CT for evaluation of acute pericardial emergencies in the ED

Abstract

Acute pericardial emergencies may present with acute chest pain. Although complete diagnosis and physiological effects of acute pericardial disease may require a combination of different imaging, CT plays a critical role in identifying the cause of chest pain in the ED. Many of these pericardial diseases can be fatal unless emergent treatment is obtained. The presentation can often be non-specific and symptoms can be overlapping with other diseases originating in the thorax or abdomen. Optimizing the CT scan is imperative when acute pericardial disease is suspected from clinical examination or preliminary imaging. The interpreting radiologist needs to be aware of the different entities which represent acute pericardial emergencies requiring urgent therapeutic intervention. Time is the essence, the clock is ticking, and every minute counts!

Introduction

Pericardium can be affected by diseases from different etiologies (Fig. 1, flowchart). The presentation can often be non-specific and symptoms can be overlap with other diseases originating in the thorax or abdomen. Acute pericardial diseases are an important cause of morbidity and mortality in patients with cardiovascular diseases [1]. Imaging plays a key role in not just identifying the etiology but also in planning the therapeutic approach. Often these patients can present to the ED with chest pain and or dyspnea. Radiographs followed by ultrasound (US) or CT may be obtained for these indications. Additionally acute pericardial emergencies may be identified on a CT performed for other indications such as coronary artery disease, aortic dissection, pulmonary embolism, or pulmonary diseases etc. Although CT is highly versatile, optimizing the scan is important in order to accurately identify the underlying etiology and also for therapeutic planning. Most pericardial abnormalities can be diagnosed on non-ECG-gated CT of thorax. In selected patients, additional ECG-gated CT acquisition can be useful.

Fig. 1

Flowchart depicting the different causes of acute pericardial diseases that may require urgent intervention or surgery

The interpreting radiologist needs to be aware of the entities which represent acute pericardial emergencies that may require urgent therapeutic intervention. Although cardiac US is considered a primary modality to identify pericardial diseases, its availability can be limited in the ED; it requires skilled operator and well-trained interpreter. US can often be limited in patients with poor acoustic windows, chest wall emphysema, or lung diseases. CT can prove to be important diagnostic modality in such patients. CT can also provide a roadmap for the treating interventionist or cardiothoracic surgeon. Surgical approach may require surgeons from more than one clinical service.

In this brief pictorial essay, we describe how an optimized CT in the ED can play a critical role in identifying, triaging, and providing a road map for optimal treatment of some of the most important pericardial emergencies (Table 1).

Table 1 Table depicting different causes of acute cardiac pericardial disease, optimal CT technique, key imaging findings, and treatment

Anatomy

The pericardium is a three-layered conical fibroserous sac comprising an outer fibrous layer and inner serous double layers (parietal and visceral). The outer fibrous and parietal layers are fused, thus forming a potential space between these two fused layers and visceral pericardium which contains 5–50 cc of serous fluid. There are two cul-de-sac in the pericardium: oblique sinus, and the transverse sinus along with several pericardial recesses [2]. The pericardium regulates ventricular compliance, minimizes chamber dilation, and protects the heart.

CT protocol

While a CT of thorax may be obtained without intravenous (i.v.) contrast, during a breath hold, administration of i.v. contrast increases senstivity for certain pericardial diseases. Newer CT scanners with dual source or wide detector array also allow for a free breathing high-pitch acquisition useful in unconscious or intubated patients, who cannot obey verbal commands. The timing of image acquisition after administration of intravenous contrast is equally important. Arterial phase is useful to identify vascular origin of pericardial emergency, while a venous phase can be useful to evaluate suspected pericarditis. ECG gating (prospective) can be used to decrease cardiac motion artifacts and is recommended when evaluating cardiac pathology such as myocardial perforation. Retrospective ECG gating is useful when evaluation of cardiac function or pericardial constriction. Oral contrast is useful when a bowel pathology such as esophageal or gastric perforation is suspected.

