Anterior Mediastinal Mass and Pericardial Effusion With Right Ventricular Outflow Tract Obstruction Secondary to Dual Compression

Abstract

Background

Anterior mediastinal masses frequently manifest with pericardial effusion and compressive symptoms, creating management challenges due to the risk of cardiovascular collapse during intervention.

Case Summary

Two patients with primary mediastinal B-cell lymphoma presented with large pericardial effusions and right ventricular outflow tract obstruction. The first patient was successfully managed with tumor-directed therapy alone. The second patient underwent emergency surgery following failed pericardiocentesis, resulting in cardiac arrest requiring mechanical circulatory support.

Discussion

These 2 cases highlight the critical decision making required when managing anterior mediastinal masses with pericardial effusion. Whereas guidelines typically recommend urgent drainage for significant effusions with tamponade physiology, this approach may be detrimental in the presence of anterior mediastinal masses.

Take-Home Messages

Emergency pericardiocentesis in the setting of malignant anterior mediastinal mass may confer greater risk than benefit. Systemic antineoplastic therapy is encouraged as first-line treatment to promote tumor reduction and mitigate compressive symptoms.

Graphical Abstract

Visual Summary.

Differing Clinical Trajectories in Primary Mediastinal B-Cell Lymphoma With Cardiac Tamponade

Case 1 demonstrates successful nonsurgical management with ultrasound (US)-guided biopsy and chemotherapy, resulting in complete recovery. Case 2 is complicated by worsening hemodynamic instability following unsuccessful pericardiocentesis, requiring surgical intervention and venoarterial extracorporeal membrane oxygenation (VA-ECMO). CXR = chest x-ray; ED = emergency department; FDG-PET = fluorodeoxyglucose positron emission tomography; LDH = lactate dehydrogenase; LVEF = left ventricular ejection fraction; PMBCL = primary mediastinal B-cell lymphoma; other abbreviations as in Figure 4.

Patient 1

History of presentation

A 40-year-old woman with no past medical history presented with 6 weeks of worsening dyspnea and orthopnea refractory to antibiotic treatment for presumed community-acquired pneumonia. The patient was tachycardic (120 beats/min, regular), hypertensive (153/103 mm Hg), and afebrile. Oxygen saturation was 95% (room air) without tachypnea (19 breaths/min), but with notable accessory muscle use. Heart sounds were muffled with an audible ejection systolic murmur, with elevation of the jugular venous pressure. Pemberton's sign was positive.

Take-Home Messages

• •In malignant anterior mediastinal masses with pericardial effusion, dual compression creates complex hemodynamic interactions.
• •In Challenging traditional management algorithms and implementing tumor-directed therapy to address both compressive mechanisms should be prioritized over immediate pericardiocentesis.

Differential diagnosis

The initial presentation of progressive dyspnea with orthopnea, muffled heart sounds, and positive Pemberton's sign raised concern for a mediastinal mass syndrome. Key differential diagnoses at this stage included lymphoma, thymoma, germ cell tumor, thyroid neoplasia, and metastatic disease. The combination of a widened mediastinum on chest x-ray with low-voltage QRS complexes suggested a space-occupying lesion with associated pericardial effusion.

Investigations

Laboratory investigations demonstrated normal hemoglobin (13.8 g/dL) with unremarkable inflammatory markers and increased lactate (2.7 mmol/L). High-sensitivity troponin was 10 ng/L (0.01 ng/mL; normal range: 0-20 ng/L or 0-0.02 ng/mL). A 12-lead electrocardiogram demonstrated sinus tachycardia with low-voltage QRS complexes and no ischemic changes. Chest x-ray demonstrated a widened mediastinum with a right pleural effusion. Transthoracic echocardiography (TTE) confirmed a large pericardial effusion (3.4 cm adjacent to the left ventricular apex) with evidence of tamponade physiology (early diastolic right ventricular collapse, respirophasic variation in mitral inflow, and dilated and fixed inferior vena cava). A large anterior mediastinal mass was visible, causing external compression of the right ventricular outflow tract (RVOT), resulting in severe obstruction (peak gradient 64 mm Hg). A computed tomography scan of the chest with contrast medium, performed with the patient in the left lateral position (owing to significant orthopnea), characterized the lesion as 17 × 14 × 11 cm in maximal dimensions with sternal invasion and left axillary lymphadenopathy (Video 1, Video 2, Video 3, Video 4, Figure 1).

