DISCUSSION and TEACHING POINT
Sinus-venosus ASD complicated by PAPVC is rare, anatomically complex, and difficult to detect by means of TTE alone, particularly in adults with limited echo window. As ASD exists at the ceiling of the atrial septum near the SVC, it is occasionally difficult to evaluate the superior defect type completely. In a report [3] verifying the diagnostic accuracy of TTE and TEE in 41 patients with ASD, 33 cases of them could be identified by TTE, whereas TEE could detect all cases. Meanwhile 6 cases of the 8 ASDs that TTE could not detect were sinus-venosus ASDs, which indicates how difficult it is to identify sinus-venosus ASD with TTE alone. Furthermore, in 7 of these 8 patients with PAPVC coexisting with ASD, PAPVCs were visualized by TEE, but TTE could not visualize the PAPVCs for all. Turner et al reported a case in which the etiology could not be clarified, while dilatation of the right heart became a clue for the final diagnosis as in our case. They reported that re-examination of TTE performed even after CT could visualize neither sinus-venosus ASD nor PAPVC; however, CT scanning clearly showed a sinus-venosus ASD complicated by PAPVC[4]. Inferior sinus-venosus ASD is rarer than the superior type, but technical points have been reported to improve the diagnostic accuracy in TTE. The complete lack of posterior rim in the modified parasternal short axis view is considered to be an effective finding that can distinguish inferior sinus-venosus ASD from ostium secundum type and other ASDs[6].
In this case report, we identified a sinus-venosus ASD complicated by two separately connected anomalous pulmonary veins at the modified right ventricular inflow view projected at the apical long-axis view. Sinus-venosus ASD may also be visualized in the bicaval view in the right thoracic or subcostal approach. Prior study however has indicated that TTE even if with such approach was able to detect only 44% of sinus-venosus ASD [7]. In this case, it was impossible because the patient was obese.