Anomalous Origin of One Pulmonary Artery Branch From the Aorta: Role of MDCT Angiography

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1 Cardiopulmonary Imaging Original Research Liu et al. CTA Evaluation of AOPA Cardiopulmonary Imaging Original Research Hui Liu 1,2 Yu-Hsiang Juan 2,3,4 Jimei Chen 5 Zhaofeng Xie 6 Qiushi Wang 1 Xiaoshen Zhang 5 Changhong Liang 1 Hongfei Huang 1 Raymond Y. Kwong 2 Sachin S. Saboo 2,7 H. Liu and Y. H. Juan contributed equally to this work. Liu H, Juan YH, Chen J, et al. Keywords: anomalous origin of one pulmonary artery branch from the aorta (AOPA), congenital heart disease, MDCT angiography (MDCTA) DOI: /AJR Received February 14, 2014; accepted after revision September 21, Supported by grant 2011B from the Guangdong Provincial Science and Technology Foundation, Guangdong, China. 1 Department of Radiology, Guangdong General Hospital, Guangdong Academy of Medical Sciences, No.106, Zhongshan 2 Rd, Guangzhou, China. Address correspondence to C. Liang (cjr.lchh@vip.163.com). 2 Cardiovascular Imaging Program, Departments of Medicine, Division of Cardiovascular Medicine, and Radiology, Brigham and Women s Hospital, Harvard Medical School, Boston, MA. 3 Department of Medical Imaging and Intervention, Chang Gung Memorial Hospital, Linkou, Chang Gung University, Taoyuan, Taiwan. 4 Healthy Aging Research Center, Chang Gung University, Taiwan. 5 Department of Cardiovascular Surgery, Guangdong General Hospital, Guangdong Academy of Medical Sciences, GuangZhou, GuangDong, China. 6 Department of Pediatric Cardiology, Guangdong General Hospital, Guangdong Academy of Medical Sciences, GuangZhou, GuangDong, China. 7 UT Southwestern Medical Center, Dallas, TX. AJR 2015; 204: X/15/ American Roentgen Ray Society Anomalous Origin of One Pulmonary Artery Branch From the Aorta: Role of MDCT Angiography OBJECTIVE. The purpose of this study was to evaluate the prevalence, MDCT angiography (MDCTA) appearance, associated congenital cardiovascular abnormalities, and prognosis of anomalous origin of one pulmonary artery from the aorta (AOPA) on the basis of MDCTA. MATERIALS AND METHODS. We conducted a retrospective search of patients with AOPA from our database in a single center, consisting of 5729 patients referred for MDC- TA with known or suspected congenital heart diseases from transthoracic echocardiography. The clinical information, subtypes of AOPA, associated cardiovascular anomalies, and surgical and clinical outcomes were retrospectively collected and analyzed. The MDCTA images were retrospectively processed for analysis, and the MDCTA and echocardiography images were interpreted by radiologist and cardiologist without knowledge of the actual diagnosis or surgical outcome. RESULTS. AOPA was seen in 19 patients (14 males and five females; median age, 3 months; range, 4 days 21 years) showing a prevalence of 0.33%. Anomalous origin of the right pulmonary artery (AORPA, 89%), proximal origin subtype of the AOPA (89%), and ipsilateral aortic wall origin of AOPA (58%) were more commonly seen. In addition to the benefit of preoperative planning, MDCTA also supplemented echocardiography by providing accurate diagnosis of AOPA and other associated cardiovascular anomalies compared with transthoracic echocardiography (TTE). We found a total of four patients (21%) with misdiagnosis by TTE, including three patients with underdiagnosis of AOPA and one patient with misdiagnosis as transposition of the great arteries. In addition, two other patients had AOPA diagnosed, but the associated patent ductus arteriosus (PDA) was not detected. MDCTA revealed 95% association with other congenital cardiovascular anomalies, including PDA (71% of AORPA), and aortic arch anomalies (100% of anomalous origin of the left pulmonary artery, AOLPA). The types of surgery depended on the MDCTA findings, including the subtype, origin sites of AOPA, and associated cardiovascular anomalies. Analysis of the pulmonary arterial sizes showed the McGoon ratios in these patients with a median value of 2.4 (range, ). Surgical treatment performed before the age of 1 year enabled normalization of pulmonary artery pressure in 92% of patients. CONCLUSION. AOPA had a prevalence of 0.33% among patients with congenital heart disease in our series. MDCTA was an important supplement for the diagnosis, delineating the different subtypes and origin sites of AOPA and permitting preoperative planning of AOPA in patients suspected on the basis of echocardiography of having AOPA because accurate diagnosis and early surgical treatment remain the mainstays in improving patient outcome. A nomalous origin of one pulmonary artery branch from the aorta (AOPA) is a rare congenital vascular anomaly characterized by the anomalous origin of one of the pulmonary arteries from the ascending aorta [1]. The estimated incidence is about 0.1% among all congenital heart diseases [2, 3]. The clinical manifestations of AOPA are nonspecific and can mimic other congenital cardiovascular anomalies with anomalous blood supply to the lungs, including patent ductus arteriosus (PDA), major collaterals between the systemic and pulmonary circulation, and truncus arteriosus [1]. Noninvasive imaging plays an essential role in the ac- AJR:204, May