Figure 1.

Doppler Evidence of Hemodynamic Compromise in Cardiac Tamponade

Pulsed-wave Doppler assessment of mitral valve inflow velocities reveals significant respiratory variation (>25% decrease during inspiration) characteristic of tamponade physiology.

Management and intervention

Following multidisciplinary discussion involving cardiology, cardiothoracic surgery, anesthesia, and radiology teams, it was decided to perform an ultrasound-guided biopsy given the risk of deterioration and possible cardiorespiratory arrest with pericardiocentesis. The biopsy was performed under procedural sedation in an intensive care setting to mitigate the risks associated with anesthetic induction (Supplemental Table 1). Simultaneous thoracocentesis was complicated by re-expansion pulmonary edema and an iatrogenic pneumothorax, managed conservatively. Histopathology confirmed primary mediastinal B-cell lymphoma (PMBCL), prompting the administration of high-dose glucocorticoids; rasburicase; and DA-EPOCH-R (dosage-adjusted etoposide [50 mg/m²/d days 1-4], prednisolone [100 mg twice daily days 1-5], vincristine [0.4 mg/m²/d days 1-4], cyclophosphamide [750 mg/m²], doxorubicin [10 mg/m²/d days 1-4], and rituximab [375 mg/m²] chemotherapy. Significant clinical improvement occurred within 4 days of starting treatment, facilitating safe transfer to the ward.

The finding of RVOT obstruction with tamponade physiology presents a therapeutic challenge. Although current guidelines recommend urgent pericardiocentesis for tamponade, this dual compression scenario requires a nuanced approach, as relief from the effusion without addressing tumor compression could potentially exacerbate RVOT obstruction. Thus management should prioritize upright positioning and optimizing volume status while obtaining tissue diagnosis. Early consideration should be given to systemic chemotherapy and steroid administration if lymphoma is suspected.

Outcome and follow-up

Follow-up TTE in 1 week showed a reduction in pericardial effusion size and RVOT obstruction (peak gradient 32 mm Hg), with no tamponade physiology. One month later, fluorodeoxyglucose positron emission tomography indicated a favorable metabolic response, with substantial tumor reduction and resolution of symptoms (Figures 2A, 2B and 3, Video 5).

Figure 2.

Serial Axial Computed Tomography Images Demonstrating Treatment Response of Anterior Mediastinal Mass

Comparison of anterior mediastinal mass on axial computed tomography demonstrates marked reduction in tumor bulk following 1 cycle of systemic chemotherapy, suggesting early therapeutic efficacy. (A) Baseline. (B) Post–cycle 1.

Figure 3.

Large Anterior Mediastinal Mass on Initial Chest Radiography

Presenting chest radiograph obtained in the anteroposterior erect position. The image reveals a prominent anterior mediastinal mass causing significant widening of the mediastinal silhouette, providing critical information for initial diagnosis and subsequent imaging evaluation.

Patient 2

History of presentation

A 30-year-old man presented with subacute constitutional symptoms, rectal bleeding, and a 3-day history of worsening dyspnea. On examination, he was tachycardic (150 beats/min), febrile (38 °C), and tachypneic (36 breaths/min), but normotensive (120/99 mm Hg). Oxygen saturation was 97% (room air). Auscultation revealed reduced heart sounds and decreased air entry to the lung bases. Discordantly, the jugular venous pressure was not elevated, with no peripheral edema. A solitary right supraclavicular lymph node was palpable.

