Congenital Abnormalities of the Pulmonary Arteries in Adults

Transcription

1 Residents Section Structured Review Carter et al. Congenital bnormalities of the Pulmonary rteries in dults Residents Section Structured Review Residents inradiology rett W. Carter 1 John P. Lichtenberger, III 2 Carol C. Wu 3 Carter W, Lichtenberger JP III, Wu CC Keywords congenital, CT, MDCT, pulmonary arteries DOI: /JR Received ugust 19, 2013; accepted after revision November 9, Department of Diagnostic Radiology, The University of Texas M. D. nderson Cancer Center, 1515 Holcombe lvd, Unit 1478, Houston, TX ddress correspondence to. W. Carter (bcarter2@mdanderson.org). 2 Department of Radiology, David Grant Medical Center, Travis F, C. 3 Department of Radiology, Massachusetts General Hospital, Harvard Medical School, oston, M. WE This is a web exclusive article. JR 2014; 202:W308 W X/14/2024 W308 merican Roentgen Ray Society Congenital bnormalities of the Pulmonary rteries in dults Key Points 1. Congenital anomalies of the pulmonary arteries in adults may be identified in symptomatic patients or discovered incidentally on imaging examinations performed for other reasons. 2. Proximal interruption of the pulmonary artery is characterized by abrupt termination of the right or left pulmonary artery at the hilum and the presence of multiple collateral vessels supplying the affected lung. 3. nomalous origin of the left pulmonary artery from the right pulmonary artery, also known as pulmonary sling, may be associated with tracheobronchial anomalies, such as complete cartilaginous rings and tracheal stenosis, as well as congenital cardiovascular abnormalities. 4. Idiopathic dilatation of the pulmonary trunk may be distinguished from entities, such as pulmonic stenosis and pulmonary arterial hypertension, by normal pressures in the pulmonary arteries and right ventricle. 5. Congenital pulmonic valvular stenosis represents approximately 10% of congenital heart disease cases and most commonly manifests as poststenotic dilatation of the pulmonary trunk and left pulmonary artery on chest radiography and MDCT. MRI may be used to determine the extent of pulmonic stenosis and to estimate volume flow rates across the valve. Radiologists can be instrumental in the diagnosis of congenital abnormalities of the pulmonary arteries in adult patients. lthough some individuals may be asymptomatic at the time of presentation, many patients with these anomalies will develop symptoms at some point in their lives. lthough congenital abnormalities of the pulmonary arteries may be detected on chest radiography, these anomalies are optimally evaluated with contrast-enhanced MDCT, which can be used to generate multiplanar reformation (MPR) images that assist in making diagnoses. In this article, we will illustrate key features of congenital pulmonary artery anomalies in adult patients on chest radiography and MDCT. The complementary role of MRI in evaluating specific abnormalities, such as congenital pulmonic stenosis, will also be discussed. The broader topic of pulmonary artery involvement in congenital heart disease is beyond the scope of this article. Normal natomy The pulmonary trunk arises from the right ventricle at the level of the pulmonic valve and bifurcates into the left and right pulmonary arteries. The right pulmonary artery passes anterior to the right main bronchus and divides into the truncus anterior, which extends into the right upper lobe, and the interlobar branch, which gives rise to lobar arteries that extend into the right middle and lower lobes. branch of the interlobar artery supplies the posterior segment of the right upper lobe in approximately 90% of patients [1, 2]. The left pulmonary artery is a shorter vessel that courses superior to the left main bronchus and branches into the left upper lobar artery that supplies the upper lobe and interlobar artery with branches that supply the lingula and lower lobe. Suggested measurements for the upper limits of normal arterial diameters have been generated from comparisons of vessel size between healthy patients and those with pulmonary arterial hypertension. These measurements are 28.6 mm for the pulmonary trunk, 28 mm for the left pulmonary artery, and 24.3 mm for the right pulmonary artery [1 3]. The ratio of the sizes of the pulmonary arterial branches and adjacent bronchi is approximately 1.3:1 to 1.4:1 beyond the origins of the upper lobe bronchi and approaches 1:1 in the lung periphery [1 3]. Pulmonary arterial branching is dichotomous, with around W308 JR:202, pril 2014

