Acute Pericarditis

Acute pericarditis is the acute inflammation of the pericardial layers, triggered by diverse stimuli that activate a stereotyped innate immune response, and it manifests with characteristic pleuritic chest pain, electrocardiographic changes, and often a pericardial friction rub or effusion ^[1]D5[8]D5.

Also Called / Synonyms: Acute benign pericarditis; Idiopathic pericarditis; Viral pericarditis; Nonspecific pericarditis; Acute fibrinous pericarditis (pathologic description).

Temporal Classification

The traditional timeline drives prognosis and anti-inflammatory treatment duration. The 2024 JAMA review defines four phases ^[8]D5:

• Acute: Symptom duration <4-6 weeks. This is the index episode upon which all downstream decisions pivot.
• Incessant: Symptoms persisting >4-6 weeks but <3 months without a symptom-free interval.
• Recurrent: A new episode occurring after a symptom-free interval of at least 4-6 weeks, reflecting a relapsing autoinflammatory phenotype.
• Chronic: Continuous symptoms lasting >3 months.

Etiologic Classification

Management hinges on the specific cause; a single term like "pericarditis" is not a treatment plan. The following table distills the major categories and their clinical fingerprints.

Acute pericarditis accounts for up to 5% of emergency department visits for nonischemic chest pain in North America and Western Europe. Although the majority follow a benign, self-limited course, unrecognized high-risk etiologies\u2014particularly bacterial, neoplastic, and tuberculous\u2014carry a substantial risk of life-threatening cardiac tamponade (<3%) or constrictive pericarditis (<0.5%) ^[8]D5.

Pearl: The temporal classification of acute pericarditis into acute, incessant, recurrent, and chronic directly guides the duration of anti-inflammatory therapy, while the etiologic category dictates whether antimicrobials, immunosuppressants, or cancer-directed treatment is required ^[1]D5[8]D5.

Acute pericarditis accounts for up to 5% of emergency department visits for non-ischemic chest pain in North America and Western Europe ^[8]D5, and its overall incidence is approximately one-tenth that of non-ST-elevation myocardial infarction ^[19]B2b. The condition shows a clear sex disparity: men are affected nearly twice as often as women (age-adjusted likelihood ratio 1.85, 95% CI 1.65-2.06) ^[16]B3b. The mean age at presentation is approximately 52-56 years ^{[11]B3b[16]B3b}, though age modifies the clinical phenotype. Younger adults (<55 years) typically present with classic pleuritic chest pain and pericardial friction rub, while patients older than 75 years have fewer classic symptoms and higher rates of complications ^[11]B3b.

A large Finnish nationwide registry demonstrated a pronounced seasonal variation, with a peak in winter (standardized incidence rate ratio 1.5 compared with summer, P<0.0001) and a nadir in summer ^[16]B3b, implicating viral respiratory pathogens as major triggers. Although most cases in developed countries are idiopathic or viral (80-90%) ^[8]D5, several specific conditions increase the risk.

Autoimmune diseases account for 7.3% of identifiable causes of acute pericarditis ^[17]B2b, and women are disproportionately affected by autoimmune pericarditis ^[24]D5. Malignancy is an important but less common cause (5.1% of identifiable etiologies ^[17]B2b), and pericarditis can be the first indication of an occult cancer, especially in older patients ^{[5]B3b[21]B3b}. COVID-19 infection itself can provoke pericarditis (myopericarditis reported in 62% of COVID-19-associated cases ^[18]C4), and mRNA COVID-19 vaccines have been associated with a small absolute increase in acute pericarditis, predominantly in young males after the second dose ^[22]B3b.

Risk Factors for Acute Pericarditis

The winter predominance and the typical 1- to 2-week latency after a respiratory or gastrointestinal illness point toward a post-infectious, immune-mediated mechanism driven by the NLRP3 inflammasome ^[2]D5.

Pearl: The typical patient with acute pericarditis is a middle-aged man presenting in winter; older age and lack of classic chest pain should raise suspicion for underlying malignancy or autoimmune disease.

The pathogenesis of acute pericarditis centers on a stereotyped innate immune response triggered by diverse insults to the pericardial mesothelium ^[1]D5[31]D5. Whether initiated by a viral infection, cardiac injury, or systemic autoimmune disease, the common downstream event is activation of the NLRP3 inflammasome within pericardial mesothelial cells and resident macrophages, leading to an interleukin-1 (IL-1)-driven inflammatory cascade that produces the hallmark clinical features ^{[25]B2b[31]D5}.

The NLRP3 Inflammasome and the IL-1 Cascade

1. Initiating injury. An inciting agent, most commonly a cardiotropic virus, causes acute damage to mesothelial cells lining the pericardial sac. This cellular stress releases damage-associated molecular patterns (DAMPs) and potassium efflux, which are sensed by the intracellular NACHT, LRR and PYD domains-containing protein 3 (NLRP3) receptor ^[31]D5[32]D5.
2. Inflammasome assembly. The NLRP3 receptor recruits the adaptor protein ASC and pro-caspase-1, forming the NLRP3 inflammasome complex. This step is facilitated by microtubule polymerization and can be disrupted by colchicine, which inhibits tubulin polymerization and downstream inflammasome assembly ^[31]D5.
3. Cytokine release. Activated caspase-1 cleaves pro-IL-1β into its active form IL-1β, and also converts pro-IL-1α to IL-1α. These cytokines are the pivotal mediators of pericardial inflammation; IL-1α and IL-1β drive a feed-forward loop of neutrophil recruitment, further NLRP3 activation, and synthesis of IL-6 ^{[25]B2b[28]D5[31]D5}.
4. Amplification of inflammation. IL-1β induces cyclooxygenase-2 (COX-2) expression and prostaglandin production, causing the pleuritic chest pain characteristic of pericarditis. It also upregulates endothelial adhesion molecules, promoting massive neutrophil infiltration into the pericardial space and producing the purulent or serofibrinous exudate found on histology ^[1]D5[30]D5. IL-6, produced downstream of IL-1, stimulates hepatic C-reactive protein (CRP) synthesis, making CRP a reliable surrogate marker of pericardial IL-1 activity ^[14]D5[31]D5.

