17 18 19 20 2010 2010 2012 2012 Subramanyan Holmes Fatih Jowett 1 1 21 2012 Jowett 22 23 2013 Murugan 2015 Gupta 24 2015 Gupta 25 26 27 2015 Bhatla 2016 Gupta 2015 Nicholsona 1 (Fig 48.8A) 2 (Fig 48.9B) 1 Aorta (lateral aspect) to pulmonary artery confluence Aorta to distal main pulmonary artery Aorta to pulmonary artery confluence, very long course Aorta to pulmonary artery confluence mimicking distal AP window Aorta to pulmonary artery confluence mimicking distal AP window Aorta to left pulmonary artery Aorta to pulmonary artery confluence 64 65 66 67 Ascending aorta to left pulmonary artery 68 67 50 68 Aorta to pulmonary artery confluence 69 Aorta to pulmonary artery confluence 70 Double-barreled aorta (left) and left pulmonary artery from 55 aorta aThis shows cases that we interpret as requiring dual or bilateral fifth arch arteries to explain the anatomy AP, Aortopulmonary Fifth Arch Artery Versus Distal Aortopulmonary Window In one of our patients with ventricular septal defect and pulmonary atresia in the setting of discordant ventriculoarterial connections, we encountered a channel arising from the lateral aspect of ascending aorta (Fig 48.8, left) This channel, along with others described in the literature,23,56,58–62,64–70 could well be an artery of the fifth arch, as could the vessel found in the setting of tetralogy of Fallot with pulmonary atresia shown in the right-hand panel of Fig 48.8 This type of connection has been interpreted by other investigators as representing a distal aortopulmonary window.23,38,59–61,67 Aortopulmonary windows, however, are intrapericardial, as opposed to either a collateral channel, or an artery of the fifth arch, both of which would occupy extrapericardial space (see Fig 48.8) Therefore the location of the lesions means that they cannot be aortopulmonary windows Localization of the channel within or outside the pericardium, nonetheless, although readily recognized during surgery, can be extremely difficult on preoperative imaging.68,70 FIG 48.8 Left, Image from a patient with discordant ventriculoarterial connections, ventricular septal defect, and pulmonary atresia The channel arises from the ascending aorta proximal to the origin of the brachiocephalic artery and terminates at the confluence of the pulmonary arteries through the arterial duct This strongly favors its origin as a fifth arch artery Right, Image from a patient with tetralogy of Fallot and pulmonary atresia The channel feeding the pulmonary arteries arises from the ascending aorta proximal to the origin of the brachiocephalic artery When traced distally, it feeds the confluence of the pulmonary arteries in retrograde manner—in other words, through the termination of the left sixth arch artery This again favors its origin as a fifth arch artery Channels From the Ascending Aorta to the Left or Right Pulmonary Artery Irrespective of prior considerations, it is not uncommon to find a channel arising from the ascending aorta that, after taking a tortuous course, terminates in one or other of the pulmonary arteries In one such case held to represent a fifth arch artery, the candidate channel is shown as arising from the ascending aorta It terminates directly in the right pulmonary artery (Fig 48.9A).23 A similar case was reported by us, and again interpreted initially as an artery of the fifth arch The channel arises from the ascending aorta proximal to the brachiocephalic artery and terminates in the discontinuous left pulmonary artery, having taking a serpentine course (see Fig 48.9B).68 Further interrogation of the computed tomographic dataset from the patient (Fig 48.10) shows well the interrelationships of the origins of the brachiocephalic artery and the serpentine channel In the setting of discontinuous pulmonary arteries, the location of the origin of a serpentine channel could just as well be interpreted to represent extensive remodeling of the arterial duct as it is to represent the fifth arch artery And since the sixth arch is universally present, probabilities favor its origin from the sixth rather than the fifth arch FIG 48.9 (A) Suggested origin of a vessel feeding the right pulmonary artery in the setting of pulmonary atresia as an artery of the fifth pharyngeal arch It is just as likely to be an aberrant arterial duct derived exclusively from the sixth aortic arch, since it terminates directly in the right pulmonary artery (B) Vascular channel arising from the ascending aorta that, after following a tortuous course, terminates in the discontinuous left pulmonary artery The precise relationships of the origins of the channel and the brachiocephalic artery are shown in Fig 48.10 The right pulmonary artery is supplied by systemic-to-pulmonary collateral arteries As was the case with the channel described by Gerlis and colleagues,23 we initially interpreted the channel as seen in (B) as an artery of the fifth arch On reflection, it could just as well be the remodeled arterial duct, with probabilities favoring the latter interpretation