Cardiac tumors in dogs and cats

February 12, 2021
Liza S. Köster, BVSc(Hons), MMedVet(Med), DECVIM-CA (Cardiology and Internal Medicine), EBVS

Liza S Köster, BVSc(Hons), MMedVet(Med), DECVIM-CA, (Cardiology and Internal Medicine), EBVS, a 1999 graduate of the University of Pretoria (South Africa) Faculty of Medicine, is a clinical assistant professor of cardiology at the University of Tennessee College of Veterinary Medicine.

,
P. Brent Lawson, DVM

P. Brent Lawson, DVM, is a 2019 University of Tennessee College of Veterinary Medicine. After practicing for a year, he returned to the university for a rotating internship. He is currently completing his internship with hopes of pursuing a residency in cardiology.

,
Josep Aisa, DVM, DECVS

Josep Aisa, DVM, DECVS, a 1999 graduate from the University of Barcelona, is an assistant professor in small animal surgery (soft tissue) at the University of Tennessee College of Veterinary Medicine.

dvm360, dvm360 March 2021, Volume 53,

Considerations for the use of echocardiography to evaluate suspected tumors located in the heart.

Although rare in veterinary medicine, cardiac tumors can cause life-threatening complications, including pericardial effusion and tamponade, congestive heart failure, blood flow obstruction, and arrhythmias.1-5 However, because presenting clinical signs in patients with cardiac tumors are usually nonspecific, a low level of suspicion often hampers diagnosis.

Reports from owners may include hyporexia, lethargy, weakness, neurologic signs, vomiting, and abdominal distention. Except for abdominal distention and perhaps weakness, however, none of these signs are likely to prompt a clinician to image the heart.5-7 Triage of emergent patients by point-of-care focused cardiac ultrasound has revolutionized the ability to diagnose pericardial effusion in clinical practice, overcoming the deficiencies of low sensitivity and specificity reported with thoracic radiography.2,8,9

The leading cause of pericardial effusion in dogs is cardiac neoplasia. Over 70% of cases have either right atrial or heart-based masses, often concurrent with pleural effusion, ascites or, more commonly, tricavitary effusions.7 Pericardial effusion is reported in at least 16% of all dogs diagnosed with cardiac tumors on necropsy, whereas 42% of dogs with antemortem echocardiographic diagnosis, later confirmed by necropsy or cytology, have a concurrent pericardial effusion.5,7 Arrhythmias are reported in dogs associated with hemangiosarcoma and chemodectoma, with ventricular ectopy or tachycardia most frequently described. Other findings include electrical alternans in dogs with concurrent pericardial effusions and, rarely, supraventricular tachycardia, atrial fibrillation, and atrioventricular and bundle branch blocks.2-4

The role of echocardiography

Echocardiography is the screening test of choice in dogs with pericardial effusion. Similarly, dogs presenting with dysrhythmias require echocardiography as structural heart diseases, including infiltrative tumors, are considered possible etiologies. Echocardiography has its limitations, but because antemortem confirmation of a cardiac tumor is rarely obtained by cytology or biopsy, necropsy is often the only means of confirming the diagnosis. Echocardiography is considered moderately accurate, with 86% agreement on location and only 65% agreement on tissue-type diagnosis when compared with necropsy.5 Diagnostic accuracy vastly improves in the presence of pericardial effusion, with a reported sensitivity of 82% and specificity of 100% for detection of a cardiac mass.2

Echocardiography can provide information on the mobility, infiltrative nature, attachment to, and hemodynamic consequences of a cardiac mass.10 Despite the high specificity quoted, the differential diagnosis should include infectious vegetations and sterile thrombi. Due to the inherent risk for false-negative echocardiographic diagnoses, particularly in the absence of pericardial effusion, it is always prudent to keep cardiac neoplasia as a potential diagnosis despite apparent negative findings on echocardiography. Factors such as patient signalment and the high rate of pericardial effusion recurrence may increase the suspicion of a tumor. In mesothelioma, a solid mass may not be visible, and this neoplasia should remain a potential working diagnosis.11 It is worth noting that these results are operator dependent and reports are based on data collected from presumptive diagnoses made by board-certified cardiologists.

