious peritonitis and suppurative pericarditis, 6 neoplastic conditions including lymphosarcoma and mesothelioma, 5 • 6 • 9 and hemopericardium from cardiac rupture have all been seen to causepericardial effusion. Hemodynamic causes of effusion include right heart failure, hypoproteinemia, renal failure, and iatrogenic fluid overload. 1 Clinical Signs
The clinical signs associated with pericardia! effusion result from inpairment of normal cardiac function. The severity of the clinical signs depends on the duration and the pressure of the intrapericardial fluid and the degree of the resulting cardiac tamponade. Acute pericardia! effusion, as in hemopericardium from cardiac rupture, may lead to severe progressive clinical signs. As the pericardium is a relatively inelastic envelope around the heart, a sudden increase in intrapericardial pressure may severely restrict diastolic filling *Staff Radiologist, The Berkeley Veterinary Medical Group, Berkeley, California
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causing circulatory embarrassment. The clinical signs are usually relative to shock; low arterial pressure, rapid pulse, shallow breathing and cool extremities are often observed. The increased venous pressure causes visually enlarged jugular veins; in small animals this is often overlooked due to the presence of hair and skinfolds on the neck. If the increase in intrapericardial pressure is rapid, cardiac tamponade and death may ensue. 1- 3 • 10 Chronic pericardia! effusion is more commonly observed. With the gradual outpouring of fluid into the pericardia! cavity, the pericardium stretches to accommodate the fluid with minimal effects on diastolic filling and venous return. Eventually the amount of effusion becomes so large that circulatory embarrassment does exist and right heart failure develops. Pleural effusion, hepatomegaly, and ascites then occur. The clinical signs usually recorded include dyspnea, tachypnea, lethargy, and weight loss. Coughing is also occasionally seen. 1- 3 • 6 • 9 • 10
AUSCULTATION Thoracic auscultation of patients with pericardia! effusion may reveal muffled heart sounds. The degree of diminished intensity depends on the severity of the pericardia! effusion and the presence of other thoracic abnormalities, e.g., pleural effusion. Differential consideration should be given to other diseases and conditions that can also cause muffled heart sounds (Table 1).
ELECTROCARDIOGRAPHY Electrocardiography may be helpful as supportive clinical evidence in the diagnosis of pericardia! effusion. The QRS complexes are usually of low amplitude. Differential consideration should be made to other diseases and conditions that can cause similar electrocardiographic changes (Table 1). As the QRS complexes are small in normal cats, careful interpretation of the electrocardiogram is essential. The electrocardiogram alone should not be the only test used in diagnosing pericardia! effusion.
THORACIC RADIOGRAPHY Lateral and dorsoventral (or ventrodorsal) projections of the thorax should be made on cats with suspected cardiac and/or pericardia! disease. Routine abdominal radiographs are also advised as many diseases are multisystemic and additional information may be obtained, e.g., ab-
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Table 1. Diseases and Conditions That Can Mimic Pericardia! Effusion DIAGNOSTIC METHOD
CONDITION
Normal Obesity Pleural effusion Pneumothorax Intrathoracic masses Diaphragmatic hernia Peritoneopericardial diaphragmatic hernia Thymic lymphosarcoma Congenital heart disease Congestive cardiomyopathy
ElectrocardiograP.hy (low amplitude QRS complexes)*
Auscultation (muffled heart sounds)
Radiography (enlarged cardiac silhouette)
+ + + + + +
+ + + + + +
+
+
+
+ + +
*The normal QRS complexes in the cat are low in amplitude (a mean of 0.5 mv. in lead II). The diagnosis of small QRS complexes is dependent on a comparison of the QRS complexes to those complexes before the effusion (if available) and to those complexes after any medical resolution of the effusion.
domina! effusion, abdominal masses, liver size, and kidney shape and SIZe.
In cats with small amounts of pericardia! effusion, a definite radiographic diagnosis of pericardia! effusion is difficult if not.impossible to make. As the pericardium is relatively inelastic, little if any distortion of the cardiac outline will be seen. Even in cases of cardiac rupture with hemopericardium and tamponade, the heart size and shape may be within normal limits. In cats with adva~ced pericardia! disease in which the effusion has accumulated over a period of time, the cardiac silhouette will be enlarged and typically globular in appearance (see Figs. 2,A andB and 3,A and B). On the lateral projection, the heart assumes a well rounded shape with increased sternal contact and dorsal elevation of the trachea and the tracheal bifurcation. Usually there is no apparent line of demarcation between the atria and the ventricles. The enlarged caudal aspect of the heart is often against the cranioventral portion of the diaphragm obscuring or overlapping the diaphragmatic shadow. On the dorsoventral projection, the enlarged silhouette usually appears very rounded, the so-called "pumpkin" or "soccer ball" appearance. The bulging occurs laterally in equal dimensions, unless other concurrent thoracic disease is also present, e.g., pleural effusion. Differential consideration should be given to other disease entities that can cause a large rounded cardiac silhouette. The most commonly confused conditions are congenital heart disease, congestive cardiomyopathy, and peritoneopericardial diaphragmatic hernia (Table 1).