2 Liu et al. curate diagnosis and early treatment of AOPA [1]. Noninvasive imaging techniques, such as MDCT angiography (MDCTA), can provide early diagnosis of AOPA, and MDC- TA can complement transthoracic echocardiography (TTE) by providing clear visualization of the associated anatomy. The timely diagnosis and clear imaging enable surgical intervention to be performed as soon as possible, which can potentially reverse the complications of AOPA, such as pulmonary hypertension. There is limited literature focusing on AOPA. Except for the previous largest series by Garg et al. [2], the previous literatures consist mostly of case reports or small case series, which are limited in the ability to show the prevalence, imaging characteristics, associated cardiovascular anomalies, and surgical results. In addition, the prior studies used different imaging modalities for diagnosis and treatment of AOPA, most commonly echocardiography and angiography, which are either invasive or limited in their ability for complete evaluation of the cardiopulmonary vascular system. Cardiovascular MR angiography (MRA) does not require the risk of radiation exposure, but it is more expensive and technically demanding. As shown by the largest series by Garg et al. [2], the follow-up MDC- TA or catheter angiography together provided additional diagnosis of AOPA in six of 17 patients as opposed to echocardiography alone. MDCTA can be beneficial in complementing the diagnosis of echocardiography; however, prior articles discussing the clinical use of MDCTA are inadequate [2, 4]. Hence, the purpose of our study was to evaluate the prevalence, MDCTA appearance, associated congenital cardiovascular abnormalities, and prognosis of AOPA on MDCTA. Materials and Methods Patient Selection and Data Collection From August 2007 to May 2013, we conducted a retrospective search of all patients with AOPA from our departmental database in a single center. The search consisted of all patients with known or suspected congenital cardiovascular diseases. All of these patients were referred for MDCTA before intervention for further evaluation of the cardiovascular anatomy and diagnostic confirmation of cardiovascular anomaly after TTE evaluation. Our institutional ethics committee approved this study and waived the need for informed consent. The clinical history, demographic information, different subtypes of AOPA, surgical technique, and outcome of these 19 patients were retrospectively reviewed and recorded. The results are expressed as number of patients and percentages. Transthoracic Echocardiography and MDCT Angiography Two-dimensional TTE (ie 33 Imaging System, Philips Healthcare) was performed in all 19 patients. All MDCTA examinations were performed either with a 64-MDCT scanner (Light-Speed VCT, GE Healthcare) or a 128-MDCT scanner (Brilliance ict, Philips Healthcare). Among the 19 patients, six examinations were performed with a 64-MDCT scanner, and 13 were performed with a 128-MDCT scanner. For patients under 5 years old or with inadequate cooperation, short-term sedation was achieved with oral administration of chloral hydrate solution with a dosage of 0.1 mg/ kg of body weight. However, for patients over 5 years old, sedation was avoided if the child could cooperate after appropriate training. The longitudinal coverage of scanning extended from the thoracic inlet to cover the entire heart. The 64-MDCTA examination was performed by using a non-ecg gated standard protocol with tube voltage of kvp, tube current of mas (varied during acquisition and according to the weight of the child), mm collimation, 350 ms gantry rotation time, and pitch of 0.676:1. A contrast medium dosage of 2.0 ml/kg (iopromide, Ultravist 300, Bayer Schering Pharma) followed by a 5-mL saline flush was injected IV with an injection rate of ml/s for neonates and 1 2 ml/s for older children. Bolus tracking was used to determine acquisition delay, and an ROI was placed in the aortic root with an automatic triggering threshold of 100 HU. The prospectively gated 128-MDCTA protocol used a step-and-shoot technique with a weightbased low-dose protocol as previously published [5]. Data were obtained at 40 50% of the RR interval, and three datasets at 40%, 45%, and 50% of the cardiac