Post-Infarction Pericarditis and Dressler Syndrome

Definition and pathophysiology

Post-infarction pericarditis encompasses two temporally and clinically distinct complications of acute myocardial infarction (AMI):

• Early infarct-associated pericarditis, which develops from several hours to approximately 4 days after infarction and is usually transient.

• Late post-acute myocardial infarction pericarditis, traditionally termed Dressler syndrome, which is a manifestation of post-cardiac injury syndrome (PCIS).

PCIS is an umbrella term that also includes post-pericardiotomy syndrome and post-traumatic pericarditis, including cases related to cardiovascular interventions. Dressler syndrome now occurs in fewer than 1% of AMI cases and is seen predominantly after larger infarctions and/or delayed reperfusion. Its typical onset is 1–2 weeks after AMI, although descriptions of the syndrome include a broader interval of approximately 1–8 weeks.

The pathogenesis is presumed to be immune mediated. Pericardial injury, necrosis, bleeding, or pleural incision may expose cardiac antigens and initiate an inflammatory response. The presence of antibodies directed against cardiac tissue, the latent interval of several weeks, improvement with anti-inflammatory treatment, and the tendency to recur all support an immunopathological mechanism. The precise cause, however, is not fully established.

At pathological examination, Dressler syndrome is generally characterized by localized fibrinous pericarditis containing polymorphonuclear leukocytes.

Important distinction from subacute cardiac rupture

A post-AMI pericardial effusion is not automatically attributable to Dressler syndrome. A pericardial effusion measuring more than 10 mm at end-diastole after AMI should prompt investigation for possible subacute cardiac rupture, particularly when the effusion develops in the early post-infarction period.

Clinical presentation and symptoms

The characteristic clinical syndrome consists of:

• Malaise

• Fever

• Pericardial or chest discomfort

• Leukocytosis

• Elevated erythrocyte sedimentation rate

• Pericardial effusion

Pericardial pain is often sharp and pleuritic. It may worsen with inspiration, coughing, lying supine, or swallowing and typically improves when the patient sits up and leans forward. Pain may be retrosternal or left precordial and can radiate to the neck, arms, or left shoulder. It may occasionally be steady and resemble myocardial ischaemia, creating diagnostic difficulty in a patient recently treated for AMI.

Dyspnoea may occur, particularly when the effusion is substantial or when haemodynamic consequences develop. In patients with pericarditis complicated by constriction, symptoms and signs of right-sided heart failure may predominate.

Pericardial effusions associated with post-infarction pericarditis are commonly mild. A rapidly developing or large effusion is clinically more concerning because it may lead to cardiac tamponade or indicate another post-AMI complication, including subacute rupture.

Evaluation and physical examination

The diagnosis of pericarditis is clinical and is supported by additional findings. A definite diagnosis requires a compatible clinical presentation plus more than one additional diagnostic criterion.

Pericardial friction rub

A friction rub is a superficial, scratchy, squeaking, rasping, or grating sound produced by contact between inflamed pericardial layers. It may have up to three components per cardiac cycle and is often best heard at end expiration with the patient upright and leaning forward.

The frequency with which a rub is detected varies among clinical descriptions. It may be present intermittently during the illness and, in some series, is reported in up to approximately one-third of patients. Its absence therefore does not exclude the diagnosis.

Findings suggesting pericardial effusion

A large effusion may cause:

• Diminished heart sounds

• Disappearance of the friction rub

• Loss of the apical impulse

• Electrical alternans on the ECG

Compression of the left lung base can produce Ewart’s sign, consisting of a zone of dullness, increased tactile fremitus, and egophony beneath the angle of the left scapula.

Physical examination must also assess for haemodynamic compromise. The source material emphasizes the importance of identifying tamponade and right-heart-failure manifestations, but does not provide a detailed haemodynamic examination algorithm.