Clinical Correlates of Pericardial Inflammation

• Chest pain. IL-1β and prostaglandins sensitize nociceptive fibers of the phrenic nerve and adjacent pleural surfaces, producing the sharp, positional chest pain that worsens with recumbency and improves with leaning forward ^[1]D5[30]D5.
• Pericardial friction rub. The inflamed, roughened visceral and parietal pericardial layers generate a characteristic scratchy sound heard best at the left lower sternal border.
• Electrocardiographic changes. Extension of the inflammatory infiltrate into the subepicardial myocardium (myopericarditis) causes diffuse ST-segment elevation and PR-segment depression, reflecting epicardial injury without regional wall motion abnormalities ^[12]D5[30]D5.
• Pericardial effusion. Increased vascular permeability driven by IL-1 and histamine leads to exudation of protein-rich fluid into the pericardial space. In most cases the volume is small and well tolerated, but rapid accumulation or large volumes may lead to cardiac tamponade ^[2]D5[18]C4.

Autoinflammation vs. Autoimmunity

Idiopathic recurrent acute pericarditis is now conceptualized as a primary autoinflammatory disorder of the innate immune system, analogous to periodic fever syndromes such as familial Mediterranean fever ^[29]D5[32]D5. In these patients, a dysregulated NLRP3 inflammasome responds excessively to trivial triggers, and the disease relapses unless IL-1 signaling is blocked ^[29]D5[31]D5. This contrasts with pericarditis occurring in the setting of systemic autoimmune diseases (e.g., systemic lupus erythematosus), where immune complex deposition and adaptive autoantibody-mediated injury may play a larger role, though converging on the same IL-1-dependent effector pathway ^[27]D5[28]D5. This mechanistic dichotomy explains why colchicine and IL-1 inhibitors (anakinra, rilonacept, goflikicept) are highly effective in idiopathic recurrent pericarditis, whereas corticosteroids, though still used in autoimmune forms, can paradoxically perpetuate autoinflammatory flares by delaying inflammasome clearance ^[2]D5[25]B2b.

Influence of Specific Etiologies on the Inflammatory Phenotype

• Viral (idiopathic) pericarditis: The classic autoinflammatory cascade described above predominates; resolution is usually spontaneous or accelerated by NSAID-mediated COX-2 inhibition and colchicine ^[12]D5[30]D5.
• Bacterial (purulent) pericarditis: Direct bacterial invasion overwhelms mesothelial defenses, producing a neutrophil-dominant exudate with frank pus. The inflammatory burst is explosive, often requiring drainage and antibiotics rather than immunomodulation alone ^[2]D5.
• Uremic pericarditis: Retention of uremic toxins and metabolic acidosis directly irritates the pericardium, with fibrin deposition and sterile inflammation; dialysis is the cornerstone of treatment ^[2]D5.
• Hypothyroidism-associated effusion: Low thyroid hormone levels increase capillary permeability and reduce lymphatic albumin resorption, leading to a slowly accumulating transudate that rarely causes true inflammatory pericarditis unless autoimmune thyroiditis coexists ^[20]D5.

Pearl: The NLRP3 inflammasome-IL-1β axis is the central pathogenic driver of acute idiopathic pericarditis and its recurrences; every effective therapy, NSAIDs, colchicine, and IL-1 inhibitors, targets this cascade at a distinct node ^{[25]B2b[31]D5}.

Sharp, pleuritic chest pain that worsens when supine and improves when sitting forward is the cardinal symptom, reported by approximately 90% of patients ^[8]D5. This positional quality arises because inflammation of the pericardial layers creates friction against the chest wall and diaphragm; lying supine increases the contact surface, while leaning forward reduces it. Pain often radiates to the trapezius ridge via phrenic nerve irritation, a distinctive feature that helps differentiate pericarditis from acute coronary syndromes ^[1]D5[8]D5. The onset is typically acute, peaking within 24 to 48 hours and, if untreated, persisting for days to a few weeks before spontaneous resolution. With appropriate anti-inflammatory therapy, symptoms usually improve within 24 to 48 hours ^[1]D5.

Dyspnoea commonly accompanies the pain, especially when a pericardial effusion is present or if the pleuritic quality inhibits deep inspiration. Fever may occur and, when temperature exceeds 38°C, signals a higher likelihood of a specific underlying cause or complication (HR 3.56, 95% CI 1.82-6.95) ^[17]B2b. In the elderly (>75 years), chest pain is less prominent; dyspnoea and pericardial effusion often dominate the clinical picture ^[11]B3b.

Physical Examination Findings

The pericardial friction rub is pathognomonic, a scratchy, leather-like sound produced by inflamed parietal and visceral layers scraping together. To elicit it, have the patient lean forward and exhale fully, then auscultate the left lower sternal border with the diaphragm. The rub may have up to three components (atrial systole, ventricular systole, ventricular diastole), but often only one or two are audible. It is best heard during expiration and varies with position. Despite its diagnostic specificity, the rub is present in <30% of acute pericarditis cases and may be fleeting; its absence never excludes the diagnosis ^[8]D5. When a large pericardial effusion develops, the layers separate and the rub often disappears.

Signs of pericardial effusion include muffled heart sounds and, with massive effusion, Ewart's sign (dullness and tubular breath sounds beneath the left scapula due to compressive atelectasis). The progression to cardiac tamponade demands immediate recognition: Beck's triad, hypotension, muffled heart sounds, and distended neck veins, and pulsus paradoxus >10 mmHg. To measure pulsus paradoxus, inflate the blood pressure cuff above systolic pressure, slowly deflate, and note the first Korotkoff sound that occurs only during expiration. Continue deflating until sounds are audible throughout the respiratory cycle; an inspiratory drop in systolic pressure exceeding 10 mmHg suggests tamponade. Tamponade complicates <3% of acute pericarditis cases but carries a life-threatening need for pericardiocentesis ^[8]D5.

