Other Pericardial Diseases

Beyond effusion, tamponade, and constriction, a handful of other pericardial entities are worth knowing well: acute pericarditis itself as a clinical syndrome (rather than simply the cause of an effusion), pericardial cysts, congenital absence of the pericardium, and pericardial involvement by tumors. Each has a genuinely distinct echocardiographic signature, and — for the anatomic entities especially — a genuinely distinct differential diagnosis worth getting right.

Acute Pericarditis

Acute pericarditis is pericardial inflammation — infiltration of inflammatory cells into the pericardium — most often idiopathic or viral, and usually self-limited. By convention it’s termed acute if it lasts under 3 months; beyond that, it’s chronic.

Diagnosis Is Clinical, Not Echocardiographic

Diagnosis rests on at least two of four criteria: typical chest pain (classically sharp, substernal, pleuritic, relieved by sitting forward), a pericardial friction rub, typical ECG changes (diffuse ST elevation with PR depression), and a new or worsening pericardial effusion. When fewer than two criteria are present, supportive data — elevated inflammatory markers (ESR, CRP), white blood cell count, troponin, or fever — help make the case. In equivocal or refractory cases, cardiac MRI with T2-weighted imaging and late gadolinium enhancement can directly identify pericardial edema and active inflammation.

What Echo Actually Shows

A substantial proportion of patients with acute pericarditis have an entirely normal echocardiogram — a normal study never excludes the diagnosis. When abnormal, findings include:

• Pericardial effusion — present in many, but not all, cases; its presence supports the diagnosis, but its absence doesn’t refute it. Size ranges from trivial to large, and distribution can be localized, loculated, or circumferential.
• Increased pericardial brightness and thickening.
• Abnormal septal bounce, which can be an early sign of transient constrictive physiology — see Constrictive Pericarditis for how this can evolve, and for how often it resolves with the same anti-inflammatory therapy used for the pericarditis itself.
• Tamponade physiology in roughly 3% of patients — worth actively screening for even in a syndrome that’s usually benign.
• Intrapericardial fibrinous strands, suggesting either an inflammatory process or clotted blood.
• Intrapericardial masses, which can reflect primary or secondary pericardial tumors, or an inflammatory process — imaging alone can’t reliably tell these apart.

Echo’s other genuinely important job is exclusion: confirming the absence of regional wall motion abnormality helps distinguish pericarditis from myocardial ischemia or injury — a real clinical need, since acute pericarditis can closely mimic ST-elevation myocardial infarction clinically. The exception worth remembering: about 5% of patients with acute pericarditis do show segmental wall motion abnormalities, presumably from associated myocardial involvement (myopericarditis) — a genuine source of diagnostic confusion, since these patients are sometimes referred directly for coronary angiography under a working diagnosis of STEMI.

Fluid Composition on CT and MRI

Beyond echo, CT attenuation values can distinguish fluid types: exudative fluid (20–60 Hounsfield units, as in purulent pericarditis) from simple transudative fluid (under 10 Hounsfield units). On CMR, exudative effusion — high in protein and cellular content — shows relatively higher T1-weighted signal intensity; late gadolinium enhancement of thickened pericardium confirms active inflammation, with reported sensitivity of 94–100% for detecting pericardial inflammation. Chronic, burnt-out fibrotic pericarditis, by contrast, shows thickening without enhancement — a genuinely useful way to separate active disease from an old, quiescent scar.

Recognized Pathologic Patterns

• Fibrinous pericarditis — diffuse fibrin deposits over both pericardial surfaces, classically associated with uremia.
• Fibrinohemorrhagic exudate — most commonly associated with neoplastic disease.
• Fibrous pericarditis — thickening of both parietal and visceral layers, the substrate for constriction; classically seen with radiation-induced disease.
• Organizing and organized (healed) pericarditis — a spectrum from active fibrin and granulation tissue to hypocellular, densely fibrotic end-stage scarring.

Treatment

Exercise restriction, aspirin or NSAIDs, and colchicine form the standard approach; in cases with poor prognostic features, more intensive therapy (NSAIDs, colchicine, and corticosteroids together) may be used, sometimes guided by imaging findings of ongoing inflammation.

Recurrent Pericarditis

A meaningful minority of patients experience recurrence after an initial episode. Recognized risk factors include fever, a subacute (rather than acute) presentation, an immunosuppressed host, myopericarditis, a large effusion or tamponade physiology at the index presentation, prior chest trauma, concurrent anticoagulant medication, an incomplete initial anti-inflammatory course, prior corticosteroid therapy, and failure to respond promptly to initial treatment.

