Case report: Imaging features of aorta-right atrial tunnel in a dog using two-dimensional echocardiography and computed tomography

Abstract

A 7-year-old castrated male Pomeranian dog weighing 5 kg presented with a right-sided continuous murmur without any clinical signs. Thoracic radiographs indicated cardiomegaly and right atrial (RA) bulging. Echocardiography revealed a tunnel originating from the right coronary sinus of Valsalva and terminating in the RA. Contrast echocardiography revealed pulmonary arteriovenous anastomoses. Computed tomography (CT) demonstrated a tortuous shunting vessel that originated from the aorta extending in a ventral direction, ran along the right ventricular wall, and was inserted into the RA. Based on these diagnostic findings, the dog was diagnosed with the aorta-RA tunnel. At the 1-year follow-up visit without treatment, the dog showed no significant change except for mild left ventricular volume overload and mildly decreased contractility. To the best of our knowledge, this is the first case report of an aorta-RA tunnel that has been described in detail using echocardiography and CT in a dog. In conclusion, the aorta-RA tunnel should be included in the clinical differential diagnoses if a right-sided continuous murmur is heard or shunt flow originating from the aortic root is identified.

Keywords: Valsalva; aorta-RA shunt; aorta-RA tunnel; aortic root; canine; cardiovascular anomaly; right atrium; right coronary sinus.

Figure 1

Two-dimensional and color Doppler echocardiogram images of the origin (A,B) and termination (C,D) of the aorta-right atrial tunnel. The tunnel originated from the right coronary sinus of Valsalva in the ventral direction and then ran rightward on the parasternal short-axis view (A,B). The tunnel running adjacent to the right ventricular and right atrial free wall was terminated in the right atrium from the modified right parasternal long-axis view (C,D). Ao, aorta; LV, left ventricle; MPA, main pulmonary artery; RA, right atrium; RV, right ventricle; TV, tricuspid valve.

Figure 2

Two-dimensional and color Doppler echocardiogram images of concurrent findings. Blood flow from the vessel (dotted arrow) within the interventricular septum to the right ventricle was confirmed from a modified right parasternal long-axis view (A,B). From the right parasternal short-axis view, blood flow (solid arrow) from the proximal aorta-right atrial tunnel runs between the aorta and the right atrium (C), and the mosaic pattern between the aorta and the main pulmonary artery (D) were identified. Ao, aorta; LA, left atrium; LV, left ventricle; MPA, main pulmonary artery; RA, right atrium; RV, right ventricle.

Figure 3

Computed tomography images of the aorta-right atrial tunnel. The tunnel originating from the right coronary sinus of Valsalva extending in a ventral ventral direction runs rightward (A), caudodorsal to the aortic root (B). After a tortuous course adjacent to the right ventricular and right atrial free wall (C), the tunnel entered the right atrium (D). Ao, aorta; LVOT, left ventricular outflow tract; MPA, main pulmonary artery; RA, right atrium.

Figure 4

Illustration of the aorta-right atrial tunnel made with reference to the three-dimensional computed tomographic reconstruction. The origin orifice can be observed on the cross-section of the heart at the aortic valve level. The tunnel’s origin from the right coronary sinus of Valsalva and entry to the right atrium through a tortuous communication was confirmed. LA, left atrium; LC, left coronary cusp; MPA, main pulmonary artery; NC, non-coronary cusp; RA, right atrium; RC, right coronary cusp; RV, right ventricle.