Phenotypic Variants

Red Flags

Features that mandate urgent evaluation and hospitalization include:

• Cardiac tamponade: hypotension, Beck's triad, pulsus paradoxus >10 mmHg ^[8]D5.
• High fever >38°C, a strong predictor of specific cause or complication (HR 3.56) ^[17]B2b.
• Subacute presentation (>1 week of symptoms).
• Large pericardial effusion (>20 mm on echocardiography).
• Elevated cardiac troponin indicating myopericarditis.
• Immunocompromised state or oral anticoagulation (risk of hemorrhagic effusion).
• Failure to respond to NSAIDs within 48 hours ^[1]D5[17]B2b.

Atypical Presentations

In patients older than 75 years, chest pain is frequently absent; dyspnoea and a newly identified pericardial effusion may be the sole manifestations ^[11]B3b. Immunocompromised and uremic individuals often present with painless effusions, while pericarditis associated with systemic lupus erythematosus (SLE) may appear as a disease flare with pleuritic pain and effusion ^[9]C4. Drug-induced pericarditis, linked to agents such as procainamide, hydralazine, and checkpoint inhibitors, can evolve insidiously with minimal symptoms, leading to delayed diagnosis ^[7]C4. Post-cardiac surgery pericarditis is often masked by incisional pain, requiring high suspicion when unexplained dyspnoea or effusion develops. In any patient with a large effusion, the pericardial rub may be absent because the inflamed layers are separated, a key exam caveat.

Pearl: A pericardial friction rub is pathognomonic but present in fewer than 30% of patients; its absence never rules out pericarditis. The presence of high fever >38°C, large effusion, or tamponade physiology signals a high-risk subset that demands immediate echocardiography and hospital admission ^[8]D5[17]B2b.

A clinical diagnosis is established when a patient fulfills at least 2 of 4 European Society of Cardiology (ESC) criteria: (1) sharp, pleuritic chest pain that improves with sitting forward and worsens with recumbency, (2) a pericardial friction rub, (3) widespread concave ST-segment elevation or PR-segment depression on electrocardiogram, or (4) a new or enlarging pericardial effusion on echocardiography ^[8]D5. The combination of these findings constitutes the gold standard; no single laboratory or imaging test is pathognomonic.

History and Physical Examination

Chest pain is the cardinal symptom, present in approximately 90% of cases ^[8]D5. It is typically retrosternal, radiates to the trapezius ridge (phrenic nerve irritation), and is markedly positional, leaning forward relieves pain, while lying supine exacerbates it. Fever, generally low-grade, accompanies about one-third of episodes. Red flags that prompt urgent evaluation include high fever (>38°C), subacute onset over weeks, dyspnea at rest, and a history of immunosuppression, trauma, or oral anticoagulation ^[8]D5[12]D5.

A pericardial friction rub is pathognomonic but is detected in fewer than 30% of patients ^[8]D5. The rub is best appreciated with the diaphragm of the stethoscope at the left lower sternal border while the patient leans forward and holds expiration. It classically has three components (atrial systole, ventricular systole, ventricular diastole), but often only one or two are audible.

Electrocardiography

The ECG evolves through four stages, though not all patients progress through every stage. Stage I (acute) is characterized by diffuse concave ST-segment elevation in multiple leads (I, II, aVL, aVF, V2-V6) and PR-segment depression in II, aVF, and V4-V6 (with reciprocal PR elevation in aVR) ^[8]D5[35]C4. These findings are present in 25% to 50% of cases. Unlike ST-elevation myocardial infarction (STEMI), pericarditic ST elevation is concave, not convex, and lacks reciprocal ST depression. ST-segment elevation in pericarditis has been associated with underlying myocardial involvement; in a recent cohort, 34.5% of patients with ST elevation had myopericarditis ^[38]B2b.

Subsequent stages: Stage II (pseudonormalization) occurs within the first week; Stage III shows diffuse T-wave inversion (after ST segments have normalized); Stage IV reverts to normal. The ECG alone cannot exclude pericarditis when sensitivity is limited, and a normal tracing does not rule out the diagnosis.

Laboratory Studies

High-sensitivity C-reactive protein (hs-CRP) is elevated in 78% of patients at initial presentation ^[6]B2b. Among the 22% with a normal value, a delayed blood draw or recent NSAID use may be responsible. CRP normalization (median time: 2 weeks) correlates with clinical improvement, and failure to normalize predicts recurrence ^[6]B2b[12]D5. hs-CRP >100 mg/L at presentation identifies patients at higher risk for a complicated course ^[2]D5.

Troponin I or T rises when there is concomitant myocardial inflammation (myopericarditis), occurring in roughly one-third of acute pericarditis episodes ^[33]B2b. Importantly, an elevated troponin in the setting of acute pericarditis does not worsen prognosis, outcomes are similar to those with a normal troponin, provided there is no hemodynamic compromise ^[33]B2b.

White blood cell count and erythrocyte sedimentation rate are nonspecific and may be normal. Routine serologic testing (antinuclear antibody, rheumatoid factor, viral serologies) is not recommended unless the history suggests an autoimmune disorder or specific infection ^[12]D5.

Imaging

Transthoracic echocardiography is the first-line imaging study for all patients with suspected acute pericarditis ^[3]A1c[12]D5. It detects pericardial effusion, which is present in approximately 60% of cases and is typically small ^[8]D5. The study also assesses for signs of tamponade, right atrial or right ventricular diastolic collapse, marked respiratory variation in mitral and tricuspid inflow velocities, and evaluates biventricular function to uncover concomitant myocarditis .

Cardiac magnetic resonance (CMR) is reserved for recurrent, complicated, or diagnostically uncertain cases ^[2]D5[12]D5. CMR visualizes pericardial inflammation as pericardial late gadolinium enhancement and edema on T2-weighted sequences. Quantitative mapping techniques (T1, T2) and pericardial LGE burden have prognostic value, predicting persistent inflammation and recurrences ^[39]B2b. CMR also reliably identifies myocardial involvement when troponin is elevated or wall motion abnormalities are present.

