What are the clinical manifestations of acute pericarditis?

Clinical Manifestations of Acute Pericarditis

Acute pericarditis is diagnosed when at least two of four cardinal features are present: (1) sharp, pleuritic chest pain that worsens supine and improves sitting forward, (2) pericardial friction rub, (3) new widespread concave ST-elevation or PR-depression on ECG, and (4) new or worsening pericardial effusion. 1

The Four Cardinal Diagnostic Features

1. Chest Pain (Most Common Presentation)

• Sharp, pleuritic chest pain that characteristically worsens when lying supine and improves when sitting forward or leaning forward 1
• Present in approximately 90% of cases, making it the most frequent manifestation 2
• The pain is typically retrosternal and has a pleuritic quality 3
• Often accompanied by shortness of breath 4

2. Pericardial Friction Rub (Highly Specific but Often Absent)

• Can be heard in up to 85% of cases but is frequently transient and may be absent on initial examination 1
• Present in less than 30% of patients in some series 2
• Highly specific for pericarditis when present, but its absence does not exclude the diagnosis 1
• Best heard at end-expiration with the patient seated and leaning forward 1
• The fleeting nature of this finding underscores the need for careful and repeated auscultation 1

3. ECG Changes (Variable and Dynamic)

• New widespread concave ST-segment elevation and PR-segment depression 1
• Classic ECG changes are observed in only 25%–60% of patients, making them an unreliable sole criterion 1
• ECG findings are highly variable and temporally dynamic, often changing rapidly during the disease course 1
• Serial ECGs are essential because patterns evolve over time 1
• The relatively low frequency (25-50%) means many patients will not demonstrate these changes 2

4. Pericardial Effusion

• Detected in approximately 60% of acute pericarditis cases 1, 2
• Most effusions are small 2
• Identified by transthoracic echocardiography, which is mandatory in all suspected cases 1

Associated Clinical Features

Systemic Inflammatory Signs

• Prodromal syndrome of fever, malaise, and myalgia is common 1
• Elderly patients may lack fever, making diagnosis more challenging 1
• Elevated inflammatory markers (CRP, ESR, WBC) are frequent and serve to monitor disease activity 1

Myocardial Involvement (Myopericarditis)

• Troponin elevation occurs when there is concurrent myocardial involvement, termed myopericarditis 5, 1
• The classical presentation includes chest pain with pericardial signs plus elevation of markers of myocardial damage (troponins, CK-MB) 5
• Troponin measurements should be obtained in 70% or more of patients to detect this complication 6
• Interestingly, elevated troponin levels are associated with lower incidence of recurrences (4% vs 17%) 6

Preceding Illness

• Many cases are preceded by or concomitant with acute respiratory illness (especially acute tonsillitis, pneumonia) or gastroenteritis 5
• In North America and Western Europe, most cases are idiopathic or viral, followed by post-cardiac procedure pericarditis 2

Critical Diagnostic Nuances

Do Not Wait for All Four Criteria

• The diagnosis is confirmed once any two criteria are met 1
• Given that classic ECG patterns appear in less than 60% and friction rubs are often absent, waiting for all four features will delay diagnosis 1

Principal Differential Diagnoses

• Acute coronary syndrome with ST-elevation is the most critical alternative diagnosis to exclude 1
• Early repolarization patterns can mimic pericarditis on ECG 1
• In cases with elevated troponin, coronary angiography is recommended to rule out acute coronary syndromes 5

Presentation Patterns and Prognosis

• Subacute presentation is an independent predictor of adverse outcomes 6
• Patients with postcardiac injury pericarditis have lower incidence of treatment failure and recurrence (13% vs 26%) compared to idiopathic pericarditis 6
• Overall, 34% of patients experience at least one adverse outcome during follow-up 6

Common Pitfalls to Avoid

• Do not rely solely on ECG changes—they are absent in 40-75% of presentations 1
• Do not dismiss the diagnosis if no friction rub is heard—it is present in less than one-third of cases 2
• Do not overlook the need for serial examinations—friction rubs and ECG changes are temporally dynamic 1
• Always obtain troponin levels—myopericarditis has different prognostic implications and paradoxically lower recurrence risk 6