2 Congenital bnormalities of the Pulmonary rteries in dults 17 separate divisions from the bifurcation of the main pulmonary artery. The three main types of pulmonary arteries are elastic, muscular, and transitional types [4]. Elastic arteries measure greater than 0.5 mm and are composed of central circular muscle and connective tissue surrounded by internal and external elastic laminae. Elastic arteries receive blood from the right ventricle. Muscular arteries measure less than 0.5 mm and are composed of more substantial central circular muscle and connective tissue surrounded by fewer internal and external elastic laminae. These arteries, more distally located, travel with the peripheral airways to the level of the terminal bronchioles. Transitional arteries feature elements of both elastic and muscular arteries. Pulmonary arterioles usually measure less than 0.15 mm, and those as small as 300 µm may be seen in the periphery on high-resolution CT [1 3]. Proximal Interruption of the Pulmonary rtery Proximal interruption of the right or left pulmonary artery, the natural occurrence of which is 1 in 200,000 individuals [5], is characterized by abnormal termination of a pulmonary artery at the level of the hilum [6]. The affected lung is supplied by collateral systemic vessels, primarily bronchial arteries, as well as branches of the intercostal, internal mammary, subclavian, and innominate arteries [6, 7]. The interrupted pulmonary artery usually occurs contralateral to the aortic arch. The right pulmonary artery is more commonly affected than the left pulmonary artery. lthough interruption of the right pulmonary artery is typically an isolated finding, interruption of the left pulmonary artery is frequently associated with right aortic arch and may be associated with other congenital cardiovascular anomalies such as tetralogy of Fallot [7]. The average age of patients at the time of diagnosis is 14 years [8]. lthough patients may be asymptomatic at the time of presentation, most will develop symptoms, the most common of which include recurrent infection, hemoptysis, and dyspnea [5]. pproximately 10% of cases are complicated by rupture of hypertrophied collateral arteries leading to pulmonary hemorrhage [9]. The most common findings on chest radiography include varying degrees of pulmonary hypoplasia and shift of the heart and mediastinum toward the affected side and compensatory hyperinflation of the contralateral lung [10] (Fig. 1). Subpleural reticular opacities may be present, representing systemic collateral vessels supplying the affected lung [6, 7]. Ipsilateral rib notching may be present when branches of the intercostal arteries serve as collateral vessels. MDCT optimally shows the abnormal pulmonary artery, which may be completely absent or end within 1 cm of its origin [10] (Fig. 1), and characterizes the network of collateral arteries supplying the lung (Fig. 2). ssociated abnormalities, such as pleural thickening and parenchymal bands within the subpleural lung representing anastomosis of transpleural collateral arteries with distal pulmonary arteries, may be identified (Fig. 3). MRI may be used to delineate the vascular anatomy, especially in young people in whom limited exposure to ionizing radiation is desirable, and is beneficial in identifying associated congenital cardiac abnormalities. nomalous Origin of the Left Pulmonary rtery nomalous origin of the left pulmonary artery is a rare developmental anomaly, also known as pulmonary sling and