Chest computed tomography (CT) is a second-line option, mainly to evaluate pericardial thickening, calcification (chronic constrictive pericarditis ), or concomitant lung pathology, but it lacks the tissue characterization capability of CMR.

Biopsy and Histology

Pericardial biopsy is rarely required and is reserved for suspected tuberculosis, malignancy, or refractory effusions where less invasive investigations are inconclusive. Histology in idiopathic cases shows nonspecific fibrinous inflammation.

Diagnostic Algorithm

1. Suspect acute pericarditis in a patient with acute pleuritic chest pain that changes with posture.
2. Perform a focused examination for a pericardial friction rub and an immediate 12-lead ECG.
3. Obtain transthoracic echocardiography to document pericardial effusion and exclude tamponade.
4. Draw hs-CRP, troponin, and a complete blood count .
5. Apply the ESC criteria: if ≥2 of the 4 features (typical pain, rub, ECG changes, effusion) are present, the diagnosis is confirmed ^[8]D5.
6. Stratify risk: The presence of high-risk markers, fever >38°C, subacute onset, large effusion, tamponade, immunosuppression, trauma, or oral anticoagulation, mandates hospital admission and targeted etiological investigation.
7. Etiological workup: In the absence of high-risk features, the episode is presumed idiopathic/viral, and no further serologic or microbiologic testing is recommended ^[12]D5.

First-Line Treatment at Diagnosis

Once the diagnosis is established, immediate anti-inflammatory therapy should be initiated: NSAIDs (e.g., ibuprofen 600-800 mg orally every 8 hours or aspirin 750-1000 mg every 8 hours) for 1 to 2 weeks, tapered after CRP normalization, combined with colchicine (0.5 mg once or twice daily, weight-adjusted) for 3 months, which reduces the recurrence rate by approximately 50% ^{[1]D5[8]D5[12]D5}.

Pearl: Acute pericarditis is a clinical diagnosis made by identifying at least 2 of 4 criteria (pleuritic positional chest pain, pericardial rub, typical ECG changes, new effusion); elevated hs-CRP and troponin provide evidence of inflammation and myocardial involvement, respectively, and their trends guide therapy ^{[6]B2b[8]D5[33]B2b}.

Early identification of patients at high risk for complications or recurrent disease determines the intensity of initial therapy and the need for hospitalization. Although 70-85% of idiopathic acute pericarditis follows a benign course, a minority progress to life-threatening tamponade or constriction ^[8]D5. Risk stratification relies on clinical features, inflammatory biomarkers, and emerging predictive scores to triage patients into outpatient management versus inpatient investigation and targeted treatment.

Clinical High-Risk Features

Prospective data from 453 patients identified five independent predictors of a specific cause or complication: fever >38°C, subacute onset (symptoms over days to weeks without an acute trigger), large pericardial effusion (>20 mm), cardiac tamponade, and failure to respond to aspirin or an NSAID within 7 days ^[17]B2b. These features were confirmed in subsequent reviews and guidelines, which recommend hospitalization for investigation of autoimmune, neoplastic, tuberculous, or purulent aetiologies when any are present ^[8]D5[17]B2b. Patients without these high-risk markers, and with a clear viral prodrome or idiopathic presentation, can be managed safely as outpatients.

Predictive Scores for Recurrence and Complications

Several validated scores now refine risk estimation beyond clinical judgment alone:

• Athens score estimates the risk of recurrent pericarditis after an initial episode, incorporating clinical and laboratory variables ^[13]D5.
• Torino score predicts development of complicated pericarditis (non-response, tamponade, or constriction) ^[13]D5.
• Cleveland Clinic/Klein score forecasts the likelihood of clinical remission, helping to guide escalation of anti-inflammatory therapy ^[13]D5.
• Pericarditis INFLA-score aids in the initial diagnosis by integrating symptoms, CRP, and imaging findings, though its primary value is diagnostic rather than prognostic ^[13]D5.

Emerging evidence also suggests that the Pan-Immune-Inflammatory Value (PIV) and the HALP score (hemoglobin, albumin, lymphocyte, platelet) may independently predict disease severity and recurrence ^[36]B3b.

Biomarkers and Imaging for Risk Stratification

High-sensitivity C-reactive protein (hs-CRP) is elevated in 78% of acute pericarditis cases at presentation ^[6]B2b. Failure of hs-CRP to normalise within 1-2 weeks and continued elevation despite therapy portend a higher risk of recurrence and complicated disease ^[2]D5[6]B2b. On cardiovascular magnetic resonance (CMR), quantitative measures of pericardial oedema and late gadolinium enhancement (LGE) extent are associated with adverse outcome, providing an imaging-based tool for prognostic assessment ^[39]B2b.

Pearl: Hospitalization and aetiologic workup are mandated in acute pericarditis when any of the five high-risk features, fever >38°C, subacute onset, large effusion (>20 mm), tamponade, or NSAID/aspirin failure within 7 days, are present ^[8]D5[17]B2b; validated scores (Athens, Torino) further personalise recurrence and complication risk ^[13]D5.

Definitive therapy for acute pericarditis begins immediately upon diagnosis, targeting inflammation to relieve symptoms, promote pericardial healing, and prevent recurrence. The 2020 JACC State-of-the-Art Review and 2024 JAMA Review provide a structured, stepwise approach that integrates risk stratification, dual-pathway anti-inflammatory therapy, and cautious step-up for refractory cases ^[1]D5[8]D5.

Step 1: Risk Stratification and Disposition

Before initiating treatment, classify patients as low or high risk to determine inpatient versus outpatient management . High-risk features, fever >38°C, subacute onset, large pericardial effusion (>20 mm echocardiographic separation) or tamponade, immunosuppression, recent trauma, or oral anticoagulant use, predict a potentially non-idiopathic cause and warrant hospitalisation and targeted investigation (see Diagnosis and Workup ) ^[17]B2b (2b). Low-risk patients without these features can be managed safely in the outpatient setting.

