Congenital complete absence of pericardium masquerading as pulmonary embolism.

Congenital absence of the pericardium is a rare cardiac condition, which can be either isolated or associated with other cardiac and extracardiac anomalies. There are six different types, depending on the severity of the involvement. Most of the patients with this defect are asymptomatic, especially the ones with complete absence of the pericardium. However, some patients are symptomatic, reporting symptoms that include chest pain, palpitations, dyspnea, and syncope. Diagnosis is established by the characteristic features on chest X-ray, echocardiogram, chest computed tomography (CT), and/or cardiac magnetic resonance imging (MRI). We present here a case of a 23 year-old-male, who presented to our hospital with complaints of pleuritic chest pain and exertional dyspnea, of a two-week duration. He was physically active and his past history was otherwise insignificant. His chest CT with contrast was interpreted as showing evidence of multiple emboli, predominantly in the left lung, and he was started on a heparin and warfarin therapy. A repeat chest CT with contrast three weeks later showed no significant change from the previous CT scan. Both scans showed that the heart was abnormally rotated to the left side of the chest. An echocardiogram raised the suspicion of congenital absence of the pericardium, with a posteriorly displaced heart. In retrospect, motion artifact on the left lung, attributed to cardiac pulsations and the lack of pericardium, resulted in a CT chest appearance, mimicking findings of pulmonary embolism. The misdiagnosis of pulmonary embolism was attributed to the artifact caused by excessive cardiac motion artifact on the chest CT scan. In non-gated CT angiograms, excessive motion causes an artifact that blurs the pulmonary vessels, reminiscent of a 'seagull' or a 'boomerang'. Physicians need to be aware of this phenomenon, as well as the characteristic radiological features of this congenital anomaly, to enable them to make a correct diagnosis.

INTRODUCTION

Congenital absence of the pericardium (CAP) is a rare cardiac condition usually identified incidentally on autopsies and surgical procedures.[1] The prevalence, including cases with other cardiopulmonary anomalies, is approximately 0.002-0.004% of the surgical and pathological series.[2] The pathogenesis is multifactorial, but the premature atrophy of the left common cardiac vein (duct of Cuvier), which compromises the blood supply to the left pleuropericardial fold accounts for the most common forms of CAP.[3] Six types of congenital absence of the pericardium have been identified including total absence, right-sided defects (complete or partial), left-sided defects (complete or partial), and diaphragmatic defects (4). CAP can be isolated or it may be associated with other cardiac and extracardiac malformations, including patent ductusarteriosus, atrial septal defects, mitral valvestenosis, bronchogenic cyst and diaphragmatic hernia, or found as a part of other syndromes, such as, the vertebrae, anus, trachea, esophagus, and renal (VATER) syndrome, the Marfan syndrome, and the Pallister, Killian syndrome.[4]

Most of the patients are asymptomatic, especially the ones with complete absence of pericardium. Common symptoms include precordial pain of variable intensity, palpitations, dyspnea, syncope, or sudden death.[5] Diagnosis is established by the characteristic findings on a chest X-ray, echocardiogram, chest CT, and cardiovascular magnetic resonance (CMR).[5]

Chest X-ray findings suggestive of CAP include levoposition of the heart without tracheal deviation, which may be mistaken for cardiomegaly.[6] The right border is not seen because it is superimposed on the spine on frontal projection. The left border is elongated and flattened, with prominence of the main pulmonary artery, which is separated from the aortic knob by a radiolucent zone (Snoopy′s sign).[7]

The 2-D echocardiogram findings include right ventricular enlargement, abnormal septal motion,[8] cardiac hypermobility with swinging motion of the heart, and teardrop appearance with bulbous ventricle and elongated atria.[9] Other more striking echocardiographic findings include, failure to obtain standard views via the usual acoustic windows. In the parasternal window, the heart long axis may not appear perpendicular to the transducer, but oblique, with the apex pointing posteriorly.[3]

The CMR and CT scans can show the abnormal rotation and displacement of the heart. Also the CMRand CT, because of the superb contrast resolution and multiplanar capability, can easily identify the absence of the pericardium.[1011]

Treatment is usually not indicated for complete defects without debilitating symptoms.[3]

CASE REPORT

We present the case of a 23-year-old white male, who presented to our hospital with complaints of pleuritic chest pain and exertional dyspnea of two weeks’ duration. There was a history of trauma to the left leg, with swelling, two weeks prior. The patient′s past history was significant for hepatitis C, substance abuse, and smoking. The patient was otherwise physically active and used to exercise for two hours daily. His vital signs were within normal limits and physical examination, including cardiovascular and respiratory system, failed to reveal any abnormality. An electrocardiogram (EKG) showed that the patient had poor r-wave progression and severe left axis deviation of minus 125 degrees. This would be typical of a heart that had rotated into the left chest, and a chest X-ray showed deviation of the cardiac silhouette to the left and clear lung fields. The Snoopy's sign was present [Figure 1]. The anterior clear space was prominent [Figure 2].

