Acute and Chronic Pulmonary Emboli: Angiography CT Correlation

Transcription

1 ngiography and T of Pulmonary Emboli ardiac Imaging Pictorial Essay D E M N E U T R Y L I M I G O F I N G onrad Wittram 1 Mannudeep K. Kalra Michael M. Maher lan Greenfield Theresa. McLoud Jo-nne O. Shepard Wittram, Kalra MK, Maher MM, Greenfield, McLoud T, Shepard J-O Keywords: cardiovascular disease, conventional angiography, T angiography, embolism, lung, thromboembolic disease DOI: /JR Received December 23, 2004; accepted after revision March 14, ll authors: Department of Thoracic Radiology, Massachusetts General Hospital, Founders 202, 55 Fruit St., oston, M 02115; and Harvard Medical School, oston, M. ddress correspondence to. Wittram (cwittram@partners.org). JR 2006; 186:S421 S X/06/1866 S421 merican Roentgen Ray Society cute and hronic Pulmonary Emboli: ngiography T orrelation OJETIVE. The objective of our study was to review the classic direct and indirect angiographic signs of acute and chronic pulmonary embolism (PE) and correlate these findings with MDT. ONLUSION. T and angiography have complementary roles in the accurate diagnosis of acute and chronic thromboembolic disease. onventional angiography should be used as a problem-solving technique after T angiography has been performed because T angiography is less invasive. ulmonary embolism (PE) is the P third most common acute cardiovascular disease, after myocardial infarction and stroke, and is a major public health problem [1]. ccurate diagnosis of PE is important because the consequences of a false-positive or falsenegative diagnosis can be rapidly fatal. In this pictorial essay, we review the classic pulmonary angiographic findings of acute and chronic PE and correlate these signs with MDT. Fig. 1 cute pulmonary embolism (PE) in 78-year-old woman., Pulmonary angiogram of right pulmonary artery shows complete obstruction of right posterior basal segmental artery. Trailing edge or concave filling defect (arrow) is shown within column of contrast material. Perfusion defect within right posterior basal segment artery (arrowhead) is also detected., Illustration of complete obstruction due to acute PE as seen on angiography. Trailing edge of thrombus forms concave filling defect within column of contrast material at level of obstruction. (Fig. 1 continues on next page) JR:186, June 2006 S421

2 Direct Signs of cute PE omplete Obstruction On pulmonary angiograms, the diagnostic sign of acute PE with complete obstruction is a concave filling defect or trailing edge that should be seen within the contrast material at the level of the obstruction [2, 3] (Fig. 1). T is able to show thrombus distal to the obstruction that cannot be seen on an angiogram. t the site of the thrombus, the diameter of the pulmonary artery may be increased because of impaction of the thrombus by pulsatile flow [4] (Fig. 1). E Nonobstructive Filling Defect nonobstructive filling defect may be central or eccentric in location. On angiography, a central filling defect is completely surrounded by contrast material [2, 3] (Fig. 2). On T, this finding is seen as a well-defined central filling defect in either an axial or a longitudinal plane with respect to the vessel [4] (Fig. 2). nonobstructive central filling defect cannot float within the center of the lumen without physically touching the vessel wall and will be attached to either a nonobstructive eccentric filling defect or the thrombus of complete obstruction. In acute PE, a nonobstructing eccentric filling defect forms acute angles with respect to the vessel wall when seen on angiography or T [4] (Fig. 2). D Fig. 1 (continued) cute pulmonary embolism (PE) in 78-year-old woman., urved coronal reformatted T image shows acute thrombus within right posterior basal segment and branch vessels (arrow). Obtained more distal to obstruction, this T image is able to show expansion of vessel with acute thrombus (arrowheads). D, Illustration of coronal reformatted T image of acute PE shows expansion of diameter of involved vessel distal to point of obstruction (arrow). E, xial T image shows impacted thrombus distal to point of occlusion (arrow) that expands vessel diameter. Indirect Sign of cute Thromboembolic Disease: Nonuniform rterial Perfusion Oligemia, or a decrease in flow rate, due to acute PE is often identified on angiography [2, 3] (Fig. 1). In our experience, this finding is more often seen on angiography than on T. Nonuniform arterial perfusion due to acute PE can uncommonly manifest as a mosaic pattern of attenuation on T. Occasionally, a large acute central PE can cause oligemia and a decrease in vessel diameter, which is reversible, can be seen on T (Fig. 3). The differential diagnosis of the indirect radiologic sign of nonuniform pulmonary arterial perfusion consists of congenital or acquired causes including S422 JR:186, June 2006