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PERICARDIOCENTESIS Pericardiocentesis is a simple and relatively safe procedure that may lead to a definitive etiologic diagnosis of pericardia! effusion. Cats with pericardia! disease or congestive heart failure should be minimally restrained. Usually no sedation is needed to perform pericardiocentesis, as most cats will lie comfortably in a prone position. If sedation is necessary, extreme caution is taken in the selection and administration of the tranquilizer. The technique of centesis of the pericardia! cavity has been well described in the dog, 2 •3 •8 • 10 and the same principles apply to the cat. The pericardia! cavity can be entered by directing a needle through the left fourth or fifth intercostal space at the junction of the lower and middle thirds of the thorax. It is suggested that thoracic radiographs be made immediately prior to the centesis, so that the correct intercostal space and position of entry can be selected. It is also advisable that an electrocardiogram be performed during the procedure so that misplacement of the needle can be detected on the electrocardiogram. If the epicardium is touched or the myocardium is entered, premature ventricular contractions are usually seen. If premature ventricular contractions are noted, the needle is withdrawn slightly and repositioned, providing that a normal sinus rhythm returns. Usually the tip of the needle can be felt to touch or enter the heart muscle, and repositioning is easily accomplished. An 18 gauge indwelling catheter is recommended for the centesis, as this will allow insertion of the catheter into the pericardia! sac and removal of the fluid. During centesis, there will be no danger of irritating the epicardium, and the pericardia! fluid is usually withdrawn without much difficulty. An 18 gauge.needle is usually sufficient; however, in cases in which the fluid is very viscous a 16 gauge needle catheter combination may be preferable. It is beneficial for both diagnostic and therapeutic purposes to remove as much pericardia! fluid as possible. This fluid is cultured and analyzed, including exfoliative cytology. After as much pericardia! fluid as possible has been removed, additional thoracic radiographs should be done. The catheter can be left in position and taped to the chest wall. The location of the catheter tip can then be determined from the thoracic radiograph and repositioned if necessary.
SPECIAL RADIOGRAPHIC PROCEDURES In a cat, where pericardia! effusion is suspected, fluoroscopy, pericardiocentesis, angiocardiography, and pneumopericardiography are special procedures that can be used in the diagnostic work-up. Usually a definitive diagnosis of pericardia! effusion can be made, and often
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the etiology can be determined when these procedures are combined with appropriate laboratory tests. If pleural effusion is present, thoracentesis is performed to remove as much fluid as possible. Fluid analysis may yield a primary diagnosis such as feline infectious peritonitis or lymphosarcoma. If the fluid is transudative, other diagnoses can be considered, such as right heart failure, hypoproteinemia, and fluid overload. If the diagnosis is still questionable or if further diagnostic tests need to be performed, repeat thoracic radiographs are taken as an initial procedure. If the pleural effusion has been adequately removed, there may then be visualization of the cardiac border, the mediastinum, the pleural surface, and the lung parenchyma. If pleural and intrapulmonary disease is absent and pericardia! effusion is still suspected, additional diagnostic studies may need be done.
Fluoroscopy Fluoroscopy or image intensification can be valuable as a noninvasive technique in determining whether pericardia! effusion is present. In the normal cat, both systolic and diastolic movements of the heart can be observed easily. If pericardia! effusion is present, cardiac contractions are difficult to see and the cardiac silhouette seems to rock back and forth. Fluid waves are occasionally observed due to the movement of the effusion secondary to cardiac movements. This technique may help differentiate between generalized cardiomegaly due to cardiac disease and an enlarged heart shadow due to pericardia! effusion. If pericardia! effusion is suspected, pericardiocentesis should be performed for additional diagnostic information. .
Angiocardiography . Selective or nonselective angiocardiography may also be of value in establishing a diagnosis of pericardia! effusion. If the right ventricle is filled with contrast medium, the combined thickness of the right ventricular wall and the pericardia! sac can be measured. This thickness is normally quite small, whereas in pericardia! effusion the thickness would be much greater due to the presence of the pericardia! fluid. In gross pericardia! effusion, the diagnosis is made easily; however, in patients with only small amounts of effusion, the diagnosis may be more difficult. Angiocardiography does have an advantage over fluoroscopy as it permits visualization of intracardiac anatomy. Ideally, both fluoroscopy and angiocardiography should be carried out, because together they can supply information on both cardiac anatomy and functional evaluation of cardiac movements.
Pneumopericardiography Pneumopericardiography is perhaps the simplest, least expensive, and most appropriate radiographic method for the evaluation of
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pericardia! disease (see Figs. 2, C and D, and 3, C and D). The use of a negative contrast agent (gas) provides adequate contrast between the water density of the heart and the pericardia! sac. To provide maximum contrast, as much pericardia! fluid as possible should be removed via pericardiocentesis and an indwelling catheter placed within the pericardia! cavity. Gas is then injected into the pericardia! sac expanding the cavity and thus providing visualization of the parietal and visceral pericardia! surfaces. The best radiographic visualization of the heart and pericardium is provided by the use of multiple radiographic projections including left and right lateral, dorsoventral and ventrodorsal views. A horizontal beam can also be utilized to obtain upright ventrodorsal and standing lateral projections. Utilizing the gravitational effect of fluid versus gas, these horizontal beam studies may be rewarding. Negative Contrast Agents. The type of gas for this negative contrast study is variable and depends on individual preference; however, some gases are safer than others. Gases that can be used include carbon dioxide, nitrous oxide, oxygen, and room air. Carbon dioxide is the safest gas to use as it is highly soluble in blood, (24 times more soluble than air) and thus is rapidly absorbed.U Usually absorption is near complete 30 minutes following instillation, thus providing ample time to obtain diagnostic radiographs. Even if the C02 is injected directly into the circulation, the absorption is so rapid that gas embolism will not occur. 11 Nitrous oxide is slightly less soluble than C0 2 and is 34 times as soluble as the nitrogen in the airY Its absorption rate is slightly slower than C0 2 , but there is no real danger of gas embolism, and its removal following instillation is optional. Oxygen and room air are the least preferable gases to use as negative contrast agents. Even though oxygen is 10 times more soluble than air, if either 0 2 or air is too rapidly absorbed or if injected directly into the circulation, gas embolism and possibly death may occur.U Some authors have reported complete safety using room air; 2 •3 • 8 however, in this author's opinion, room air should be used only if other gases are not available. Following the completion of the study, it is recommended to remove as much gas as possible. Carbon dioxide is the gas of choice and is preferred by the author. C0 2 is readily available utilizing a Corkmaster* containing a cartridge of carbon dioxide. The needle tip of this instrument can be readily adapted to intravenous connector tubing. A three-way stopcock can be fitted into the connector tubing, thus allowing precise measurement of the volume of gas injected into the patient (Fig. 1). 4 The volume of gas injected into the pericardia! sac is variable and *Made by The British Oxygen Company, Ltd., London, England; distributed by Leland Industries, Inc., South Plainfield, New Jersey 07080.
