The pericardium is the fibroelastic sac that covers the heart. Besides acting as a protective barrier, it also affects cardiac hemodynamics. Constrictive pericarditis is a condition in which granulation tissue formation in the pericardium results in loss of pericardial elasticity leading to restriction in the ventricular filling. It is usually a chronic condition however subacute, transient and occult variants have been described.
Worldwide, the leading cause of constrictive pericarditis is tuberculosis, and the incidence is about 50% of patients with tuberculous pericardial effusion despite antitubercular therapy. In developed nations, the leading cause of this condition is idiopathic or post-viral infection with incidence being 40% to 60% of total cases. It is also a known complication of any cardiac surgery and is a fairly common complication of mediastinal radiation therapy with an incidence ranging from 2% to 30% in patients treated with radiation. It has also been associated with connective tissue disorders such as rheumatoid arthritis and systemic lupus erythematosus (SLE). The diagnosis of constrictive pericarditis may be fairly simple however most of the time it is much more difficult to establish a cause. In many cases, a cause cannot be identified and is attributed to be an asymptomatic episode of viral pericarditis. 
Approximately 9% of patients with acute pericarditis develop constrictive physiology. In the developing world, infectious etiologies (tuberculosis) remain the most common cause. The condition is rare in adults and very rare children. It is more common in those who have undergone cardiac surgery. There is a 3:1 male predominance. There is no known racial predilection.
Pathophysiology of chronic constrictive pericarditis involves obliteration of pericardial cavity by granulation tissue during healing of an acute episode of fibrinous or serofibrinous pericarditis or resorption of chronic pericardial effusion. The granulation tissue gradually contracts over time and encases the heart and may get calcified. This rigid thickened pericardium limits the ventricular filling as the elastic limit of the diseased pericardium is much lesser than that of a normal pericardium. Ventricular filling in early diastole is not affected and is only impeded when the elastic limit of the pericardium is reached in contrast to cardiac tamponade where the ventricular filling is impeded throughout the diastole. This results in decreased end diastolic volume and decreased stroke volume and cardiac output. The thickened and scarred pericardium prevents the normal inspiratory decrease in intrathoracic pressure from being transferred to the heart chambers.
There are dissociation intrathoracic and intracardiac pressures. This leads to decreased venous return with inspiration as pulmonary venous pressure decreases. However, the left atrium pressure does not, and pulmonary veins to left atrial (LA) flow decreases on inspiration. This intrathoracic and intracardiac pressure dissociation is a distinguishing feature from cardiac tamponade as in cardiac tamponade the changes in intrathoracic pressure are still conducted to the heart and there is an increase in systemic venous return with inspiration.
In both disorders, there is equalization of the right atrial (RA), right ventricular (RV), left ventricular (LV), and pulmonary wedge pressure however cardiac tamponade the pressure decreases with inspiration whereas in constrictive pericarditis the RA pressure remains constant while the pulmonary wedge pressure decreases.
Patients will often present with chronic symptoms. Their symptoms may be related to volume overload like weight gain and swelling or may be related to decreased cardiac output like progressive fatigue and dyspnea on exertion. They may also complain of increasing abdominal girth or abdominal discomfort. Abdominal complaints are secondary to either ascites or congestive hepatomegaly.
On physical examination, the jugular venous pressure (JVP) is usually elevated, however, may be normal in early constrictive pericarditis. JVP does not decrease with inspiration, and this is known as Kussmaul's sign. Kussmaul's sign is also present in tricuspid valve disease, and right-sided heart failure.Pulsus paradoxus (more than 10 mm Hg drop in systolic blood pressure during inspiration) can be seen however this is more common in patients with cardiac tamponade. An accentuated heart sound heard earlier than third heart sound called pericardial knock can be heard in almost half of the patients. Abdominal examination may reveal ascites or hepatomegaly. Other signs of chronic illness like muscle wasting may be present based upon the etiology. Peripheral edema may be present as well.
The American College of Cardiology and the European Society of Cardiology guidelines recommend the use of echocardiography for diagnosis of constrictive pericarditis and any other pericardial disease. Two-dimensional echocardiography may show increased pericardial thickness without or without calcification. Two-dimensional echocardiography may also reveal dilatation of the inferior vena cava with the absence of inspiratory collapse. A sharp halt in diastolic filling may be seen along with the abrupt transient movement of intraventricular septum towards the right side which is also known as septal bounce.
The M mode is very important to rule out constrictive pericarditis. The following features are frequently seen in constrictive pericarditis and An absence these features on M mode makes the diagnosis of constrictive pericarditis very unlikely.
Doppler ECHO is used to evaluate hemodynamics of the disease and may reveal the following:
There are no specific signs of constrictive pericarditis on ECG which may reveal nonspecific ST changes and low voltage. Advanced and long-standing cases may show atrial fibrillation secondary to elevated atrial pressures.
CT scan and cardiac MRI are also frequently done especially before surgical management of constrictive pericarditis. These can reveal thickened pericardium and presence of calcifications. CT scans can detect calcifications better compared to cardiac MRI. Cardiac MRI is better to differentiate small effusions from pericardial thickening.
Myocardial fibrosis or atrophy seen on CT or MRI is associated with a poor surgical outcome.
Occasionally patients undergo right heart catheterization for hemodynamic studies which may reveal increased right atrial pressure, increased RV end-diastolic pressure, prominent x and y descent on venous and atrial pressure tracings and greater inspiratory fall in pulmonary capillary wedge pressure compared to the left ventricular diastolic pressure.
Pericardiectomy is the only definitive management of chronic constrictive pericarditis and effort should be made to remove as much of the pericardium as possible. Extensive penetration of the myocardium by fibrosis and calcification is associated with poor outcome. Operative mortality ranges from 55% to 10%. It should be considered very cautiously in patients with the mild disease with few symptoms or patients with advanced disease and other comorbidities due to the high mortality of the procedure. Diuretics can be used to reduce edema or elevated venous pressures before the surgery or for palliative control of symptoms in patients who are not surgical candidates.
A subset of patients may have a spontaneous resolution or may respond to medical management, and they are said to have transient constrictive pericarditis. Patients with newly diagnosed constrictive pericarditis who are hemodynamically stable and do not have stigmas of chronic constriction may be treated with anti-inflammatory agents for up to three months with close monitoring. If these patients develop signs of chronic constriction and hemodynamic instability they should undergo prompt surgical treatment.
In the US, constrictive pericarditis is not common, and long-term data are scarce. Anecdotal reports suggest that when the diagnosis is made early, the outcomes are good. But if the disorder is misdiagnosed or untreated, mortality rates in excess of 90% are common. For patients who undergo pericardiectomy, the 10-year survival is about 50%. Medical therapy alone leads to a poor life expectancy. The long-term survival after constrictive pericarditis depends on the cause. The worst outcomes are in patients with radiation-induced constrictive pericarditis and the best outcomes are seen in patients following open heart surgery. Negative prognostic factors include advanced age, renal malfunction, low ejection fraction and elevated pulmonary artery pressures. Most patients who are untreated quickly develop multiorgan dysfunction, hypoxia and metabolic acidosis. Patients should be promptly referred to a tertiary care center which specializes in the management of constrictive pericarditis when treatment is not available at the presenting hospital. (Level V)