Figure 1

Snoopy sign. Lung tissue between aorta and pulmonary artery

Figure 2

Prominent anterior clear space

A chest CT with contrast and a pulmonary embolism (PE) protocol showed evidence of multiple emboli, predominantly in the left lung. The patient was started on heparin and warfarin therapy. Further history and workup for deep vein thrombosis (DVT) and a hereditary hypercoagulable state failed to identify a cause for PE. The patient was discharged, but later on readmitted to the hospital with chest pain and palpitations.

Telemetry monitoring of the patient showed that the heart rate changes were from 30/minute to episodes where it went up to 112/minute. There was evidence of premature atrial contractions (PACs) and sinus arrythmias.

A repeat chest CT with contrast showed no significant change from the previous CT scan, showing the heart to be abnormally rotated to the left side of the chest [Figures 3 and 4]. The pericardium was absent.

Figure 3

Interposition of the lung between the aorta and pulmonary artery

Figure 4

Levoposition of the heart

An echocardiogram confirmed the abnormal orientation of the heart, with the apex of the left ventricle sitting deeply in the left chest and a moderate amount of pulmonary hypertension [Figure 5]. A diagnosis of congenital absence of pericardium was made. The misdiagnosis of pulmonary embolism was attributed to the motion artifact of the swinging heart (Figure 6 showing abnormal CT scan compared with a normal chest CT; Figure 7). As the patient's symptoms did not prevent him from carrying out his daily activities, he was discharged with regular Outpatient follow-up. He was told to cease his daily regimen of an intense two-to-three hour workout. His symptoms usually came during this work out.

Figure 5

Seagulls or ghosting artifact. Computed tomography scan of the chest with contrast showing false impression of pulmonary embolism caused by motion artifact of the heart in the absence of a pericardium

Figure 6

Normal Computed tomography scan of the chest with IV contrast for comparison

Figure 7

(a) Shows position of the probe for the apical four-chamber view of a 2-D echocardiogram, (b) a normal 2-D echo with interventricular septum pointing toward the probe, (c) 2-D echo in a patient with congenital absence of pericardium, with left ventricle flopped to the left side and interventricular septum pointing to the left side

DISCUSSION

Congenital absence of pericardium is a rare condition with most of the cases being asymptomatic.[1] Patients who are symptomatic have rather non-specific complaints of chest pain, palpitations, dyspnea, and syncope.[5] Diagnosis is suggested by the relevant findings on EKG, chest X-ray, and echocardiogram, and it can be confirmed by a CT scan or an MRI.[5] Timely diagnosis can be complicated by the rarity of the disease and a physician or a radiologist may not come across even a single case in their life time. Motion artifacts are well-recognized pitfalls of a chest CT scan and can lead to a spurious diagnosis of pulmonary embolism.[12] The most common is the respiratory motion, which obscures the diagnosis by decreasing the arterial opacification. Cardiac motion is usually less of a problem than respiratory motion and may result in a ‘ghosting artifact’[13] or ‘seagulls’ [Figure 6].

We have presented here a unique case of CAP, where the cardiac motion artifact led to a misdiagnosis of PE. The cardiac motion was exacerbated by the lack of pericardium support in our patient. In our patient the diagnosis of CAP was missed initially, despite the pertinent chest X-ray findings and the patient was treated for pulmonary embolism. This illustrates the importance of an increased awareness of the typical presentation and radiological features among physicians, so that a diagnosis is not missed. A CT pulmonary angiogram with cardiac gating will usually freeze the vessel motion and prevent misdiagnosis.

CONCLUSION

Congenital absence of pericardium should be included in the differential diagnosis of atypical chest pain and palpitations, and the physicians should be accurate in recognizing the specific radiological findings suggestive of CAP, so that early diagnosis is made.