Cardiac tamponade

Etiology

• In cattle the most common cause is penetration of the pericardium (and resulting infection) from reticular foreign body Traumatic reticulitis which has migrated cranially penetrating first the diaphragm then the pericardium.
• Hematogenous spread of infection (such as pasteurellosis, salmonellosis Salmonellosis etc).
• Cardiac neoplasia (lymposarcoma is the most common cardiac tumor in cattle), idiopathic inflammatory disease or trauma.

Pathophysiology

• Pericardial disease → gradual accumulation of pericardial fluid → impaired diastolic function (compliance failure) → decreased end-diastolic volumes → poor cardiac output → sympathetic nervous system and renin-angiotensin-aldosterone system activation → tachycardia, vasoconstriction, retention of sodium and water → increased end-diastolic pressures in atria → increased ventricular filling pressures → backward heart failure → right side more susceptible (thinner walled) → increased central venous pressure (distended jugular veins, hepatic venous congestion, ascites, pleural effusion).
• With acute pericardial effusion, compensatory mechanisms are unable to respond to the sudden decrease in cardiac output, resulting in precipitous output failure and collapse.
•  With chronic cases, effusive pericarditis involves fibrin deposition, this leads to a fibrinous pericarditis. Fibrosis of the pericardium can in turn lead to a restrictive pericarditis.

Timecourse

• Insidious subclinical course and progressive edema with chronic disease.
• Acute presentation: may result from hemorrhage (left atrial rupture, ruptured neoplasm, and trauma).