3 ngiography and T of Pulmonary Emboli D E F Fig. 2 cute pulmonary embolism (PE) in 78-year-old woman (same patient as shown in Fig. 1)., Left pulmonary angiogram shows central filling defect (arrow) within posterior segment of left upper lobe. In this patient, all three segmental arteries of left upper lobe arise directly from main pulmonary artery. Nonuniform arterial perfusion (arrowhead) is seen on arteriogram., urved coronal reformatted T image shows central nonobstructive filling defect (arrow). T also shows more proximal nonobstructive thrombus (arrowhead) within main pulmonary artery, more easily seen on T than on angiogram ()., Illustration shows that eccentric acute thrombus (arrow) makes acute angles with vessel wall. D, xial T image shows central filling defect within posterior segmental artery (arrow) of left upper lobe. E, Illustration shows acute PE central filling defect on T image viewed perpendicular to plane of thrombus; well-defined central thrombus is completely surrounded by contrast material. F, Illustration shows acute PE central filling defect on T image viewed in long axis of thrombus. ontrast material can be seen on either side of well-defined thrombus forming the railroad track sign. (Fig. 2 continues on next page) chronic PE, emphysema, infection, compression or invasion of a pulmonary artery, atelectasis, pleuritis, and pulmonary venous hypertension [2]. Direct Signs of hronic PE omplete Obstruction On angiography, complete vessel cutoff due to chronic embolism has a convex margin with respect to the contrast material and has been described as a pouch defect [5] (Fig. 4). This differs from the appearance of a complete obstruction caused by acute PE in JR:186, June 2006 S423

4 G H Fig. 2 (continued) cute pulmonary embolism (PE) in 78-year-old woman (same patient as shown in Fig. 1). G, xial T image, obtained more cephalad than D, shows eccentric filling defect within pulmonary artery (arrow). H, Illustration shows acute PE eccentric filling defect on T image viewed perpendicular to plane of thrombus; well-defined thrombus (arrow) forms acute angles with vessel wall. Fig. 3 cute pulmonary embolism in 55-year-old man., Right pulmonary artery angiogram shows large filling defect in right pulmonary artery (arrow). Nonuniform arterial perfusion is shown affecting majority of right lung with sparing of anterior segmental artery of right upper lobe. There is reflux of contrast material into left pulmonary artery. Unusual pulmonary artery catheter course due to azygos continuation of anomalous inferior vena cava is also seen., T image obtained distal to large thrombus shows pulmonary arteries to have decreased in vessel diameter (arrows) with respect to adjacent bronchi and contralateral vessels., Obtained 3 weeks after embolectomy, T image shows pulmonary arteries (arrows) have returned to their normal diameter. S424 JR:186, June 2006

5 ngiography and T of Pulmonary Emboli that a concavity can be seen within the contrast material due to the trailing edge of thrombus [2] (Fig. 1). On T, an additional finding is a decrease in the diameter of the vessel distal to the complete obstruction [4]. This permanent reduction in vessel diameter D Fig. 4 hronic pulmonary embolism (PE) in 40-year-old woman., ngiogram shows complete obstruction (arrows) is affecting subsegmental vessels of posterior segment of left upper lobe and anterior and posterior basal segmental arteries. Resultant nonuniform arterial perfusion (arrowheads) is also well shown., Line drawing shows complete obstruction of vessel with convex margin with respect to contrast material. This is the pouch defect of chronic PE seen on angiography., urved coronal reformatted T image viewed on lung windows shows pouch defect of anterior basal segment of right lower lobe (arrow). ontracted artery (arrowheads) is smaller than adjacent bronchus. D, Illustration of reformatted T image of complete obstruction in chronic PE shows contracted thrombus (arrow) distal to pouch defect. is due to contraction of thrombus in chronic PE (Figs. 4 and 4D). Nonobstructive Filling Defects The organized thrombus of chronic PE can cause intimal irregularities, bands and webs, and abrupt vessel narrowing; any of these can lead to a pulmonary artery stenosis. Intimal Irregularities Intimal irregularities are broad-based, smooth, margined abnormalities that create JR:186, June 2006 S425

