Case Studies In Small Animal

Cardiovascular Medicine

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Case 1

Case Discussion

This dog had clinical evidence of right heart failure at the time of presentation. His heart was normal in size on the thoracic radiographs and the echocardiogram. Dogs that have right heart failure due to intrinsic cardiac disease almost always have a severely enlarged right atrium and usually have a markedly enlarged right ventricle. This dog had neither. Consequently, it was surmised that he most likely had pericardial disease and that his intrapericardial pressure was most likely markedly increased causing his right heart failure. Instead of having a large amount of pericardial effusion like most dogs with pericardial disease that produces right heart failure, he had a small amount of pericardial effusion. Because of this, it was presumed that he a thickened and therefore very stiff pericardium that resulted in a marked increase in intrapericardial pressure with only a small amount of effusion. The right ventricular pressure waveform at cardiac catheterization was consistent with the diagnosis of constrictive pericarditis. With constrictive pericarditis, the right ventricle is able to fill normally during very early diastole but during filling it rapidly reaches a point where the pericardium restricts its ability to fill. When this occurs, pressure increases rapidly as volume within the ventricle increases. The demarcation between normal filling and abnormal filling is abrupt resulting in a sudden change from normal to abnormal filling. Once filling stops, the pressure plateaus resulting in the characteristic square root appearance to the diastolic pressure waveform.

The clinical diagnosis of constrictive pericarditis was confirmed by taking the dog to surgery. At surgery the pericardium was markedly thickened. A subtotal pericardiectomy was performed and the pericardium submitted for histopathologic examination.

Surgery and Pathology Specimens

Surgical Resection                                            Pathology Specimen - Pericardium

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The arrow on the surgical specimen indicates the apex of the thickened pericardium partially resected and lifted toward the site of the median sternotomy (the dog is on its back with its head at the bottom of the picture and the tail at the top). The partially resected pericardium is being flipped up off the heart, which sits below. The pathology specimen is the resected pericardium. On histopathology, the pericardium was markedly thickened by dense fibrous connective tissue. There were scattered inflammatory cells consisting of lymphocytes.

Follow-up

The dog went home three days later and was clinically normal as of 6 months following the surgery.

 

Mark D. Kittleson, D.V.M., Ph.D. All rights reserved.