Imaging visualization of fluid
The primary and most accessible method for detecting effusion is echocardiography (EchoCG). In standard B-mode, the accumulation is defined as an anechoic zone, most commonly localized along the anterior wall of the heart. If a life-threatening condition—cardiac tamponade—develops, EchoCG records impaired diastolic blood flow velocities, changes in the right-sided venous system, and the absence of adequate inspiratory collapse of the inferior vena cava.
When performing chest radiography, characteristic patterns are also observed. In the posteroanterior view, the "double contour" sign of the left third arch is visualized. In the lateral view, fluid accumulation appears as a retrosternal opacity clearly demarcated by radiolucent layers of prepericardial and epicardial fat.
Tomographic methods are indicated when complications such as haemorrhage, loculation, or constriction are suspected. Computed tomography (CT) excels at differentiating the nature of the contents based on X-ray attenuation: transudates have low values (0–20 HU), whereas haemopericardium or purulent exudates demonstrate a density of 50 HU and higher.
Magnetic resonance imaging (MRI) is indispensable for assessing the effect of fluid on ventricular diastolic filling. On T2-weighted images (T2-weighted), as well as in GRE and SSFP pulse sequences, fluid produces a high-intensity signal (while GRE and SSFP sequences can visualize fibrin strands of clotted blood). On T1-WI, the signal depends on the composition: simple transudates appear hypointense, whereas proteinaceous or haemorrhagic fluids are hyperintense (although the signal may occasionally be lost due to flow-void effects). Additional signs, such as irregularity and nodularity of the contours, may indicate a malignant lesion.
Etiology and pathomorphology of pericardial inflammation
Fluid accumulation is frequently a consequence of an inflammatory process—pericarditis. Idiopathic inflammation accounts for about 30% of all cases. Infectious causes can be viral, bacterial, or fungal. It is important to remember that in immunocompromised patients, a tuberculous etiology must be ruled out first.
Systemic causes include rheumatoid arthritis, scleroderma, and systemic lupus erythematosus. Secondary inflammation frequently develops against the background of severe uraemia. Post-infarction conditions constitute a separate group:
- Acute epistenocarditic pericarditis (occurring immediately after transmural myocardial infarction).
- Dressler syndrome (Dressler syndrome)—a delayed complication with an autoimmune mechanism.
Inflammation can also be triggered by direct or indirect chest trauma, or by radiation therapy in the treatment of lung cancer, breast cancer, or mediastinal tumors.
Clinically, the acute phase manifests with chest pain, although a subclinical course also occurs. Morphologically, highly vascularized granulation tissue forms during this period, fluid accumulates, and fibrin is deposited, which poses a future risk of adhesion formation. Upon transition to the chronic stage, the pericardial layers undergo progressive sclerosis: fibroblasts and collagen fibers are deposited, and the tissue thickens and loses elasticity, which is typical of constrictive pericarditis.
Tomographic presentation of pericarditis
CT and MRI allow for a detailed examination of changes in the pericardial layers themselves. Key CT signs of inflammation include increased pericardial thickness, active contrast enhancement, blurring of the outer contours, and increased density of the adjacent adipose tissue. If the effusion is scant, it can be extremely difficult to visually differentiate from simple layer thickening. In the absence of fluid ("dry" pericarditis), CT may reveal only mild diffuse thickening with contrast enhancement.
Computed tomography is preferred for detecting calcifications. On MRI, areas of ossification produce a focal hypointense signal that merges with areas of coarse fibrosis, significantly complicating interpretation. Important clinical note: pericardial thickening alone does not always indicate the development of constrictive pericarditis—functional assessment is required for this.
Briefly: answers to topical questions
What causes idiopathic pericardial inflammation?
The cause of idiopathic pericardial inflammation cannot be established. This form accounts for about 30% of all disease cases. Idiopathic inflammation can lead to acute nonspecific idiopathic pericarditis, accompanied by the formation of serous or sero-haemorrhagic exudate. In some cases, constrictive pericarditis is idiopathic in nature, where the pericardial sac turns into an inelastic fibrous shell.
What are the main causes leading to haemopericardium?
The main causes of haemopericardium (haemopericardium) development are trauma, cardiovascular emergencies, and iatrogenic interventions. Accumulation of blood in the pericardial sac is caused by:
- Trauma—penetrating wounds, closed injuries, and blunt cardiac trauma.
- Cardiovascular pathologies—myocardial rupture in infarction, dissection and rupture of aneurysms of the ascending aortic arch, cardiac aneurysm rupture, arrhythmogenic right ventricular dysplasia.
- Infections—myocardial abscesses and sepsis.
- Cardiosurgical interventions—percutaneous coronary interventions, pacemaker implantation, radiofrequency ablation.
What are the differences between Dressler syndrome and acute epistenocarditic pericarditis?
The main differences lie in the timing of onset, etiology, and duration of the conditions.
| Characteristic | Acute epistenocarditic pericarditis | Dressler syndrome (Dressler syndrome) |
|---|---|---|
| Timing of onset | From several hours to 4 days from the onset of infarction | 1–2 weeks after infarction |
| Etiology | Acute inflammation following transmural infarction | Autoimmune etiology |
| Course | Usually resolves spontaneously and quickly | Symptoms may persist for several weeks |
| Features | An early form | A late form; the classical fully developed polyserositis is extremely rare |
Class and exam questions
How to differentiate transudate from haemopericardium on CT based on density?
The main criterion is the X-ray attenuation of the contents. Transudates have a density from 0 to 20 HU, whereas the density of haemorrhagic or purulent effusion is significantly higher, reaching 50 HU and more.
Which imaging modality best visualizes pericardial calcification?
CT is the optimal method for detecting calcifications. On MRI, areas of ossification appear hypointense and may visually merge with fibrous tissue, making them difficult to distinguish.
Does thickening of the pericardial layers on tomograms always indicate constrictive pericarditis?
No, anatomical thickening of the layers does not always mean the development of constriction. To confirm constrictive pericarditis, it is necessary to assess the functional impact on the diastolic filling of the heart.
How does proteinaceous effusion appear on T1-weighted MRI images?
Proteinaceous or haemorrhagic effusion typically produces a high-intensity signal on T1-WI. However, the signal may occasionally become hypointense due to flow-void effects.
What else to study on this topic
- Assessment of cardiac diastolic function and detection of constriction using MRI
- Hemodynamic features of cardiac tamponade on EchoCG
- Differential diagnosis of malignant and inflammatory effusions on tomograms
- Mechanisms of development and imaging presentation of Dressler syndrome
- Diagnostic specifics of tuberculous pericarditis in immunocompromised patients
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