Acute pericardial diseases

Congenital pericardial absence (Fig. 2) results from abnormal early regression of the common cardinal vein, resulting in incomplete formation of the pleuropericardial membrane. Partial absence of the pericardium which is limited to the left pericardium is more common than complete absence of pericardium which is extremely rare [3, 4]. On several instances, this entity may be acquired following percutaneous cardiac interventions or lung transplantation. Pericardial tears in blunt trauma most commonly occur along the left pleuropericardium parallel to the phrenic nerve [5]. Findings on CT include leftward mediastinal shift, herniation of lung parenchyma into the aortopulmonary window (due to lack of superior pericardial recess), or between the base of heart and diaphragm, enlargement of the right heart chambers and left atrial appendage. Although the majority of patients are asymptomatic, complications include herniation of cardiac structures such as the left atrial appendage through the defect resulting in torsion and ischemic necrosis. In these conditions, pericardioplasty with mesh placement is the recommended management [6, 7].

Fig. 2

Preoperative non-ECG-gated axial contrast-enhanced CT in a 24-year-old patient presenting with an intrapulmonary bronchogenic cyst identifies complete absence of pericardium (white arrows indicating normal location of pericardium), instead undulating left ventricle epicardium is present with mediastinal shift towards left. At the time of surgical resection of the bronchogenic cyst, complete absence of pericardium was confirmed. Complete absence of the pericardium may be associated with developmental anomalies of the lung (particularly left upper lobe) including bronchogenic cyst and sequestration

Pericardial effusion is defined as the accumulation of more than 50 ml of fluid in the pericardial sac. Criteria for quantifying it by echocardiography is based on identification of fluid throughout the cardiac cycle, (in both systole and diastole). Pericardial effusion is semi-quantitatively quantified on echocardiography by measuring the separation between parietal and visceral pericardium in end-diastole as trivial (seen only in systole), small (less than 1 cm), moderate (1–2 cm), and large (more than 2 cm) [8]. On CT simple or transudative effusions, measure less than 10 HU’s and an exudative pericardial effusion measures between 20 and 40 HU. Hemorrhagic pericardial effusion is better characterized on unenhanced CT and measures between 40 and 60 HU. Hemopericardium can be seen in the setting of left ventricular free wall rupture after myocardial infarction, ventricular or coronary aneurysmal rupture, postsurgical, trauma, and malignancy (Fig. 3) [9].

Fig. 3

Axial non-contrast non-ECG-gated CTA in a patient presented with acute chest pain identifies high attenuation in the transverse sinus (white arrows). With attenuation of more than 45 HU, this is concerning for pericardial hemorrhage. Contrast-enhanced CTA (not shown) identified an ascending thoracic aortic aneurysm with type A dissection

Pericardial tamponade is defined as the accumulation of pericardial fluid under pressure. The amount of fluid required to compromise diastolic ventricular filling is dependent on how fast the fluid accumulates rather than the amount or characteristics of fluid itself [9, 10]. In the acute setting for example in a patient with type A aortic dissection with rupture into the pericardium, only 150–200 ml of hemorrhagic fluid can lead to tamponade. In the chronic setting as the fluid accumulates gradually, increased compliance due to the elastic fibers can allow up to 1000 ml of fluid (20 times the normal physiologic amount) without hemodynamic decompensation [11]. Diagnostic criteria on CT (Fig. 4) include the following: flattened heart sign (flattening of the RV free wall with right atrial indentation), SVC/thoracic aortic ratio equal or greater than 1, IVC/abdominal aortic ratio greater than 2, and distention of the IVC and azygous arch. Reflux of contrast into the IVC, hepatic veins and azygous vein can also be seen [6, 9].