Diagnostic criteria

Pericarditis is defined as an inflammatory pericardial syndrome, with or without effusion. Diagnostic support may come from:

• Typical pericardial chest pain

• A pericardial friction rub

• New or worsening pericardial effusion

• Characteristic ECG abnormalities

• Elevated inflammatory markers or neutrophilic leukocytosis

• Pericardial inflammation on CT or cardiovascular magnetic resonance (CMR)

In the post-infarction setting, these findings must be interpreted alongside the timing of symptoms, infarct size, reperfusion history, ventricular function, and the characteristics of any effusion.

Electrocardiography

Acute pericarditis pattern

In acute pericarditis without a massive effusion, ECG changes reflect acute subepicardial inflammation and may evolve through four stages:

• Initial stage: widespread, usually concave ST-segment elevation involving multiple limb leads and precordial leads, with reciprocal depression mainly in aVR and occasionally another right-sided lead. PR-segment depression may occur and can precede the ST changes.

• Normalization of ST segments: the ST segments return toward baseline after several days.

• T-wave inversion: T waves may invert after ST-segment normalization.

• Late normalization: the ECG may return to normal over subsequent weeks or months.

The pericardium itself is electrically silent. Accordingly, ECG changes in a patient with pericarditis imply associated myocardial or epicardial inflammation and should prompt consideration of myocardial involvement.

Distinguishing pericarditis from recurrent infarction

Pericarditis may produce extensive ST-segment elevation, but the pattern is typically widespread and upwardly concave, with limited reciprocal depression. By contrast, infarction more commonly produces upwardly convex ST elevation with more prominent reciprocal changes.

The distinction may be difficult in a recent AMI patient, particularly when myocardial biomarkers are elevated. In pericarditis with superficial epicardial myocardial injury, biomarker elevation is generally modest relative to the extent of ECG changes, whereas AMI usually produces a greater biomarker release.

Effusion-related ECG findings

Large effusions may produce electrical alternans. QRS changes are usually absent unless the effusion is substantial.

Imaging

Transthoracic echocardiography

Transthoracic echocardiography (TTE) is the principal imaging modality for detecting and characterizing pericardial effusion. It is non-invasive, readily available, suitable for bedside use, and permits:

• Confirmation of pericardial fluid

• Estimation of effusion size

• Assessment of its distribution

• Evaluation for haemodynamic consequences

• Assessment of left and right ventricular function

On two-dimensional TTE, fluid is visualized as a relatively echo-free space between the posterior pericardium and the left ventricular epicardium and/or between the anterior right ventricle and the parietal pericardium.

In patients with post-AMI effusion, an end-diastolic thickness greater than 10 mm should lead to evaluation for possible subacute cardiac rupture rather than being assumed to represent uncomplicated Dressler syndrome.

Chest radiography

A large effusion may enlarge the cardiac silhouette and produce a characteristic “water-bottle” configuration. The radiograph may nevertheless be normal when the effusion is small.

Computed tomography

CT can confirm pericardial fluid or thickening and may be superior to echocardiography for identifying:

• Loculated effusions

• Pericardial thickening

• Pericardial masses

Contrast enhancement of an inflamed pericardium can provide evidence of active inflammation.

Cardiovascular magnetic resonance

CMR offers high-resolution tissue characterization and is particularly useful when the diagnosis is uncertain or when concomitant myocardial involvement is suspected. Pericardial inflammation may be demonstrated by:

• Pericardial oedema

• Pericardial late gadolinium enhancement

• Contrast enhancement of the inflamed pericardium

CMR can also delineate the extent of myocardial injury after infarction. Areas of infarction demonstrate late gadolinium enhancement because gadolinium enters the expanded extracellular space of injured myocardium, whereas normal myocardium shows little delayed contrast accumulation.

Biomarkers and laboratory findings

The inflammatory laboratory profile may include:

• Elevated C-reactive protein

• Elevated erythrocyte sedimentation rate

• Neutrophilic leukocytosis or other leukocytosis

C-reactive protein is elevated in a large proportion of patients with acute pericarditis, and ESR and leukocytosis provide additional supportive evidence.

Troponin elevation may occur when inflammation extends to the epicardium or myocardium. In predominantly pericarditic disease, the increase is generally modest compared with AMI despite potentially extensive ST-segment elevation. Troponin elevation should therefore prompt assessment for myocardial involvement rather than being interpreted in isolation.

