- Email: [email protected]
Therapeutic Pericardiocentesis in the Dog and Cat
Therapeutic Pericardiocentesis in the Dog and Cat Josh Gidlewski, DVM, Dip ACVIM (Cardiology),* and Jean-Paul Petrie, DVM, Dip ACVIM (Cardiology)† Pericardial effusion is a potentially life-threatening problem leading to a rise in the intrapericardial pressure resulting in varying degrees of hemodynamic compromise. Cardiac tamponade occurs when the intrapericardial pressure equals or exceeds right ventricular diastolic filling pressures leading to a decreased cardiac output. In dogs, the most common causes of pericardial effusion that require pericardiocentesis are cardiac neoplasia and idiopathic pericardial effusion (IPE). The incidence of cardiac neoplasia in dogs is low, and it is rare in cats. In dogs, hemangiosarcoma and chemodectoma are the two most common types of cardiac neoplasia. In cats, lymphosarcoma is the most common form of cardiac neoplasia, but they are more likely to develop pericardial effusion secondary to congestive heart failure or feline infectious peritonitis. Common histories include lethargy, dyspnea, anorexia, collapse, and abdominal distension. Pericardiocentesis is used to stabilize animals with life-threatening cardiac tamponade, relieve the pressure leading to right-sided heart failure, and obtain fluid samples for diagnostic evaluation. The fluid should be quantified and characterized. Serious complications associated with pericardiocentesis are rare. Complications include cardiac puncture, arrhythmias, and laceration of a tumor or coronary artery resulting in intrapericardial hemorrhage or sudden death. Clin Tech Small Anim Pract 20:151-155 © 2005 Elsevier Inc. All rights reserved. KEYWORDS pericardial effusion, pericardiocentesis, idiopathic pericardial effusion, hemangiosarcoma, chemodectoma, heart base tumors
P
ericardiocentesis is a relatively simple procedure that rapidly relieves the symptoms of cardiac tamponade secondary to idiopathic pericardial effusion (IPE) or cardiac neoplasia.1,2 Ultrasonography is a safe, noninvasive, sensitive, and specific tool used to aid in the diagnosis, treatment, and prognostication in the patient with pericardial effusion. Improved technology is helping to hasten the diagnosis and treatment of pericardial effusion in domestic animals. With each new generation of ultrasound machines, the image quality improves and the relative cost decreases. It is imperative to bear in mind that ultrasound is meant to augment, but not replace, information obtained from the physical examination and thoracic radiography.
Clinical Signs and Diagnostic Tests Radiographic findings in the animal with pericardial effusion include a globoid cardiac silhouette, pleural effusion,
*Garden State Veterinary Specialists, Tinton Falls, NJ. †The Animal Medical Center, New York, NY. Address reprint requests to Josh Gidlewski, DVM, Dip ACVIM (Cardiology), Garden State Veterinary Specialists, One Pine St., Tinton Falls, NJ 07753. E-mail: [email protected]
1096-2867/05/$-see front matter © 2005 Elsevier Inc. All rights reserved. doi:10.1053/j.ctsap.2005.05.002
and enlargement of the caudal vena cava. Nodular or interstitial pulmonary parenchymal changes may also be seen with metastatic disease. In some cases, when a large amount of pericardial effusion is absent, there may be a regional enlargement of the cardiac silhouette associated with the presence of a tumor at the right atrium or heart base.3,4-8 Radiographic findings may be normal or only mildly abnormal in some cases with pericardial effusion. Acute hemorrhage leads to cardiac tamponade with relatively small accumulations of fluid; hence the importance of physical examination and ultrasound in these patients.9,10 The size of the cardiac silhouette depends on the chronicity of the disease; pericardial effusion which accumulates over a longer period of time generally produces a larger cardiac silhouette than pericardial effusion which accumulates rapidly. Dogs who develop pericardial effusion secondary to either endocardiosis or dilated cardiomyopathy may show generalized cardiomegaly that is not definitely identified as pericardial effusion.9 Electrocardiographic abnormalities are often present in dogs with pericardial effusion, the most common being sinus tachycardia and low voltage QRS complexes.3,9 Electrical alternans is an uncommon finding, but is highly specific for pericardial effusion.9 Various arrhythmias resulting from myocardial involvement of a tumor may also be seen.3 151
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152
Idiopathic Pericardial Effusion in Dogs Idiopathic pericardial effusion is an uncommon condition that usually affects males of large or giant breeds. Most cases have a history suggestive of chronic right-sided heart failure (ascites, lethargy, weight loss), although they may also develop acute cardiac tamponade. Muffled heart sounds are the most consistent physical abnormality; weak pulses are occasionally present. A diminished QRS complex on the electrocardiogram (ECG) is a common finding but electrical alternans is not.9 The reason for the effusion remains elusive in these patients despite even the most thorough diagnostic evaluations.