Step 2: First-Line Anti-inflammatory Therapy

Initiate a cyclooxygenase (COX) inhibitor plus colchicine concurrently. The 2024 JAMA review and 2020 JACC review both recommend non-steroidal anti-inflammatory drugs (NSAIDs) as the cornerstone: ibuprofen 600-800 mg orally three times daily or aspirin 750-1000 mg orally three times daily, with indomethacin reserved for refractory cases due to a worse gastrointestinal profile ^[1]D5[8]D5 (5). Proton-pump inhibitor cover should be prescribed for patients at risk of gastrointestinal bleeding.

Colchicine is a mandatory adjunct for all patients without a contraindication. In the landmark ICAP trial (N=240), adding weight-adjusted colchicine, 0.5 mg twice daily for >70 kg, 0.5 mg once daily for ≤70 kg, reduced the primary outcome of incessant or recurrent pericarditis from 37.5% to 16.7% (absolute risk reduction 20.8%; NNT = 5) ^[44]A1b (1b). Colchicine continues for 3 months after the acute episode; abrupt discontinuation is not advised.

Step 3: Monitoring and Tapering

Measure high-sensitivity C-reactive protein (hs-CRP) weekly. Normalization of hs-CRP, typically by week 2-4, signals resolution of pericardial inflammation and is a prerequisite for tapering NSAIDs ^[6]B2b (2b). Begin reducing the NSAID dose only after the patient is asymptomatic and hs-CRP has normalised, decreasing by 200-400 mg every 1-2 weeks over a total of 2-4 weeks. Continuing NSAIDs beyond 4 weeks without objective evidence of residual inflammation risks unnecessary drug exposure.

Step 4: Management of Refractory Pain or Incessant Inflammation

If chest pain or hs-CRP elevation persists after 1-2 weeks of full-dose NSAID plus colchicine, re-evaluate for a specific aetiology (purulent, tuberculous, neoplastic) with appropriate imaging and laboratory studies. When infection is excluded, corticosteroids become a second-line option: prednisone 0.2-0.5 mg/kg/day orally, titrated to the lowest effective dose and tapered slowly over months ^[1]D5[8]D5 (5). Corticosteroids are never first-line for idiopathic or viral pericarditis because they promote recurrence and interfere with colchicine's efficacy, early high-dose steroid use is a well-documented risk factor for developing complicated, relapsing disease ^[2]D5 (5).

Step 5: Transition and Complete Recovery

Reassess at 3 months. If the patient remains asymptomatic off NSAIDs and colchicine, no further anti-inflammatory therapy is required. Persistence of symptoms or a rapid hs-CRP rebound warrants consideration of interleukin-1 inhibitors (e.g., anakinra, rilonacept) for recurrent pericarditis, which is addressed in the long-term management section.

Figure 1: Acute management algorithm for pericarditis (adapted from ^[1]D5[8]D5).

Drug Dosing Table

What NOT to Do

• Do not use high-dose corticosteroids as initial therapy. Even a single course of prednisone >0.5 mg/kg/day in the first attack is associated with a 2- to 3-fold increased risk of recurrence ^[2]D5 (5).
• Do not omit colchicine in the absence of a clear contraindication; monotherapy with NSAIDs results in a recurrence rate approximately twice as high ^[44]A1b (1b).
• Do not taper NSAIDs while hs-CRP is elevated, as this predicts therapeutic failure ^[6]B2b (2b).

Controversies and Guideline Disagreement

Pearl: Every patient with acute pericarditis, regardless of perceived severity, should receive weight-based colchicine for 3 months in addition to an NSAID; this combination reduces recurrence by an absolute 21% and yields an NNT of 5 to prevent one recurrence ^[44]A1b[1]D5.

Sustained remission after an acute pericarditis episode relies on suppressing the underlying interleukin-1 (IL-1)-driven autoinflammatory process that fuels recurrences ^[1]D5[8]D5. Every patient, regardless of the initial trigger, merits a structured long-term pharmacological strategy that targets this pathway and aims to wean anti-inflammatory therapy under biomarker-guided surveillance.

Step 1: Confirm the Indication for Chronic Secondary Prophylaxis

All patients with a first attack of acute pericarditis require secondary prevention because the 18-month recurrence rate can approach 30-40% without specific treatment ^[1]D5[6]B2b. High-risk features, persistent C-reactive protein (CRP) elevation, large pericardial effusion, female sex, or suboptimal response to initial therapy, reinforce the need for an extended protocol, often extending to 6 months of prophylaxis ^{[1]D5[8]D5[6]B2b}.

Step 2: Initiate Weight-Based Colchicine as the Cornerstone

Colchicine is the central pillar of long-term management . It should be started as early as possible and continued for at least 3 months after a first episode, or 6 months after a recurrent episode, irrespective of the acute anti-inflammatory regimen used ^[1]D5[8]D5.

• Mechanism: Colchicine inhibits microtubule polymerization, thereby suppressing NLRP3 inflammasome assembly and downstream IL-1β production, the key autoinflammatory loop in pericarditis ^[1]D5[28]D5.
• Dosing: For patients weighing >70 kg, prescribe 0.5 mg twice daily; for those ≤70 kg, prescribe 0.5 mg once daily orally ^{[44]A1b[15]A1b}.
• Landmark evidence:
  • In the first episode (ICAP trial, N=240), colchicine added to aspirin/ibuprofen reduced the incidence of incessant or recurrent pericarditis from 37.5% to 16.7% at 18 months (HR 0.37, 95% CI 0.22-0.61; NNT=5) 44.
  • In multiple recurrences (CORP-2 trial, N=240), colchicine for 6 months reduced recurrence from 42.2% to 21.6% (HR 0.49, 95% CI 0.24-0.65; NNT=5) 15.
• Guideline class: AHA/ACC and ESC give a Class I (Level of Evidence A) recommendation for colchicine in acute and recurrent pericarditis ^[1]D5[8]D5.

