Pericardium
Sac that envelopes the heart, root of aorta and pulmonary artery, termination of vena cava, pulmonary veins, and azygous vein
Thin layer of fibrous tissue covered by pleura of the mediastinum
Visceral layer consists of mesothelium
Maintains the heart in normal anatomic position
Prevents cardiac over-distention
Acts as a barrier between pleural space and the heart
Usually filled with small amount of fluid (serum ultrafiltrate)
Non-compliant with small reserve volume
Pericardial Effusion
Categorized by clinical pathologic features:
Transudate:
Congestive heart failure
PPDH
Hypoalbuminemia
Increased vascular permeability
Exudate:
Infectious or non-infectious pericarditis
FIP
Feline cardiomyopathy
Fungal (Coccidioides)
Hemorrhage:
Trauma
Neoplasia
Rodenticide intoxication
Aneurysmal rupture
Idiopathic
Cardiac Tamponade
Pericardial pressure increases after 50–60 mL of fluid accumulates
Slower fluid accumulation allows pericardium to hypertrophy to some degree
Elevation of pericardial pressure increases diastolic pressure within the heart, reducing stroke volume
First equilibrates with right ventricular filling pressure, and the left ventricular filling pressure, significantly reducing cardiac output
Activation of renin-angiotensin-aldosterone system
Diagnosis
Clinical signs depend on rate of fluid accumulation and rise in intraperitoneal pressure
Acute pressure increases result in hypotension, weakness, dyspnea, collapse, and cardiogenic shock
Chronic effusion presents with exercise intolerance, lethargy, anorexia, dyspnea and weakness. Gradual onset of abdominal distention is reported.
Classic sign is muffled heart sounds, weak femoral pulses, and distended veins
Radiographs reveal a large, globoid shaped heart
ECG often reveals electrical alternans and decreased R wave amplitude
Echocardiography reveals a large accumulation of fluid within the pericardial sac
Treatment
Ultrasound guided or blind pericardiocentesis can alleviate the acute crisis
Sample submitted for cytologic exam and fluid analysis, C&S, etc.
Pericardectomy
Curative for idiopathic effusions (however, in my experience most idiopathic effusions are actually non-diagnosed neoplasia)
Palliative for others
Subtotal, partial, thorascopic pericardial window
Subtotal via median sternotomy
Able to remove most of pericardium
Complete has no advantage of sub-total
Partial via right lateral thoracotomy
Thorascopically guided pericardial window
Just as effective in palliation
Minimal invasive
Performed in dorsal recumbency
Selective intubation not necessary, but helpful
One port placed transdiaphragmatically (for scope)
2 additional ports placed in the 4th and 7th intercostal space on the right (for instruments)
Graspers and Metzenbaum scissors are utilized to remove a window (3 cm X 3 cm) of pericardium at the level of the ventricles
Constrictive Pericarditis
Nondistensible, thickened, fibrotic pericardium
Parietal pericardium usually more effected
Severe adhesions may be present
Effusive-constrictive pericarditis may occur
Pathophysiology
Affects late diastole
Limits ventricular filling in late diastole
Elevated pulmonary wedge pressure, right atrial pressure, left ventricular diastolic pressure
Diminished cardiac output
Fluid retention and signs of right heart failure
Diagnosis
Exercise intolerance, weakness, dyspnea, and collapse
Signs of right sided heart failure on PE
Globoid heart shape on radiographs
Echocardiography for DDx
Treatment
Subtotal or complete pericardectomy is treatment of choice
Good outcome if only pericardium affected
Decortication of affected epicardium necessary if affected
Laceration of coronary artery, PTE, arrhythmias can occur