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Abstract
In pneumopericardium, a rare but potentially life threatening differential diagnosis of chest pain with a broad variety of causes, rapid diagnosis and adequate treatment are crucial. In upright posteroanterior chest radiography, the apical limit of a radiolucent rim, outlining both the left ventricle and the right atrium, lies at the level of the pulmonary artery and ascending aorta, reflecting the anatomical limits of the pericardium. The band of gas surrounding the heart may outline the normally invisible parts of the diaphragm, producing the continuous left hemidiaphragm sign in an upright lateral chest radiograph. If haemodynamic conditions are stable, the underlying condition should be treated and the patient should be monitored closely. Acute haemodynamic deterioration should prompt rapid further investigation and cardiac tamponade must be actively ruled out. Spontaneous pneumopericardium in a 20 year old man is presented, and its pathophysiology described.
- pneumopericardium
- chest pain
- intensive care
- thoracic radiography
- review
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Pneumopericardium is a rare condition, less common than either isolated pneumothorax or pneumomediastinum. Nevertheless, clinicians should be familiar with this differential diagnosis of chest pain and its clinical and radiographic manifestations, since prompt recognition and treatment of potential complications—most importantly, pericardial tamponade—may be life saving.
CASE REPORT
A previously healthy 20 year old man was admitted to the hospital two hours after the acute onset of left sided chest pain radiating to his left arm and neck, worsening in the left lateral recumbent position and exacerbated by deep inspiration. Symptoms had developed one hour after he had been chopping wood. He reported rhinitis of two weeks’ duration but did not have other respiratory tract symptoms or fever. He had a smoking history of two pack years.
On physical examination the patient was in moderate distress, his temperature was 36.6°C, pulse 74 beats/min, and blood pressure 130/65 mm Hg without pulsus paradoxus. Cardiac examination was notable for a left parasternal rub, but there was no clinically evident right heart failure or subcutaneous emphysema. Routine laboratory tests were within normal limits, including white cell count, C reactive protein, creatine phosphokinase, and troponin I. The ECG showed a sinus rhythm with normal repolarisation. Plain radiographs of the chest showed a pneumopericardium (fig 1) with the continuous left hemidiaphragm sign (fig 2) and a discrete pneumomediastinum. Transthoracic echocardiography was unremarkable.
Posteroanterior chest radiograph. Continuous radiolucent stripes follow the right and left cardiac borders and are outlined by a fine line (arrows) representing the pericardial sac. The stripes are limited at the level of the pulmonary artery and ascending aorta by the pericardial reflection.
Upright lateral chest radiograph. The normally invisible ventral part of the left hemidiaphragm (arrows) is outlined by a radiolucent rim, producing the continuous left hemidiaphragm sign. The air bubble in the stomach identifies the left hemidiaphragm.
Three days after admission with resolution of the radiographic findings, the patient’s symptoms subsided spontaneously. He remained asymptomatic 12 months after discharge from the hospital.