aberrant left pulmonary artery, in which the left pulmonary artery arises from the extrapericardial segment of the right pulmonary artery and courses between the trachea and the esophagus to reach the left hilum. The natural occurrence is 59 per 1,000,000 individuals [11]. lthough patients with pulmonary sling may have a normal tracheobronchial pattern of development, others may have associated tracheobronchial and cardiovascular anomalies. The former group is more likely to include asymptomatic adults, whereas the latter group is more likely to include children and infants who develop symptoms and have higher morbidity and mortality rates. Symptomatic patients typically present with stridor, wheezing, and recurrent pulmonary infections. The most common tracheobronchial anomaly associated with pulmonary sling is complete cartilaginous rings resulting in tracheal stenosis [12]. In this group of patients, tracheal reconstruction may be necessary [13]. The most characteristic finding on chest radiography is a rounded opacity located between the trachea and the esophagus on the lateral radiograph. Fluoroscopic esophagrams may show focal indentation of the anterior wall of the esophagus by the anomalous artery. MDCT shows the abnormal origin and course of the artery (Fig. 4) and facilitates evaluation of the airway for complete tracheal rings and tracheal stenosis through MPR and 3D reconstructive techniques, such as virtual bronchoscopy (Fig. 5). MRI may alternatively be used to evaluate the vascular anatomy and generate volumetric reconstructions of the airway [14] (Fig. 6). Idiopathic Dilatation of the Pulmonary Trunk Idiopathic dilatation of the pulmonary trunk is a rare congenital abnormality, the natural occurrence of which is unknown. It is characterized by abnormal enlargement of the pulmonary trunk, with or without enlargement of the right and left pulmonary arteries [15]. ffected patients are asymptomatic. The diagnosis is typically made after pulmonary and cardiac causes of pulmonary artery dilatation have been excluded. The primary differential considerations include congenital pulmonic valvular stenosis and pulmonary arterial hypertension, which result in elevated pressures in the pulmonary arteries and right ventricle, whereas idiopathic dilatation of the pulmonary trunk does not [16]. The most common finding on chest radiography is enlargement of the pulmonary trunk, which manifests as a convex opacity in the left aspect of the mediastinum. MDCT effectively shows enlargement of the pulmonary trunk greater than 29 mm [16] (Fig. 7). Pulmonic Stenosis Pulmonic stenosis is congenital in 95% of cases and accounts for approximately 10% of patients with congenital heart disease [17]. Valvular pulmonic stenosis accounts for 90% of cases and is the most common type, followed by subvalvular and supravalvular types. The abnormality is characterized by fusion of the valve leaflets at the commissures, resulting in restricted opening of the leaflets during systole [18]. Symptoms at presentation depend on the severity of pulmonic stenosis, which is determined by the pressure gradient across the pulmonic valve. Patients with trivial or mild pulmonic stenosis are typically asymptomatic. However, individuals with moderate or severe pulmonic stenosis may show signs and symptoms of systemic venous congestion mimicking congestive heart failure. The most characteristic finding on chest radiography is enlargement of the pulmonary trunk and left pulmonary artery, representing poststenotic dilatation (Fig. 8). JR:202, pril 2014 W309