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Figure I. A Corkmaster (CM) containing a cartridge of carbon dioxide (C02 ) is shown adapted to a piece of extension tubing. Csing a 3-wa y stopcock (3) , the volume of C02 can be dete rmined before injecting the gas through the catheter (at).
depends upon the volume of fluid removed from the pericardia! sac and the tolerance of the patient to the gas pressure within the pericardia! cavity. Under no circumstances should more gas be injected than the volume of fluid withdrawn. Usu ally one-half to three-quarters of the fluid needs to be r eplaced with gas. Equal replacement with gas for fluid has also been used and found to be safe. Interpretation. In the normal cat, it is difficult if not impossible to study the pericardia! cavity with negative contrast agents. ln the normal state, there is a small amount of fluid within the pericardia! sac which serves as a lubricant for pericardia! movements during cardiac contractions. Although the pericardium is pliable, there is virtually no free space in the pericardia! cavity that would allow a n eedle to be placed transthoracically into the pericardia! cavity. The pericardium is like an elastic envelope around the heart and in normal circumstances does not permit iatrogenic enlargement without detrimental compromise of diastolic filling and cardiac tamponade. In those diseases in which pericardia! fluid exists, the results of the pneumopericardiogram will be d ependent on the extent of pericardia! disease and involvement of the pericardium itself as well as the affection of the epicardial surface.
CASE REPORTS Case 1 Signalment. One and o ne-half year old female domestic shorthaired cat. History. The owner reported a progressive history of anorexia, lethargy,
and an occasional n onprodu ctive cough.
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Physical Examination. On physical examination the cat was afebrile, depressed, moderately dehydrated, and exhibited an increased respiratory rate. Auscultation of the heart and lungs revealed sounds of diminished intensity. Moderate hepatomegaly was present on abdominal palpation. Clinical Course. An electrocardiogram showed normal sinus rhythm with QRS complexes of low a mplitude . Survey thoracic radiographs r evealed a markedly enlarged globular-shaped heart silhouette (Fig. 2, A and B) . The cl inical, radiographic, and electrocardiographic examinations suggested pericardia! effusion .
Figure 2 . T h e su rvey lateral (A) an d dorsoventra l (B ) radiographs or the thorax show pro minent dorsal elevation of the trachea a nd gene ra lized cardiomegaly. A pne urnopericard iogram of case l is illustrated inC a nd D . C, The recumbent rig h t lateral pro jection shows a rnultilobu la tecl mass adherent to the cranioventral aspect of the parietal pericar clium (ojJen arrows ). D, An upright ventrodorsal projection u tilizing a horizontal beam shows a thin pe ricardia! sac (open anows) and right sided pleural effusion. The d iagnosis was pe ricardia! mesothelio ma (see text). (FTOm Tille y, L. P., Owens, ]. M., Wilkins, R. J., et al. : Pericardia! mesothelioma causing effusion in a cat. J.A.A.H.A., 11:60 , 1975, with permission.)
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A laboratory evaluation consisting of a complete blood count, an SMA-12 biochemical profile and a urinalysis noted a mild anemia and a leukocytosis (40,800 per cu mm) with a regenerative left shift. The cat was also hypoproteinemic (total protein: 4.8 gm per 100 ml with 2.4 gm of albumin per 100 ml). Pericardiocentesis was performed at the junction of the lower and middle thirds of the left fifth intercostal space with an 18 gauge catheter. The catheter was introduced into the pericardia! sac and then connected to a three-way stopcock; 200 ml of dark nonclotting serosanguineous fluid was removed. Following pericardiocentesis and intravenous fluid therapy, the cat became more alert and its respirations returned to normal. On analysis, the pericardia! fluid had a specific gravity of 1.027, a total protein of 3.8 gm per 100 ml, and a white blood cell count of 19,000 per cu mm, thus classifying it as an exudate rather than a transudate. The cytologic examination revealed the presence of chronic active mesothelial proliferation. On the next day, thoracic radiographs showed a reduction in the size of the cardiac silhouette. Pericardiocentesis was repeated, and another 40 ml of serosanguineous fluid was removed. Approximately 35 ml of carbon dioxide was injected into the pericardia! sac. Right lateral and ventrodorsal radiographs were made, and an upright ventrodorsal projection utilizing a horizontal beam was also done. The radiographs showed a multilobulated mass adherent to the parietal lining of the cranioventral portion of the pericardia! sac. The cardiac size appeared within normal limits (Fig. 2,C and D). On exploratory thoracotomy, the pericardium was incised and multiple cauliflower-type growths (8 to 12 mm in size) were observed on the cranioventral portion of the parietal surface of a thickened pericardium, and a few smaller lesions were observed on the epicardium. Postoperatively, the cat did poorly and died. On pathologic examination of the excised pericardium and of the necropsy tissues, a histologic diagnosis of primary pericardia! mesothelioma was confirmed. Diagnosis. Primary pericardia! mesothelioma.