Cardiac and Pericardial Neoplasia In small animals, cardiac and pericardial neoplasia is relatively uncommon. Despite their low incidence, these tumors are important because of their potential effects on the cardiovascular system. Late diagnosis and invasiveness of these tumors make treatment difficult. Cardiac neoplasia comprised only 0.19% of all canine cases in The Veterinary Medical Database at Purdue University between 1982 and 1995.11,12 Other studies of two necropsy populations reported an incidence of intrapericardial tumors between 2.7 and 3.1%.13,14 In cats, cardiac neoplasia is rare accounting for only 0.03% of all the feline cases in the Veterinary Medical Database between 1982 and 1993.12 In dogs, hemangiosarcoma is the most commonly reported cardiac neoplasia with incidences ranging between 40.5 and 69%.11,13,14 Chemodectomas are the second most prevalent tumor with incidences between 5 and 17.3%.11,13,14 Lymphosarcoma and thyroid carcinoma are the next most common types of cardiac neoplasia identified. A small number of other histological tumor types account for 12 to 28% of intrapericardial tumors.11,13,14 In cats, the most common histologic diagnosis of cardiac neoplasia is lymphosarcoma.3,15 Some estimations report that lymphosarcoma comprises greater than 30% of all feline cardiac neoplasms.3 The tumor typically involves the myocar-
dium, but usually results in pericardial effusion. Lymphosarcoma often times can be diagnosed by cytological evaluation of the pericardial effusion obtained by pericardiocentesis. The remainder of the feline cardiac neoplasms reported are various carcinomas (19%), hemangiosarcoma (8.6%), aortic body tumors (3.4%), and fibrosarcomas (3.4%).12 Mesothelioma is an uncommon malignant neoplasm in the dog affecting the parietal and visceral pericardium as well as the pleural and peritoneal mesothelial surfaces. The tumor may affect multiple body cavities leading to fluid accumulation within the pericardial, pleural, and peritoneal spaces. Mesothelioma can be difficult to diagnosis because of the similarity between neoplastic and reactive mesothelial cells seen on cytological evaluation of effusions. Mesothelioma should be included as a differential diagnosis when a thickened pericardium is seen on ultrasound evaluation. Surgical or thorascopic biopsy is necessary for definitive diagnosis.16-18 Mesothelioma has been reported, but is rare in the cat.19 Cardiac tumors disrupt the normal function of the tissues from which they arise leading to altered cardiovascular function. The physiological effects of a tumor are influenced by its size, location, and the presence of pericardial effusion. Small tumors without pericardial effusion can be clinically silent. Presenting complaints are often nonspecific including anorexia, lethargy, exercise intolerance, abdominal distension, weakness, collapse, dyspnea, and syncope. Clinical signs are usually secondary to concurrent pericardial effusion and tamponade and include: poor pulses, jugular venous distension, muffled heart and lung sounds, arrhythmias, hepatosplenomeagly, dyspnea, tachycardia, and ascites.3,4-8
Role of Echocardiography with Pericardial Effusion Echocardiography is the most sensitive noninvasive diagnostic test for the detection of pericardial effusion and intrapericardial neoplasia.9 Historically, more invasive diagnostic tests such as positive-contrast pericardiography, pneumopericardiography, and angiography were used to make the diagnosis. Recently cardiac troponins have been used to aid in the
Figure 1 (a) A four chamber long axis view as imaged from the right hemithorax. Note the right atrial mass and pericardial effusion (left picture). (b) A short axis view at the level of the papillary muscles as viewed from the right hemithorax. Note the pericardial effusion (right picture).
Therapeutic pericardiocentesis in the dog and cat
153 ization of the heart base and auricles leading to a better detection of cardiac masses.