cycle were reconstructed for review. Effective dose in millisieverts (msv) was estimated from the dose-length product on the basis of the corresponding patient age groups [6]. Image Postprocessing and Analysis The MDCTA data were subsequently transferred to external workstations (Cardiac Viewer, Extended Brilliance Workspace, Philips Healthcare or Advantage Workstation 4.3, GE Healthcare) for postprocessing, and standard postprocessing reconstruction techniques, such as multiplanar reformation (MPR), maximum intensity projection (MIP), and volume rendering, were used to generate images that were retrospectively processed for analysis. The MDCTA and echocardiography images were interpreted by a radiologist and a cardiologist without knowledge of the actual diagnosis or surgical outcome. We calculated the prevalence of AOPA on MDCTA. Two main types of AOPA were classified depending on the side of the anomalous pulmonary artery. Type I revealed an anomalous origin of the right pulmonary artery (AORPA), whereas type II showed an anomalous origin of the left pulmonary artery (AOLPA) [7]. The anomalous pulmonary artery was then subdivided into the proximal or distal subtype, depending on the proximal or distal origin of the anomalous pulmonary artery from the ascending aorta [7, 8]. In the proximal subtype, the aberrant pulmonary artery originated from the proximal ascending aorta and near the aortic valve, and in the distal subtype, the aberrant pulmonary artery originated from the ascending aorta near the innominate artery orifice [7, 8]. The presence of associated congenital cardiovascular anomalies, radiation exposure from MDCTA, surgical procedures, clinical outcomes, and follow-up were also assessed. The results are expressed as numbers and percentages of patients as necessary. Results Demographic Data In this series of 5729 patients, AOPA was seen in a total of 19 patients, thus revealing a prevalence of 0.33% among patients with known or suspected congenital cardiovascular anomalies. There were more males (74%, 14 patients) than females (26%, five patients). The median age of diagnosis was 3 months (range, 4 days 21 years). We found a total of four patients (21%) with misdiagnosis by TTE, including three patients with underdiagnosis of AOPA and one patient with misdiagnosis as transposition of great arteries (TGA). In addition, two other patients had AOPA diagnosed, but associated PDA was not detected. On the basis of the TTE information only, two of these three patients underwent PDA closure after echocardiography. After the PDA closure, postoperative pulmonary artery hypertension (PAH) developed in both of these patients, which lead to the accurate diagnosis of AOPA after MDCTA. The demographic results are summarized in Table 1. Types of AOPA AORPA (Fig. 1) was the more common type (89%, 17/19), whereas AOLPA (Fig. 2) was seen in only 11% of the patients (2/19). The proximal subtype (Fig. 1) was more commonly seen (89%, 17/19) compared with the distal subtype (Fig. 3, 11%, 2/19); 88% (15/17) of AORPA and 100% of AOLPA (2/2) were of proximal origin. The details of the different types of AOPA are summarized in Table AJR:204, May 2015

3 CTA Evaluation of AOPA TABLE 1: Summary of Demographic Data of 19 Patients With Anomalous Origin of One Pulmonary Artery Patient Characteristics Values Age Median (range) 3 mo (4 d 21 y) Sex Male 14 (74) Female 5 (26) Patient age and surgery Yes 14 (74) < 1 y 12 (63) > 2 y 2 (11) No 5 (26) < 1 y 2 (11) > 2 y 3 (16) Postoperative follow-up Median (range) 12 mo (1 84 mo) Note Except where indicated otherwise, data are number with percentage in parentheses. Data may not total 100% because of rounding. Origin Sites of AORPA and AOLPA Ipsilateral AOPA origin was the more common form (11/19, 58%), followed by posterior origin (5/19, 26%). Contralateral AOPA origin was seen only in the proximal subtype of AORPA (3/19, 16%). AORPA originated most commonly from the right posterolateral aortic wall (9/19, 47%) and less commonly from the posterior and left posterolateral ascending aortic walls. In contrast to the proximal subtype, both patients with the distal subtype revealed origin only from the right posterolateral wall. Of the two patients with AOLPA, one had proximal origin from the left posterolateral wall of the ascending aorta (1/19, 5%), and the other had distal origin from the left lateral wall of the ascending aorta (1/19, 5%). The origins of AOPA from the wall of the ascending aorta are summarized in Table 2, and the different origin sites of the AOPA are illustrated in Figure 4. Radiation Exposure From MDCT Angiography The median value and range of the estimated effective dose calculated on the basis of age group on 64- and 128-MDCT scanners were 2.4 msv ( msv) and 1.46 msv ( msv), respectively. Associated Congenital Cardiovascular Anomalies AOPA occurred almost exclusively in association with other congenital anomalies. Of the 19 patients, 95% (18/19) of AOPA was associated with other congenital cardiovascular anomalies, whereas in only 5% (1/19) of patients, MDCTA did not reveal other cardiovascular anomalies. Among all patients with AOPA, PDA (Fig. 1) and atrial septal defect were the most commonly identified associated congenital anomalies, and both of these were seen in 63% (12/19) of the patients with AOPA, followed by aortic arch anomalies in 26% (5/19). Atrial septal defect was present in 65% (11/17) of patients with AORPA and 50% (1/2) of patients with AOLPA. Other less-common associated cardiovascular anomalies included ventricular septal defect, aortopulmonary septal defect (APSD) (Fig. 5), and tetralogy of Fallot. No airway obstruction secondary to compression by anomalous cardiovascular vessels was found in our series. Evaluation of the pulmonary arterial sizes showed the median value of McGoon ratios in these patients to be 2.4 (range, ). Further analysis showed one patient with tetralogy of Fallot had peripheral pulmonary arterial stenosis and fine aortopulmonary collateral arterial supplies from the descending aorta. AORPA was most commonly associated with patients with PDA (71%, 12/17), whereas AOLPA was most commonly associated with patients with aortic arch anomalies (100%, 2/2) and ventricular septal defect (100%, 2/2). Aortic arch anomalies were present in 18% (3/17) of patients with AOR- PA, including aberrant right subclavian artery, left aortic arch and right descending aorta with aberrant right subclavian artery, and coarctation of aorta. Patients with AOL- PA showed different forms of aortic arch anomalies, including right-side aortic arch with mirror branch of aortic arch and rightside aortic arch with aberrant left subclavian artery. The associated congenital cardiovascular anomalies are summarized in Table 3. Surgical Treatment, Clinical Outcomes, and Follow-Up Among the 19 patients with AOPA, 74% (14/19) underwent surgical treatment (Table 1), which included 13 patients with AORPA and one with AOLPA. Preoperative evaluation of the pulmonary artery pressure with echocardiography showed pulmonary hypertension in all of the 19 patients. Among the 14 patients who required surgical intervention, 13 had severe PAH (range, mm Hg) and one had moderate PAH (67 mm Hg) on echocardiography. The pulmonary arterial pressures improved substantially after the operations. Postoperative follow-up of pulmonary artery pressure revealed only two patients who had residual PAH, one with mild and one with moderate PAH, whereas normal pulmonary artery pressure was achieved in the remaining 12 patients. Among patients who underwent surgical correction, 12 of 14 were younger than 1 year old, and 92% of all patients (11/12) had good follow-up results with normalization of pulmonary artery pressure. Three of five patients older than 2 years did not undergo surgery because of high operative risk, whereas one of the two patients who underwent surgery still had moderate PAH on postoperative follow-up. The median postoperative follow-up time was 12 months (1 84 months) (Table 1). No anastomotic stenosis was suspected on postoperative follow-up TTE. The choice of surgery was made on the basis of the side of the anomalous pulmonary TABLE 2: Summary of Types of Anomalous Origin of One Pulmonary Artery (AOPA) and Original Sites of AOPA From Wall of Ascending Aorta Type of AOPA Values Type I: AORPA 17 (89) Proximal 15 (79) Right (ipsilateral) 7 (37) posterolateral wall Posterior wall 5 (26) Left (contralateral) 3 (16) posterolateral wall Distal 2 (11) Right (ipsilateral) 2 (11) posterolateral wall Type II: AOLPA 2 (11) Proximal 2 (11) Left (ipsilateral) 1 (5) lateral wall Left (ipsilateral) 1 (5) posterolateral wall Distal 0 (0) Note Data are number with percentage in parentheses. Data according to the total 19 patients with AOPA may not total 100% because of rounding. AORPA = anomalous origin of the right pulmonary artery, AOLPA = anomalous origin of the left pulmonary artery. AJR:204, May