Case 2 Signalment. Four year old female domestic shorthaired cat. History. The patient was presented to the hospital with a history of acute
onset of anorexia and dyspnea. Physical Examination. On physical examination, the cat was noted to be alert, of good flesh, -afebrile, and well hydrated. Prominent dyspnea was observed with obvious abdominal respiratory movements. The mucous membranes were cyanotic and on auscultation of the thorax, the heart sounds were muffled. Clinical Course. The laboratory evaluation consisted of a complete blood count and an SMA-12 biochemical profile. The white blood cell count was 12,500 per cu mm with a degenerative left shift. The rest of the hemogram and the biochemical profile were within normal limits. Survey radiographs of the thorax revealed bilateral pleural effusion and a large poorly defined cardiac silhouette (Fig. 3,A and B). A thoracocentesis was then done with the collection of 150 ml of clear transudative fluid. The thoracic radiographs were repeated, and revealed a small residual amount of pleural effusion and an enlarged cardiac shadow. An electrocardiogram showed a heart rate of 180 beats per minute and small QRS complexes. The clinical, radiographic, and electrocardiographic examinations supported a diagnosis of pericardia! effusion. On the second hospital day, the cat was sedated, and pericardiocentesis through the left fifth intercostal space was done. An 18 gauge catheter was
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Figure 3. Survey lateral (A) and dorsoventral (B) thoracic r adiographs of Case 2 show a poorly defined , enlarged cardiac silhouette and bilateral pleural effusion. C and D, following thoracocentesis and pericardiocentcsis, th e pneumopericardiogram shows an irregu lar and slightly thickened pericardia! sac. The diagnosis was septic pericarditis (see tex t).
inserted into the pericardia! cavity and approximately 200 m l of a thick pinkishyellow fluid was removed . A three-way stopcock was then adapted to the intrapericard ial catheter and approximately 150 ml or carbon dioxide was injected into the pericardia! sac. Dorsoventral and right lateral radiographs were then made (Fig. 3,C and D). The pneumopericardiogram showed a thickened irregular pericardium. The heart appeared to be of normal size. Fluid analysis of the pericardia! fluid showed the f'luicl to be an exudate with a specific gravity o f 1.035 and a total protein content of 5.5 grn per 100 ml. Cytologic examination noted a reel blood cell count of 1.22 x 106 cu m rn and a white blood cell count of 7,100 p er cu mm. The differe ntial count of the white blood cells showed 90 per cent. neutrophils, 2 per cent bands, 4 per cent lymphocytes, and 4 per cent macrophages. T he cytologic diagnosis was that of an acute suppurative process with toxic inflammatory cells, compatible with a diagnosis of septic pericarditis. Aerobic culture grew Pasteurella spp. and Flavobacterium.
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An exploratory thoracotomy was done on the following day. A total pericardectomy was performed. The suppurative process appeared equal throughout the entire pericardium; however, no definite etiology of the septic process could be determined. Postoperative complications were septic pleuritis, fever, anemia, and pneumothorax. The cat died on the llth hospital day. Diagnosis. Septic pericarditis due to Pasteurella-undetermined pathogenesis. ACKNOWLEDGMENT
The author acknowledges the support of the Berkeley Veterinary Research Foundation, Berkeley, California, in the preparation of this manuscript.
REFERENCES l. Bolton, G. R.: Pericardia! Diseases. In Ettinger, S. E. (ed.): Textbook of Veterinary
Internal Medicine. Philadelphia, W. B. Saunders Co., 1975. 2. Ettinger, S. E.: Pericardiocentesis. VET. CuN. NoRTH AM., 4:403, 1974. 3. Ettinger, S. E., and Suter, P. F.: Canine Cardiology. Philadelphia, W. B. Saunders Co., 1970. 4. Ferron, R. R.: Low-cost, pocket-sized C0 2 dispenser for medical use. J.A.V.R.S., 17:18, 1976. 5. Liu, S.-K.: Pathology of feline heart disease. In Kirk, R. W. (ed.): In Current Veterinary Therapy V. Philadelphia, W. B. Saunders Co., 1974. 6. Owens,]. M.: Unpublished data, 1974. 7. Tashjian, R. ]., Das, K. M., Palich, W. E., eta!.: Studies on cardiovascular diseases in the cat. Ann. N.Y. Acad. Sci., 127:581, 1965. 8. Ticer, ]. W., and Ettinger, S. E.: Pneumopericardiography. In Ticer, ]. W. (ed.): Radiographic Technique in Small Animal Practice. Philadelphia, W. B. Saunders Co., 1975. 9. Tilley, L. P., Owens,]. M., Wilkins, R. ]., et a!.: Pericardia! mesothelioma causing effusion in a cat. J.A.A.H.A., 11:60, 1975. 10. Tilley, L. P., and Wilkins, R. J.: Pericardia! disease. In Kirk, R. W. (ed.): Current Veterinary Therapy V. Philadelphia, W. B. Saunders Co., 1974. 11. Weigen, J. F., and Thomas, S. F.: Complications of Diagnostic Radiology. Springfield, Charles C Thomas, 1973, pp. 491-492. The Berkeley Veterinary Medical Group 800 University Avenue Berkeley, California 94710
Pericardial Effusion in the Cat Jerry M. Owens, D.V.M.*
With the increased recognition of heart disea~e in cats, diseases of the pericardium are now being found. Congenital absence of the pericardia! sac and restrictive pericarditis have been seen; 5 •6 however, pericardia! effusion accounts for the majority of recognized pericardia! disease. 5 • 9 The purpose of this article is to discuss the diagnostic methods as well as the differential diagnosis of pericardia! effusion. Physical examination, auscultation, electrocardiography, and thoracic radiography are all vital diagnostic modalities. All of these methods are easily employed in private practice. Through pericardiocentesis, cytologic analysis, and special radiographic contrast procedures, an etiologic diagnosis can often be made. Causes