Pericardial Effusion and Pericardiocentesis
Figure 2 An intraoperative view through the right hemithorax of the right heart and a right atrial hemangiosarcoma.
diagnosis of dogs with pericardial effusion, as dogs with pericardial effusion have a significantly higher concentration of cTnI than do normal dogs.20 Ultrasound permits the direct visualization and assessment of the tumor and its effect on cardiac function. Examination from both the left and right thorax should be performed providing the clinician with a more accurate localization of the tumor origin. The reader is referred to Thomas, Gaber, Jacobs, and co-workers21 for a detailed description of the recommended standard imaging views for small animal two dimensional echocardiography. The histologic classification of the tumor can often be suspected based on its location within the heart and/or pericardium. A mass arising from the right atrium or auricle in the dog is most likely a hemangiosarcoma (Fig. 1a, Fig. 2, and Fig. 3b).12,3 Whereas a mass located adjacent to the heart base between the aorta and pulmonary artery is most likely a chemodectoma.3 Echocardiography does not identify 100% of the intrapericardial tumors present. Four separate studies have shown a sensitivity of between 16.7 and 69% for the detection of cardiac masses.7,9,22,23 Serial echocardiographic exams may be necessary before a mass is identified in the heart. Pericardial effusion in many cases allows better visual-
Pericardial effusion is a common occurrence in animals secondary to cardiac neoplasia.3 Echocardiographically, pericardial effusion is seen as an anechoic or hypoechoic space between the epicardium and the pericardium (Fig. 1b). Pericardial effusion leads to a rise in the intrapericardial pressure resulting in varying degrees of hemodynamic compromise. Cardiac tamponade occurs when the intrapericardial pressure equals or exceeds right ventricular diastolic filling pressures leading to a decreased cardiac output. Clinical signs of right sided heart failure and cardiogenic shock ensue. The intrapericardial pressure depends on the volume of the effusion, the rate of the fluid accumulation and the physical characteristics of the pericardium. Small volumes of pericardial effusion that accumulate rapidly can cause large rises in intrapericardial pressure. Whereas, large volumes of pericardial effusion that accumulate slowly can result in only small rises in intrapericardial pressure and be of little hemodynamic significance.3 A reduction of pericardial compliance can be seen with either pericardial neoplasia or chronic pericardial inflammation. Collapse of the right atrium or ventricle may be noted during diastole on the echocardiogram suggesting cardiac tamponade (Fig. 3a). Pericardiocentesis is the recommended means to restore normal intrapericardial pressures and ventricular filling. Pericardiocentesis is used to stabilize animals with lifethreatening cardiac tamponade and obtain fluid samples for diagnostic evaluation. Sedation may be required in some patients to avoid unexpected and sudden movements as the needle is inserted. In those patients that are critically ill, local anesthesia of the intercostal muscles and parietal pleura may be adequate. Pericardiocentesis is performed from the right hemithorax with the dog in left lateral recumbency. The right sided approach is used to avoid laceration of the left extramural coronary artery and the presence of a larger cardiac notch in the right lung lobes. The cardiac notch is a small area
Figure 3 (a) A four chamber long axis view as imaged from the right hemithorax. Note the severe late diastolic/early systolic collapse of the right atrium (left picture). (b) Apical four chamber view as imaged from the left hemithorax. Note the large right atrial mass (right picture).