Treatment: a prolonged course of NSAIDs, with colchicine added or used as monotherapy. Corticosteroids provide rapid symptomatic relief but are generally avoided as initial therapy specifically because they’ve been shown to increase the risk of further recurrence — an important, somewhat counterintuitive point, since the concern isn’t that steroids don’t work, but that they make the underlying tendency to recur worse. Pericardial or epicardial biopsy can be considered for relapsing pericardial effusion when the diagnosis can’t be reached through imaging and laboratory testing alone.

Pericardial Cysts

Pericardial cysts are benign intrathoracic lesions, accounting for about 6% of all mediastinal masses. They’re typically unilocular, contain serous fluid, and range from 1 to 5 cm in diameter, though giant cysts have been reported. Inflammatory cysts and pseudocysts arise from prior pericardial inflammation or a loculated effusion — following surgery, trauma, pericarditis, or chronic bacterial or tuberculous infection. A parasitic (hydatid) cyst is typically multilocular — a genuinely useful distinguishing feature from a simple cyst.

Clinical Presentation

Most cysts are incidental findings on imaging done for another reason. Up to a third of patients report atypical chest pain, dyspnea, or a persistent cough. Recognized complications, though uncommon, include infection, hemorrhage or rupture, erosion into adjacent structures (the SVC or RV free wall), tamponade, RV outflow tract obstruction, atrial fibrillation, obstruction of the right main bronchus, and — rarely — sudden death.

Imaging

Chest x-ray classically shows a rounded, well-circumscribed radiodense mass at the right cardiophrenic angle — the most common location — though left cardiophrenic, hilar, and superior mediastinal locations are all reported. On echocardiography, a cyst appears as a rounded, echolucent, cystic structure adjacent to the right atrium. The single most important echocardiographic distinguishing feature: it does not communicate with the pericardial space. TEE can offer better delineation than TTE. Large cysts can compress right-sided chambers and produce symptoms directly. CT or CMR is typically pursued to confirm the diagnosis, define anatomic detail, and exclude a neoplasm or aneurysm.

The Key Differential: Pericardial Diverticulum

A pericardial diverticulum is an extremely rare outpouching through a defect in the parietal pericardium. Unlike a true cyst, a diverticulum does communicate with the pericardial space through that defect, and — because of this communication — it can change size and shape with repositioning and respiration, something a true cyst never does. Other entries in the differential include cardiac and mediastinal tumors, noncardiac cysts, abscesses, and visceral hernias.

Treatment

Asymptomatic cysts warrant periodic surveillance — typically serial CT or CMR every 1 to 2 years. Symptomatic cysts, or those with diagnostic ambiguity, are managed with percutaneous aspiration, sometimes with ethanol sclerosis; thoracoscopic or open surgical resection is reserved for genuine diagnostic uncertainty or recurrence after percutaneous attempts. A specific and important exception: echinococcal (hydatid) cysts should never be surgically excised directly — the risk of anaphylaxis or dissemination from cyst content spillage is real. Instead, albendazole pretreatment followed by ethanol or silver nitrate instillation is the recommended approach.

Congenital Absence of the Pericardium

Absence of the pericardium is rare and can be either congenital or acquired — the acquired form is almost always the consequence of surgical pericardiectomy.

Epidemiology and Pathogenesis

Congenital absence is uncommon (under 1 in 100,000), with a 3:1 to 4:1 male predominance. Left-sided absence is by far the most common pattern, accounting for about 67% of cases; total absence, right-sided absence, and diaphragmatic defects are all rarer. It arises from premature atrophy of the left common cardiac vein (the duct of Cuvier) during fetal development, leading to pericardial hypoperfusion and agenesis.

Associated Anomalies

About 30% of patients have a coexisting anomaly. Cardiac associations include atrial septal defect, a bicuspid aortic valve (see Aortic Stenosis for the broader bicuspid valve picture), patent ductus arteriosus, and tetralogy of Fallot. Extracardiac associations include pulmonary sequestration, bronchogenic cysts, and congenital diaphragmatic hernia. Reported syndromic associations include VATER syndrome, Marfan syndrome, and Pallister-Killian syndrome.

Clinical Presentation

Most patients are asymptomatic, with the diagnosis made incidentally on imaging, at cardiac surgery, or at autopsy. Both the clinical picture and the imaging findings stem from loss of pericardial restraint, allowing an exaggerated leftward and posterior swing of the heart. The classic symptomatic presentation is a young man with intermittent, nonexertional, stabbing chest pain, dyspnea, or palpitations specifically brought on by lying in the left lateral position — a genuinely distinctive clinical clue. Rarely, chordal rupture or annular dilation causes tricuspid regurgitation, or the heart can actually herniate through the defect. Physical examination may show only a laterally displaced apical impulse or a nonspecific systolic murmur. Complete pericardial absence is usually entirely benign; partial absence carries the real risk — cardiac entrapment through the defect itself.

