Pericarditis

Introduction

Pericarditis is common in cattle and uncommon in horses and small animals. It usually is caused by an infective agent, causing inflammatory fluid to gather in the pericardial sac. As with non-inflammatory accumulation of fluid in the pericardial sac, the main complication of the condition, as well as severe systemic infection, is the restriction of ventricular movement. Clinical signs seen are therefore those of circulatory failure along with pyrexia and a general depression.

Pericarditis. Courtesy of A. Jefferies

The spread of the infectious agent may be haematogenous, following generalised infection. This is most often seen in cattle and pigs. It can also occur as an extension of infection from surrounding tissues; for example from the lungs, pleura, mediastinum or rarely, extension of infection from myocardium. The most commonly cause of the condition in cattle is from traumatic penetration of the pericardium from foreign bodies from the oesophagus or reticulum; traumatic reticulo-peritonitis. Fractured ribs; e.g. RTAs in small animals and equine sport injuries can also cause the condition.

Pericarditis can be subdivided into two main categories; fibrinous pericarditis and suppurative pericarditis.

Fibrinous pericarditis

Fibrinous pericarditis. Courtesy of A. Jefferies

This is the most common form of pericarditis. Grey strands of fibrin cover the epicardium and a small amount of fluid only, will accumulate. Close apposition of the parietal and visceral pericardium layers allows adhesion formation within approximatley 7-10 days. Such adhesions may resolve with little residual pathology or may become focal or diffuse adhesive pericarditis lesions. Such little fluid accumulation will not compromise the funciton of the heart. This condition is most commonly caused by the haematogenous spread of organisms. Common bacteria include Pasturella species, Haemophilus species and Streptococcus species.

Fibrinous pericarditis produces a crackiling sound on auscultation.

Suppurative pericarditis

Traumatic pericarditis. Courtesy of A. Jefferies

Purulent pericarditis indicates the presence of pyogenic organisms e.g. Staphylococcal species. It is most commonly seen in cattle as a result of traumatic penetration of the pericardial sac with a sharp metallic object or wire. This is Traumatic reticulo-peritonitis → Traumatic Pericarditis. It is most commonly caused by the indiscriminate feeding of cattle. Objects become lodged in the rumen and are then forced into the reticulum and cranially into the diaphragm and pericardium, by ruminal contractions. They may also penetrate the liver. Large amount of purulent material, up to 4 litres, can accumulate in the pericardium, causing severe constriction of the ventricles.

Death usually occurs before organisation of the exudate can occur as a constrictive pericarditis and toxaemia become apparent in the early stages of the conditon.

Traumatic pericarditis. Courtesy of A. Jefferies

Traumatic pericarditis. Courtesy of A. Jefferies

Clinical Signs

Signs include signs of right sided heart failure such as jugular pulses, ascites and hepatomegaly. The physcial examination will reveal muffled heart sounds and variable pulse quality. In cases of 'wire' the cow may elicit a pain response upon pressure being exerted in between the front limbs. If the pericarditis is of an infectious cause, then pyrexia will also be observed.

Diagnosis

Clinical signs, animal specie and history are very suggestive of the condition. This is usually diagnostic in cattle. In small animals or horses, echocardiography is usually performed, along with pericardiocentesis for a definitive diagnosis.

Treatment and Control

Drainage of the pericardium can be attempted and systemic antibiotics can be administered for cases of suppurative disease. Where economoically viable, the wire can be removed from the cow by ruminal surgery, where the veterinarian will perform a rumenotomy and then reach into the reticulum and manually remove the wire. Most farmers will tend to prefer the option of slaughtering the animal on welfare grounds.

Prognosis

The condition can resolve without any further clinical significance. As described above, death is a common outcome in the suppurative form of the disease. Adhesions may occur, due to organisation of fibrin, leading to a 'bread and butter' appearance. As the condition worsens, if not treated, gradual constriction may occur, causing cardiac tamponade.

Test yourself with the Paericardial Pathology Flashcards

Pericardial Pathology Flashcards