4 Liu et al. TABLE 3: Summary of Associated Anomalies of 19 Patients With Anomalous Origin of One Pulmonary Artery Associated Cardiovascular Anomalies Values Presence of other cardiovascular anomaly None or solitary 1 (5) Other associated anomalies 18 (95) All AORPA patients and associated cardiovascular anomalies a 17 (100) Patent ductus arteriosus 12 (71) Atrial septal defect 11 (65) Aortic arch anomalies 3 (18) Aberrant right subclavian artery 1 (6) Left aortic arch and right descending aorta plus aberrant right 1 (6) subclavian artery Coarctation of aorta 1 (6) Ventricular septal defect 2 (12) APSD 2 (12) All AOLPA patients and associated cardiovascular anomalies a 2 (100) Aortic arch anomalies 2 (100) Right-side aortic arch with mirror branching of aortic arch 1 (50) Right-side aortic arch with aberrant left subclavian artery 1 (50) Ventricular septal defect 2 (100) Atrial septal defect 1 (50) Tetralogy of Fallot 1 (50) Note Data are number with percentage in parentheses. Data according to the total 19 patients with anomalous origin of one pulmonary artery from the aorta may not total 100% because of rounding. AORPA = anomalous origin of the right pulmonary artery, AOLPA = anomalous origin of the left pulmonary artery, APSD = aortopulmonary septal defect. a Denotes percentages of patients within AORPA or AOLPA. The total may be more than 100% because more than one associated anomaly can be present in a patient. artery and the site of origin from aorta. All 14 patients with AOPA underwent direct implantation of the AOPA to the main pulmonary artery trunk. For all patients with AORPA and an origin site from the right posterolateral or posterior wall of the ascending aorta (11/14), the pulmonary artery was carefully separated from the aorta with or without inclusion of the part of aortic wall depending on the length of the pulmonary artery needed to maintain adequate length. This was done to reduce the chance of an anastomotic stenosis. The excised pulmonary artery and aortic wall subsequently underwent direct end-to-side anastomosis to the main pulmonary artery. The aortotomy site was sutured primarily or with an autologous pericardial patch. In the two patients with AORPA with posterior or left posterolateral origin, the aorta was incised transversely at the level of the anomalous origin of pulmonary artery to create an aortic flap, and the right lateral wall of the pulmonary trunk was incised in the longitudinal direction to create another flap. An anastomosis of the anomalous origin of the pulmonary artery to the pulmonary trunk was created with the two flaps forming the proximal segment of the pulmonary artery. Because the right pulmonary artery was partially connected with the pulmonary trunk in one patient with AORPA associated with APSD (Fig. 5), the connection was preserved and the APSD was incised along the longitudinal direction of the right pulmonary artery after transverse incision of the ascending aorta, and the proximal segment of right pulmonary artery was sutured with an autologous pericardial patch. The ascending aorta was reconstructed by direct end-toend anastomosis. Other associated procedures were also performed for these patients to correct the A B C Fig day-old boy with type I (anomalous origin of right pulmonary artery from aorta, AORPA) anomalous origin of pulmonary artery from aorta with patent ductus arteriosus (PDA). A C, Axial maximum-intensity-projection (MIP) (A), oblique coronal MIP (B), and oblique sagittal MIP (C) MDCT angiography images show anomalous right pulmonary artery (RPA) origin from proximal ascending aorta (AAO) with normal origin of left pulmonary artery (LPA) from main pulmonary artery (MPA). Note step-off artifact due to patient movement and ectasia of pulmonary arteries and presence of PDA (arrow, C). RVOT = right ventricular outflow tract, DAo = descending aorta, LV = left ventricle, RV = right ventricle. (Fig. 1 continues on next page) 982 AJR:204, May 2015

5 CTA Evaluation of AOPA other associated congenital cardiovascular anomalies, including PDA ligation, atrial septal defect closure, tricuspid valvuloplasty, and ventricular septal defect repair. D Fig. 1 (continued) 19- day-old boy with type I (anomalous origin of right pulmonary artery from aorta, AORPA) anomalous origin of pulmonary artery from aorta with patent ductus arteriosus (PDA). D, Transthoracic echocardiography image in parasternal short-axis view shows corresponding findings compared with A. Discussion Since its first description by Fraentzel in 1868, AOPA remains a rare congenital cardiovascular anomaly [9]. Our study showed a prevalence of 0.33% in AOPA. The cause of AOPA is uncertain, and different theories exist regarding the embryology of the different types of AOPA [7, 9]. In the proximal subtype of AORPA, the origin of the right pulmonary artery from the posterior aspect of the ascending aorta shows that the anomaly is likely secondary to incomplete leftward migration of the right pulmonary artery [7]. On the other hand, the distal subtype of AORPA would most likely be caused by the development of a fifth aortic arch, whereas the proximal pulmonary artery as well as the distal part of the sixth arch disappear, which could explain the right pulmonary artery originating from the ascending aorta near the base of the innominate artery [7]. As for AOLPA, the proximal subtype has been reported to be secondary to the disappearance of the fifth and sixth arches on the left, whereas the distal subtype occurs with a persistent fifth and absent sixth aortic arch [9]. We found that AORPA was eight times (17/19, 89%) more common than AOLPA (2/19, 11%), which was slightly higher than the surgery-based study by Kutsche and Van Mierop [7], which found AORPA to be about 4 5 times more common than AOLPA. The proximal subtype was also found to be about 4 5 times more common than the distal subtype in AOPA patients [7, 8, 10], whereas we found proximal subtype to be eight times more common than the distal subtype (89% versus 11%), which was higher than other reported results. In our series, ipsilateral AOPA origin was the most common form (58%), whereas contralateral AOPA origin was only seen in the proximal subtype of AORPA (16%). This contralateral origin was not seen in any patients with distal AORPA, distal AOLPA, or proximal AOLPA origin. The explanation is that the site of origin of the AOPA is usually from the ipsilateral wall of the ascending aorta [7, 11]; however, few cases can originate from the contralateral wall of the ascending aorta, as in our study. Although AOPA may be isolated or associated with other congenital cardiovascular anomalies, about 80% of the cases reported in the literature were associated with other congenital cardiovascular anomalies [10]. Our study revealed higher association (95% of the patients) with other congenital cardiovascular anomalies, and only one patient had no other identifiable associated cardiovascular anomalies. Overall, we found PDA and atrial septal defect to be the most commonly associated congenital anomalies in the patients with AOPA. Among the subtypes, previous studies reported that more than two thirds of AORPA was associated with PDA, whereas 15% of the proximal subtype of AORPA was associated with APSD [7]. A B C Fig. 2 9-month-old boy with type II (anomalous origin of left pulmonary artery from aorta, AOLPA) with right-sided aortic arch. A, Oblique coronal volume rendering MDCT angiography image shows anomalous origin of ectatic left pulmonary artery (LPA) from proximal ascending aorta (AAO), diagnostic of AOLPA. Note normal origin of ectatic right pulmonary artery (RPA) (arrow) from dilated main pulmonary artery (MPA) and presence of right-sided aortic arch. B, Oblique coronal thin maximum-intensity-projection image shows AOLPA and perimembranous type of ventricular septal defect (VSD) (arrow). RV = right ventricle, LV = left ventricle. C, Transthoracic echocardiography image in subcostal long-axis view of left ventricular outflow tract shows corresponding findings as MDCTA with AOLPA from AAO. Note the green cross marker for length measurement. AJR:204, May

6 Liu et al. A B C Fig month-old boy with distal subtype of anomalous origin of the right pulmonary artery (AORPA). A, Axial maximum-intensity-projection MDCT angiography image reveals ectatic right pulmonary artery (RPA) arising from distal part of ascending aorta close to aortic arch (ARC) with left pulmonary artery (LPA) arising normally from ectatic main pulmonary artery (MPA). B, Three-dimensional volume rendering image shows AORPA with RPA originating close to origin of innominate artery (INOA) (arrow), representing distal subtype. Note ectatic MPA. AAO = ascending aorta. C, Transthoracic echocardiography image in parasternal long-axis view of left ventricle shows RPA (arrow) origin from AAO. LV = left ventricle, RV = right ventricle, LA = left atrium. A B C D E Fig. 4 Axial maximum-intensity-projection MDCT angiography images show different anomalous origin of one pulmonary artery (AOPA) sites in five patients. A C, Proximal subtypes of anomalous origin of the right pulmonary artery (AORPA) with origin from ipsilateral right posterolateral (A), in 7-year-old boy, posterior (B), in 3-month-old boy, and contralateralposterolateral (C) walls of proximal ascending aorta (AAO) in 1-month-old girl. MPA = main pulmonary artery, RPA = right pulmonary artery, DAo = descending aorta. LPA = left pulmonary artery. D, Distal subtype of AOPA with RPA arising from right posterolateral wall of distal AAO in 1.5-month-old boy. ARC = aortic arch. E, Proximal subtype of AOLPA with LPA arising from left posterolateral wall of proximal AAO in 14-yearold girl. Our study revealed similar higher associated PDA rates of 71% in patients with AORPA. AOLPA has a known, strong association with tetralogy of Fallot (74%) and aortic arch anomalies (63%) [7]. Our study revealed that 100% of AOLPA patients had aortic arch anomalies, whereas tetralogy of Fallot was present in 50%. Right-sided aortic arch has been reported in 50 75% of patients with AOLPA [11]. Our study showed that 100% of such patients had a right-sided aortic arch, which is also higher than the reported cases in the literature. 984 AJR:204, May 2015