J. Gidlewski and J.-P. Petrie
154 where the lungs do not cover the heart, and the pericardium is located adjacent to the body wall.24 The right lateral thorax is shaved and surgically prepared between the second and eighth intercostal spaces. Echocardiography can be helpful in finding the most optimal intercostal space. If echocardiography is not available, beginning at the fourth or fifth intercostal space just dorsal to the costochondral junction is recommended. Several different catheter types may be used for the procedure. This author prefers the use of a 14- or 16-gauge central venous catheter in dogs (Fig. 4). The needle of the catheter is inserted through the skin into the thoracic cavity and is slowly advanced toward the pericardium. An initial flash of clear serosanguinous fluid may be seen in the catheter when pleural effusion is present. The needle should be advance until a flash of pericardial effusion is seen within the catheter. Pericardial fluid is generally hemorrhagic or “port wine” in color. The catheter should then be advanced over the needle into the pericardium. Once the catheter is positioned within the pericardium, the needle is removed from the thorax and placed in a needle guard. The stylet should be removed from the catheter (Fig. 5). A large 30 to 60 mL syringe and a three-way stop cock are then attached to the catheter and aspiration of the fluid is performed. The catheter position may need to be adjusted during the procedure to remove as much fluid as possible from the pericardial space. The fluid should be quantified and characterized. If the etiology of the effusion is not known, a sample of the fluid should be submitted for fluid analysis and cytology. Determining the pH of the pericardial fluid was previously suggested to help distinguish neoplastic from nonneoplastic effusions.25 However, Fine and co-workers demonstrated that determining the pH of the pericardial fluid was not reliably helpful in distinguishing neoplastic from nonneoplastic effusions.26 Serious complications associated with pericardiocentesis are rare. Complications include cardiac puncture, arrhythmias, and laceration of the tumor or coronary artery resulting in intrapericardial hemorrhage. Cardiac puncture occurs when the catheter is inadvertently advanced into the heart. This may not result in significant complications if the catheter is quickly withdrawn and repositioned. If there is any doubt as to whether or not the fluid being aspirated is from the pericardium, some fluid should be set aside and observed frequently for clot formation. Fluid from the pericardium
Figure 5 (A) Dog in left lateral recumbency, right hemithorax clipped and scrubbed. (B) Needle aseptically passed through the skin and right thoracic wall into the pericardium at the right fourth intercostal space, (C) Bloody fluid aspirated from the pericardium via central venous catheter.
should not clot unless it is from an ongoing or very recent hemorrhage. A sample of the fluid can also be collected, centrifuged, and examined for characteristics of pericardial effusion and packed cell volume should be calculated. The supernatant from pericardial effusion is very often xanthochromic and the PCV is often much lower than that of peripheral blood.3 Electrocardiographic monitoring should be performed while the pericardiocentesis is being performed. Contact of the catheter or needle with the heart can induce supraventricular or ventricular ectopy and may necessitate withdrawal of the catheter and/or antiarrhythmic therapy. In the cat, pericardiocentesis is typically performed using a 22-gauge 1 or 1.5 inch needle or butterfly catheter attached to a 12 mL syringe. The author prefers that pericardiocentesis in the cat is performed using echocardiographic guidance because of the small pericardial effusion volumes and low safety margin. Cats almost always require some level of sedation.
Conclusion When performed properly, pericardiocentesis is a safe and relatively easy procedure to relieve life-threatening pericardial tamponade associated with pericardial effusion. Echocardiography plays a significant role in the patient with cardiac neoplasia. This role continues to evolve as ultrasound technology advances providing a pivotal tool for the diagnosis, treatment, and prognostication of cardiac neoplasia and pericardial effusion.
References Figure 4 Instruments for pericardiocentesis, (a) bowl for fluid collection, (b) syringes and three way stop cock, (c) central venous catheter, (d) sterile gloves, and (e) surgical scrub.
1. Jones CL: Pericardial effusion in the dog. Compend Contin Educ Pract 680-686, 1979 2. Lombard CW: Pericardial disease. Vet Clin North Am 13:337-353, 1983 3. Fox PR, Sisson D, Moïse NS. Pericardial Disease and Cardiac Tumors,
Therapeutic pericardiocentesis in the dog and cat
4.
5. 6. 7.
8.
9. 10.
11. 12. 13. 14.