Many causes of pericardia! effusion have been recognized. Infectious processes incl~ding feline infectious peritonitis and suppurative pericarditis, 6 neoplastic conditions including lymphosarcoma and mesothelioma, 5 • 6 • 9 and hemopericardium from cardiac rupture have all been seen to causepericardial effusion. Hemodynamic causes of effusion include right heart failure, hypoproteinemia, renal failure, and iatrogenic fluid overload. 1 Clinical Signs
The clinical signs associated with pericardia! effusion result from inpairment of normal cardiac function. The severity of the clinical signs depends on the duration and the pressure of the intrapericardial fluid and the degree of the resulting cardiac tamponade. Acute pericardia! effusion, as in hemopericardium from cardiac rupture, may lead to severe progressive clinical signs. As the pericardium is a relatively inelastic envelope around the heart, a sudden increase in intrapericardial pressure may severely restrict diastolic filling *Staff Radiologist, The Berkeley Veterinary Medical Group, Berkeley, California
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causing circulatory embarrassment. The clinical signs are usually relative to shock; low arterial pressure, rapid pulse, shallow breathing and cool extremities are often observed. The increased venous pressure causes visually enlarged jugular veins; in small animals this is often overlooked due to the presence of hair and skinfolds on the neck. If the increase in intrapericardial pressure is rapid, cardiac tamponade and death may ensue. 1- 3 • 10 Chronic pericardia! effusion is more commonly observed. With the gradual outpouring of fluid into the pericardia! cavity, the pericardium stretches to accommodate the fluid with minimal effects on diastolic filling and venous return. Eventually the amount of effusion becomes so large that circulatory embarrassment does exist and right heart failure develops. Pleural effusion, hepatomegaly, and ascites then occur. The clinical signs usually recorded include dyspnea, tachypnea, lethargy, and weight loss. Coughing is also occasionally seen. 1- 3 • 6 • 9 • 10
AUSCULTATION Thoracic auscultation of patients with pericardia! effusion may reveal muffled heart sounds. The degree of diminished intensity depends on the severity of the pericardia! effusion and the presence of other thoracic abnormalities, e.g., pleural effusion. Differential consideration should be given to other diseases and conditions that can also cause muffled heart sounds (Table 1).
ELECTROCARDIOGRAPHY Electrocardiography may be helpful as supportive clinical evidence in the diagnosis of pericardia! effusion. The QRS complexes are usually of low amplitude. Differential consideration should be made to other diseases and conditions that can cause similar electrocardiographic changes (Table 1). As the QRS complexes are small in normal cats, careful interpretation of the electrocardiogram is essential. The electrocardiogram alone should not be the only test used in diagnosing pericardia! effusion.
THORACIC RADIOGRAPHY Lateral and dorsoventral (or ventrodorsal) projections of the thorax should be made on cats with suspected cardiac and/or pericardia! disease. Routine abdominal radiographs are also advised as many diseases are multisystemic and additional information may be obtained, e.g., ab-
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Table 1. Diseases and Conditions That Can Mimic Pericardia! Effusion DIAGNOSTIC METHOD
CONDITION
Normal Obesity Pleural effusion Pneumothorax Intrathoracic masses Diaphragmatic hernia Peritoneopericardial diaphragmatic hernia Thymic lymphosarcoma Congenital heart disease Congestive cardiomyopathy
ElectrocardiograP.hy (low amplitude QRS complexes)*
Auscultation (muffled heart sounds)
Radiography (enlarged cardiac silhouette)
+ + + + + +
+ + + + + +
+
+
+
+ + +
*The normal QRS complexes in the cat are low in amplitude (a mean of 0.5 mv. in lead II). The diagnosis of small QRS complexes is dependent on a comparison of the QRS complexes to those complexes before the effusion (if available) and to those complexes after any medical resolution of the effusion.
domina! effusion, abdominal masses, liver size, and kidney shape and SIZe.
In cats with small amounts of pericardia! effusion, a definite radiographic diagnosis of pericardia! effusion is difficult if not.impossible to make. As the pericardium is relatively inelastic, little if any distortion of the cardiac outline will be seen. Even in cases of cardiac rupture with hemopericardium and tamponade, the heart size and shape may be within normal limits. In cats with adva~ced pericardia! disease in which the effusion has accumulated over a period of time, the cardiac silhouette will be enlarged and typically globular in appearance (see Figs. 2,A andB and 3,A and B). On the lateral projection, the heart assumes a well rounded shape with increased sternal contact and dorsal elevation of the trachea and the tracheal bifurcation. Usually there is no apparent line of demarcation between the atria and the ventricles. The enlarged caudal aspect of the heart is often against the cranioventral portion of the diaphragm obscuring or overlapping the diaphragmatic shadow. On the dorsoventral projection, the enlarged silhouette usually appears very rounded, the so-called "pumpkin" or "soccer ball" appearance. The bulging occurs laterally in equal dimensions, unless other concurrent thoracic disease is also present, e.g., pleural effusion. Differential consideration should be given to other disease entities that can cause a large rounded cardiac silhouette. The most commonly confused conditions are congenital heart disease, congestive cardiomyopathy, and peritoneopericardial diaphragmatic hernia (Table 1).