Differential diagnosis

This presentation demonstrated some features that required urgent attention; the combination of constitutional symptoms with acute deterioration, compressive symptoms, and palpable lymphadenopathy strongly suggested a rapidly progressive lymphoproliferative disorder. The absence of increased jugular venous pressure in the setting of RVOT obstruction is unusual and may be consistent with hypovolemia or complex hemodynamics from the mass effect. The presence of rectal bleeding raises concern for systemic involvement or a paraneoplastic coagulopathy.

Investigations

Laboratory results revealed microcytic anemia (hemoglobin: 123 g/L), mild thrombocytosis (453 × 10⁹/L), markedly elevated lactate dehydrogenase (724 U/L), and a lactate level of 2.9 mmol/L. Renal function was preserved. A 12-lead electrocardiogram recorded sinus tachycardia with reduced voltages globally. An erect chest x-ray showed mediastinal widening and bilateral pleural effusions. TTE confirmed a large circumferential pericardial effusion (largest along apex and right ventricular free wall: 3.3 cm) with tamponade physiology. A heterogeneous anterior mediastinal mass measuring 18.5 × 5.0 × 10.9 cm was identified on computed tomography (CT), performed with the patient sitting upright.

Management and intervention

Emergency pericardiocentesis via an apical approach was unsuccessful due to guidewire insertion difficulties, raising concerns about pleuropericardial tract formation. Clinical deterioration with worsening tachypnea and pulse pressure variation (>50 mm Hg per beat) necessitated surgical intervention. Extracorporeal membrane oxygenation line placement was prevented by significant orthopnea. On anesthetic induction, the patient experienced cardiac arrest owing to the overwhelming compressive effect of the mediastinal mass on the RVOT, requiring emergency sternotomy for tumor debulking and decompression. Transesophageal imaging demonstrated complete obliteration of the right atrium by the mass. Cardiopulmonary bypass was initiated to repair injuries to the superior vena cava and innominate vein, but the patient developed severe coagulopathy and biventricular failure, necessitating venoarterial extracorporeal membrane oxygenation (VA-ECMO) support.

The rapid clinical deterioration created a challenging scenario in which intervention appeared necessary, despite carrying substantial risk. The development of severe biventricular failure following sternotomy highlighted the complex pathophysiology of these cases, where sudden relief of subacute or chronic compression could lead to acute cardiorespiratory decompensation. This case illustrates why mechanical circulatory support should be considered early, ideally before clinical deterioration necessitates emergency surgery.

Outcome and follow-up

Immediate postoperative TTE demonstrated severe left ventricular dysfunction (left ventricular ejection fraction 15%) with lateral and apical hypokinesis, consistent with stress cardiomyopathy. Given the rising lactate dehydrogenase (3,000 U/L), high-dose dexamethasone (20 mg) was initiated. Histology confirmed PMBCL. Initial chemotherapy was modified to single-agent vincristine to mitigate potential anthracycline-induced cardiotoxicity. The patient was transferred to a specialized heart-lung transplant center where staged management included limited tumor debulking followed by R-CEOP (rituximab, cyclophosphamide, etoposide, vincristine, and prednisone) chemotherapy. Hemodynamic improvement following tumor size reduction enabled VA-ECMO decannulation on day 11 and successful extubation by day 21. Despite progression to ward-level care, recovery was complicated by significant deconditioning and nosocomial infection (Figure 4).

Figure 4.

Proposed Management Flowchart for Anterior Mediastinal Mass Associated With Pericardial Effusion

A lactate cutoff of ≥2.0 mmol/L has been selected in concordance with the Updated Society for Cardiovascular Angiography and Intervention SHOCK Classification Consensus to indicate evidence of tissue hypoperfusion. Arrows indicate the proposed direction of clinical decision making. CT = computed tomography; CTS = cardiothoracic surgery; CW = continuous wave; ECMO = extracorporeal membrane oxygenation; ECG = electrocardiogram; GA = general anesthetic; ICU = intensive care unit; IVC = inferior vena cava; JVP = jugular venous pressure; LAD = lymphadenopathy; MDT = multidisciplinary team; PLAX = parasternal long axis; RV = right ventricle; RVOT = right ventricular outflow tract; SVC = superior vena cava; TTE = transthoracic echocardiography.