DISCUSSION
Pneumopericardium is a rare but important differential diagnosis of chest pain. Symptoms such as radiation of pain towards the shoulders, the back, or the epigastrium, as well as dyspnoea and palpitations, are not always present and depend on the extent of pneumopericardium and the underlying disease. Clinical signs such as distant heart sounds, shifting precordial tympany, and a succussion splash with metallic tinkling (referred to as the mill wheel murmur, or “bruit de moulin” in hydropneumopericardium and first described by Bricketeau in 1844)1,2 and ECG findings such as low voltage, ST segment changes, and T wave inversion are non-specific and unreliable. Hamman’s crunch of pneumomediastinum and palpable crepitation of subcutaneous emphysema should heighten suspicion.3
Sufficient accumulation of pericardial gas may impair right ventricular filling, resulting in pericardial tamponade with increase and equalisation of intracardiac pressures, pulsus paradoxus, arterial hypotension, and cardiogenic shock.4,5 The diagnosis of pneumopericardium can be confirmed by conventional chest radiographs,6 computed tomography, or echocardiography.7,8
Radiographic findings of pneumopericardium and pneumomediastinum can be similar in the lower mediastinum. In posteroanterior chest radiographs, a continuous thin radiolucent rim of air follows the cardiac silhouette and is outlined by a fine line representing the pericardial sac (fig 1). At the base of the heart, the gas may outline the superior surface of the normally obscured parts of the diaphragm, which can be seen on the lateral radiograph as the continuous left hemidiaphragm sign6,9 (fig 2) and on a frontal radiograph as the continuous diaphragm sign.6
Some radiographic signs may help differentiate pneumopericardium from pneumomediastinum, although for pathophysiological reasons, both can coincide. In pneumopericardium a single band of gas, which is curved and sharply marginated by the pericardial sac, outlines both the left ventricle and the right atrium, and its apical limit lies at the level of the pulmonary artery and ascending aorta, reflecting the anatomical limits of the pericardium (fig 1). Air outlining the aortic arch, the superior vena cava above the azygos vein, or the distal left pulmonary artery must be outside the pericardium.6 If present, any pericardial thickening or effusion (hydropneumopericardium) helps distinguish the two conditions.6 In pneumomediastinum, gas does not usually surround the heart completely, is not confined to the region of the heart, and can be seen as multiple thin streaks of gas extending to the superior mediastinum and neck. The mediastinal pleura follows the contours of the pericardium except in the perihilar region and behind the sternum. In lateral decubitus radiographs, gas in the pericardial (and pleural) space shifts to the non-dependent side, whereas intramediastinal air is trapped within the soft tissue and does not cross to the contralateral side.6 In tension pneumopericardium the cardiothoracic ratio may decrease and the heart may appear extremely slender (small heart sign).10
It has been suggested that shearing forces rupturing the marginal alveolar bases, dissecting the peribronchial and perivascular sheaths with resulting escape of air towards either the pleural space, the hilum, or both, are involved in the pathogenesis of pneumothorax and pneumomediastinum in barotrauma, as well as in blunt chest trauma.3,11 Air spreading peripherally along the pulmonary arteries and veins dissecting through the pericardium along these vessels can result in pneumopericardium.12 Histological preparations have identified a site of potential weakness where the parietal pericardium is reflected on the visceral pericardium near the ostia of the pulmonary veins.13 The pleural or tracheobronchial and pericardial spaces may be directly connected as a consequence of pericardial tear or rupture in chest trauma.3,14 Congenital pleuropericardial defects have been described.15 Positive pressure ventilation with large tidal volumes or high end expiratory pressure may cause or worsen the condition, particularly in neonates or infants.13,16–21 Since pneumopericardium in case of a pre-existing fistula to the pericardium may be worsened by insufflation of pressurised air during gastrointestinal endoscopy, this examination should be performed in a well controlled setting with access to emergency pericardiocentesis or surgery.22 Visualisation of the fistula with contrast media may be helpful.23
As table 1 summarises, pneumopericardium has been reported to result from blunt and penetrating chest trauma,3,24,25 as a complication of invasive procedures,24,26–42 from abnormal communications such as fistulas from the pericardium to the adjacent structures containing air from different causes,9,23,24,43–59 from barotrauma,12,13,16–21,60–72 and from pericardial infections.25,73,74
Causes of pneumopericardium
In our patient we hypothesise that barotrauma (Valsalva manoeuvre) during physical effort and probably impaired alveolar integrity resulting from upper airway infection ultimately caused a pneumopericardium, which was accompanied by slight pneumomediastinum.
Acute haemodynamic deterioration in a patient with pneumopericardium should prompt further investigation and cardiac tamponade should be actively ruled out. In tension pneumopericardium, rapid fluid resuscitation and emergent pericardiocentesis with echocardiographic guidance and haemodynamic monitoring, followed by pericardial fenestration and pericardial drainage, should be performed.3,25 With stable haemodynamic conditions and absent tamponade, the underlying condition should be treated and the patient should be monitored closely.
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