7 CTA Evaluation of AOPA AOPA has a reported mortality rate as high as 70% among those patients who did not undergo surgical repair within 1 year of life; the main cause of the high mortality rate was PAH and irreversible pulmonary vascular disease [12]. This can be explained by the AOPA, which receives high pressure from the systemic circulation and, as the pulmonary resistance decreases after birth, the flow through the anomalous pulmonary artery increases, leading to PAH and congestive heart failure and subsequently irreversible pulmonary vascular disease [13]. This sequence can occur as early as the third month of life in AOPA [14]; hence, surgery should be considered as early as possible, which can lead to good short- and long-term outcomes [8, 15, 16]. Our study showed the importance of early surgical treatment; 12 of 14 patients (63%) who underwent surgical correction were younger than 1 year old. Among these 12 patients, 92% had good follow-up results after surgery, with subsequent normalization of central pulmonary artery pressure. On the other hand, one of the two patients who underwent surgery after the age of 2 years developed moderate PAH on postoperative follow-up. In addition, three of five patients were older than 2 years and could not undergo correction of the anomaly because of high operative risk and were lost to follow-up. To decrease the occurrence of stenosis at the anastomotic site, different surgical techniques to implant the AOPA to the main pulmonary artery can be used on the basis of the A Fig. 5 1-month-old girl with anomalous origin of the right pulmonary artery (AORPA) and aortopulmonary septal defect (APSD). A, Axial maximum-intensity-projection MDCT angiography image shows anomalous origin of right pulmonary artery (RPA) from proximal ascending aorta (AAO) with small visible defect in AAO main pulmonary artery (MPA) septum (arrow), diagnostic of proximal subtype of AORPA with associated APSD. Note ectatic RPA arising from contralateral-posterolateral wall of proximal AAO, whereas left pulmonary artery (LPA) arises normally from MPA. DAo = descending aorta. B, Transthoracic echocardiography image in parasternal short-axis view at level of pulmonary artery reveals AORPA and APSD with small APSD (arrow). anatomy and origin site of the AOPA [10, 13, 17, 18]. The surgical methods for AORPA include the use of an autologous pericardial patch and aortic flap and simultaneous aortic and pulmonary flaps, depending on the length of the pulmonary artery required. This corresponds to the partial aortic wall excision or transverse aortic excision in our patients. Because the anomalous pulmonary artery is close to the main pulmonary artery, patients with AOLPA can be surgically treated with direct anastomosis [10, 13, 17, 18], but part of the aortic wall can also be excised along with the pulmonary artery if the elongation of the pulmonary artery is considered necessary by the surgeon. As for our series, we saw remarkable improvement in the postoperative pulmonary arterial gradient, which corresponded to the absence of stenosis in the anastomotic sites during follow-up. The risk of postoperative complications and the outcome also can be affected by the presence of the associated cardiovascular anomalies [19]. Although previous studies focusing on the clinical use of MDCTA on AOPA are lacking, studies regarding the clinical performance of MDCTA from other congenital cardiovascular examinations exist, such as the evaluation of congenital coronary anomalies [20 22]. MDCTA is beneficial in the preoperative evaluation of congenital heart disease and potentially in the evaluation of both intracardiac and extracardiac anatomy, especially the pulmonary arteries because of its high inherent spatial resolution, short scanning time, wide clinical availability, and lack of operator dependency [23]. Multiplanar and 3D reconstructions can directly display the spatial relationship of the AOPA, ascending aorta, and main pulmonary artery from any angle, as we have shown (Figs. 1 5) [21, 23 25]. Prior studies focusing on infants have shown that MDCTA can even replace coronary angiography in the initial evaluation of complex congenital heart diseases [23, 24]. In our series, we found a total of four patients (21%) with misdiagnosis by TTE, including three patients with underdiagnosis of AOPA and one patient with misdiagnosis as TGA. In addition, two other patients had AOPA diagnosed, but the associated PDA was not detected. We also found that patients with AOPA had a high prevalence of PDA and aortic arch anomalies, and MDCTA is more suitable for the delineation of cardiovascular anomalies compared with TTE. Furthermore, MDCTA can display the spatial relationship of the great arteries of extracardiac structure more clearly. The ionizing radiation and administration of iodinated contrast agents are disadvantages of MDCTA; however, we used a weight-based low-dose MDCTA protocol to reduce the overall radiation exposure to 2.4 and 1.46 msv with 64- and 128-MDCT scanners, respectively. In addition to MDCTA, several other diagnostic tools have been used to evaluate AOPA, including echocardiography, MRA, and catheter angiography [2, 4, 26, 27]. Echocardiography is a safe noninvasive tool B AJR:204, May