in Fox PR, Sisson D, Moise NS, (ed): Textbook of Canine and Feline Cardiology. Philadelphia, PA, Saunders, 1999, pp 679-701 Vicari ED, Brown DC, Holt DE, et al: Survival times of and prognostic indicators for dogs with heart base masses: 25 cases (1986-1999). J Am Vet Med Assoc 219:485-487, 2001 Southerland EM, Miller RT, Jones CL: Primary right atrial chondrosarcoma in a dog. J Am Vet Med Assoc 203:1697-1698, 1993 Willis R, Williams AE, Schwarz T, et al: Aortic body chemodectoma causing pulmonary oedema in a cat. J Small Anim Pract 42:20-23, 2001 Dunning D, Monnet E, Orton EC, et al: Analysis of prognostic indicators for dogs with pericardial effusion: 46 cases (1985-1996). J Am Vet Med Assoc 212:1276-1280, 1998 Holt D, Van Winkle T, Schelling C, et al: Correlation between thoracic radiographs and postmortem findings in dogs with hemangiosarcoma: 77 cases (1984-1989). J Am Vet Med Assoc 200:1535-1539, 1992 Berg RJ, Wingfield W: Pericardial effusion in the dog: A review of 42 cases. J Am Anim Hosp Assoc 20:721-724, 1984 Brisson BA, Holmberg DL: Use of pericardial patch graft reconstruction of the right atrium for treatment of hemangiosarcoma in a dog. J Am Vet Med Assoc 218:723-725, 2001 Ware WA. Cardiac Neoplasia, in Bonagura J (ed): Kirk’s Current Veterinary Therapy XII. Philadelphia, PA, Saunders, 1995, pp 873-876 Ware WA, Hopper DL: Cardiac tumors in dogs: 1982-1995. J Vet Intern Med 13:95-103, 1999 Girard C, Helie P, Odin M: Intrapericardial neoplasia in dogs. J Vet Diagn Invest 11:73-78, 1999 Walter JH, Rudolph R: Systemic, metastatic, eu- and heterotope tumours of the heart in necropsied dogs. Zentralbl Veterinarmed 43:3145, 1996
155 15. Rush JE, Keene BW, Fox PR: Pericardial disease in the cat: A retrospective evaluation of 66 cases. J Am Anim Hosp Assoc 26:39-46, 1990 16. McDonough S, MacLachlan NJ, Tobias AH: Canine pericardial mesothelioma. Vet Path 29:256-60, 1992 17. Morrison WB, Trigo FJ: Clinical characterization of pleural mesothelioma in seven dogs. Compend Contin Educ Pract Vet 6:342-348, 1984 18. Stepien RL, Whitley NT, Dubielzig RR: Idiopathic or mesotheliomarelated pericardial effusion: Clinical findings and survival in 17 dogs studied retrospectively. J Small Anim Pract 41:342-347, 2000 19. Tilley LP, Owens JM, Wilkins RJ, et al: Pericardial mesothelioma with effusion in a cat. J Am Anim Hosp Assoc 11:60-65, 1975 20. Shaw SP, Rozanski EA, Rush JE: Cardiac Troponins I and T in Dogs with Pericardial Effusion. J Vet Intern Med 18:322-324, 2004 21. Thomas WP, Gaber CE, Jacobs GJ, et al: Recommendations for standards in transthoracic two-dimensional echocardiography in the dog and cat. Echocardiography Committee of the Specialty of Cardiology, American College of Veterinary Internal Medicine. J Vet Intern Med 7:247-252, 1993 22. Fruchter AM, Miller CW, O’Grady MR: Echocardiographic results and clinical considerations in dogs with right atrial/auricular masses. Can Vet J 33:171-174, 1992 23. Kerstetter KK, Krahwinkel DJ, Millis DL: Pericardectomy in dogs: 22 cases (1978-1994). J Am Vet Med Assoc 211:736-740, 1997 24. Evans H (ed): Miller’s Anatomy of the Dog. Philadelphia, PA, Saunders, 1993 25. Edwards NJ: The diagnostic value of pericardial fluid pH determination. J Am Anim Hosp Assoc 32:63-67, 1996 26. Fine DM, Tobias AH, Jacob KA: Use of pericardial fluid pH to distinguish between idiopathic and neoplastic effusions. J Vet Intern Med 17:525-529, 2003
P
ericardiocentesis is a relatively simple procedure that rapidly relieves the symptoms of cardiac tamponade secondary to idiopathic pericardial effusion (IPE) or cardiac neoplasia.1,2 Ultrasonography is a safe, noninvasive, sensitive, and specific tool used to aid in the diagnosis, treatment, and prognostication in the patient with pericardial effusion. Improved technology is helping to hasten the diagnosis and treatment of pericardial effusion in domestic animals. With each new generation of ultrasound machines, the image quality improves and the relative cost decreases. It is imperative to bear in mind that ultrasound is meant to augment, but not replace, information obtained from the physical examination and thoracic radiography.