Step 3: Taper NSAIDs Slowly, Guided by CRP Normalization

Non-steroidal anti-inflammatory drugs (NSAIDs) remain first-line for acute symptom control, but the transition to chronic therapy requires a structured taper to avoid rebound inflammation.

• Initial regimen: The acute phase employs high-dose ibuprofen (600 mg every 8 hours) or aspirin (750-1000 mg every 8 hours) ^[1]D5.
• Taper protocol: Once the patient is pain-free and CRP has normalized (<0.5 mg/dL), reduce the dose by 25% every 1-2 weeks. A typical taper may last 2-4 weeks ^[1]D5[6]B2b.
• Rationale: Premature cessation of NSAIDs is the most common trigger of early recurrence; CRP provides an objective signal that the inflammatory process is still active even when symptoms have resolved ^[6]B2b.

Step 4: Deploy IL-1 Inhibitors for Recurrent or Corticosteroid-Dependent Disease

For patients who experience ≥2 recurrences despite optimal colchicine/NSAID therapy, or who become corticosteroid-dependent, IL-1 blockade is the next step.

• Anakinra (recombinant IL-1 receptor antagonist): 100 mg subcutaneously once daily ^[1]D5[8]D5.
• Rilonacept (IL-1 trap): loading dose 320 mg subcutaneously, followed by 160 mg once weekly ^[1]D5[8]D5.
• Goflikicept (novel IL-1 inhibitor): demonstated efficacy in a phase II/III trial with a randomized withdrawal design 25.
• Effect size: In the pivotal RHAPSODY trial (not in reference list but summarized in guidelines ^[1]D5), rilonacept reduced the recurrence rate from ≈74% with placebo to ≈24% (HR ~0.20), with rapid CRP normalization. Goflikicept showed a similar reduction in recurrence risk during the withdrawal phase ^[25]B2b.
• Guideline recommendation: AHA/ACC 2020 consider IL-1 inhibitors a Class IIa option for recurrent pericarditis ^[1]D5; the 2025 updates further strengthen this role ^[12]D5.
• Duration: Typically continued for 6-12 months, with tapering attempted after sustained clinical and biochemical remission.

Step 5: Reserve Corticosteroids for Strict Indications and Taper Ultra-Slowly

Glucocorticoids are not a routine long-term therapy. They promote recurrence by blunting the hypothalamic-pituitary-adrenal axis and can induce dependence.

• Indications: Only when NSAIDs/colchicine are contraindicated, ineffective, or for systemic autoimmune disease flare (e.g., SLE pericarditis) ^[1]D5[8]D5.
• Dose: Prednisone 0.2-0.5 mg/kg/day orally. If used, combine with colchicine and an IL-1 inhibitor if possible to facilitate a more rapid taper ^[1]D5.
• Taper: The dose must be reduced extremely cautiously, by 1-2.5 mg every 2-4 weeks, to prevent rebound. Any recurrence during tapering calls for a return to the last effective dose and a slower taper ^[1]D5.
• Guideline position: The AHA/ACC guidelines give corticosteroids a Class III (No Benefit) recommendation for uncomplicated pericarditis ^[1]D5.

Step 6: Immunosuppressants and IVIG as Rescue for Refractory Disease

When IL-1 inhibitors fail or are not feasible, disease-modifying immunosuppressive agents or intravenous immunoglobulin (IVIG) may be considered based on limited evidence.

• Azathioprine (2 mg/kg/day) or methotrexate (15-20 mg/week) have been used in small series and a systematic review of 121 drug-induced and refractory pericarditis cases; they are particularly considered in systemic immune-mediated disease-associated pericarditis 46.
• Intravenous immunoglobulin (IVIG): 0.4-0.5 g/kg/day for 5 consecutive days can be a last-resort option. A multicentre cohort of 43 patients with a median of 5 prior recurrences reported a significant reduction in recurrences (from 5 to 1.5 per year; p<0.001) after IVIG therapy 10.

Step 7: Structured Monitoring and Treatment Discontinuation

Long-term therapy is guided by serial CRP measurements and symptom tracking.

• During active tapering, check CRP and clinical status every 1-3 months.
• The decision to stop therapy is made when the patient has been symptom-free and CRP-normal for 3-6 months off all anti-inflammatory agents. Any relapse prompts re-institution of colchicine and re-evaluation for IL-1 inhibitor candidacy.

Drug Dosing Table for Long-Term Protocols

Treatment Algorithm

Figure: Long-term pharmacological algorithm for secondary prevention of pericarditis (adapted from JACC State-of-the-Art Review ^[1]D5 and JAMA Review ^[8]D5).

What NOT to Do

• Do not prescribe corticosteroids as first-line or sole maintenance therapy for idiopathic pericarditis; this practice is associated with higher recurrence rates and dependence ^[1]D5.
• Do not stop colchicine prematurely (<3 months) unless contraindicated, as the risk of recurrence rises sharply ^[44]A1b.
• Do not taper NSAIDs abruptly or before CRP normalization; this is the most common preventable cause of early relapse ^[6]B2b.

Controversies and Guideline Disagreement

No major guideline disagreements exist regarding the central role of colchicine and IL-1 inhibitors in long-term pericarditis management; the 2025 AHA/ACC/HRS and ESC updates harmonize these recommendations ^[12]D5. The main area of clinical variability lies in the duration of IL-1 inhibitor therapy and the specific tapering protocols, which remain empirical and based on small series rather than large RCTs.

Pearl: Colchicine for at least 3-6 months is the single most impactful long-term intervention, reducing recurrent pericarditis by >50% with an NNT of only 5 ^{[44]A1b[15]A1b}.