6 obtuse angles with the vessel wall. They may be unilateral or bilateral [4 6] (Fig. 5). Pulmonary artery intimal irregularities can also be due to plaques secondary to pulmonary hypertension. ands and Webs band is defined as a delicate ribbonlike structure anchored to the vessel wall at two ends with a free unattached mid portion. band generally ranges from 0.3 to 2 cm in length and from less than 0.1 to 0.3 cm in width. It is often orientated in the direction of blood flow along the long axis of the vessel [7]. web is a descriptive term for bands that have branches and form networks of varying complexity [7]. ands and webs are seen as thin lines surrounded by contrast material on angiography [5] or T (Fig. 6). brupt Vessel Narrowing brupt vessel narrowing, often the result of recanalization, manifests angiographically as an abrupt convergence of contrast material that leads to a thin column of intravascular contrast material distally [5]. This nonreversible finding can also be detected on T images, which can be used to identify the cause of the stenosis [4] (Fig. 7). Indirect Signs of hronic Thromboembolic Disease Poststenotic Dilatation Poststenotic dilatation or aneurysm commonly occurs as a manifestation of chronic thromboembolic disease [5] (Figs. 5, 5, and 5D). The differential diagnosis includes congenital causes for example, Marfan syndrome or acquired causes. cquired causes include mycotic aneurysms secondary to septic emboli or adjacent pulmonary infection, pseudoaneurysms resulting from extra- or endovascular trauma (e.g., pulmonary artery catheterization), ehçet disease, and Takayasu s arteritis. Tortuous Vessels Tortuous pulmonary vessels have been well described in patients with pulmonary artery hypertension. This radiologic sign is also seen in patients with pulmonary artery hypertension secondary to chronic thromboembolic disease [8] (Figs. 5 and 5). Enlargement of the Main Pulmonary rtery Enlargement of the main pulmonary artery, greater than 33 mm [9], occurs in patients with precapillary, capillary, and post- Fig. 5 hronic pulmonary embolism (PE) in 60-year-old man., Right pulmonary angiogram shows multiple intimal irregularities (straight arrows). Poststenotic dilatation (arrowhead) is shown affecting posterior segment of right upper lobe. lso noted within right lower lobe is tortuous vessel (curved arrow)., oronal reformatted T image shows organized thrombus (arrows) as cause of intimal irregularities. In addition, poststenotic dilatation (arrowhead) is shown affecting posterior segmental artery. gain shown within right lower lobe is tortuous vessel (curved arrow). (Fig. 5 continues on next page) S426 JR:186, June 2006

7 ngiography and T of Pulmonary Emboli capillary causes of pulmonary artery hypertension. This radiologic finding is commonly identified in patients with pulmonary artery hypertension secondary to chronic thromboembolic disease [8]. Enlargement of ronchial rteries Enlarged bronchial arteries are often identified in patients with chronic thromboembolic disease. Other causes of this finding include congenital vascular anomalies, bronchiectasis, acute or chronic lung abscesses, and mycobacterial and fungal infections. Enlargement of the bronchial artery collateral supply is easily seen on T E Fig. 5 (continued) hronic pulmonary embolism (PE) in 60-year-old man., Illustration of intimal irregularity of chronic PE as seen on angiography. This broad-based, smooth, margined abnormality can affect one or both sides of vessel; it forms obtuse angles with vessel wall (arrow). D, xial T image obtained at level of poststenotic aneurysm shows that posterior segment of right upper lobe (arrow) is affected. E, xial T image obtained at level of right lower lobe pulmonary artery shows eccentric chronic thrombus (arrow). F, Illustration of intimal irregularity of chronic PE viewed in axial plane. This broad-based, smooth, margined, eccentric filling defect forms obtuse angles with vessel wall (arrow). angiography but cannot be identified on conventional angiography of the pulmonary artery. Nonuniform rterial Perfusion hronic PE can cause a nonuniform arterial perfusion pattern identifiable on angiography and can manifest as a mosaic pattern of lung attenuation on T [4] (Fig. 8). In addition, on T one can see that the affected pulmonary arteries are permanently small relative to the accompanying bronchi [4, 6] (Figs. 4 and 8) and that unaffected arteries are often larger than their accompanying bronchi. The mosaic pattern of lung attenuation has two other major causes: F small airways disease, in which the mosaic pattern of lung attenuation is accentuated by expiratory T, and ground-glass opacification, in which it is not. Summary The direct radiologic signs, shown on angiography or T angiography, are required to make the diagnosis of acute or chronic pulmonary thromboembolic disease. The indirect signs are helpful as indicators of the sites of the direct radiologic signs of PE. oth T angiography and angiography have complementary D JR:186, June 2006 S427