Fig. 4

Axial non-ECG-gated contrast-enhanced CT in a patient presenting to the ED with chest pain and past history of mitral valve replacement identifies a high-attenuation pericardial effusion (white arrows) causing extrinsic compression on right atrium and right ventricle. On an ECG-gated CTA diastolic flattening of right ventricular free wall, prolonged systolic notching of right atrial wall and in the presence of large effusion, swinging of the heart within the pericardial sac can be identified

Penetrating cardiovascular injury can be caused by firearms or less commonly by knife and other objects [12]. It has a very high mortality with overall survival of less than 20% [13]. Right ventricle being more anteriorly placed cardiac chamber is often the site of entry. Prognosis is worse when the left ventricle is injured [14]. The bullet can traverse the mediastinum injuring vessels and other organs. The projectile can lodge in the pericardium, atria, or the ventricles (Fig. 5). Bullet fragments can also embolize distally.

Fig. 5

Axial contrast-enhanced CT in a patient with acute chest and abdomen pain presenting to the ED after gunshot injury identifies round metallic projectiles in the pericardium and right ventricle

Intrapericardial diaphragmatic hernia are rare [15]. These can be congenital [16] or may arise as a complication of diaphragmatic rupture from blunt trauma, which results from sudden rise in intra-abdominal pressure. The presentation can be immediate or may be delayed by more than 20 years. Often asymptomatic, these can also present with symptoms from bowel obstruction or cardiac dysfunction. Clinical examination may reveal bowel sounds in the thorax, absent point of maximal cardiac impulse, etc. Herniated viscera may include stomach (Fig. 6), colon, liver (Fig. 7), or a combination of these.

Fig. 6

Axial non-contrast CT in a 35-year-old patient with recent history of blunt abdominal injury demonstrates the presence of stomach (white arrow) in the pericardium (arrowheads) abutting the right ventricle. This finding is consistent with posttraumatic intrapericardial diaphragmatic herniation of stomach (movie 1)

Fig. 7

Coronal post contrast CT in a 60-year-old patient with recent history of motor vehicle accident identifies portion of left lobe of liver protruding into the pericardial cavity abutting the right ventricle (white arrows). The presence of hepatic vessels extending across the diaphragm is useful in differentiating this hepatic herniation from other pericardial masses and tumors

Fistula can develop between the pericardium and skin, esophagus, gastrointestinal tract, lung, or liver. Gastropericardial fistula is characterized by communication between the stomach and pericardium (Fig. 8). This is a surgical emergency as it can result in cardiac tamponade and sepsis [17]. These fistulas can be seen in patients with prior history of gastroesophageal surgery or from peptic ulceration in a hiatus hernia. On CT, the presence of water-soluble oral contrast in the pericardium along with the fistula’s communication with esophagus or stomach can be identified. Surgery involves emergent pericardial decompression, resection of fistula, and repair of any associated hernia.

Fig. 8

Axial CT in a patient with prior esophageal cancer post esophagectomy and gastric interposition graft placement presenting to the ED with new onset chest pain identifies presence of oral contrast in the pericardium through focal defect (arrowhead) in the gastric graft. This finding is suggestive of gastropericardial fistula (movie 2)

Pericardiocutaneous fistula (Fig. 9) is a rare complication of cardiac surgery [18]. It has also been described after transapical approach for transcatheter aortic valve replacement [19] and from infections [20]. These patients may develop draining sinuses on skin. CT or MRI can demonstrate the communication between the skin and pericardium. Treatment may require surgical resection with repair of the pericardial defect often by an omental patch.

Fig. 9

Venous phase axial contrast-enhanced CTA in a patient with recent surgical aortic valve replacement and new onset fluid discharge from the sternal wound identifies the presence of a fistula tract communicating with the overlying skin. This finding is concerning for a pericardiocutaneous fistula (movie 3)

Left atrial ablation is increasingly being used to treat refractory atrial arrhythmias. A potential complication of this procedure involves thermal injury of the esophageal mucosa [21]. These can present as asymptomatic esophageal lesions, esophageal hemorrhage (Fig. 10) with esophagopericardial fistula and in rare cases with atrioesophageal fistula. On CT, air can be identified in the pericardium and sometimes also in the left atrium. In the case of atrioesophageal fistula, a one-way valve is created with leakage of esophageal contents into the left atrium [22]. Early surgical repair is essential. Endoscopic interventions should be avoided as they increase the risk for air emboli. Interposing tissue between the repaired esophagus and the LA decreases postoperative complications. Infection from the lung or adjacent mediastinal structures can also extend into the pericardium (Fig. 11). This can lead to rapid spread of infection to myocardium and cardiac valves. In immune compromised patients, these may require surgical resection and drainage using minimally invasive video-assisted thoracic surgery.