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PERICARDIOCENTESIS Pericardiocentesis is a simple and relatively safe procedure that may lead to a definitive etiologic diagnosis of pericardia! effusion. Cats with pericardia! disease or congestive heart failure should be minimally restrained. Usually no sedation is needed to perform pericardiocentesis, as most cats will lie comfortably in a prone position. If sedation is necessary, extreme caution is taken in the selection and administration of the tranquilizer. The technique of centesis of the pericardia! cavity has been well described in the dog, 2 •3 •8 • 10 and the same principles apply to the cat. The pericardia! cavity can be entered by directing a needle through the left fourth or fifth intercostal space at the junction of the lower and middle thirds of the thorax. It is suggested that thoracic radiographs be made immediately prior to the centesis, so that the correct intercostal space and position of entry can be selected. It is also advisable that an electrocardiogram be performed during the procedure so that misplacement of the needle can be detected on the electrocardiogram. If the epicardium is touched or the myocardium is entered, premature ventricular contractions are usually seen. If premature ventricular contractions are noted, the needle is withdrawn slightly and repositioned, providing that a normal sinus rhythm returns. Usually the tip of the needle can be felt to touch or enter the heart muscle, and repositioning is easily accomplished. An 18 gauge indwelling catheter is recommended for the centesis, as this will allow insertion of the catheter into the pericardia! sac and removal of the fluid. During centesis, there will be no danger of irritating the epicardium, and the pericardia! fluid is usually withdrawn without much difficulty. An 18 gauge.needle is usually sufficient; however, in cases in which the fluid is very viscous a 16 gauge needle catheter combination may be preferable. It is beneficial for both diagnostic and therapeutic purposes to remove as much pericardia! fluid as possible. This fluid is cultured and analyzed, including exfoliative cytology. After as much pericardia! fluid as possible has been removed, additional thoracic radiographs should be done. The catheter can be left in position and taped to the chest wall. The location of the catheter tip can then be determined from the thoracic radiograph and repositioned if necessary.
SPECIAL RADIOGRAPHIC PROCEDURES In a cat, where pericardia! effusion is suspected, fluoroscopy, pericardiocentesis, angiocardiography, and pneumopericardiography are special procedures that can be used in the diagnostic work-up. Usually a definitive diagnosis of pericardia! effusion can be made, and often
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the etiology can be determined when these procedures are combined with appropriate laboratory tests. If pleural effusion is present, thoracentesis is performed to remove as much fluid as possible. Fluid analysis may yield a primary diagnosis such as feline infectious peritonitis or lymphosarcoma. If the fluid is transudative, other diagnoses can be considered, such as right heart failure, hypoproteinemia, and fluid overload. If the diagnosis is still questionable or if further diagnostic tests need to be performed, repeat thoracic radiographs are taken as an initial procedure. If the pleural effusion has been adequately removed, there may then be visualization of the cardiac border, the mediastinum, the pleural surface, and the lung parenchyma. If pleural and intrapulmonary disease is absent and pericardia! effusion is still suspected, additional diagnostic studies may need be done.
Fluoroscopy Fluoroscopy or image intensification can be valuable as a noninvasive technique in determining whether pericardia! effusion is present. In the normal cat, both systolic and diastolic movements of the heart can be observed easily. If pericardia! effusion is present, cardiac contractions are difficult to see and the cardiac silhouette seems to rock back and forth. Fluid waves are occasionally observed due to the movement of the effusion secondary to cardiac movements. This technique may help differentiate between generalized cardiomegaly due to cardiac disease and an enlarged heart shadow due to pericardia! effusion. If pericardia! effusion is suspected, pericardiocentesis should be performed for additional diagnostic information. .
Angiocardiography . Selective or nonselective angiocardiography may also be of value in establishing a diagnosis of pericardia! effusion. If the right ventricle is filled with contrast medium, the combined thickness of the right ventricular wall and the pericardia! sac can be measured. This thickness is normally quite small, whereas in pericardia! effusion the thickness would be much greater due to the presence of the pericardia! fluid. In gross pericardia! effusion, the diagnosis is made easily; however, in patients with only small amounts of effusion, the diagnosis may be more difficult. Angiocardiography does have an advantage over fluoroscopy as it permits visualization of intracardiac anatomy. Ideally, both fluoroscopy and angiocardiography should be carried out, because together they can supply information on both cardiac anatomy and functional evaluation of cardiac movements.
Pneumopericardiography Pneumopericardiography is perhaps the simplest, least expensive, and most appropriate radiographic method for the evaluation of
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pericardia! disease (see Figs. 2, C and D, and 3, C and D). The use of a negative contrast agent (gas) provides adequate contrast between the water density of the heart and the pericardia! sac. To provide maximum contrast, as much pericardia! fluid as possible should be removed via pericardiocentesis and an indwelling catheter placed within the pericardia! cavity. Gas is then injected into the pericardia! sac expanding the cavity and thus providing visualization of the parietal and visceral pericardia! surfaces. The best radiographic visualization of the heart and pericardium is provided by the use of multiple radiographic projections including left and right lateral, dorsoventral and ventrodorsal views. A horizontal beam can also be utilized to obtain upright ventrodorsal and standing lateral projections. Utilizing the gravitational effect of fluid versus gas, these horizontal beam studies may be rewarding. Negative Contrast Agents. The type of gas for this negative contrast study is variable and depends on individual preference; however, some gases are safer than others. Gases that can be used include carbon dioxide, nitrous oxide, oxygen, and room air. Carbon dioxide is the safest gas to use as it is highly soluble in blood, (24 times more soluble than air) and thus is rapidly absorbed.U Usually absorption is near complete 30 minutes following instillation, thus providing ample time to obtain diagnostic radiographs. Even if the C02 is injected directly into the circulation, the absorption is so rapid that gas embolism will not occur. 11 Nitrous oxide is slightly less soluble than C0 2 and is 34 times as soluble as the nitrogen in the airY Its absorption rate is slightly slower than C0 2 , but there is no real danger of gas embolism, and its removal following instillation is optional. Oxygen and room air are the least preferable gases to use as negative contrast agents. Even though oxygen is 10 times more soluble than air, if either 0 2 or air is too rapidly absorbed or if injected directly into the circulation, gas embolism and possibly death may occur.U Some authors have reported complete safety using room air; 2 •3 • 8 however, in this author's opinion, room air should be used only if other gases are not available. Following the completion of the study, it is recommended to remove as much gas as possible. Carbon dioxide is the gas of choice and is preferred by the author. C0 2 is readily available utilizing a Corkmaster* containing a cartridge of carbon dioxide. The needle tip of this instrument can be readily adapted to intravenous connector tubing. A three-way stopcock can be fitted into the connector tubing, thus allowing precise measurement of the volume of gas injected into the patient (Fig. 1). 4 The volume of gas injected into the pericardia! sac is variable and *Made by The British Oxygen Company, Ltd., London, England; distributed by Leland Industries, Inc., South Plainfield, New Jersey 07080.
