+ General Considerations

  • Right atrium is a primary site for HSA and accounts for 30%-50% canine HSA
  • HSA is the most common cardiac tumor in dogs and accounts for 40.4%-60.5% of cardiac tumors
  • HSA has also been reported in the right ventricular free wall, interventricular septum, and main pulmonary artery
  • Primary cardiac HSA has not been reported in cats, but the heart is a common site for metastatic HSA


  • Breed predisposition: GSD, Poodle, Golden Retriever, English Setter, and Scottish Terrier
  • No sex predisposition but neutered females have > 5-times risk of cardiac HSA compared to intact females
  • 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
  • Cardiac tumors may present for reasons other than cardiac tamponade such as CHF, arrhythmia or low cardiac output secondary to obstruction of proximal great vessels
  • Thoracic radiographs: enlarged cardiac silhouette, pulmonary edema, and pleural effusion
  • Echocardiography: pericardial effusion ± right atrial mass
  • Pericardiocentesis is both diagnostic and therapeutic
  • Cytologic analysis of pericardial fluid for the diagnosis of malignant effusions is usually unrewarding
  • pH > 7.5 is consistent with neoplasia and pH < 7.5 is consistent with idiopathic pericardial effusion
  • However, others show no difference in pH between idiopathic and neoplastic effusions
  • Serum cardiac troponin I concentrations, which is a marker for myocardial ischemia and necrosis, are significantly higher in dogs with pericardial effusions and significantly higher in dogs with right atrial HSA compared to dogs with idiopathic pericardial effusions

+ Clinical Staging

  • Metastatic rate approaches 100%
  • Lungs are the most common metastatic site (64%-67%), followed by spleen (36%-60%), kidneys (55%), liver (41%-55%), brain (20%), intestines (20%), adrenal glands (20%), skeletal muscle (20%), visceral lymph nodes (15%), skin and subcutaneous tissue (15%), left ventricle (10%), and mesentery and omentum (10%)
  • Metastasis to other parts of the heart (i.e., ventricles, left auricle, and pericardium) occur in 43% dogs


+ Pericardiocentesis

  • Pericardiocentesis is both diagnostic and therapeutic
  • Pericardiocentesis alleviates cardiac tamponade and provides immediate relief of clinical signs

+ Pericardiectomy

  • Pericardiectomy is a palliative procedure
  • Surgical techniques include:
  • Pericardial window via thoracoscopic surgery or left 4th intercostal thoracotomy
  • Subtotal pericardiectomy via left 4th intercostal thoracotomy

+ Right Atrial Appendage Resection

  • Indications: HSA of right atrial appendage or atrial free wall
  • Approach: median sternotomy or right 5th intercostal thoracostomy
  • Atrial appendage is clamped with vascular forceps and appendage excised
  • Atriotomy is closed with a continuous mattress suture pattern oversewn with a simple continuous pattern
  • Complications: atrial and ventricular arrhythmia, anemia, DIC, and pneumonia

+ Right Atrial Patch Graft Reconstruction

  • Pericardial patch graft can be used for reconstruction of atrial wall defects following resection of large atrial lesions to achieve tumor-free margins

+ Chemotherapy

  • Doxorubicin-based protocols significantly improve MST (175 days v 42 days)

+ Prognosis

  • Prognosis is better for older dogs and dogs with stage I disease
  • Prognosis is poor with MST 16 days following pericardiectomy and 4 months following right atrial appendage resection
  • Prognosis is significantly improved when surgery (pericardiectomy) is combined with adjunctive doxorubicin-based chemotherapy protocols, with a MST of 175 days compared to 42 days without chemotherapy


T0 No evidence of neoplasia
T1 Tumor confined within the medulla and cortex - Primary Tumor
T2 Tumor extends beyond the periosteum
M0 No evidence of lymph node involvement
M1 Evidence of distant metastasis with site specified - Metastasis
T0 No evidence of neoplasia - Primary Tumor
T1 Tumor confined to primary site
T2 Tumor confined to primary site, but ruptured
T3 Tumor invading adjacent structures
N0 No evidence of lymph node involvement
N1 Bronchial lymph node involvement - Node
N2 Distant lymph node involvement
M0 No evidence of metastasis
M1 Metastasis in thoracic cavity - Metastasis
M2 Distant metastasis with site specified

Clinical Stage

I II III T T1 T1-2 T2-3 N N0 N0-1 N1-2 M M0 M1 M2