Clinical Signs and Diagnostic Tests Radiographic findings in the animal with pericardial effusion include a globoid cardiac silhouette, pleural effusion,
*Garden State Veterinary Specialists, Tinton Falls, NJ. †The Animal Medical Center, New York, NY. Address reprint requests to Josh Gidlewski, DVM, Dip ACVIM (Cardiology), Garden State Veterinary Specialists, One Pine St., Tinton Falls, NJ 07753. E-mail: [email protected]
1096-2867/05/$-see front matter © 2005 Elsevier Inc. All rights reserved. doi:10.1053/j.ctsap.2005.05.002
and enlargement of the caudal vena cava. Nodular or interstitial pulmonary parenchymal changes may also be seen with metastatic disease. In some cases, when a large amount of pericardial effusion is absent, there may be a regional enlargement of the cardiac silhouette associated with the presence of a tumor at the right atrium or heart base.3,4-8 Radiographic findings may be normal or only mildly abnormal in some cases with pericardial effusion. Acute hemorrhage leads to cardiac tamponade with relatively small accumulations of fluid; hence the importance of physical examination and ultrasound in these patients.9,10 The size of the cardiac silhouette depends on the chronicity of the disease; pericardial effusion which accumulates over a longer period of time generally produces a larger cardiac silhouette than pericardial effusion which accumulates rapidly. Dogs who develop pericardial effusion secondary to either endocardiosis or dilated cardiomyopathy may show generalized cardiomegaly that is not definitely identified as pericardial effusion.9 Electrocardiographic abnormalities are often present in dogs with pericardial effusion, the most common being sinus tachycardia and low voltage QRS complexes.3,9 Electrical alternans is an uncommon finding, but is highly specific for pericardial effusion.9 Various arrhythmias resulting from myocardial involvement of a tumor may also be seen.3 151
J. Gidlewski and J.-P. Petrie
152
Idiopathic Pericardial Effusion in Dogs Idiopathic pericardial effusion is an uncommon condition that usually affects males of large or giant breeds. Most cases have a history suggestive of chronic right-sided heart failure (ascites, lethargy, weight loss), although they may also develop acute cardiac tamponade. Muffled heart sounds are the most consistent physical abnormality; weak pulses are occasionally present. A diminished QRS complex on the electrocardiogram (ECG) is a common finding but electrical alternans is not.9 The reason for the effusion remains elusive in these patients despite even the most thorough diagnostic evaluations.
Cardiac and Pericardial Neoplasia In small animals, cardiac and pericardial neoplasia is relatively uncommon. Despite their low incidence, these tumors are important because of their potential effects on the cardiovascular system. Late diagnosis and invasiveness of these tumors make treatment difficult. Cardiac neoplasia comprised only 0.19% of all canine cases in The Veterinary Medical Database at Purdue University between 1982 and 1995.11,12 Other studies of two necropsy populations reported an incidence of intrapericardial tumors between 2.7 and 3.1%.13,14 In cats, cardiac neoplasia is rare accounting for only 0.03% of all the feline cases in the Veterinary Medical Database between 1982 and 1993.12 In dogs, hemangiosarcoma is the most commonly reported cardiac neoplasia with incidences ranging between 40.5 and 69%.11,13,14 Chemodectomas are the second most prevalent tumor with incidences between 5 and 17.3%.11,13,14 Lymphosarcoma and thyroid carcinoma are the next most common types of cardiac neoplasia identified. A small number of other histological tumor types account for 12 to 28% of intrapericardial tumors.11,13,14 In cats, the most common histologic diagnosis of cardiac neoplasia is lymphosarcoma.3,15 Some estimations report that lymphosarcoma comprises greater than 30% of all feline cardiac neoplasms.3 The tumor typically involves the myocar-
dium, but usually results in pericardial effusion. Lymphosarcoma often times can be diagnosed by cytological evaluation of the pericardial effusion obtained by pericardiocentesis. The remainder of the feline cardiac neoplasms reported are various carcinomas (19%), hemangiosarcoma (8.6%), aortic body tumors (3.4%), and fibrosarcomas (3.4%).12 Mesothelioma is an uncommon malignant neoplasm in the dog affecting the parietal and visceral pericardium as well as the pleural and peritoneal mesothelial surfaces. The tumor may affect multiple body cavities leading to fluid accumulation within the pericardial, pleural, and peritoneal spaces. Mesothelioma can be difficult to diagnosis because of the similarity between neoplastic and reactive mesothelial cells seen on cytological evaluation of effusions. Mesothelioma should be included as a differential diagnosis when a thickened pericardium is seen on ultrasound evaluation. Surgical or thorascopic biopsy is necessary for definitive diagnosis.16-18 Mesothelioma has been reported, but is rare in the cat.19 Cardiac tumors disrupt the normal function of the tissues from which they arise leading to altered cardiovascular function. The physiological effects of a tumor are influenced by its size, location, and the presence of pericardial effusion. Small tumors without pericardial effusion can be clinically silent. Presenting complaints are often nonspecific including anorexia, lethargy, exercise intolerance, abdominal distension, weakness, collapse, dyspnea, and syncope. Clinical signs are usually secondary to concurrent pericardial effusion and tamponade and include: poor pulses, jugular venous distension, muffled heart and lung sounds, arrhythmias, hepatosplenomeagly, dyspnea, tachycardia, and ascites.3,4-8
