Pericarditis, Constrictive

Introduction

The pericardium is a sac that surrounds the heart and serves to protect the heart, as well as maintain its position and shape. The pericardium is comprised of an outer fibrous layer and an inner serous layer. The fibrous outer layer is composed of collagen and elastin. The serous layer is composed of a single layer of mesothelial cells. The serous pericardium lines the inside of the fibrous layer, where it is known as the parietal layer, and also overlies the heart, where it is referred to as the visceral layer of the serous pericardium. The pericardial cavity is the space between the visceral and parietal layers, which usually contains a very small amount of fluid.

Constrictive pericarditis results from thickening and fibrosis of the parietal and/or visceral pericardium, which become very rigid. This prevents the heart from filling adequately in diastole. The pericardial layers may fuse, obliterating the pericardial space, or the pericardial space may contain a small volume of fluid (constrictive-effusive disease).

The rigid pericardium increases the ventricular interdependence. The decrease in left ventricle filling with inspiration causes increased right ventricle filling, causing the interventricular septum to shift to the left (paradoxical septal motion).

Diagnosis

History and Physical Examination

• Abdominal distension due to hepatosplenomegaly and ascites
• Pericardial knock may be detected on auscultation. This is the sound produced by the sudden deceleration of blood as it hits the non-distensible ventricular walls in early diastole.

Thoracic Radiographs

• May be unremarkable
• Cardiac silhouette may appear rounded
• Dilation of the caudal vena cava may be observed

Echocardiography

• Paradoxical septal motion
• Increased early diastolic filling (E-wave) velocity (Doppler)
• Short E-wave deceleration time, as early diastolic filling stops abruptly after left ventricular pressures are elevated
• Difficult to differentiate from restrictive cardiomyopathy (RCM)

Management

Surgical pericardiectomy is the treatment of choice.

Prognosis

Dependent on severity of disease. In cases with involvement of the visceral pericardium (epicardium), prognosis is poor even with surgical pericardiectomy.

References

Fossum, T. W. et. al. (2013) Small Animal Surgery (fourth edition), Elsevier Mosby

Luis Fuentes, V, Johnson, L.R, Dennis, S. (2010) BSAVA Manual of Canine and Feline Cardiorespiratory Medicine (second edition)