3 Carter et al. ecause the right pulmonary artery is normal in size, the hila may appear asymmetric. MDCT reveals poststenotic dilatation of the pulmonary trunk and the left pulmonary artery (Fig. 8). Right ventricular enlargement may also be seen. The pulmonic valve leaflets may appear thickened and immobile on MDCT or cardiac-gated CT angiography and calcification may be present (Fig. 9). Focal pericardial calcification involving the thoracic aorta and the pulmonary trunk has been reported as a rare acquired cause of pulmonic stenosis [19]. MRI is useful in evaluating pulmonic valve morphology and characterizing the direction, size, and extent of the abnormal flow jet associated with pulmonic stenosis (Fig. 10). Thickening and fusion of valve leaflets and narrowing of the valve orifice may be present (Fig. 10). dditional morphologic abnormalities, such as bulging of the pulmonic valve, reduced valve movement, and right ventricular hypertrophy and thickening, may be identified [20]. Conclusion Congenital anomalies of the pulmonary arteries in adults may initially be detected on chest radiography, but specific diagnoses are typically made with MDCT. These abnormalities may be identified in symptomatic patients or discovered incidentally on imaging examinations performed for other reasons. Therefore, it is important for the radiologist to recognize these congenital anomalies on radiologic studies and convey their clinical importance to clinicians. References 1. Parker MS, Rosado-de-Christenson ML, bbott GF. Normal thoracic anatomy. In: Parker MS, Rosado-de-Christenson ML, bbott GF. Teaching atlas of chest imaging. New York, NY: Thieme Medical Publishers, 2006:8 2. McLoud TC, oiselle PM. Thoracic radiology: imaging methods, radiographic signs, and diagnosis of chest disease. In: McLoud TC, oiselle PM. Thoracic radiology: the requisites, 2nd ed Philadelphia, P: Elsevier, 2010:8 3. Carter W, bbott GF. Pulmonary arteries. In: bbars S, Kalva SP, eds Problem solving in cardiovascular imaging. Philadelphia, P: Elsevier, 2013: Frazier, Galvin JR, Franks TJ, Rosado-de- Christenson ML. From the archives of the FIP: pulmonary vasculature hypertension and infarction. RadioGraphics 2000; 20: ouros D, Pare P, Panagou P, Tsintiris K, Siafakas N. The varied manifestation of pulmonary artery agenesis in adulthood. Chest 1995; 108: Kieffer S, mplatz K, nderson RC, Lillehei CW. Proximal interruption of a pulmonary artery. m J Roentgenol Radium Ther Nucl Med 1965; 95: Sherrick DW, Kincaid OW, Dushane JW. genesis of a main branch of the pulmonary artery. m J Roentgenol Radium Ther Nucl Med 1962; 87: Ten Harkel D, lom N, Ottenkamp J. Isolated unilateral absence of a pulmonary artery: a case report and review of the literature. Chest 2002; 122: Reñe M, Sans J, Dominguez J, Sancho C, Valldeperas J. Unilateral pulmonary artery agenesis presenting with hemoptysis: treatment by embolization of systemic collaterals. Cardiovasc Intervent Radiol 1995; 18: Ryu DS, Spirn PW, Trotman-Dickenson, et al. HRCT findings of proximal interruption of the right pulmonary artery. J Thorac Imaging 2004; 19: Yu JM, Liao CP, Ge S, Weng ZC, Hsiung MC, Chang JK, Chen FL. The prevalence and clinical impact of pulmonary artery sling on school-aged children: a large-scale screening study. Pediatr Pulmonol 2008; 43: Siripornpitak S, Reddy GP, Schwitter J, Higgins C. Pulmonary artery sling: anatomical and functional evaluation by MRI. J Comput ssist Tomogr 1997; 21: Fiore C, rown JW, Weber TR, Turrentine MW. Surgical treatment of pulmonary artery sling and tracheal stenosis. nn Thorac Surg 2005; 79:38 46; discussion, Zylak CJ, Eyler WR, Spizarny DL, Stone CH. Developmental lung anomalies in the adult: radiologic-pathologic correlation. RadioGraphics 2002; 22(spec no):s25 S Deshmukh M, Guvenc S, entivoglio L, Goldberg H. Idiopathic dilatation of the pulmonary artery. Circulation 1960; 21: Ugolini P, Mousseaux E, Sadou Y, et al. Idiopathic dilatation of the pulmonary artery: report of four cases. Magn Reson Imaging 1999; 17: Waller F, Howard J, Fess S. Pathology of pulmonic valve stenosis and pure regurgitation. Clin Cardiol 1995; 18: Ryan R, bbara S, Colen RR, et al. Cardiac valve disease: spectrum of findings on cardiac 64- MDCT. JR 2008; 190:[web]W294 W Hwang YJ, Park CH, Jeon Y, Park KY. Severe pulmonary artery stenosis by a calcified pericardial ring. Eur J Cardiothorac Surg 2006; 29: Didier D, Ratib O, Lerch R, Friedli. Detection and quantification of valvular heart disease with dynamic cardiac MR imaging. RadioGraphics 2000; 20: ; discussion, Fig year-old woman with recurrent pulmonary infections., Posteroanterior chest radiograph shows marked volume loss in left hemithorax and leftward shift of heart and mediastinum., Contrast-enhanced axial MDCT image shows proximal interruption of left pulmonary artery. Multiple collateral vessels are present in left mediastinum and hilum (arrows). In proximal interruption of pulmonary artery, affected vessel may be completely absent or abruptly terminate at hilum. W310 JR:202, pril 2014

