Acute Pericarditis

Acute Pericarditis: Comprehensive Academic Review

Introduction

Acute pericarditis is defined as an inflammatory condition affecting the pericardium, the specialized fibroserous sac that encapsulates the heart. The pericardial function is critical in cardiac mechanics and protection, primarily involving:

Myocardial defense against infection and trauma.
Constraint of excessive diastolic cardiac chamber distension.
Maintaining the stable anatomical positioning of the heart within the mediastinum.

Pericardial inflammation is a non-specific response that can be triggered by systemic disorders, infections, or localized injury, resulting in a characteristic clinical syndrome often accompanied by pathognomonic electrocardiographic changes.

Pathophysiology

The pericardium is composed of two main structural layers:

Fibrous Pericardium: The dense, inelastic outer layer that anchors the heart to surrounding structures and limits abrupt, excessive cardiac dilatation.
Serous Pericardium: The internal, delicate layer, which is subdivided into the parietal layer (lining the fibrous sac) and the visceral layer (the epicardium, which is adherent to the myocardium).

The potential space between the parietal and visceral layers, the pericardial cavity, physiologically contains 15 to 50 mL of clear serous fluid (ultrafiltrate) to ensure near-frictionless cardiac movement.

Inflammatory Response and Effusion

Acute pericardial inflammation is histologically characterized by the infiltration of the pericardial membranes with inflammatory cells, including neutrophils, lymphocytes, and macrophages. This cellular reaction is accompanied by the increased permeability of the visceral and parietal membranes, leading to the exudation of protein-rich fluid into the pericardial space. The resultant effusion's fluid properties can vary significantly—it may be serous, fibrinous, purulent, or hemorrhagic—depending on the underlying etiology.

Hemodynamic Sequelae

The rate and volume of fluid accumulation determine the hemodynamic consequences. A rapid or substantial increase in pericardial fluid volume elevates intrapericardial pressure, which directly impairs ventricular diastolic filling. This physiological state, known as cardiac tamponade, severely compromises cardiac output. Conversely, chronic or recurrent inflammatory insults may result in persistent changes, including pericardial thickening, fibrosis, and the formation of constrictive adhesions. These changes compromise normal pericardial compliance, leading to the restrictive hemodynamics characteristic of constrictive pericarditis.

Etiologies

The causes of acute pericarditis are heterogeneous, spanning a broad spectrum of infectious, immunological, metabolic, malignant, and iatrogenic origins.

1. Infectious Causes

Viral (Predominant Etiology): Viral pathogens are the leading cause globally. Coxsackievirus (Group B), echovirus, influenza virus, and adenovirus are the most frequently isolated agents. Clinical presentation commonly follows a mild, non-specific viral prodrome (fever, myalgia, malaise) culminating in pleuritic chest pain.

Specific Pathogens:

Tuberculosis (TB): Remains a critical and prevalent cause in endemic regions.
Bacterial: Infrequent, typically resulting from hematogenous spread or postoperative infection. Rare agents include Staphylococcus aureus, Streptococcus pneumoniae, and Neisseria meningitidis.
Fungal: Opportunistic fungi such as Histoplasma capsulatum or Coccidioides immitis may be implicated, particularly in immunocompromised hosts.

2. Autoimmune and Inflammatory Causes

Systemic inflammatory disorders frequently involve the pericardium, often as a component of generalized serositis. Recognized examples include Systemic Lupus Erythematosus (SLE), Rheumatoid Arthritis (RA), and Systemic Sclerosis.

3. Metabolic Causes

Uremic Pericarditis: This form occurs exclusively in patients with acute or chronic renal failure. It is primarily attributed to the retention of metabolic toxins. The onset is variable, though some patients develop pericarditis when the serum blood urea nitrogen (BUN) concentration exceeds approximately 60 mg/dL.

4. Myocardial Injury-Related Syndromes

Peri-infarction Pericarditis: Localized epicardial inflammation directly contiguous with the infarcted myocardium, generally occurring within the first four days post-acute myocardial infarction (AMI). Early reperfusion therapy has reduced its incidence.
Post-Cardiac Injury Syndrome (PCIS): An immune-mediated inflammatory process that develops weeks to months following myocardial or pericardial trauma, such as cardiac surgery, trauma, or percutaneous intervention. When precipitated by AMI, it is historically referred to as Dressler's Syndrome.

5. Neoplastic and Iatrogenic Causes

Malignant Pericarditis: Most often secondary to metastatic disease originating from primary lung, breast, or lymphatic cancers. Tumor invasion or lymphatic obstruction leads to effusion, which is often hemorrhagic.
Iatrogenic/Radiation: Pericardial inflammation can be a sequela of thoracic radiation therapy (presenting acutely or as a late fibrotic process), cardiac surgery, or procedural trauma.

