Constructive Pericarditis

Definition and Etiology

• Constrictive pericarditis is a rare, chronic condition resulting from recurrent or prolonged pericardial inflammation that leads to progressive fibrosis, thickening, and frequently calcification of the pericardium.
• This fibrotic process encases the heart, creating a stiff, noncompliant sac that restricts the normal diastolic expansion and filling of all cardiac chambers equally.
• The etiology of constrictive pericarditis is diverse, and the order of frequency varies significantly based on geographic and historical contexts.
• In developed nations, idiopathic causes account for nearly half of all cases, followed closely by iatrogenic causes such as prior cardiac surgery and radiation therapy applied to the mediastinum for malignancies like Hodgkin disease or lymphoma.
• Post-infectious causes include pyogenic bacterial infections (purulent pericarditis caused by Staphylococcus aureus, Haemophilus influenzae, and pneumococcus) and viral pathogens.
• Tuberculous pericarditis remains a leading cause of pericardial constriction worldwide, particularly in developing nations, despite becoming exceedingly rare in developed countries.
• Other recognized etiologies include autoimmune and connective tissue disorders (e.g., systemic lupus erythematosus, rheumatoid arthritis), neoplastic infiltration, metabolic conditions like uremia, and drug-induced lupus or reactions to chemotherapeutic agents.
• A significant minority of patients (nearly 20%) may experience "transient constriction," where the constrictive physiology resolves spontaneously or following a period of adequate anti-inflammatory therapy.

Pathophysiology and Hemodynamics

• The central pathophysiologic defect is the loss of pericardial compliance, which profoundly impairs the diastolic filling of the heart, leading to elevated and equalized filling pressures across all four cardiac chambers.
• Due to the rigid pericardial shell, the total cardiac volume becomes fixed; consequently, any increase in the volume of one ventricle mandates a reciprocal decrease in the volume of the other ventricle, a phenomenon known as enhanced ventricular interdependence.
• In a normal heart, the inspiratory drop in intrathoracic pressure is transmitted to the intracardiac chambers; however, the thickened pericardium acts as a shield, preventing this transmission.
• During inspiration, the pulmonary venous pressure drops in tandem with intrathoracic pressure, but the left atrial pressure does not decrease proportionately due to the pericardial shielding.
• This reduced pressure gradient between the pulmonary veins and the left atrium transiently diminishes left-sided venous return and left ventricular stroke volume.
• Simultaneously, the intact transmission of negative intrathoracic pressure to the intra-abdominal systemic veins augments venous return to the right heart.
• To accommodate this increased right-sided volume within a fixed total pericardial space, the interventricular septum bulges dramatically toward the left ventricle during inspiration, further compromising left ventricular filling.
• During expiration, these hemodynamics are entirely reversed: left-sided filling increases, the septum shifts back toward the right ventricle, and right-sided filling is impaired.
• Over time, this unrelenting restriction limits stroke volume and cardiac output, forcing the heart to rely entirely on compensatory tachycardia to maintain systemic perfusion.
• In a subset of patients, an active pericardial effusion may coexist with a noncompliant visceral pericardium, resulting in "effusive-constrictive pericarditis," which classically manifests when elevated right atrial pressures persist even after the pericardial effusion has been drained via pericardiocentesis.

Clinical Manifestations

• The clinical presentation of constrictive pericarditis in children closely mirrors that seen in adults, typically manifesting with a subacute or chronic course predominated by signs of severe systemic venous hypertension and right-sided heart failure.
• Progressive right-sided failure manifests as profound jugular venous distention, massive hepatomegaly, pulsatile liver, peripheral edema, and the development of ascites, which may be accompanied by unilateral or bilateral pleural effusions.
• Left-sided filling impairment results in a fixed, reduced cardiac output, leading to exertional dyspnea, progressive fatigue, exercise intolerance, and, in severe or advanced cases, cardiac cachexia.
• Other associated, albeit non-specific, symptoms may include chest pain, palpitations, and vague abdominal discomfort secondary to hepatic congestion.
• Kussmaul’s sign—a paradoxical rise or failure to fall of the jugular venous pressure during inspiration—is frequently observed, reflecting the rigid right heart's inability to accommodate the augmented inspiratory venous return.
• Pulsus paradoxus, defined as an abnormally large drop in systolic blood pressure (>10 mm Hg) during inspiration, may be present due to the exaggerated ventricular interdependence, though it is more classically a hallmark of cardiac tamponade.

