What Ultrasounds, Sometimes, Cannot See: A Case of Posterior Pericardial Cyst.

Pericardial cysts (PCs) are very rare, often congenital, mediastinal masses. Usually, they are located in the right cardiophrenic angle and only in 8% of cases in the anterior or posterior mediastinum. Computed tomography and/or magnetic resonance imaging are accurate tools for the diagnosis and characterization of mediastinal masses. However, echocardiography is, in many cases, a good screening technique. If asymptomatic, they do not require surgical excision. The authors describe a case of posterior mediastinum PC; in these cases, echocardiography cannot see the mass and three-dimensional imaging techniques are required. The clinical management of this case is discussed.

INTRODUCTION

Pericardial cysts (PCs) are rare, often congenital, mediastinal masses. In the middle mediastinum, 61% of presenting masses are cysts, of whom, only 6% are PCs.[1]

Usually, they are located in the right cardiophrenic angle and only rarely (8% of cases) in the anterior or posterior mediastinum.[2]

PCs have an average size of 1-5 cm, if they are >5 cm are called “giants”.[3]

PCs usually are asymptomatic although they may result in compression of the neighboring structures and manifest with nonspecific symptoms.[4]

Echocardiography is a good screening tool because it is able to display in many cases an anechoic image near the heart; however, the diagnosis, the extension, and compressive phenomena require the use of a second-level diagnostic examinations. We present a case of a PC in a patient with congestive heart failure that required a multidisciplinary approach for diagnosis and therapy.

CASE REPORT

An 81-year-old Caucasian woman presented to our unit with a history of dyspnea for mild efforts, orthopnea, and worsening of peripheral edemas. She had permanent atrial fibrillation (AF) and hypertensive heart disease with preserved ejection fraction (EF).

Blood tests showed normal values except for an elevation of C-reactive protein, end-systolic volume, and B-type natriuretic peptide. An arterial blood gas showed respiratory acidosis with metabolic control.

Echocardiography showed left and right atrium dilatation, left ventricular hypertrophy with normal ventricular diameters, kinesis and function (ejection fraction: 56%); at color Doppler, there was a mild tricuspid insufficiency with moderate pulmonary hypertension (pulmonary artery pressures 45 mmHg). Diastolic function was impaired (peak acceleration rate of mitral E velocity: 2100 cm/s2, E/E’: 18 and isovolumic relaxation time: 50 ms).[5]

Considering clinical and instrumental framework, it was added diuretic therapy, with subsequent patient's improvement.

The chest X-ray highlighted “oval opacity, projected in the left paracardiac region” [Figure 1].

Figure 1

Chest X-ray anteroposterior projection (a) and laterolateral projection (b): Evidence of oval opacity, projected in the left paracardiac region

So that, a chest computed tomography (CT) scan was performed to better characterize the mass and exclude a malignant lesion. It showed a 60 mm × 23 mm oval fluid-contained formation located in the posterior left paracardiac region [Figures 2–6]. The final diagnosis was mediastinal cyst.

Figure 2

Chest computed tomography coronal plane after contrast medium: Oval formation, 60 mm × 23 mm (arrow), evidence of maximum extension craniocaudal

Figure 6

Chest computed tomography, axial plane: The cyst seems have a pedicle originates from the pericardial withdrawal of the left lung

Chest computed tomography, axial plane before (a) and after (b) administration of contrast medium: The mass has a wall thickness of 1.8 cm; the absence of enhancement after contrast medium injection lays for the diagnosis of cysts

Chest magnetic resonance imaging, axial plane: Hyperintense mass in T2 sequence (a) and hypointense mass in T1 sequence (b), that confirms the suspect of cyst

Cardiac magnetic resonance imaging (MRI) confirmed the presence of a mass along the pericardial leaflet of the left ventricular free wall, suggestive of pericardial coelomatic cyst [Figures 4–7].