Discussion

The anterior mediastinum, anatomically located between the sternum anteriorly and the heart posteriorly, can host rare and potentially life-threatening masses that cause extrinsic cardiac or vessel compression, leading to hemodynamic compromise. Causes include lymphoma (Hodgkin and non-Hodgkin subtypes), thymoma, thyroid goiters, and germ cell malignancies. Anterior mediastinal masses can cause extrinsic cardiac compression and/or indirectly the formation of pericardial effusion. Clinical complexities arise in situations with mass effect from both the tumor and the pericardial effusion. Managing these cases involves significant anesthetic and procedural challenges owing to the proximity of critical structures and the potential for hemodynamic compromise. Pericardiocentesis, though commonly used to manage tamponade, may exacerbate hemodynamic instability in this context and compromise airway patency, while also delaying crucial interventions such as biopsy, corticosteroids, and chemotherapy. A multidisciplinary approach is essential to optimize outcomes for these patients. We describe 2 cases of PMBCL presenting with pericardial tamponade and RVOT obstruction due to mediastinal mass compression. The above cases highlight the need for careful clinical evaluation, diagnostic strategies, and individualized management plans.

Anterior mediastinal masses comprise up to 50% of all mediastinal tumors. Malignancy rates in this region are high (up to 60%), particularly in younger patients, with lymphomas accounting for a significant proportion of cases.¹ Patients with PMBCL often present with compressive symptoms owing to the proximity of the mediastinum to vital structures, including the heart, great vessels, tracheobronchial tree, and esophagus.² Clinical manifestations range from cough and dyspnea to hemodynamic compromise secondary to mass effect or associated pericardial effusion.

In cases of large pericardial effusion with an anterior mediastinal mass, CT evaluation is essential even if the patient cannot lie supine because. CT localizes the mass, defines its characteristics, and assesses its relationship to surrounding structures, aiding in differentiation, staging, and treatment planning.

Pericardial effusion is a common feature in PMBCL, occurring in 30% to 50% of cases.³ In the setting of mediastinal masses, the hemodynamic impact reflects a complex interaction between effusion and tumor compression. Aggressive drainage through pericardiocentesis without addressing the tumor burden can potentially worsen hemodynamic instability by altering these compressive forces, exacerbating RVOT obstruction and potentially provoking hemodynamic collapse.⁴ This underscores the importance of assessing both effusion and mass-related compression when planning interventions, with consideration of systemic therapies that may address both components simultaneously.

Management of these presentations carries significant risks of respiratory and cardiovascular collapse during anesthesia or sedation. First recognized in pediatric populations in the 1970s to 1980s, the lower incidence in adults makes this syndrome less familiar to adult physicians, underscoring the importance of our discussion.⁵ The mechanisms underlying malignant RVOT obstruction involves mass effect on the airways and cardiovascular structures, which can be exacerbated by changes in patient positioning, muscle relaxation, and establishment of positive-pressure ventilation.

During anesthetic induction, supine positioning reduces thoracic cavity volume, increasing mediastinal pressure on adjacent structures. This is compounded by physiologic changes associated with general anesthesia, including decreased inspiratory muscle tone and bronchial smooth muscle relaxation, consequently increasing airway compressibility. Positive-pressure ventilation and neuromuscular blockade further exacerbate airway and vascular compression by reducing transpleural pressure gradients and venous return.^6,7 These factors can precipitate life-threatening scenarios such as airway compromise, worsening RVOT obstruction, and pulmonary artery compression, leading to severe hypoxia or even cardiovascular collapse. The loss of spontaneous breathing and initiation of controlled ventilation can exacerbate a phenomenon known as mediastinal mass syndrome by increasing airway pressures and reducing venous return, further compromising cardiac output.⁸ In severe, premorbid hemodynamic compromise, early VA-ECMO may be required before anesthesia induction.

Biopsy under local anesthesia, without sedation, via fine-needle aspiration or core biopsy is preferred in the first instance. Potential risk of tumor cell seeding is concerning in hematologic malignancies. Successful histopathology can guide strategies to reduce tumor size, such as corticosteroids or targeted systemic therapies.