The material does not provide a specific laboratory panel or biomarker threshold for diagnosing Dressler syndrome.

Differential diagnosis and diagnostic priorities

The principal diagnostic issues after AMI are:

Recurrent or extension myocardial infarction

Pericarditic pain and diffuse ST elevation may resemble recurrent ischaemia. The distribution and morphology of ECG changes, the degree of biomarker release, symptoms, and imaging findings must be integrated.

Subacute cardiac rupture

A substantial post-AMI effusion, particularly one exceeding 10 mm at end-diastole, requires evaluation for subacute rupture. This is a critical distinction because treatment directed solely at inflammation could delay management of a mechanical complication.

Myopericarditis or perimyocarditis

Pericarditis with elevated myocardial biomarkers but no new focal or diffuse impairment of left ventricular function is termed myopericarditis. When myocardial involvement is predominant, with new left ventricular dysfunction in the setting of elevated biomarkers and pericardial features, the condition is termed perimyocarditis. Management follows the predominant component: myopericarditis is managed as pericarditis, whereas perimyocarditis is managed as myocarditis.

Other causes of post-cardiac injury syndrome

The broader PCIS spectrum includes post-pericardiotomy and post-traumatic pericarditis. Cardiovascular interventions, device implantation, and arrhythmia ablation are increasingly recognized contexts for post-cardiac injury syndromes.

Treatment and management

Initial risk stratification

Risk assessment should occur at the first presentation, whether in an emergency or ambulatory setting. Hospital admission is recommended for high-risk cases. Patients without high-risk features may be managed as outpatients, provided that close follow-up is arranged within 1–2 weeks.

Features associated with increased risk of a non-viral aetiology or complications include:

In post-AMI patients, the threshold for imaging and observation should be particularly low because pericardial effusion may reflect rupture rather than inflammation.

Anti-inflammatory treatment

The established treatment for Dressler syndrome is aspirin together with colchicine.

Aspirin may be administered at a dose of 650 mg as often as every 4 hours, according to clinical need and tolerance. The source material does not specify a colchicine dose or duration.

Clinical response, inflammatory markers, symptoms, ventricular function, and the size and haemodynamic effect of the effusion should guide ongoing management. The duration of treatment should be individualized according to the clinical and imaging course; a specific Dressler-syndrome treatment duration is not provided.

Drugs to avoid early after STEMI

Glucocorticoids and non-steroidal anti-inflammatory drugs are best avoided during the first 4 weeks after STEMI in patients with Dressler syndrome. The stated concerns are:

• Impaired infarct healing

• Increased risk of ventricular rupture

• Increased coronary vascular resistance

This caution is especially important when the diagnosis has not been securely separated from a mechanical post-infarction complication.

Colchicine and recurrence prevention

Colchicine is part of the recommended treatment for Dressler syndrome. More broadly, colchicine reduces the frequency of recurrent pericarditis: recurrence affects approximately 20%–30% of patients who are not treated with colchicine.

Patients with persistent symptoms, multiple recurrences, poor response to conventional treatment, or evidence of an inflammatory phenotype may require specialist assessment. Anti-interleukin-1 agents have become available for recurrent pericardial disease with poor response to conventional therapy, although specific agents, doses, and treatment algorithms for Dressler syndrome are not provided here.

Management of effusion and tamponade

The material emphasizes echocardiographic assessment of effusion and recognition of tamponade, but does not provide procedural criteria or a detailed drainage protocol. A rapidly developing or large effusion requires urgent evaluation for tamponade and subacute rupture.

Guideline-based management principles

The principal recommendations relevant to post-infarction pericarditis and Dressler syndrome are:

• Identify the timing of the syndrome. Early infarct-associated pericarditis occurs within hours to 4 days; late post-AMI or Dressler syndrome generally occurs 1–2 weeks after AMI.

• Investigate significant effusion for rupture. A post-AMI effusion greater than 10 mm at end-diastole should prompt assessment for subacute cardiac rupture.