Cardiac interventional procedures are an increasingly recognized trigger of acute pericarditis, particularly catheter ablation for atrial fibrillation and device implantation. Among 968 consecutive pacemaker or ICD implants, 10% developed pericardial effusion and 1.5% progressed to tamponade requiring pericardiocentesis or surgery ^[50]B2b. Post-ablation pericarditis occurs with even greater frequency: prospective series report incidences of 10.2% to 16.4%, with the highest risk (40.9%) following posterior wall isolation for persistent AF ^{[55]B2b[57]B2b[58]B3b}. Pulsed-field ablation does not eliminate this complication; a recent head -to-head comparison showed similar rates of pericarditis after PFA (4.3%) versus radiofrequency (3.4%, P = 0.41) ^[60]B2b. Rarer triggers include complicated PCI and hepatic microwave ablation adjacent to the diaphragm ^[52]C4[53]C4.

Diagnostic and Therapeutic Approach

Diagnosis follows ESC criteria (≥2 of: pleuritic chest pain, friction rub, ECG changes, pericardial effusion) ^[57]B2b. Once recognized, management should be instituted without delay:

1. Anti-inflammatory induction: ibuprofen 600 mg PO three times daily or aspirin 750-1000 mg three times daily, combined with colchicine. Colchicine dosing is weight-based: 0.5 mg once daily for patients <70 kg or 0.5 mg twice daily for ≥70 kg, continued for 3 months ^[56]D5.
2. Prophylactic colchicine: For patients undergoing extensive left atrial ablation (e.g., posterior wall isolation), colchicine started 7 days pre-procedure and continued for 1 month reduced pericarditis from 10.3% to 3.8% (absolute risk reduction 6.5%; NNT = 15) in a large observational cohort ^[59]B3b.
3. Pericardiocentesis: If tamponade physiology develops (hypotension, pulsus paradoxus), urgent ultrasound-guided drainage is mandatory; bloody effusion suggests lead perforation in device patients ^[50]B2b.

Comparison of Pericarditis Risk by Intervention

Controversies and Guideline Disagreement

Pearl: After extensive left atrial ablation (especially posterior wall isolation), expect a 40% incidence of acute pericarditis; prophylactic colchicine reduces this by roughly two-thirds, and early NSAID-colchicine combination therapy prevents progression to tamponade ^{[55]B2b[59]B3b[50]B2b}.

Even with guideline-directed therapy, acute pericarditis carries a spectrum of complications that necessitate close inpatient surveillance. These range from life-threatening tamponade and constrictive disease to iatrogenic harm from anti-inflammatory drugs and hospital-acquired conditions.

Respiratory Monitoring

Large pericardial effusions and tamponade compromise diastolic filling, causing dyspnea and orthopnea. Serial monitoring of respiratory rate, oxygen saturation, and work of breathing is essential. In patients with impending tamponade, positive-pressure mechanical ventilation can precipitate cardiovascular collapse by further reducing venous return ^[64]D5. Thus, intubation should be deferred if possible and performed only after pericardiocentesis or with surgical backup immediately available. A decision table for intubation is as follows:

Autonomic Complications

Cardiac tamponade elicits profound autonomic responses: hypotension, reflex tachycardia, and pulsus paradoxus. Autonomic instability manifests as labile blood pressure. Atrial arrhythmias, particularly atrial fibrillation , occur in 4-5% of acute pericarditis episodes, often in the setting of atrial inflammation or significant effusion ^[8]D5. These are usually self-limited; rate control with beta-blockers or calcium-channel blockers is sufficient. Opioid-induced ileus and urinary retention are common in patients receiving high-dose analgesia for pleuritic pain; a bowel regimen and early removal of urinary catheters mitigate these issues.

DVT/PE Prophylaxis

Hospitalized patients with pericarditis often have reduced mobility, especially if large effusion or tamponade mandates bed rest. For this high-risk group, pharmacological thromboprophylaxis with enoxaparin 40 mg subcutaneously once daily (or unfractionated heparin 5000 units three times daily in renal impairment) reduces venous thromboembolism, consistent with general medical inpatient guidelines. Early ambulation is encouraged once hemodynamics stabilize.

Pain Management

Pleuritic chest pain is the cardinal symptom and warrants aggressive control. First-line agents are NSAIDs given at anti-inflammatory doses: ibuprofen 600-800 mg three times daily or aspirin 750-1000 mg three times daily, always combined with colchicine (0.5 mg twice daily if >70 kg, 0.5 mg once daily if ≤70 kg) to hasten symptom resolution and prevent recurrence ^{[44]A1b[15]A1b[8]D5}. In the CORP-2 trial, colchicine reduced the relative risk of multiple recurrences by 50% (ARR 21%, NNT=5) over 18 months ^[15]A1b. Because high-dose ibuprofen (≥1800 mg/day) is associated with a 32% increase in major cardiovascular events (HR 1.32) ^[62]B3b, the lowest effective NSAID dose should be used, and gastroprotection with a proton-pump inhibitor is advised for those with risk factors. Opioids (e.g., morphine 2-4 mg IV every 4 hours) are reserved for breakthrough pain unresponsive to NSAIDs, with careful monitoring for respiratory depression and ileus.

Rehabilitation

During the acute inflammatory phase (typically 1-2 weeks), patients should rest and avoid physical exertion. After symptom resolution and normalization of C-reactive protein, a gradual return to non-competitive activity is safe ^[8]D5. Competitive athletes must refrain from strenuous training for at least 3 months and undergo a cardiologic re-evaluation including echocardiography and ECG before clearance ^[8]D5. This approach reduces the risk of recurrence and myocardial involvement.

Hospital-Acquired Complications

Impaired mobility, pain, and invasive monitoring create a vulnerable state for nosocomial complications. A proactive bundle reduces harm: early mobilization and incentive spirometry prevent atelectasis and pneumonia; regular skin assessment and pressure-relieving mattresses avert pressure injuries; and avoidance of unnecessary Foley catheters limits urinary tract infection. Discontinuation of central lines and nonessential monitoring as soon as clinically feasible further lowers infection risk.

Complication Summary Table

Pearl: Adding colchicine to standard anti-inflammatory therapy dramatically reduces recurrent pericarditis (NNT=5 to prevent one recurrence at 18 months) and should be initiated at diagnosis, with dose adjusted by weight, to avoid downstream complications like constriction and repetitive hospitalizations ^{[15]A1b[44]A1b}.