Diagnostic Investigations

Auscultation

• The precordium is generally quiet, and the apical impulse may be poorly palpable.
• The first and second heart sounds typically maintain normal intensity.
• The hallmark auscultatory finding is a "pericardial knock," which is an early, high-pitched third heart sound occurring shortly after the second heart sound.
• This sound is generated by the sudden, abrupt deceleration of rapid early diastolic ventricular filling as the expanding myocardium violently impacts the rigid, unyielding pericardial shell.
• Distant or muffled heart sounds may be present, particularly if there is a coexisting pericardial effusion.

Electrocardiogram (ECG)

• The ECG typically shows low voltage QRS complexes across all leads and non-specific ST-segment and T-wave abnormalities.
• Left atrial or biatrial enlargement patterns (broad, notched P waves) may be observed.
• Arrhythmias, particularly atrial fibrillation and atrial flutter, are common due to the chronic elevation of atrial pressures and subsequent atrial dilation.
• Evidence of right axis deviation or a right ventricular hypertrophy pattern is occasionally present.

Chest Radiograph (CXR)

• The overall cardiac silhouette is usually normal in size, or occasionally mildly enlarged, contrasting sharply with the massive cardiomegaly seen in large pericardial effusions.
• The cardiac borders may appear ragged or shaggy, and a prominent superior vena cava shadow is frequently noted merging with the right atrial margin.
• The pathognomonic finding, present in roughly 25% to 50% of cases, is prominent calcification of the pericardium, which is optimally visualized on the lateral projection extending over the anterior and diaphragmatic surfaces of the right ventricle.
• Bilateral or unilateral pleural effusions and signs of interstitial pulmonary edema may be evident.

Echocardiography and Advanced Imaging

Cardiac Catheterization

• Invasive hemodynamic evaluation is the gold standard for confirming constrictive physiology, demonstrating simultaneous elevation and complete equalization (within 5 mm Hg) of the right atrial, right ventricular end-diastolic, pulmonary artery diastolic, and pulmonary capillary wedge pressures.
• The right ventricular pressure tracing classically demonstrates the "dip-and-plateau" or "square root" sign, characterized by an early, rapid diastolic dip followed by a sudden plateau as ventricular filling is abruptly halted.
• Right ventricular end-diastolic pressure is characteristically elevated to more than one-third of the peak right ventricular systolic pressure.
• The right atrial pressure tracing displays a steep 'y' descent and prominent 'a' and 'v' waves resulting in an "M" or "W" configuration.
• Simultaneous biventricular pressure recording confirms exaggerated ventricular interdependence, quantified by a right-to-left ventricle systolic area index ratio greater than 1.1.

Differential Diagnosis

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Management

Medical Management

• Medical therapy plays a limited, predominantly supportive role in the management of classic, chronic constrictive pericarditis.
• Cautious administration of loop diuretics (e.g., furosemide) is utilized to alleviate the symptoms of systemic venous congestion, ascites, and peripheral edema, but must be titrated carefully to avoid dropping the preload so severely that cardiac output collapses.
• For patients demonstrating features of "transient constriction" or evidence of active, ongoing pericardial inflammation on CMR (i.e., prominent T2 edema and late gadolinium enhancement), a vigorous empiric trial of anti-inflammatory therapy is indicated.
• This medical regimen typically involves a combination of non-steroidal anti-inflammatory drugs (NSAIDs), colchicine, and occasionally corticosteroids, administered for 2 to 3 months to facilitate potential spontaneous resolution of the constrictive physiology.
• If tuberculosis is established or highly suspected as the underlying etiology, a full, prolonged course of multidrug anti-tuberculous chemotherapy is mandatory. The adjunctive use of corticosteroids in tuberculous pericarditis remains controversial but is frequently employed to mitigate the fibrotic response.

Surgical Management

• Radical surgical pericardiectomy (decortication of the heart) is the definitive and only effective, curative treatment for chronic, medically refractory constrictive pericarditis.
• Surgical intervention is unequivocally indicated for patients with severe symptoms of heart failure (NYHA Class III or IV), cachexia, or progressive hepatic and renal dysfunction secondary to venous congestion.
• A median sternotomy is the preferred surgical approach, as it provides maximal, extensive access to the entire pericardium and facilitates the institution of cardiopulmonary bypass, which is frequently required for complete resection.
• The goal is extensive "complete" or "anterior" resection, extending phrenic nerve to phrenic nerve and including the diaphragmatic surfaces, to fully liberate both ventricles and the great vessels.
• The procedure carries significant operative morbidity and mortality, heavily influenced by the degree of myocardial atrophy, the depth of fibrotic infiltration into the underlying myocardium, and the pre-operative status of the patient's liver and kidney function.
• Following successful decortication, hemodynamic abnormalities may normalize immediately, though some patients experience a delayed recovery of ventricular compliance and function due to prolonged myocardial constriction and secondary disuse atrophy.