Aorto‐left ventricular (LV) tunnel is a rare congenital communication between the ascending aorta and the left ventricle. Incidence is estimated at less than 1 in 1000 infants born with congenital heart disease [1]. Levy and colleagues first described three cases of aorto‐LV tunnel in 1963 [2]. Affected patients presented with symptoms of congestive heart failure and dilation of the ascending aorta within the first weeks to months of life. Following surgical repair, the prognosis is excellent, although long‐term progressive aortic insufficiency occurs in some patients.

Pathophysiology and Anatomy

Aorto‐LV tunnel is an abnormal, paravalvular, endothelialized communication between the ascending aorta and the left ventricle that creates a bidirectional flow of blood from the aorta to the left ventricle (Figure 33.1) [3]. The paravalvular aorto‐LV tunnel typically originates from an aortic orifice cephalad to the sinotubular junction adjacent to the right coronary cusp and follows a descending path along the aortopulmonary window, before entering the fibrous trigone of the left ventricle immediately below the left–right commissure of the aortic valve. Most cases arise from the right coronary sinus, and origin from the left coronary sinus is rare [4–6]. In a literature review of 37 patients, the aortic opening was reported to be above the right coronary artery ostium in 14 (38%) of the patients, below the right coronary artery in 9 (24%), at the level of the right coronary artery in 6 (16%), and unknown in 6 (16%) [5]. Aortic origin off the left coronary sinus [7–9] and the noncoronary sinus [10] are rare, but have also been described. Additionally, the surgeon should be aware that the coronary arteries may arise directly from the tunnel [11, 12]. There are also rare case reports of aorto‐right ventricular (RV) tunnel [3, 13].

On gross inspection, a visible bulge is usually apparent along the anterolateral aspect of the aorta, which represents the fibromuscular tunnel wall that lies in direct histologic continuity with the aorta. The posterior wall contains the true aortic wall, with the inferomedial aspect or the floor of the tunnel involving the muscle of the RV outflow tract [14]. Hovaguimian and associates have classified aorto‐LV tunnels into four types (Figure 33.2): those with a slit‐like aortic orifice with no valvular distortion (type I); those with a larger, oval‐shaped aortic orifice with an aneurysmal extracardiac component with or without valvular distortion (type II); those with an oval aortic orifice and an aneurysmal septal (intracardiac) component with or without RV outflow tract obstruction (type III); and those with a combination of type II and III (classified as type IV) [5].

Interestingly, careful analysis of several pathologic specimens by Ho and colleagues [14] suggests that despite this classification scheme, the tunnels never engage or cross the interventricular septum, but rather travel downward in the fibrofatty plane between the aortic root and the subpulmonary infundibulum to enter the LV outflow tract in the immediate subcommissural triangle below the right and left valvular cusps, just superficial to the intracardiac myocardium and immediately above the actual aorto‐ventricular junction. The anatomic relations of the tunnel have both pathophysiologic and therapeutic implications. Considerations must be given to the etiology of aortic valvular insufficiency as well as coronary flow, particularly when the right coronary artery arises within the tunnel.

Pathogenesis

Although the exact pathogenesis of aorto‐LV tunnel formation is not known, possible etiologies include in utero rupture of a sinus of Valsalva aneurysm [4, 15–17], degeneration of the true aortic wall analogous to in utero cystic medial necrosis [18], dissection of an aberrant or anomalous coronary artery [1], and malformation of the bulbus cordis [1, 4, 19]. The bulbus cordis matures into components of both the subpulmonary infundibulum and the aortic vestibule and comprises the territory through which the developing coronary arteries move to attach to the sinus segment. Aberrant maturation of the bulbus cordis may account for the association between aorto‐LV tunnel and valvular pulmonary stenosis, valvular aortic stenosis, and proximal coronary artery anomalies [19]. Aorto‐LV tunnel typically originates from an aortic orifice cephalad to the sinus segment of the aorta, and it is thus unlikely that a rupture of a sinus of Valsalva aneurysm could account for the typical appearance of this anomaly. Myers suggests instead that sinus aneurysm rupture occurs only in the rare occurrence of aortic to right ventricle fistualization [16]. Although Myers’ suggestion is an attractive hypothesis, Vargas and co‐workers [13] clearly document an aortic origin of an aortic‐RV tunnel cephalad to the left sinotubular junction, which would make antecedent sinus rupture equally unlikely.

Presentation and Diagnosis

The age at presentation and severity of symptoms depend entirely on the size of the tunnel. Neonatal and infant presentation usually reflects a large communication with severe LV volume overload. Accurate prenatal diagnosis of aorto‐LV tunnel is becoming more frequent. Cook and colleagues from London reported four fetal cases in 1995 [20]. Three fetuses died during gestation. Additional case reports have been published with 1–2 cases each [21, 22]. Prenatal echocardiography usually demonstrates preserved general cardiac architecture with valvular aortic insufficiency and/or stenosis with dysplastic valve leaflets and severe LV hypertrophy and dilatation. A distinct paravalvular tunnel with regurgitant diastolic flow can be identified in most cases. Patients with sufficient regurgitant flow to allow early prenatal diagnosis may represent the most severe end of the clinical spectrum. Reported postmortem examination of these pathologic hearts invariably demonstrated extensive myocardial fibrosis and severe aortic valve dysplasia.

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