Role of Echocardiography with Pericardial Effusion Echocardiography is the most sensitive noninvasive diagnostic test for the detection of pericardial effusion and intrapericardial neoplasia.9 Historically, more invasive diagnostic tests such as positive-contrast pericardiography, pneumopericardiography, and angiography were used to make the diagnosis. Recently cardiac troponins have been used to aid in the
Figure 1 (a) A four chamber long axis view as imaged from the right hemithorax. Note the right atrial mass and pericardial effusion (left picture). (b) A short axis view at the level of the papillary muscles as viewed from the right hemithorax. Note the pericardial effusion (right picture).
Therapeutic pericardiocentesis in the dog and cat
153 ization of the heart base and auricles leading to a better detection of cardiac masses.
Pericardial Effusion and Pericardiocentesis
Figure 2 An intraoperative view through the right hemithorax of the right heart and a right atrial hemangiosarcoma.
diagnosis of dogs with pericardial effusion, as dogs with pericardial effusion have a significantly higher concentration of cTnI than do normal dogs.20 Ultrasound permits the direct visualization and assessment of the tumor and its effect on cardiac function. Examination from both the left and right thorax should be performed providing the clinician with a more accurate localization of the tumor origin. The reader is referred to Thomas, Gaber, Jacobs, and co-workers21 for a detailed description of the recommended standard imaging views for small animal two dimensional echocardiography. The histologic classification of the tumor can often be suspected based on its location within the heart and/or pericardium. A mass arising from the right atrium or auricle in the dog is most likely a hemangiosarcoma (Fig. 1a, Fig. 2, and Fig. 3b).12,3 Whereas a mass located adjacent to the heart base between the aorta and pulmonary artery is most likely a chemodectoma.3 Echocardiography does not identify 100% of the intrapericardial tumors present. Four separate studies have shown a sensitivity of between 16.7 and 69% for the detection of cardiac masses.7,9,22,23 Serial echocardiographic exams may be necessary before a mass is identified in the heart. Pericardial effusion in many cases allows better visual-
Pericardial effusion is a common occurrence in animals secondary to cardiac neoplasia.3 Echocardiographically, pericardial effusion is seen as an anechoic or hypoechoic space between the epicardium and the pericardium (Fig. 1b). Pericardial effusion leads to a rise in the intrapericardial pressure resulting in varying degrees of hemodynamic compromise. Cardiac tamponade occurs when the intrapericardial pressure equals or exceeds right ventricular diastolic filling pressures leading to a decreased cardiac output. Clinical signs of right sided heart failure and cardiogenic shock ensue. The intrapericardial pressure depends on the volume of the effusion, the rate of the fluid accumulation and the physical characteristics of the pericardium. Small volumes of pericardial effusion that accumulate rapidly can cause large rises in intrapericardial pressure. Whereas, large volumes of pericardial effusion that accumulate slowly can result in only small rises in intrapericardial pressure and be of little hemodynamic significance.3 A reduction of pericardial compliance can be seen with either pericardial neoplasia or chronic pericardial inflammation. Collapse of the right atrium or ventricle may be noted during diastole on the echocardiogram suggesting cardiac tamponade (Fig. 3a). Pericardiocentesis is the recommended means to restore normal intrapericardial pressures and ventricular filling. Pericardiocentesis is used to stabilize animals with lifethreatening cardiac tamponade and obtain fluid samples for diagnostic evaluation. Sedation may be required in some patients to avoid unexpected and sudden movements as the needle is inserted. In those patients that are critically ill, local anesthesia of the intercostal muscles and parietal pleura may be adequate. Pericardiocentesis is performed from the right hemithorax with the dog in left lateral recumbency. The right sided approach is used to avoid laceration of the left extramural coronary artery and the presence of a larger cardiac notch in the right lung lobes. The cardiac notch is a small area
Figure 3 (a) A four chamber long axis view as imaged from the right hemithorax. Note the severe late diastolic/early systolic collapse of the right atrium (left picture). (b) Apical four chamber view as imaged from the left hemithorax. Note the large right atrial mass (right picture).
