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
Clinical Features
- 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
Treatment
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
RIGHT ATRIAL HEMANGIOSARCOMA
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
N0
No evidence of regional lymph node involvement
N1
Bronchial lymph node involvement
Node
M0
No evidence of metastasis
M1
Metastasis in thoracic cavity
Metastasis
T3
Tumor invading adjacent structures
N2
Distant lymph node involvement
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