Clinical Features AOPA occurs most commonly as an isolated cardiac anomaly, with the right PA arising from the ascending aorta (and the left PA arising normally from the main PA) being eight times more common than the left PA arising from the aorta.38 However, associated heart defects can exist and may include simple defects such as patent arterial duct and atrial or VSD, or more complex ones, including variants of tetralogy of Fallot.39,40 There is a 2 : 1 preponderance of males to females with AOPA.38 The physiology of this condition, in the absence of other defects, involves the entirety of the systemic venous return flowing to the normally connected PA via the right ventricle and main PA, representing the effective pulmonary blood flow The affected (i.e., typically right) PA receives blood via the ascending aorta without any proximal stenosis and is hence at systemic pressure Flow to the affected PA represents a left-to-right shunt and leads to excess pulmonary venous return to the left atrium and left ventricle, leading to the expected left heart dilation Indeed, congestive heart failure is the presenting symptom in 95% of cases and is usually present in the first year of life.38 Management Interestingly, the PA that is normally connected to the main PA (i.e., typically the left PA) is frequently found to have elevated (near-systemic) pressures, a puzzling and poorly understood phenomenon, albeit well described.37,41 Mortality among unoperated patients is very high, estimated at 30% in the first month of life and 70% at 1 year.38 Medical management of AOPA, such as use of diuretics, serves only to temporize until definitive surgical repair can be accomplished Surgical management of AOPA consists of transection of the PA that arises from the aorta with reimplantation into the main PA Whenever possible, reimplantation should be performed directly (without a graft), a technique initially described by Kirkpatrick and colleagues.42 Avoidance of a graft (particularly synthetic grafts) is desirable because these grafts have no growth potential and need to be replaced to accompany a child's growth Large series describing the management and outcomes of patients with AOPA are lacking because of the rarity of this condition A series of 16 patients over a period of 36 years published from the Hospital for Sick Children, Toronto, revealed that 12 of 16 cases involved anomalous origin of the right PA and 4 involved the left; none of the anomalous PAs had preexisting stenosis at the site of aortic origin Their series reported a 25% mortality rate (2 of 16 were not offered surgery, whereas 3 suffered intraoperative deaths).43 Of the 11 operative survivors, 8 developed stenosis at the PA reimplantation site Another series by Peng described 9 patients over a 29-year period,40 with all cases having anomalous origin of the right PA above the aortic sinus, and all being free of preexisting stenosis at the aortic origin Two-thirds of patients had no major associated defects, and one-third had right ventricular outflow tract obstruction in the form of tetralogy of Fallot or a variant thereof Anastomosis of the right PA was performed in all, without operative mortality However, the incidence of anastomotic stenosis was not provided The largest series to date, from Children's Hospital Boston, described 29 patients, of which 27 had aortic origin of the right PA and only 2 with aortic origin of the left.44 Stenosis at the anastomotic site developed in 79% of patients, most of whom underwent successful catheter-based interventions to relieve stenosis Aortoventricular Tunnels In most instances, these lesions produce communications from the aortic sinuses to the cavity of the left ventricle (Fig 51.13) The tunnels can also extend between the aortic root and the cavity of the right ventricle (Fig 51.14).45 On rare occasions, they can open to the cavity of the right atrium However, the morphology of the tunnels terminating in the right atrium is quite different from those extending to open to the ventricles It is arguable that the right atrial tunnels would better be described as fistulous communications With regard to the tunnels producing anomalous connections with the ventricles, the majority of those reported thus far have produced connections with the left ventricle, with only approximately one-eighth of reported cases involving the right ventricle It is well established that the histologic appearance of the aortic end of the tunnel differs markedly from the ventricular component This is hardly surprising because the essence of the tunnels is that, when communicating with the left ventricle and taking their origin from an aortic valvar sinus, they bypass the hinge of the aortic valve (Fig 51.15) FIG 51.13 Aortoventricular tunnel terminating in the left ventricle (A) Enlarged wall of the right coronary sinus as seen from the front (B) Probe passed through the tunnel, which bypasses the hinge of the right coronary aortic leaflet, opening into the right ventricle through the unguarded interleaflet triangle between the two coronary aortic valvar sinuses