Aorta–Right Atrial Tunnel
Is Surgical Correction Mandatory?
An asymptomatic 31-year-old man with chronic hepatitis B and a 7-year history of lamivudine use was referred to our hospital for evaluation of a heart murmur. The patient had no family history of congenital heart disease or collagen vascular disease. Cardiac auscultation revealed a grade 3/6 continuous murmur at the right parasternal border. Transthoracic echocardiography revealed a round, tunnel-like structure from the left aortic sinus to the right atrium (RA; Figure 1A and 1B, arrows, and Movie IA and IB in the online-only Data Supplement) without any evidence of RA or right ventricular enlargement. Modified parasternal short-axis view (Figure 1C and Movie II in the online-only Data Supplement) of the aortic valve level demonstrated an anastomosis site to the RA with continuous turbulent flow on color Doppler examination. Continuous-wave Doppler obtained from the shunt indicated a high flow velocity with systolic and diastolic pattern at the anastomosis site to the RA (Figure 1D). Cardiac catheterization showed a normal pulmonary artery pressure (systolic/diastolic, 24/7 mm Hg) and normal mean RA pressure (4 mm Hg), and the Qp/Qs ratio was 1.3:1. Aortography confirmed a large tunnel beginning in the left aortic sinus and ending in the RA (Figure 2, asterisk, and Movie III in the online-only Data Supplement), with normal-looking left coronary arteries arising independently from different proximal portions of the tunnel. Importantly, no coronary myocardial branches originated from the tunnel, which is the key point to discriminate from coronary-cameral fistula. For better visualization of the shunt anatomy, computed tomographic angiography was performed. Computed tomographic angiography (Figure 3) and 3-dimensional reconstructed images (Figure 4 and Movie III in the online-only Data Supplement) delineated the extracardiac structure, showing a large, tortuous, tunnel-like structure originating from the left sinus of Valsalva, running through the posterior side of the aortic root, and terminating in the RA. Interestingly, the distal portion of the tunnel showed a stenotic opening (so-called isthmus; Figure 3, dotted box) with an aneurysmal dilation before terminating in the RA. We think that this finding was a possible reason for the low Qp/Qs ratio in cardiac catheterization despite the large size of the tunnel.
From multiple imaging studies, we could confirm the diagnosis of aorta-RA tunnel (ARAT). Because the patient was asymptomatic, the Qp/Qs ratio was <1.5:1, and he showed no evidence of right-sided heart overload, we decided to observe the patient closely without surgical treatment. At the 12- and 24-month follow-up transthoracic echocardiography, the size of ARAT diameter was still unchanged without any hemodynamic alterations. During 36-month follow-up period, the patient was still asymptomatic and showed a good performance state without any complications. Additionally, he underwent phase-contrast cine magnetic resonance imaging (PC-MRI) to quantify the ratio of Qp/Qs and shunt volume of the tunnel (Figure 5). The Qp/Qs ratio assessed by PC-MRI was 1.54:1. Left-to-right shunt volume assessed by PC-MRI may overestimate shunt amount compared with cardiac catheterization.1 We could ensure the result of Qp/Qs, which was performed by cardiac catheterization. In addition, shunt volume assessment by PC-MRI within the tunnel plane (Figure 5D) was performed (37 mL), and the result was not significantly different compared with the difference in pulmonary and aortic flow volume (Qp−Qs=42 mL).
ARAT is an extremely rare congenital anomaly. It is an extracardiac tunnel-like vasculature originating from the aortic sinus and terminating in the RA. The cause of ARAT remains elusive; however, the most acceptable pathogenesis is aortic elastic lamina deficiency of the aortic media.2 It is rare and difficult to diagnose; however, the number of reported cases has increased dramatically over the past decade, mainly because of advances in imaging technology. In this case, we provide high-resolution and well-defined images of ARAT compared with previously reported ARAT cases and demonstrate the relative merits of echocardiography, aortography, and computed tomographic angiography in providing complementary diagnostic information for the evaluation of ARAT. Moreover, we performed PC-MRI to validate the shunt amount noninvasively, which showed fairly good agreement with invasive right-sided catheterization. To the best of our knowledge, this is the first report of shunt quantification by PC-MRI in a patient with ARAT.
Although surgical or transcatheter closure of ARAT has been recommended as the main therapeutic option in previous reports,3,4 the need for closure in asymptomatic patients remains controversial. A complex surgical method including coronary artery reimplantation, which requires experience and skills, procedures such as sternotomy and cardiopulmonary bypass, and limited visualization of the posterior course of ARAT in the surgical field, may increase the risk and technical challenge of surgery. Moreover, catheter closure methods have been reported in only a few case reports and can be recommended only in specific proper anatomical conditions. Of course, the continued presence of fistulous tract arising from the aorta is a matter of concern; however, benefit versus risk in the correction of ARAT in asymptomatic patients without evidence of right-sided heart volume overload should be assessed first. In addition, patient selection for surgery and proper surgical timing in asymptomatic ARAT patients need further consideration and more convincing substantiation.
The online-only Data Supplement is available with this article at http://circ.ahajournals.org/lookup/suppl/doi:10.1161/CIRCULATIONAHA.115.020161/-/DC1.
- © 2016 American Heart Association, Inc.