In physiology, constrictive pericarditis is due to a thickened, fibrotic pericardium, which prevents the heart from expanding during diastole (relaxation).

Etiology

In many cases, constrictive pericarditis is a late sequela of an inflammatory condition of the pericardium. The inflammatory condition is usually an infection that involves the pericardium, but it may be after a heart attack or after heart surgery.

Almost half the cases of constrictive pericarditis in the developing world are idiopathic in origin. In regions where tuberculosis is common, it is the cause in a large portion of cases.

Causes of constrictive pericarditis include:

• Idiopathic
• Post Viral Pericarditis
• Tuberculosis
• Postsurgical
• Prior Mediastinal Radiation Therapy
• Chronic Renal Failure
• Connective Tissue Disorders
• Neoplastic Pericardial Infiltration
• Incomplete Drainage of Purulent pericarditis
• Fungal and Parasitic Infections
• Following Pericarditis Associated with Acute Myocardial Infarction
• Following Postmyocardial Infarction (Dressler) Syndrome
• In Association with Pulmonary Asbestosis

Pathophysiology

Constrictive pericarditis is due to a thickened, fibrotic pericardium that forms a non-compliant shell around the heart. This shell prevents the heart from expanding when blood enters it. This results in significant respiratory variation in blood flow in the chambers of the heart.

During inspiration, the negative pressure in the thoracic cavity will cause increased blood flow into the right ventricle. This increased volume in the right ventricle will cause the interventricular septum to bulge towards the left ventricle, leading to decreased filling of the left ventricle. Due to the Frank-Starling law , this will cause decreased pressure generated by the left ventricle during systole.

During expiration, the amount of blood entering the right ventricle will decrease, allowing the interventricular septum to bulge towards the right ventricle, and increased filling of the left ventricle and subsequent increased pressure generated by the left ventricle during systole.

This is known as ventricular interdependence, since the amount of blood flow into one ventricle is dependent on the amount of blood flow into the other ventricle.

Diagnosis

The diagnosis of constrictive pericarditis often difficult to make. In particular, restrictive cardiomyopathy has many similar clinical features to constrictive pericarditis, and differentiating them in a particular individual is often a diagnostic dilemma.

Treatment

The definitive treatment for constrictive pericarditis is pericardial stripping, which is a surgical procedure where the entire pericardium is peeled away from the heart. This procedure has significant risk involved, since the thickened pericardium is often adherent to the myocardium and coronary arteries. In patients who have undergone coronary artery bypass surgery with pericardial sparing, there is danger of tearing a bypass graft while removing the pericardium.

If any pericardium is not removed, it is possible for bands of pericardium to cause localized constriction which may cause symptoms and signs consistent with constriction.

Due to the significant risks involved with pericardial stripping, many patients are treated medically, with judicious use of diuretics.