• Use multimodality imaging when needed. TTE is the primary test for effusion and ventricular assessment; CT and CMR can better define thickening, loculation, masses, and active pericardial inflammation.

• Risk-stratify at presentation. High-risk patients should be admitted; lower-risk patients require close outpatient review within 1–2 weeks.

• Treat Dressler syndrome with aspirin and colchicine.

• Avoid NSAIDs and glucocorticoids during the first 4 weeks after STEMI because of concerns regarding infarct healing, ventricular rupture, and coronary vascular resistance.

• Assess myocardial involvement when troponin is elevated or ECG abnormalities are present. The distinction between myopericarditis and perimyocarditis determines whether management follows a pericarditis or myocarditis pathway.

• Individualize physical activity restriction. Active inflammatory myopericardial disease warrants restriction of physical activity. Complete clinical remission should include normalization of symptoms, biomarkers, and imaging before resumption of exercise, with the return to activity tailored to the individual.

Prognosis and follow-up

Expected course

Acute pericarditis usually enters clinical remission within 4–6 weeks after medical treatment. Approximately 10% of patients may have persistent symptoms without clinical remission; this pattern is termed incessant pericarditis and may progress to constriction over several months.

Recurrence is the most frequent problematic complication. It occurs in approximately 20%–30% of patients who do not receive colchicine. Multiple recurrences are possible but are not typical of uncomplicated presumed viral pericarditis and should prompt evaluation for an underlying cause.

The overall in-hospital mortality of acute pericarditis is approximately 1%, although risk may be higher in older patients and in those with severe co-infections. The risk of constrictive pericarditis is low after presumed viral or idiopathic disease, intermediate with immune-mediated causes and PCIS, and higher with bacterial pericarditis.

Follow-up strategy

Patients managed as outpatients should be reviewed within 1–2 weeks. Follow-up should reassess:

• Symptoms and functional status

• Temperature and signs of systemic inflammation

• Pericardial rub

• ECG evolution

• Inflammatory biomarkers

• Effusion size and haemodynamic effect by echocardiography when clinically indicated

• Left ventricular function when myocardial involvement is suspected

Additional diagnostic work-up is warranted when there are high-risk features, an atypical course, incomplete response to anti-inflammatory therapy, persistent biomarker abnormalities, or concern for myocardial involvement or mechanical complications.

In patients with overlapping myocardial and pericardial inflammation, follow-up should include clinical evaluation, rhythm assessment, laboratory testing, and multimodality imaging. Complete remission requires resolution of symptoms and normalization of ECG, biomarkers, echocardiographic findings, and CMR abnormalities where those modalities were initially abnormal.

Physical activity and return to exercise

Active inflammatory disease warrants restriction of physical activity. During acute myocardial involvement, complete rest is advised because exercise has been associated with arrhythmias and sudden cardiac death. Return to activity should not be based solely on a fixed interval; it should follow individualized evidence of remission, including clinical, biochemical, rhythm, and imaging recovery.

Key clinical points

• Dressler syndrome is a late post-AMI manifestation of PCIS, usually appearing 1–2 weeks after infarction and now occurring in fewer than 1% of cases.

• The syndrome is presumed to be immune mediated and typically presents with fever, malaise, pericardial pain, leukocytosis, elevated inflammatory markers, and pericardial effusion.

• A post-AMI effusion exceeding 10 mm at end-diastole requires evaluation for subacute cardiac rupture.

• TTE is the first-line imaging modality; CT and CMR provide additional information about loculated fluid, thickening, masses, oedema, and late gadolinium enhancement.

• ECG changes may be widespread and pericarditic, but ECG abnormalities imply associated myocardial or epicardial inflammation.

• Treatment consists of aspirin, including a regimen of 650 mg as often as every 4 hours, together with colchicine.

• NSAIDs and glucocorticoids should generally be avoided during the first 4 weeks after STEMI.

• Close early follow-up is essential because recurrence, persistent inflammation, constriction, tamponade, and myocardial involvement may complicate the course.