Constrictive pericarditis

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.

Causes

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:

• Infectious:
  • Tuberculosis
  • Incomplete drainage of purulent pericarditis
  • Fungal and parasitic infections
• Inflammatory and autoimmune
  • Chronic pericarditis
  • Postviral pericarditis
  • Postsurgical
  • Following pericarditis associated with acute myocardial infarction
  • Following post-myocardial infarction (Dressler's) syndrome
  • In association with pulmonary asbestosis
• Prior mediastinal radiation therapy
• Chronic renal failure
• Connective tissue disorders
• Neoplastic pericardial infiltration

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 is 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.

In constrictive pericarditis, imaging will demonstrate a thickened pericardium and you will see an increased early diastolic filling with reduced filling in mid-diastole. While with restrictive cardiomyopathy you have an increased resistance to ventricular filling due to increased myocardial stiffness. Imaging features of restrictive cardiomyopathy demonstrate an increased left ventricular thickness with infiltration of the myocardium.

CXR: - pericardial calcification (common but not specific), pleural effusions are common Echocardiography, CT and MRI are useful.

BNP Blood Test: (FDA approved in 2002) tests for the existence of the cardiac hormone B-Type Natriuretic Peptide which is only present in RCMP but not in CP, and is particularly helpful in determining the specific CHF type.

Clinical features:- Kussmaul's sign (raised JVP on inspiration); increased JVP (almost universal); rapid y descent (prominent diastolic collapse of JVP); pericardial knock in around 50% cases; hepatomegaly, may be pulsatile; ascites; fatigue; peripheral edema.

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,^[1] with mortality rates of 6% or higher in major referral centers.^[2][3] The high risk of the procedure is attributed to adherence of the thickened pericardium 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.

References