Figure 4

Chest magnetic resonance imaging, axial plane, T2 sequence with removal of adipose tissue signal: Evidence of fluid composition

Figure 7

Chest magnetic resonance imaging, axial plane: Is confirmed the pedicle in withdrawal of the left lung pericardial

Serial echocardiography does not allow the visualization of the mediastinal mass (because rear) even in the off-axis sections.

In brief, the echocardiography is a good screening tool for PCs located in anterior or lateral mediastinum but does not allow visualization of posterior mediastinal masses because they are located in a blind spot for ultrasound; the chest X-ray identifies the mass, locates it but does not define its spatial relationships. Conversely, CT scan reveals the cystic nature of the mass, its craniocaudal excursion, its relationship with the lateral walls of left atrium and ventricle with a pedicle that apparently originates from the pericardium only the; RMI showed the complete anatomy of cysts, its location, its relationship with cardiac chambers, and the correct localization of the pedicle allowing the final diagnosis of PCs.

The clinical and instrumental data have led us to some considerations for pathophysiological mechanism and clinical management. From a pathophysiological point of view, arterial hypertension for many years is “alone” a cause of diastolic function impairment; but, it cannot rule out that the large size of the PC may have contributed to changes in diastolic function and the onset of AF. So that, in our case, the increase of diuretic therapy has allowed the regression of symptoms and the improvement of clinical condition. Considering patient's age and clinical improvement, after a multidisciplinary assessment, we have chosen a conservative approach with only medical therapy.

The patient was discharged after pharmacological therapy optimization, with the recommendation of carry out follow-up of the mediastinal lesion.

DISCUSSION

Primary PCs represent 19%–25% of all mediastinal masses and occur more frequently in the third to fourth decade of life, with equal prevalence in both sexes.[6] Most cysts are congenital and represent the incomplete or nonfusion of one of the mesenchymal lacunae that form the pericardial sac; only a few cases are represented by acquired cysts secondary to neoplastic infiltration of the pericardium, trauma, previous cardiac surgery, or infection.[789]

PCs are characterized by a single wall of mesothelial cells, usually uniloculate, they contain a clear water-likefluid and thus referred to as “spring water cysts.”[101112] They adhere to the pericardium or directly or by means of a peduncle.[3] The shape is circular or oval. The size varies between 1 and 5 cm; the giant cysts are much less frequent.[3]

The 70%–75% are located in the cardiophrenic right angle, 22% left, and the remaining are located in the upper mediastinum back or front.[2] Were reported variable sizes between 1 and 15 cm and many of these are increased in volume over many years.[6] It is not clear what features (size and location) make PCs more prone to rupture.

Since most of the PCs are asymptomatic, they are found incidentally by a chest X-ray or echocardiography; however, only CT and MRI show the complete anatomy of the cyst, the location, the size, and the relationship with the heart and other mediastinal organs.[1314]

The natural history of PCs is not completely known, but the long-term prognosis is excellent with good clinical conditions and without complications.[15] PCs can cause nonspecific symptoms and in some cases, get complicated by AF, extrinsic compression, obstruction of the right main bronchus, partial erosion of the inferior vena cava, the anterior wall of the left ventricle and right ventricle free wall, atypical chest pain, spontaneous internal bleeding, cardiac tamponade, and infection.[1617]

While the best therapy for mediastinal cysts is surgical excision, for congenital PCs, the asymptomatic patients do not require surgical excision or aspiration and are referred to conservative therapy.[18] In our case, both PC and hypertensive heart disease could be responsible for symptoms, making the therapeutic choice more difficult.

In patients with PCs located in the posterior mediastinum instrumental follow-up should be performed with CT or MRI, while in all other cases, echocardiography may be the most resonable choice.[19]

CONCLUSIONS

Echocardiography is a good screening investigation for PCs with usual localization, but it shows major limitations when there are masses with atypical positions.

In these cases, the integration with other instrumental examinations, as CT and RMI, allows an accurate diagnosis and clinical management. Finally, choosing the best clinical management should be carefully evaluated according to the clinical condition and comorbidities.

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Conflicts of interest

There are no conflicts of interest.