Cross-sectional Echocardiographic Characterization of Atelectatic Lung Segments: DISCUSSION
Cross-sectional echocardiography is a useful noninvasive method for diagnosing both intracardiac and extracardiac masses, including mediastinal cysts and tumors, pericardial cysts and tumors, intrathoracic neoplasms, and left ventricular pseudoaneu- rysms. Although atelectatic segments of lung are encountered frequently during routine echocardiography studies, this entity has not been described well in the literature. Furthermore, these lung masses are usually distinctly separate from the heart and are easily recognized as free-floating, brightly reflective, echo-dense objects. In the present unique series of patients the atelectatic segments appeared to be adherent to the heart, which rendered the initial diagnosis of the mass somewhat more difficult. Indeed, in two of the patients (patients 1 and 2) an extramural cardiac tumor was considered initially, based on the following constellation of findings: the echo-dense mass appeared to be adherent to the heart from the posterolateral to the inferoposterior aspect of the left ventricle; the mass moved synchronously with the heart; the mass was contiguous with hypokinetic segments of the ventricle, which suggested the possibility of myocardial injury secondary to tumor infiltration; there was no clear-cut pericardial stripe between the mass and the ventricular wall in any of the tomographic views; the initial admitting chest roentgenogram did not suggest the presence of coexisting pulmonary atelectasis. To the best of our knowledge, the present case reports represent the first description of an atelectatic lung segment mimicking an extracardiac mass.
Important to the above discussion of the differential diagnosis of extracardiac masses are several echocardiography signs that may prove useful in separating pulmonary atelectasis from less benign extracardiac masses. First, in our series the atelectatic lung segments always occurred in the presence of a moderate to large left pleural effusion. Thus, the echo-dense lung mass will appear sharply outlined against the sonolucent area of the pleural effusion (Fig 1A and 1С). As evidenced by the third patient in our series, this effusion need not be long-term to result in this finding, but it may also occur in subacutely developing effusions. Second, in real-time examination the atelectatic lung mass generally appears solid, with a characteristic brightly reflective ground-glass appearance. The solid, homogeneous appearance of the lung mass is useful in differentiating atelectasis from a number of sonolucent extracardiac masses, including pericardial and anterior mediastinal cysts and left ventricular pseudoaneurysms. Third, there was no evidence of extrinsic compression of the heart by the lung mass, which might be expected based on the composition of pulmonary tissue, which is comprised of elastic and reticular fibers, along with thin layers of epithelial tissue. This latter feature may be useful in differentiating atelectasis from other large extracardiac masses that might be expected to compress the heart by virtue of their mass. Fourth, the mass resolved completely following thoracentesis and drainage of the pleural effusion. Finally, as demonstrated by the first patient in our series, CT examination may sometimes be useful as an ancillary technique in clarifying the abnormality in question.
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