6. Idiopathic Pericarditis

A substantial number of cases remain without a definitively identified etiology despite comprehensive evaluation. These are labeled as idiopathic and are generally presumed to represent unrecognized or subclinical viral processes.

Clinical Presentation

The classical clinical picture of acute pericarditis is distinctive and results primarily from inflammation of the pericardial layers. The cardinal manifestations include chest pain, pericardial friction rub, and electrocardiographic changes. Fever and pericardial effusion are frequent but variable findings.

1. Chest Pain

Chest pain is the hallmark symptom, reported in more than 95% of patients. The pain is typically sharp, pleuritic, and retrosternal, often radiating to the neck, shoulders, or back. It characteristically intensifies with deep inspiration, coughing, or swallowing and is alleviated by sitting up and leaning forward, while worsening in the supine position. This positional quality is highly suggestive of pericarditis and aids in distinguishing it from ischemic cardiac pain, which is usually pressure-like and unrelated to posture or respiration.

2. Fever

Low-grade fever commonly accompanies acute pericarditis and reflects systemic inflammation or an underlying infectious etiology. High-grade fever, rigors, or systemic toxicity should raise suspicion for bacterial or tuberculous causes.

3. Pericardial Friction Rub

A pericardial friction rub is the most specific physical finding. It is a superficial, high-pitched, scratchy, or squeaking sound produced by friction between the inflamed pericardial layers. The rub is best heard along the left lower sternal border with the patient leaning forward at end-expiration.

It may have up to three components corresponding to atrial systole, ventricular systole, and early ventricular diastole. Because the rub may be transient, repeated auscultation is often necessary.

4. Pericardial Effusion

A variable amount of pericardial effusion is present in most cases. Small effusions may be asymptomatic, whereas large or rapidly accumulating collections can restrict diastolic filling, leading to cardiac tamponade. Clinical evidence of tamponade includes hypotension, tachycardia, elevated jugular venous pressure, and pulsus paradoxus. Other nonspecific findings may include dyspnea (from decreased cardiac output or pain-related splinting), dysphagia (due to esophageal compression), or hiccups (from diaphragmatic irritation).

Diagnosis

The diagnosis of acute pericarditis is established by integrating clinical, electrocardiographic, imaging, and laboratory findings. In most patients, diagnosis can be made on clinical grounds without invasive procedures.

1. Clinical Evaluation

A detailed history and physical examination remain the cornerstone. Key features include:

Sharp, pleuritic, and positional chest pain.
Pericardial friction rub on auscultation.
Absence of features typical of myocardial ischemia.
Associated symptoms of viral illness or autoimmune disease should be actively sought.

2. Electrocardiography (ECG)

ECG changes in acute pericarditis are characteristic and occur in up to 90% of cases. Typical features include:

Diffuse ST-segment elevation with an upward concave morphology (“smiling” ST elevation) not confined to a coronary artery territory.
PR-segment depression, reflecting atrial epicardial inflammation.
ST/T-wave ratio >0.25 in lead V6 favors pericarditis over early repolarization.

These findings usually evolve through four stages:

Diffuse ST elevation with PR depression (acute stage).
Normalization of ST segments (within days).
T-wave inversion (after resolution of ST changes).
Return to baseline ECG.

Uremic pericarditis may not exhibit these ECG findings, as inflammation is limited to the pericardium without significant myocardial involvement.

3. Chest Radiography

Chest X-ray findings are generally normal in uncomplicated cases. However, cardiomegaly may be observed if there is a large pericardial effusion. The cardiac silhouette may appear globular or flask-shaped. Pulmonary findings may indicate alternative or associated pathology (e.g., pneumonia, tuberculosis).

4. Echocardiography (TTE)

Transthoracic echocardiography (TTE) is an essential noninvasive tool for evaluating pericardial effusion and hemodynamic consequences. Echocardiography should be performed in all suspected cases of pericarditis to exclude tamponade and guide management.

Findings include:

Presence and size of effusion.
Right atrial or right ventricular diastolic collapse indicating tamponade physiology.
Exaggerated respiratory variation in transvalvular Doppler inflow velocities.

5. Laboratory Investigations

Inflammatory markers: Elevated C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) are common and useful for monitoring disease activity.
Complete blood count: Leukocytosis may indicate infection; eosinophilia may suggest hypersensitivity or parasitic etiology.
Cardiac biomarkers: Mild troponin elevation may occur due to epicardial inflammation (myopericarditis) but should not follow a typical infarction pattern.
Renal function tests: Elevated BUN and creatinine support uremic pericarditis.

6. Pericardial Fluid Analysis

Pericardiocentesis with fluid analysis is indicated when:

Tamponade is suspected,
The effusion is large or rapidly increasing, or
There is concern for bacterial, tuberculous, or malignant disease.