Fig. 10

Axial non-contrast-enhanced CT in a patient who had recently undergone left atrial ablation for atrial fibrillation presenting to the ED with new onset chest pain. High attenuation seen in the esophagus consistent with esophageal hematoma (white arrow). In addition, focal specks of air are also present in the oblique sinus of pericardium (arrowhead). These findings are suggestive of esophageal injury with resultant esophagopericardial fistula (movie 4)

Fig. 11

Non-ECG-gated contrast-enhanced CT in an immunosuppressed patient with recent bone marrow transplant and new onset chest pain and heaviness presenting to the ED demonstrate a well-defined fluid collection along with consolidation in lingual lingula (asterisk) consistent with a lung abscess. In addition, there is a left pericardial effusion (white arrow) which is contiguous with this abscess and concerning for pericardial infection. This patient failed conventional treatment; FNA was suggestive of fungal infection but the patient did not respond well to conventional antifungal therapy also. Minimally invasive thoracic surgery was performed with resection which confirmed pericardial fungal infection (movie 5)

Acute pericardial disease may also be seen from iatrogenic injury. Pericardiocentesis can lead to inadvertent puncture of ventricles (Fig. 12). Port catheters are commonly used for central access. Lead tip of the port catheter can perforate the relatively thin-walled right atrium (Fig. 13). Pacemakers and implantable cardiac devices are commonly used to treat arrhythmias and congestive heart failure. Pacemaker lead perforation can be seen in up to 15% of patients and is often asymptomatic [23] but can lead to pneumopericardium, hemopericardium, or hemothorax (Fig. 14). Atrial lead perforation is more common than ventricle lead perforation. In rare instances, malposition of other devices such as gastrostomy tube, thoracostomy tubes can occur. Inadvertent transthoracic placement of the gastrostomy tube can occur (Fig. 15) which can lead to formation of direct communication between the stomach and pericardium.

Fig. 12

Seventy-one-year-old patient presenting with increasing chest pain after pericardiocentesis for pericardial effusion. Non-ECG-gated axial contrast-enhanced CT demonstrates focal contrast outpouching emanating from the right ventricle (arrowhead) extending into the pericardium. This finding is consistent with right ventricle pseudoaneurysm with hemopericardium

Fig. 13

Non-contrast-enhanced axial prospectively ECG-gated CT performed immediately after port catheter placement identifies the port catheter tip in the pericardium (arrowhead) which is beyond the epicardial fat. High-attenuation pericardial fluid (white arrow) is due to the intravenous from the contrast injected at the time of through the port catheter (movie 6)

Fig. 14

Axial non-contrast prospectively ECG-gated CT performed in a patient with recent pacemaker lead placement and new onset chest pain. The right atrial lead is identified outside the atrium; tip is beyond the epicardial fat. In addition, the lead extended into the right pleural cavity with right hydropneumothorax (movie 7). These findings are consistent with perforated pacemaker lead

Fig. 15

Coronal image from a contrast-enhanced axial chest and abdominal CT in a patient with new onset chest pain after recent percutaneous gastrostomy tube placement identifies the G-Tube traversing the pericardium (arrowhead), diaphragm before extending into the stomach (movie 8). In addition, pneumopericardium is also present (arrow)

Conclusion

Pericardial emergencies can have high morbidity and mortality. CT imaging is central in the evaluation of these patients and recognition of abnormalities is important for timely management. In many cases the CT may be obtained suspecting a non pericardial disease. The radiologist plays a crucial role in ensuring that the CT study is correctly protocoled and acquired. Familiarity with potential complications of certain diseases or procedures can prove life-saving in this patient population.