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Figure I. A Corkmaster (CM) containing a cartridge of carbon dioxide (C02 ) is shown adapted to a piece of extension tubing. Csing a 3-wa y stopcock (3) , the volume of C02 can be dete rmined before injecting the gas through the catheter (at).
depends upon the volume of fluid removed from the pericardia! sac and the tolerance of the patient to the gas pressure within the pericardia! cavity. Under no circumstances should more gas be injected than the volume of fluid withdrawn. Usu ally one-half to three-quarters of the fluid needs to be r eplaced with gas. Equal replacement with gas for fluid has also been used and found to be safe. Interpretation. In the normal cat, it is difficult if not impossible to study the pericardia! cavity with negative contrast agents. ln the normal state, there is a small amount of fluid within the pericardia! sac which serves as a lubricant for pericardia! movements during cardiac contractions. Although the pericardium is pliable, there is virtually no free space in the pericardia! cavity that would allow a n eedle to be placed transthoracically into the pericardia! cavity. The pericardium is like an elastic envelope around the heart and in normal circumstances does not permit iatrogenic enlargement without detrimental compromise of diastolic filling and cardiac tamponade. In those diseases in which pericardia! fluid exists, the results of the pneumopericardiogram will be d ependent on the extent of pericardia! disease and involvement of the pericardium itself as well as the affection of the epicardial surface.
CASE REPORTS Case 1 Signalment. One and o ne-half year old female domestic shorthaired cat. History. The owner reported a progressive history of anorexia, lethargy,
and an occasional n onprodu ctive cough.
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Physical Examination. On physical examination the cat was afebrile, depressed, moderately dehydrated, and exhibited an increased respiratory rate. Auscultation of the heart and lungs revealed sounds of diminished intensity. Moderate hepatomegaly was present on abdominal palpation. Clinical Course. An electrocardiogram showed normal sinus rhythm with QRS complexes of low a mplitude . Survey thoracic radiographs r evealed a markedly enlarged globular-shaped heart silhouette (Fig. 2, A and B) . The cl inical, radiographic, and electrocardiographic examinations suggested pericardia! effusion .
Figure 2 . T h e su rvey lateral (A) an d dorsoventra l (B ) radiographs or the thorax show pro minent dorsal elevation of the trachea a nd gene ra lized cardiomegaly. A pne urnopericard iogram of case l is illustrated inC a nd D . C, The recumbent rig h t lateral pro jection shows a rnultilobu la tecl mass adherent to the cranioventral aspect of the parietal pericar clium (ojJen arrows ). D, An upright ventrodorsal projection u tilizing a horizontal beam shows a thin pe ricardia! sac (open anows) and right sided pleural effusion. The d iagnosis was pe ricardia! mesothelio ma (see text). (FTOm Tille y, L. P., Owens, ]. M., Wilkins, R. J., et al. : Pericardia! mesothelioma causing effusion in a cat. J.A.A.H.A., 11:60 , 1975, with permission.)
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A laboratory evaluation consisting of a complete blood count, an SMA-12 biochemical profile and a urinalysis noted a mild anemia and a leukocytosis (40,800 per cu mm) with a regenerative left shift. The cat was also hypoproteinemic (total protein: 4.8 gm per 100 ml with 2.4 gm of albumin per 100 ml). Pericardiocentesis was performed at the junction of the lower and middle thirds of the left fifth intercostal space with an 18 gauge catheter. The catheter was introduced into the pericardia! sac and then connected to a three-way stopcock; 200 ml of dark nonclotting serosanguineous fluid was removed. Following pericardiocentesis and intravenous fluid therapy, the cat became more alert and its respirations returned to normal. On analysis, the pericardia! fluid had a specific gravity of 1.027, a total protein of 3.8 gm per 100 ml, and a white blood cell count of 19,000 per cu mm, thus classifying it as an exudate rather than a transudate. The cytologic examination revealed the presence of chronic active mesothelial proliferation. On the next day, thoracic radiographs showed a reduction in the size of the cardiac silhouette. Pericardiocentesis was repeated, and another 40 ml of serosanguineous fluid was removed. Approximately 35 ml of carbon dioxide was injected into the pericardia! sac. Right lateral and ventrodorsal radiographs were made, and an upright ventrodorsal projection utilizing a horizontal beam was also done. The radiographs showed a multilobulated mass adherent to the parietal lining of the cranioventral portion of the pericardia! sac. The cardiac size appeared within normal limits (Fig. 2,C and D). On exploratory thoracotomy, the pericardium was incised and multiple cauliflower-type growths (8 to 12 mm in size) were observed on the cranioventral portion of the parietal surface of a thickened pericardium, and a few smaller lesions were observed on the epicardium. Postoperatively, the cat did poorly and died. On pathologic examination of the excised pericardium and of the necropsy tissues, a histologic diagnosis of primary pericardia! mesothelioma was confirmed. Diagnosis. Primary pericardia! mesothelioma.