8 Liu et al. and very effective as a first-line diagnostic method for AOPA. Other than showing structural abnormalities, echocardiography can also be used to estimate and monitor the change in pressure gradient of the pulmonary artery before and after surgery. However, echocardiography can be limited by several factors, including operator dependence and limited acoustic window, and thus provide a false-negative diagnosis of AOPA [10, 15]. In our series, three patients (16%) were missed by echocardiography alone, and one patient (5%) was misdiagnosed with TGA. Cardiac MRI and MRA are more expensive and more technically demanding. Catheter angiography provides valuable information regarding hemodynamic change and pulmonary vascular resistance, but angiography requires ionizing radiation and administration of contrast agents in addition to being invasive and potentially causing complications, especially in patients with severe PAH. AOPA should be differentiated from other congenital cardiovascular anomalies associated with an anomalous blood supply to the lungs, including persistent truncus arteriosus and TGA. In patients with persistent truncus arteriosus, both pulmonary arteries originate from the aorta and have a common semilunar valve as opposed to separate semilunar valves in AOPA. AOPA can also be misdiagnosed as TGA on echocardiography [17], such as seen in our study, but MDCTA and catheter angiography can complement each other by showing the aorta separate from the pulmonary artery. We believe that MDCTA can complement echocardiography as a routine clinical tool in the diagnosis of AOPA and preoperative planning. Our study has some limitations. This was a retrospective study with a small number of patients. We found that the composition of the different types of AOPA is generally similar in trend in the literature, but some of the subtypes were more commonly seen in our series. This can be due to the difference in patient population. As previously mentioned, AOPA is a rare congenital cardiovascular anomaly with only limited literature; hence, further studies may be necessary for further description of the MDCTA findings of this entity. ease. AORPA was eight times more common than AOLPA, and among the subtypes, the proximal subtype was also eight times more common than distal. Ipsilateral origin of AOPA from the ascending aorta was also more commonly seen than contralateral origin. MDCTA revealed a 95% association with other congenital cardiovascular anomalies, such as PDA and aortic arch anomalies. MDCTA was, in our experience, an important supplement to echocardiography in confirming diagnosis, delineating the different subtypes, determining origin sites, and preoperative planning because accurate diagnosis and early surgical treatment remain the mainstays in improving patient outcome. References 1. Penkoske PA, Castaneda AR, Fyler DC, Van Praagh R. 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Pediatr Neonatol Conclusion AOPA showed a prevalence of 0.33% among patients with congenital heart dis- 986 AJR:204, May 2015

9 CTA Evaluation of AOPA 2010; 51: Tomasian A, Lell M, Currier J, Rahman J, Krishnam MS. Coronary artery to pulmonary artery fistulae with multiple aneurysms: radiological features on dual-source 64-slice CT angiography. Br J Radiol 2008; 81:e218 e Pepeta L, Takawira FF, Cilliers AM, Adams PE, Ntsinjana NH, Mitchell BJ. Anomalous origin of the left pulmonary artery from the ascending aorta in two children with pulmonary atresia, subaortic ventricular septal defect and right-sided major aorto-pulmonary collateral arteries. Cardiovasc J Afr 2011; 22: Fujiwara K, Takeuchi T, Suzuki H, Uemura S. Tetralogy of Fallot with anomalous origin of the right pulmonary artery from the ascending aorta and hypoplastic left pulmonary artery. Pediatr Cardiol 2005; 26: FOR YOUR INFORMATION The comprehensive book based on the ARRS 2014 annual meeting categorical course on The Radiology M and M Meeting: Misinterpretations, Misses, and Mimics is now available! For more information or to purchase a copy, see AJR:204, May