ECG and Chest X-Ray

ECG can show right axis deviation, incomplete right bundle branch block, and poor R-wave progression across the precordial leads — and, distinctively, the axis and ST-T wave morphology can change with body position, a genuine diagnostic clue in the right clinical context. Chest x-ray can show levoposition of the heart, an elongated LV silhouette, and a radiolucent band of interposed lung tissue between the heart and the diaphragm or great vessels — lung filling space the pericardium would normally occupy.

Echocardiographic Findings

• An unusually lateral transducer position is needed for both parasternal and apical windows — itself a practical clue during the study that something about the cardiac position is abnormal.
• Levoposition with exaggerated posterior mobility of the heart produces abnormal paradoxical septal motion and an appearance of right-sided chamber enlargement.
• “Teardrop shape” — elongated atria with a rounded ventricle — is a specific descriptive term used for this appearance.
• M-mode shows the septum moving anteriorly in systole and posteriorly in diastole — an abnormal, paradoxical pattern, mechanistically distinct from the septal motion seen with RV volume overload, since here it reflects loss of pericardial restraint rather than competition between the ventricles for a fixed space.
• The heart’s swinging motion is directly visible on 2D imaging, particularly from the parasternal long-axis view.
• With partial absence, focal constriction or entrapment of a herniated segment can be seen directly — sometimes producing a “teardrop”-shaped right ventricle with focal narrowing at the site of entrapment, which is the specific finding that flags the higher-risk partial variant.

Pericardial Involvement by Tumors

Primary pericardial tumors are rare; pericardial involvement more often reflects either direct extension from a cardiac tumor or metastatic disease. A pericardial effusion — particularly a hemorrhagic one — is itself a meaningful clue to malignancy when a cardiac or paracardiac mass is being evaluated: in one CMR series, concurrent pericardial effusion was present in 41% of malignant tumors versus only 7% of benign ones, alongside infiltration into the free wall (54% vs. 0%) and infiltration into adjacent structures (49% vs. 0%) as other markers favoring malignancy. Angiosarcoma and cardiac hemangioma are both specifically associated with hemorrhagic pericardial effusion. CMR adds further discriminating value beyond echo: first-pass perfusion and late gadolinium enhancement were both present in 100% of malignant tumors in one series, though each was also seen in a meaningful minority of benign tumors, so neither is fully specific on its own — a combination of imaging features, not any single one, is what points toward malignancy.

A Note on Pneumopericardium

Air within the pericardial space — from trauma, recent cardiac surgery, or a bronchopericardial fistula — is a genuine technical limitation worth remembering: air in the pericardial space inhibits ultrasound transmission and can make the heart difficult or impossible to image adequately by echo. When pneumopericardium is suspected clinically but echo windows are poor or unrevealing, this itself should be recognized as an expected limitation rather than a failed or inadequate study, and chest x-ray or CT should be pursued instead.

How to Approach These Entities Diagnostically

1. For suspected acute pericarditis, apply the four clinical criteria first; use echo primarily to detect an effusion, screen for tamponade physiology (present in about 3%), and exclude a regional wall motion abnormality that might otherwise be mistaken for acute coronary syndrome — while remembering that about 5% of true pericarditis patients do show a wall motion abnormality.
2. For a cystic-appearing structure adjacent to the heart, confirm it doesn’t communicate with the pericardial space (a true cyst) versus does (a diverticulum, with size/shape change on repositioning or with respiration); note whether it’s unilocular (simple/inflammatory) or multilocular (raising the possibility of a hydatid cyst); and pursue CT or CMR to exclude a neoplasm before assuming a benign cyst.
3. For an unusual transducer position, exaggerated cardiac swinging motion, or paradoxical septal motion without an obvious volume-overload explanation, consider congenital absence of the pericardium — look specifically for the “teardrop” chamber appearance, and, if partial absence is suspected, look deliberately for focal entrapment of a herniated segment.
4. For any pericardial effusion found in the setting of a known or suspected cardiac mass, treat a hemorrhagic or exudative-appearing effusion as a marker that raises, rather than lowers, concern for malignancy, and pursue CMR for further characterization.
5. When echo windows are unexpectedly poor in a post-surgical or trauma patient, consider pneumopericardium as an explanation before assuming technical failure, and move to CT.

Clinical Importance

These entities share a common thread: each has a distinctive echocardiographic signature once specifically looked for, but each can also be missed or misread if the underlying mechanism isn’t kept in mind — a normal echocardiogram in a patient with classic pericarditic chest pain, a cystic structure dismissed without checking whether it communicates with the pericardial space, or an oddly positioned, swinging heart attributed to poor technique rather than absent pericardium. Recognizing the mechanism behind each finding is what turns an unusual echo appearance into a specific diagnosis.