J. Gidlewski and J.-P. Petrie
154 where the lungs do not cover the heart, and the pericardium is located adjacent to the body wall.24 The right lateral thorax is shaved and surgically prepared between the second and eighth intercostal spaces. Echocardiography can be helpful in finding the most optimal intercostal space. If echocardiography is not available, beginning at the fourth or fifth intercostal space just dorsal to the costochondral junction is recommended. Several different catheter types may be used for the procedure. This author prefers the use of a 14- or 16-gauge central venous catheter in dogs (Fig. 4). The needle of the catheter is inserted through the skin into the thoracic cavity and is slowly advanced toward the pericardium. An initial flash of clear serosanguinous fluid may be seen in the catheter when pleural effusion is present. The needle should be advance until a flash of pericardial effusion is seen within the catheter. Pericardial fluid is generally hemorrhagic or “port wine” in color. The catheter should then be advanced over the needle into the pericardium. Once the catheter is positioned within the pericardium, the needle is removed from the thorax and placed in a needle guard. The stylet should be removed from the catheter (Fig. 5). A large 30 to 60 mL syringe and a three-way stop cock are then attached to the catheter and aspiration of the fluid is performed. The catheter position may need to be adjusted during the procedure to remove as much fluid as possible from the pericardial space. The fluid should be quantified and characterized. If the etiology of the effusion is not known, a sample of the fluid should be submitted for fluid analysis and cytology. Determining the pH of the pericardial fluid was previously suggested to help distinguish neoplastic from nonneoplastic effusions.25 However, Fine and co-workers demonstrated that determining the pH of the pericardial fluid was not reliably helpful in distinguishing neoplastic from nonneoplastic effusions.26 Serious complications associated with pericardiocentesis are rare. Complications include cardiac puncture, arrhythmias, and laceration of the tumor or coronary artery resulting in intrapericardial hemorrhage. Cardiac puncture occurs when the catheter is inadvertently advanced into the heart. This may not result in significant complications if the catheter is quickly withdrawn and repositioned. If there is any doubt as to whether or not the fluid being aspirated is from the pericardium, some fluid should be set aside and observed frequently for clot formation. Fluid from the pericardium
Figure 5 (A) Dog in left lateral recumbency, right hemithorax clipped and scrubbed. (B) Needle aseptically passed through the skin and right thoracic wall into the pericardium at the right fourth intercostal space, (C) Bloody fluid aspirated from the pericardium via central venous catheter.
should not clot unless it is from an ongoing or very recent hemorrhage. A sample of the fluid can also be collected, centrifuged, and examined for characteristics of pericardial effusion and packed cell volume should be calculated. The supernatant from pericardial effusion is very often xanthochromic and the PCV is often much lower than that of peripheral blood.3 Electrocardiographic monitoring should be performed while the pericardiocentesis is being performed. Contact of the catheter or needle with the heart can induce supraventricular or ventricular ectopy and may necessitate withdrawal of the catheter and/or antiarrhythmic therapy. In the cat, pericardiocentesis is typically performed using a 22-gauge 1 or 1.5 inch needle or butterfly catheter attached to a 12 mL syringe. The author prefers that pericardiocentesis in the cat is performed using echocardiographic guidance because of the small pericardial effusion volumes and low safety margin. Cats almost always require some level of sedation.
Conclusion When performed properly, pericardiocentesis is a safe and relatively easy procedure to relieve life-threatening pericardial tamponade associated with pericardial effusion. Echocardiography plays a significant role in the patient with cardiac neoplasia. This role continues to evolve as ultrasound technology advances providing a pivotal tool for the diagnosis, treatment, and prognostication of cardiac neoplasia and pericardial effusion.
References Figure 4 Instruments for pericardiocentesis, (a) bowl for fluid collection, (b) syringes and three way stop cock, (c) central venous catheter, (d) sterile gloves, and (e) surgical scrub.
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