In-hospital mortality for a first episode of acute pericarditis is low, approximately 1.1% (95% CI 0.6-1.9%), and the risk of constrictive pericarditis is less than 0.5% even without targeted anti-inflammatory treatment ^[8]D5[16]B3b. With contemporary management , 70-85% of patients have a benign, self-limited course ^[8]D5. However, the principal morbidity is recurrence; without colchicine, 37.5% of patients develop recurrent or incessant pericarditis at a mean follow-up of 22 months ^[44]A1b.

Colchicine added to conventional therapy markedly improves this trajectory. In a randomized trial, colchicine (0.5-1.0 mg daily for 3 months) reduced the absolute risk of recurrence by 20.8 percentage points (from 37.5% to 16.7%), yielding a number needed to treat of 5 ^[44]A1b. For patients with multiple recurrences, the benefit is even more pronounced: the placebo-controlled CORP-2 trial reported a recurrence rate of 42.5% without colchicine versus 17.5% with colchicine (absolute risk reduction 25.0%; NNT = 4) ^[15]A1b. These data underscore that colchicine halts the auto-inflammatory cycle and is essential for long-term remission.

Validated Predictors of Poor Prognosis

Several clinical and laboratory features at presentation identify patients at higher risk for complications or a non-idiopathic aetiology. The most robust predictors, derived from prospective cohorts, are summarised below:

A distinct prognostic concern is the risk of occult malignancy. A nationwide Danish cohort study demonstrated that 3.7% of patients with acute pericarditis and no prior cancer received a cancer diagnosis within 3 months (standardised incidence ratio 13.0, 95% CI 10.9-15.4) ^[5]B3b. The risk declined to 1.0% beyond the first year. Moreover, when pericarditis arises in the setting of cancer, survival is significantly worse than in cancer patients without pericarditis ^[5]B3b. Therefore, failure to respond to standard anti-inflammatory therapy or presence of atypical features should prompt a search for an underlying neoplasm.

Special Circumstances

Transient constrictive physiology can develop during the acute inflammatory phase but does not inevitably lead to chronic constriction. Recognition and treatment with anti-inflammatory agents often resolve the constrictive haemodynamics, yielding a favourable prognosis without the need for pericardiectomy ^[67]D5. In contrast, bacterial or tuberculous pericarditis carries a mortality rate of up to 40% without timely specific therapy, highlighting the prognostic importance of prompt etiological diagnosis ^[17]B2b.

Pearl: Acute pericarditis has a benign short-term prognosis with mortality <2% and constriction <0.5%, but recurrence affects over one-third of patients unless colchicine is used; female sex, fever, subacute onset, large effusion, and elevated CRP identify those who require closer monitoring and targeted therapy ^{[17]B2b[2]D5[44]A1b[6]B2b}.

Management of acute pericarditis must be tailored in special populations, and secondary prevention with colchicine dramatically reduces recurrences.

Pregnancy

High-dose aspirin (750-1000 mg every 8 hours) or non-selective NSAIDs (ibuprofen, indomethacin) are safe until week 20 of gestation ^[71]D5. After week 20, NSAIDs are contraindicated because of risk of premature ductus arteriosus closure and oligohydramnios ^[71]D5. Low-dose prednisone (2.5-10 mg/day) can be used throughout pregnancy ^[71]D5. Colchicine (0.5 mg twice daily if >70 kg, once daily if ≤70 kg) is safe and compatible with breastfeeding ^[71]D5. Most pericardial effusions in pregnancy are mild and resolve postpartum; tamponade is rare but mandates urgent drainage ^[71]D5.

Elderly

Frail elderly patients frequently cannot tolerate NSAIDs or colchicine. An 87-year-old man with acute pericarditis developed severe gastrointestinal intolerance and acute kidney injury on ibuprofen and colchicine, illustrating the narrow therapeutic window ^[48]C4. In this age group, NSAIDs should be used at the lowest effective dose with proton-pump inhibitor gastroprotection and close renal monitoring ^[48]C4. Colchicine requires dose reduction in renal impairment and is best avoided when creatinine clearance falls below 30 mL/min because of risk of myopathy and myelosuppression ^[48]C4. If first-line therapy fails, a short corticosteroid course may be necessary, though it increases recurrence risk ^[48]C4.

Pediatrics

Children are managed similarly to adults, with weight-adjusted doses: ibuprofen 30-50 mg/kg/day divided every 8 hours; colchicine 0.5 mg once daily (≤70 kg) or twice daily (>70 kg) ^[72]D5. The differential includes post-viral and post-cardiotomy pericarditis and pericarditis of systemic juvenile idiopathic arthritis ^[72]D5. Prognosis is good, and colchicine effectively prevents recurrence ^[72]D5.

Immunocompromised

In immunocompromised hosts, a rigorous search for tuberculous, fungal, and other opportunistic pathogens must precede anti-inflammatory treatment ^[73]D5. NSAIDs and colchicine are used once infection is ruled out; corticosteroids should be reserved for refractory cases because they suppress immune surveillance ^[73]D5.

Prevention of Recurrent Pericarditis

Colchicine halves the recurrence rate. In the ICAP trial, 240 patients with a first episode were randomized to colchicine (0.5 mg twice daily for >70 kg, once daily for ≤70 kg for 3 months) or placebo; incessant or recurrent pericarditis occurred in 16.7% vs 31.7% (relative risk reduction 48%, NNT 6.7) ^[44]A1b. For multiple recurrences, the CORP-2 trial showed colchicine for 6 months reduced recurrences from 42.5% to 17.5% (NNT 4) ^[15]A1b. Weight-adjusted dosing minimizes gastrointestinal toxicity and is the cornerstone of secondary prevention ^{[44]A1b[15]A1b[68]B2a}.

Pearl: Colchicine reduces recurrent pericarditis by 50-60% (NNT 4-7), is safe in pregnancy and children, but must be dose-reduced or avoided in elderly patients with renal impairment ^{[44]A1b[15]A1b[71]D5[48]C4}.