8 Fig. 6 hronic pulmonary embolism (PE) in 51-year-old man., Oblique view of left-sided pulmonary angiogram shows abrupt vessel narrowing (arrow) and complete obstruction of posterior basal segment of left lower lobe (arrowhead). It was difficult to see vascular band or web in this patient., xial T image obtained near origin or posterior basal segmental artery of left lower lobe shows band or web (arrow)., Illustration of nonobstructive filling defect of chronic PE. and or web can be identified as thin dark line surrounded by contrast material, often orientated in direction of blood flow. Fig. 7 hronic pulmonary embolism (PE) in 65-year-old man., brupt vessel narrowing (arrow) is shown affecting posterior basal subsegmental artery of right lower lobe., urved coronal T image shows similar appearance, with abrupt convergence of contrast material leading to thin column of more distal intravascular contrast material. In addition, organized thrombus (arrows) is identified adjacent to column of contrast material., Illustration of abrupt vessel narrowing of chronic PE as seen on angiography. This finding is recognized by abrupt convergence of contrast material leading to thin column of intravascular contrast material. S428 JR:186, June 2006

9 ngiography and T of Pulmonary Emboli roles in the accurate diagnosis of acute and chronic thromboembolic disease. onventional angiography should be used as a problem-solving technique after T angiography because T angiography is less invasive. cknowledgments We thank Susan Loomis for the illustrations and Sally Pinho for the image reconstruction processing. References 1. Goldhaber SZ. Pulmonary embolism. Lancet 2004; 363: Fig. 8 hronic pulmonary embolism in 60-year-old man., Left-sided pulmonary angiogram shows complete occlusion of left lower lobe with nonuniform arterial perfusion and large perfusion defect affecting left lower lobe (arrowheads)., xial T image viewed on lung window settings shows occluded, contracted left lower lobe pulmonary artery (arrowhead). There is decrease in lung attenuation of left lower and right upper lobes, and more normally perfused lung contributes to mosaic pattern of lung attenuation (arrows). Incidental note is made of centrilobular emphysema. 2. Sagel SS, Greenspan RH. Nonuniform pulmonary arterial perfusion: pulmonary embolism? Radiology 1970; 99: Dalen JE, rooks HL, Johnson LW, et al. Pulmonary angiography in acute pulmonary embolism: indications, techniques, and results in 367 patients. m Heart J 1971; 81: Gottschalk, Stein PD, Goodman LR, Sostman HD. Overview of prospective investigation of pulmonary embolism diagnosis II. Semin Nucl Med 2002; 32: uger WR, Fedullo PF, Moser KM, uchbinder M, Peterson KL. hronic major-vessel thromboembolic pulmonary artery obstruction: appearance at angiography. Radiology 1992; 182: ergin J, Sirlin, Hauschildt JP, et al. hronic thromboembolism: diagnosis with helical T and MR imaging with angiographic and surgical correlation. Radiology 1997; 204: Korn D, Gore I, lenke, ollins DP. Pulmonary arterial bands and webs: unrecognized manifestation of organized pulmonary emboli. m J Pathol 1962; 40: Tardivon, Musset D, Maitre S, et al. Role of T in chronic pulmonary embolism: comparison with pulmonary angiography. J omput ssist Tomogr 1991; 17: Edwards PD, ull RK, oulden R. T measurement of main pulmonary artery diameter. r J Radiol 1998; 71: JR:186, June 2006 S429