Systemic air embolism is a rare but potentially fatal complication of percutaneous transthoracic needle biopsy of the lung. Coronary air embolism can result in myocardial infarction, cardiac arrest, or dysrhythmias. We present the first case of cardiac arrest and myocardial infarction confirmed by ECG and cardiac enzymes in the presence of air in the left coronary artery documented by CT scan in a 77-year-old man after CT-guided transthoracic needle biopsy of the lung.
Key words: air embolism; CT-guided biopsy; myocardial infarction; needle lung biopsy
CT-guided needle biopsy has become a common procedure to diagnose a broad range of pulmonary pathologic conditions. (1) However, this procedure is not without risks. Frequent complications include pneumothorax and hemoptysis, which tend to be mild and self-limiting. However, there are severe complications, such as air embolism and pulmonary hemorrhage. (2) We report a case of cardiac arrest and myocardial infarction secondary to air embolism after CT-guided percutaneous needle biopsy of the lung.
A 77-year-old man was admitted to the hospital for evaluation of generalized weakness, anorexia, and weight loss of 30 lb during the past 6 months. His medical history was significant for coronary artery disease and COPD. His surgical history included triple-vessel coronary artery bypass grafting and abdominal aortic aneurysm repair.
His workup included a chest radiograph and a CT scan, which revealed a 2.0 x 2.8-cm mass in the right lower lobe. A CT-guided biopsy was undertaken to establish a diagnosis. Under CT guidance (CT fluoroscopy) with the patient in prone position, a 22-gauge Rotex screw needle with a stylet (Ursus Konsult AB; Stockholm, Sweden) was inserted into the mass. The needle tip with the stylet in place passed through the mass by approximately 8 mm into a pulmonary vein. Following the procedure, the patient became unresponsive, pulseless, hypotensive, and was found to be in ventricular fibrillation. He was defibrillated into sinus rhythm, orotracheally intubated, and placed on 100% fraction of inspired oxygen through mechanical ventilation. A 12-lead ECG revealed new ST-segment elevation in the anterolateral leads (Fig 1).
[FIGURE 1 OMITTED]
In the ICU, his vital signs were as follows: BP, 151/79 mm Hg; heart rate, 119 beats/min; respiratory rate, 22 breaths/min; he was afebrile. Neurologic examination results were grossly normal; both cardiac and lung examination results were normal. A repeat chest radiograph excluded any evidence of barotrauma. A repeat ECG showed sinus tachycardia with resolving ST-segment elevation. The patient sustained an acute myocardial infarction confirmed by cardiac enzymes.
A closer review of the chest CT scan at the time of the incident demonstrated air entering the pulmonary vein and advancing to the left atrium, left ventricle, aorta, and eventually the left anterior descending coronary artery (Fig 2). The sequence of CT-scan images enabled us to establish the diagnosis of acute myocardial infarction secondary to coronary artery air embolism. After 40 h of supportive treatment with 100% oxygen and aspirin, the patient was extubated without sustaining any neurologic deficit.
[FIGURE 2 OMITTED]
With advances in chest radiology, patients are undergoing percutaneous needle biopsy of pulmonary nodules or masses. Systemic air embolism is a rare but potentially fatal complication of lung needle biopsy with a reported incidence of 0.07%. (2) Needle biopsy of the lung is a much less frequent cause of systemic air embolism than are cardiac surgery, coronary angiography, neurosurgical procedures in upright position, or barotrauma due to positive-pressure ventilation. (3,4)
There are three possible mechanisms whereby air can enter the systemic circulation during needle biopsy of the lung. First, when the needle tip is placed within the pulmonary vein and the stylet has been removed, it can create a direct communication between the atmosphere and the pulmonary vein. Air can easily enter the systemic circulation if the patient inspires and creates a negative pleural pressure. Second, a bronchovenous fistula can be created when the needle is passing through the lung parenchyma. Intra-alveolar or intrabronchial air can get introduced into the pulmonary venous circulation through the fistula. A Valsalva maneuver, coughing, or positive-pressure ventilation may increase air introduction by causing an elevation in the intra-alveolar pressures. Finally, air may be introduced in the pulmonary arterial circulation and later reach the pulmonary venous circulation by traversing the pulmonary microvasculature, even in the absence of arteriovenous malformation. (3,5,6) We believe that the mechanism behind systemic air embolism in our patient was a transient bronchovenous fistula allowing introduction of air from lung parenchyma into the pulmonary venous circulation without barotrauma.
Air in the pulmonary vein will go directly to the left atrium and ventricle and eventually enter the systemic circulation. Ischemia can be induced by three mechanisms. First, air embolism can obstruct the blood flow. Second, it can cause intense vasospasm while passing through the vessel. Finally, air embolism can induce platelet activation with microthrombi formation leading to further ischemia. Coronary artery air embolism can induce ECG changes typical of ischemia and infarction, dysrhythmias, and cardiac arrest. (7,8)
Treatment of systemic air embolism consists of supplying 100% oxygen by a tight-fitting mask or endotracheal intubation to promote the exchange of oxygen for nitrogen within the air bubble. Use of positional therapy, such as Trendelenburg or left lateral decubitus, is controversial and may be more helpful in shock induced by right ventricular air emboli. (8,9) Hyperbaric oxygen reduces the bubble size by promoting counterdiffusion of oxygen into the nitrogen bubble facilitating nitrogen resorption. (10) Air embolism can be prevented by avoiding needle biopsy of cystic, cavitary, or bullous lung parenchyma. In addition, a stylet or occlusion of the hollow needle at all times can prevent a direct communication between the atmosphere and pulmonary venous system. (5) The patient should refrain from coughing or straining while the biopsy of the mass is being performed, especially when the stylet has been removed. It is crucial to select an insertion site where the needle penetrates the least amount of lung parenchyma to reach the mass. Performing the biopsy under CT-guided fluoroscopy may decrease the incidence of this complication. (11)
Although systemic air embolism inducing myocardial infarction has been described previously, (5,11-13) this report represents the first case with clear radiologic description of events. Our patient had ventricular fibrillation and acute myocardial infarction confirmed by ECG and cardiac enzymes in the presence of air in the left coronary artery documented by CT scan.
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* From the Louis A. Weiss Memorial Hospital, University of Chicago, Chicago, IL.
Manuscript received May 14, 2001; revision accepted August 6, 2001.
Correspondence to: Babak Mokhlesi, MD, Division of Pulmonary and Crititcal Care, Cook County Hospital and Rush Medical College, 1900 West Polk St, Room 914, Chicago, IL 60612; e-mail: Babak_Mokhlesi@rush.edu
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