Pericardial effusion management in these cases is particularly challenging due to the late presentation, rapid deterioration, risk of exacerbating hemodynamic instability, and worsening extrinsic compression. Most interventions require the patient to tolerate the supine position, which is often difficult secondary to orthopnea. The European Society of Cardiology guidelines emphasize urgent pericardiocentesis as the standard of care in patients who meet criteria based on suspected etiology, clinical presentation, and imaging findings; as per the European Society of Cardiology algorithm for tamponade, criteria for urgent drainage in the absence of contraindications is ≥6 points; the cases presented scored 7.5.⁹ Contraindications to pericardiocentesis in tamponade include the following: 1) uncorrected coagulopathy; 2) anticoagulant therapy with international normalized ratio >1.5; 3) platelet count <50 × 10⁹/L; 4) small, posterior, and loculated effusions; and 5) effusions resolving under anti-inflammatory treatment.

Existing case reports suggest pericardiocentesis in the presence of a large anterior mediastinal mass should be reconsidered, given the risk of developing pericardial decompression syndrome—a paradoxical worsening of hemodynamics after drainage of a large pericardial effusion.^4,10 This is driven by an increase in venous return that follows the rapid removal of pericardial fluid, driving significant right ventricular expansion with a reduction in effective left ventricular output and subsequent failure.

Targeted medical management of the tumor itself, through systemic antineoplastic therapies and early administration of glucocorticoids, can promote spontaneous resolution of malignant pericardial effusions, thus avoiding complications and the need for emergent surgical interventions.

Conclusions

These 2 cases highlight the challenges in managing patients with anterior mediastinal masses associated with large pericardial effusion and RVOT obstruction. An early, multidisciplinary discussion and use of CT imaging is essential to guide a management plan. Pericardial effusions act as an additional compressive factor, necessitating cautious consideration before pericardiocentesis owing to potentially significant hemodynamic consequences. This approach ultimately ensured a positive clinical outcome in case 1, highlighting the importance of timely and coordinated care in complex mediastinal pathologies.

Funding Support and Author Disclosures

Dr Tan is supported by a Postgraduate Scholarship from the National Health and Medical Research Council of Australia, a PhD Scholarship from the National Heart Foundation of Australia, and an Australian Government Research Training Program Scholarship. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.

Appendix

Video 1

Echocardiographic Features of a Large Pericardial Effusion in the Apical 4-Chamber View

Transthoracic echocardiography shows a significant pericardial effusion with a maximal depth of 3.4 cm measured from the left ventricular apex.

Video 2

Parasternal Long Axis View Demonstrating a Large Anterior Mediastinal Mass Causing Extrinsic Compression of the Right Ventricular Outflow Tract, Associated With a Large Pericardial Effusion

Video 3

Dynamic Assessment of Inferior Vena Cava Collapsibility in Cardiac Tamponade

Transthoracic echocardiography shows inferior vena cava dynamics during respiratory maneuvers. The inferior vena cava exhibits reduced collapsibility (<50% collapse during sniff test), consistent with elevated right atrial pressures and supporting the presence of hemodynamically significant pericardial effusion with tamponade physiology.

Video 4

Computed Tomography Visualization of Anterior Mediastinal Mass With Mass Effect

Sagittal computed tomography sequence demonstrates the extent of a large anterior mediastinal mass with significant mass effect, highlighting compression of adjacent mediastinal structures and associated pericardial effusion. The dynamic display allows appreciation of the three-dimensional relationships between the mass and critical thoracic structures.

Video 5

Treatment Response Assessment of Pericardial Effusion Following Initial Chemotherapy

Repeat transthoracic echocardiography in the apical 4-chamber view following cycle 1 of systemic chemotherapy. The marked reduction in pericardial effusion size compared with initial imaging demonstrates robust therapeutic response to medical management, without the need for pericardiocentesis.

Supplemental Table 1

Equipment List for Computed Tomography–Guided Percutaneous Biopsy