Tumor classification and echocardiographic phenotype

Cardiac tumors are either primary or secondary (metastatic) and benign or malignant.6,12 Clinical diagnosis in dogs is predominantly of primary and malignant tumors, with the most common etiologies being hemangiosarcoma followed by chemodectoma (also known as a neuroendocrine tumor, chromaffin cell tumor, aortic body tumor, and carotid body tumor). Cardiac metastatic disease may be more prevalent and silent than clinically seen, with up to 86% of cardiac tumors in dogs diagnosed as metastatic at the time of necropsy and 36% of malignant neoplasias metastasizing to the heart.6,7,13 In cats, cardiac tumors are almost exclusively primary and the majority are extranodal lymphomas.6,14,15 Excluding lymphomas, which tend to develop at an earlier age, cardiac tumors usually affect dogs ranging in age from 7 to 15 years.7 There is no reported gender predisposition, and the risk may be lower in intact animals.7 Breed consideration is important; breeds with reported high cardiac tumor incidence include the Saluki, French bulldog, Irish water spaniel, flat-coated retriever, golden retriever, boxer, Afghan hound, English setter, Scottish terrier, Boston terrier, bulldog, and German shepherd.7

Knowledge of the echocardiographic phenotypic appearance of cardiac tumors is helpful to the clinician, as it remains the undisputed antemortem diagnostic test of choice for this condition. This understanding will allow the clinician to provide appropriate treatment options and give an estimate of prognosis. As noted earlier, antemortem cytologic and histologic diagnosis is often not possible.

Treatment and prognosis

Tumors are often described according to anatomic location (Figure 1), including right atrium, heart base, inflow or outflow tract of the left or right heart chambers, atrioventricular valves, ventricular walls (including the interventricular septum), and pericardium. Tumor histologic prediction is invariably made by a combination of signalment, echocardiographic phenotype, and anatomic location within the heart. Treatment options and prognosis for the most common cardiac tumors seen in dogs and cats are described in the Table.12 (Figures 2 to 4) depict the typical echocardiographic appearance of the most common cardiac neoplasia encountered in small animal practice: hemangiosarcoma, aortic body tumor, and lymphoma.

Tumors are often described according to anatomic location (Figure 1), including right atrium, heart base, inflow or outflow tract of the left or right heart chambers, atrioventricular valves, ventricular walls (including the interventricular septum), and pericardium. Tumor histologic prediction is invariably made by a combination of signalment, echocardiographic phenotype, and anatomic location within the heart. Treatment options and prognosis for the most common cardiac tumors seen in dogs and cats are described in the Table.12 (Figures 2 to 4) depict the typical echocardiographic appearance of the most common cardiac neoplasia encountered in small animal practice: hemangiosarcoma, aortic body tumor, and lymphoma.

Conclusion

Although uncommon, cardiac tumors can have catastrophic consequences for dogs and cats. Knowledge of the sonographic appearance and location of cardiac tumors can help the clinician make a tentative diagnosis. Although invaluable when formulating appropriate management and treatment options, consider the limitations of echocardiography.

Liza S Köster, BVSc(Hons), MMedVet(Med), DECVIM-CA, (Cardiology and Internal Medicine), EBVS, a 1999 graduate of the University of Pretoria (South Africa) Faculty of Medicine, is a clinical assistant professor of cardiology at the University of Tennessee College of Veterinary Medicine.

P. Brent Lawson, DVM, is a 2019 University of Tennessee College of Veterinary Medicine. After practicing for a year, he returned to the university for a rotating internship. He is currently completing his internship with hopes of pursuing a residency in cardiology.

Josep Aisa, DVM, DECVS, a 1999 graduate from the University of Barcelona, is an assistant professor in small animal surgery (soft tissue) at the University of Tennessee College of Veterinary Medicine.

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