General Considerations

+ Chemoreceptor Cells

  • Chemoreceptor cells are sensitive to oxygen and carbon dioxide tensions in blood
  • Chemoreceptors cells are involved in the regulation of respiration and cardiac rate
  • Chemoreceptor cells are present in clusters:
  • Aortic root (= aortic body)
  • Carotid bifurcation (= carotid body)
  • Other (i.e., glomus pulmonale and glomus jugulare)

+ Aortic Body Chemodectoma

  • Synonym: non-chromaffin paraganglioma
  • Chemodectomas can arise from the aortic body at the base of the heart or carotid body in the neck
  • Aortic body chemodectoma is more common and accounts for 80% of all chemodectomas
  • Aortic body chemodectomas are the 2nd most common cardiac tumor and account for 5.0%-17.3% of tumors
  • Aortic body chemodectoma occur in several locations at the base of the heart:
  • Between aorta and pulmonary artery
  • Between aorta and right atrium
  • Between pulmonary artery and left atrium
  • Risk of chemodectoma is increased at high altitudes and chronic hypoxia
  • Chemodectoma is rare in cats
  • Chemodectoma is highly vascular and slow growing with moderate local invasiveness and low metastatic rate
  • Chemodectoma has a propensity for local invasion of lymphatic (43%) and vascular (46%) structures
  • Metastatic rate varies from 12%-43% with sites such as lungs (common), left atrium, pericardium, and kidney
  • Chemodectoma can be multiple and associated with other endocrine tumors

+ Carotid Body Chemodectoma

  • Carotid body tumors present as a cranial cervical mass
  • Carotid body tumors characterized by local invasion, neurovascular complications, and propensity to metastasize to multiple sites
  • Treatment: surgery or radiation therapy
  • 40% perioperative morbidity rate due to laryngeal paralysis and Horner's syndrome
  • Prognosis: MST 25.5 months

+ Clinical Features

  • Breed predisposition: Boxer, English Bulldog, and Boston Terrier
  • No sex predisposition, but neutered females have > 4-times risk of chemodectoma compared to intact females
  • Mean age 10.3 years
  • Clinical signs: ascites, weight loss, respiratory disease, inappetance, lethargy, and collapse
  • Dogs with ascites have pericardial effusion
  • Acute or chronic cardiac tamponade is the most common presentation due to intrapericardial hemorrhage:
  • Restricted ventricular filling secondary to external cardiac compression with muffled heart sounds
  • Venous congestion with abdominal effusion
  • Poor cardiac output with weak peripheral pulses
  • Arrhythmias
  • Aortic body tumors can also cause right-sided CHF secondary to obstruction of atria ± vena cava with clinical signs such as exercise intolerance, dyspnea, abdominal distension, arrhythmia, weak arterial pulses, abnormal heart sounds, coughing, vomiting, cyanosis, hydrothorax, ascites, peripheral edema, and hepatic and pulmonary congestion
  • Thoracic radiographs: enlarged cardiac silhouette, pulmonary edema, and pleural effusion
  • Echocardiography: pericardial effusion ± heart base mass
  • ECG: 33% dogs have electrical alterans
  • Aortic body masses are frequently an incidental finding during thoracic radiography or echocardiography


+ General Considerations

Surgical risk and slow growing behaviour of incidental and asymptomatic chemodectomas should be considered

+ Surgical Management

  • Surgical excision depends on size, location, and degree of invasiveness
  • Concurrent pericardiectomy is recommended if pericardial effusion is also present
  • Surgical approach depends on location
  • Tumor resection often involves sharp dissection from walls of the great vessels, atria, or both
  • Risk of inadvertent cardiac or great vessel rupture during dissection
  • Electrocautery is useful because of high vascularity
  • Pericardiectomy provides sustained palliation without increasing risk of death

+ Prognosis

  • Prolonged survival is possible with successful surgical resection
  • MST 42-129 days with medical management (i.e., diuretics ± chemotherapy)
  • MST 661-730 days following pericardiectomy
  • Mean survival time for dogs treated with pericardiectomy is significantly longer than medical management (661 days v 129 days)
  • MST for dogs treated with pericardiectomy is significantly longer than medical management (730 days v 42 days)