4 Congenital bnormalities of the Pulmonary rteries in dults Fig year-old man with proximal interruption of left pulmonary artery. Contrast-enhanced axial MDCT image shows marked volume loss in left hemithorax. Numerous enlarged collateral vessels are present in mediastinum (arrowhead) and posterior chest wall (arrow). ffected lung is typically supplied by bronchial collateral vessels, although branches of intercostal, internal mammary, subclavian, and innominate arteries may also serve as collateral vessels. Fig year-old woman with proximal interruption of left pulmonary artery. Contrastenhanced axial MDCT image shows linear opacities (arrow) perpendicular to pleural surface, representing transpleural collateral arteries. Fig. 4 symptomatic 54-year-old woman. and, Contrast-enhanced axial () and coronal reformatted () MDCT images show origination of left pulmonary artery from right pulmonary artery (arrow, ) and passage of vessel (arrow, ) between anteriorly located trachea and posteriorly located esophagus. lso known as pulmonary sling, this aberrant vessel may exert mass effect on distal trachea or right main bronchus and impede respiration to all or portions of lungs. JR:202, pril 2014 W311

5 Carter et al. Fig year-old boy with pulmonary sling. Three-dimensional reconstructed image generated from MDCT shows focal narrowing of proximal left main bronchus (arrow) caused by anomalous vessel. Reconstructive techniques facilitate evaluation of airways for regions of focal narrowing, as in this case, and tracheobronchial anomalies, such as complete tracheal rings and tracheal stenosis. Fig day-old boy with pulmonary sling., xial T1-weighted MRI shows origination of left pulmonary artery (arrow) from right pulmonary artery., Coronal reformatted T1-weighted MRI shows narrowing of long segment of trachea (arrow) beginning at level of aortic arch. W312 JR:202, pril 2014

6 Congenital bnormalities of the Pulmonary rteries in dults Fig. 7 symptomatic 71-year-old woman. Contrastenhanced axial MDCT image shows enlargement of pulmonary trunk and proximal pulmonary arteries. Right heart catheterization showed normal pressures within pulmonary arterial system and right ventricle. These findings distinguish idiopathic dilatation of pulmonary trunk from pulmonary arterial hypertension and congenital pulmonic valvular stenosis, in which these pressures are elevated. Fig year-old man with congenital pulmonic stenosis., xial T2-weighted MRI shows enlargement of pulmonary trunk and left pulmonary artery. and C, Sagittal reformatted T2-weighted MR images show region of signal dephasing (arrows, ) arising from pulmonic valve and thickening of pulmonic valve leaflets (arrow, C). MRI provides both anatomic and functional information regarding pulmonic stenosis, including morphology of pulmonic valve and severity of stenosis. Fig. 8 symptomatic 37-year-old man., Posteroanterior chest radiograph shows enlargement of pulmonary trunk (arrow) and left pulmonary artery (arrowhead)., Contrast-enhanced axial MDCT image confirms enlargement of these vessels, consistent with pulmonic stenosis. Fig. 9 symptomatic 52-year-old man. Contrastenhanced axial MDCT shows thickening (arrowhead) and calcification (arrow) of pulmonic valve leaflets in pulmonic stenosis. lthough pulmonic valve leaflets are best evaluated with cardiac-gated CT angiography, abnormalities, such as thickening and calcification of leaflets, may be identified on routine CT of chest. C JR:202, pril 2014 W313