Investigations performed on aspirated fluid include:

Cytology (to detect malignant cells),
Gram stain and bacterial culture,
Acid-fast bacilli staining and mycobacterial culture, and
Polymerase chain reaction (PCR) for specific pathogens.

Routine biochemical analysis (protein, LDH, glucose) has limited diagnostic utility; pleural “Light’s criteria” are not applicable to pericardial effusions.

Management

Management of acute pericarditis depends upon the underlying etiology, the severity of inflammation, and the presence of complications such as effusion or tamponade. The primary goals of therapy are symptom relief, suppression of inflammation, and prevention of recurrence.

1. Viral or Idiopathic Pericarditis

Viral and idiopathic forms constitute the majority of cases and are generally self-limited.

Pharmacologic therapy

Nonsteroidal anti-inflammatory drugs (NSAIDs): First-line treatment. Common regimens include ibuprofen (600–800 mg every 6–8 hours) or aspirin (650–1000 mg every 6 hours). Therapy is continued until complete symptom resolution and normalization of CRP, followed by gradual tapering.
Colchicine: Used as an adjunct to NSAIDs to reduce recurrence rates (0.5 mg twice daily for patients > 70 kg, once daily if ≤ 70 kg). Recommended duration: 3 months for initial episodes.
Indomethacin: Reserved for cases unresponsive to the above due to its higher gastrointestinal and renal adverse-effect profile.
Glucocorticoids: Not first-line. Indicated only when NSAIDs are contraindicated (e.g., renal failure, late pregnancy, peptic ulcer) or when the pericarditis is autoimmune or connective-tissue-related. Prednisone 0.25–0.5 mg/kg/day is typical, with a slow taper over weeks to minimize relapse.

Non-pharmacologic measures

Hospitalization for high-risk features (fever > 38 °C, subacute onset, large effusion, immunosuppression, or suspected bacterial/TB origin).
Strict rest and avoidance of strenuous physical activity during the acute phase to reduce mechanical irritation and recurrence risk.

2. Post-Myocardial-Infarction Pericarditis

Two distinct forms are recognized:

Peri-infarction pericarditis: Appears within the first 4 days following infarction due to localized inflammation. Treatment: Aspirin + Colchicine are preferred because non-aspirin NSAIDs can impair myocardial scar formation and interfere with healing. Corticosteroids should be avoided unless inflammation persists.
Dressler (Post-cardiac-injury) syndrome: Develops weeks to months after infarction or cardiac surgery and is thought to be immune-mediated. Treatment: Similar—Aspirin + Colchicine. Corticosteroids may be used in refractory cases after exclusion of infection.

3. Uremic Pericarditis

Occurs in advanced renal failure due to toxin accumulation. Definitive therapy is dialysis, which usually results in rapid improvement. If tamponade is suspected, urgent pericardiocentesis should precede dialysis.

4. Bacterial, Tuberculous, or Malignant Pericarditis

Management is directed at the underlying cause:

Bacterial pericarditis: Requires prompt intravenous antibiotics tailored to culture results, with pericardial drainage or surgical pericardiectomy if purulent.
Tuberculous pericarditis: Treated with standard antituberculous therapy (isoniazid, rifampicin, pyrazinamide, ethambutol ± steroids).
Malignant effusion: Managed with systemic chemotherapy or radiotherapy for the primary malignancy; recurrent large effusions may need pericardial window or sclerosis.

Complications

Cardiac Tamponade

Rapid accumulation of pericardial fluid compresses all cardiac chambers, impairing diastolic filling and reducing cardiac output. Clinical findings: hypotension, tachycardia, elevated jugular venous pressure, muffled heart sounds, and pulsus paradoxus. Immediate treatment is pericardiocentesis.

Recurrent Pericarditis

Defined as recurrence of symptoms and inflammation after complete resolution of the initial episode, occurring in approximately 15–30 % of patients. Colchicine markedly lowers recurrence risk.

Constrictive Pericarditis

Chronic inflammation and fibrosis lead to a rigid pericardial shell that limits diastolic expansion. Manifestations include elevated JVP, peripheral edema, ascites, and hepatomegaly resembling right-sided heart failure. Treatment may require pericardiectomy in advanced cases.

Prognosis

The outlook for acute idiopathic or viral pericarditis is excellent when appropriately managed. Most patients experience complete resolution within 2–6 weeks. Recurrence or progression to constriction is uncommon when colchicine is used.

In contrast, the prognosis of secondary pericarditis (e.g., malignant, uremic, or bacterial) depends on the primary disorder and may carry a higher risk of morbidity and mortality. Severe complications such as cardiac tamponade can be acutely fatal if not recognized and treated promptly.

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