Case 2 Signalment. Four year old female domestic shorthaired cat. History. The patient was presented to the hospital with a history of acute
onset of anorexia and dyspnea. Physical Examination. On physical examination, the cat was noted to be alert, of good flesh, -afebrile, and well hydrated. Prominent dyspnea was observed with obvious abdominal respiratory movements. The mucous membranes were cyanotic and on auscultation of the thorax, the heart sounds were muffled. Clinical Course. The laboratory evaluation consisted of a complete blood count and an SMA-12 biochemical profile. The white blood cell count was 12,500 per cu mm with a degenerative left shift. The rest of the hemogram and the biochemical profile were within normal limits. Survey radiographs of the thorax revealed bilateral pleural effusion and a large poorly defined cardiac silhouette (Fig. 3,A and B). A thoracocentesis was then done with the collection of 150 ml of clear transudative fluid. The thoracic radiographs were repeated, and revealed a small residual amount of pleural effusion and an enlarged cardiac shadow. An electrocardiogram showed a heart rate of 180 beats per minute and small QRS complexes. The clinical, radiographic, and electrocardiographic examinations supported a diagnosis of pericardia! effusion. On the second hospital day, the cat was sedated, and pericardiocentesis through the left fifth intercostal space was done. An 18 gauge catheter was
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Figure 3. Survey lateral (A) and dorsoventral (B) thoracic r adiographs of Case 2 show a poorly defined , enlarged cardiac silhouette and bilateral pleural effusion. C and D, following thoracocentesis and pericardiocentcsis, th e pneumopericardiogram shows an irregu lar and slightly thickened pericardia! sac. The diagnosis was septic pericarditis (see tex t).
inserted into the pericardia! cavity and approximately 200 m l of a thick pinkishyellow fluid was removed . A three-way stopcock was then adapted to the intrapericard ial catheter and approximately 150 ml or carbon dioxide was injected into the pericardia! sac. Dorsoventral and right lateral radiographs were then made (Fig. 3,C and D). The pneumopericardiogram showed a thickened irregular pericardium. The heart appeared to be of normal size. Fluid analysis of the pericardia! fluid showed the f'luicl to be an exudate with a specific gravity o f 1.035 and a total protein content of 5.5 grn per 100 ml. Cytologic examination noted a reel blood cell count of 1.22 x 106 cu m rn and a white blood cell count of 7,100 p er cu mm. The differe ntial count of the white blood cells showed 90 per cent. neutrophils, 2 per cent bands, 4 per cent lymphocytes, and 4 per cent macrophages. T he cytologic diagnosis was that of an acute suppurative process with toxic inflammatory cells, compatible with a diagnosis of septic pericarditis. Aerobic culture grew Pasteurella spp. and Flavobacterium.
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An exploratory thoracotomy was done on the following day. A total pericardectomy was performed. The suppurative process appeared equal throughout the entire pericardium; however, no definite etiology of the septic process could be determined. Postoperative complications were septic pleuritis, fever, anemia, and pneumothorax. The cat died on the llth hospital day. Diagnosis. Septic pericarditis due to Pasteurella-undetermined pathogenesis. ACKNOWLEDGMENT
The author acknowledges the support of the Berkeley Veterinary Research Foundation, Berkeley, California, in the preparation of this manuscript.
REFERENCES l. Bolton, G. R.: Pericardia! Diseases. In Ettinger, S. E. (ed.): Textbook of Veterinary
Internal Medicine. Philadelphia, W. B. Saunders Co., 1975. 2. Ettinger, S. E.: Pericardiocentesis. VET. CuN. NoRTH AM., 4:403, 1974. 3. Ettinger, S. E., and Suter, P. F.: Canine Cardiology. Philadelphia, W. B. Saunders Co., 1970. 4. Ferron, R. R.: Low-cost, pocket-sized C0 2 dispenser for medical use. J.A.V.R.S., 17:18, 1976. 5. Liu, S.-K.: Pathology of feline heart disease. In Kirk, R. W. (ed.): In Current Veterinary Therapy V. Philadelphia, W. B. Saunders Co., 1974. 6. Owens,]. M.: Unpublished data, 1974. 7. Tashjian, R. ]., Das, K. M., Palich, W. E., eta!.: Studies on cardiovascular diseases in the cat. Ann. N.Y. Acad. Sci., 127:581, 1965. 8. Ticer, ]. W., and Ettinger, S. E.: Pneumopericardiography. In Ticer, ]. W. (ed.): Radiographic Technique in Small Animal Practice. Philadelphia, W. B. Saunders Co., 1975. 9. Tilley, L. P., Owens,]. M., Wilkins, R. ]., et a!.: Pericardia! mesothelioma causing effusion in a cat. J.A.A.H.A., 11:60, 1975. 10. Tilley, L. P., and Wilkins, R. J.: Pericardia! disease. In Kirk, R. W. (ed.): Current Veterinary Therapy V. Philadelphia, W. B. Saunders Co., 1974. 11. Weigen, J. F., and Thomas, S. F.: Complications of Diagnostic Radiology. Springfield, Charles C Thomas, 1973, pp. 491-492. The Berkeley Veterinary Medical Group 800 University Avenue Berkeley, California 94710