Discussion
Eustachian valve is a remnant of the embryonic sinus venosus valve. It is a fibromuscular triangular flap of tissue that extends from the lateral margin of the IVC orifice anteriorly and leftwards till the mouth of coronary sinus(2). It may be persisting as a large and redundant structure in the right atrium (more than 10 mm length) and may interfere with assessment and device closure of ASDs(3). It can be mistaken for the postero-inferior rim of the ASD(4). The device delivery cable may cause entrapment of the EV and inadvertent extraction of the EV(5). Furthermore, the prominent EV prevents apposition of the RA disc onto the septum and there may be residual atrial septal level shunt and predisposition to thrombus formation(6). There are reports of inadvertent surgical closure of a prominent Eustachian valve which was mistaken for an ASD where the patient presented with features of worsening cyanosis and IVC obstruction(7)(8). Butera et al reported on the pull push technique to avoid interferences of the EV with the delivery system(6).
Although all the prior reports describe the adverse effects of a redundant Eustachian valve, we describe a procedure where the EV actually helped to stabilize the device. We agree that caution needs to be exercised when planning for device closure of ASDs in patients with a prominent Eustachian valve. The index patient had borderline mitral rim measuring 4 mm which may have precluded device closure. However, the prominent EV near the mitral rim gave us confidence to attempt device closure. The prominent EV tissue prevented prolapse of the device during deployment because of the additional support offered in the antero inferior region (Figure 2B, Figure 3, Video 2). We antecedently chose the right upper pulmonary vein approach in this patient because of the borderline rims. The device closure was successful in the first attempt itself. There were no conduction disturbances. Development of AV conduction block during device closure of ASDs have been linked to the larger device size, proximity to AV node especially in deficient AV rims and injury during manipulation of the hardware(9)(10). The redundant EV in our case prevented slippage of the RA disc towards the atrioventricular junction and might have helped in avoiding injury to the AV node. We confirmed stability of the device by TEE in standard views and also confirmed uninterrupted IVC flow post deployment. There was no interference during cable manipulation as we had confirmed that the sheath was coursing freely across to the left atrium and the cable along with device was fully within the sheath prior to deployment.
We demonstrate successful ASD device closure facilitated by the redundant Eustachian valve in a patient with deficient mitral rims. Heightened caution is required following the recognition of this anomaly. However, it may prove beneficial in certain circumstances as elaborated.
Author contributions: Concept/ data collection/ drafting article- HKN; HKN, AGK, DSK, VG, KMK critically reviewed the manuscript. All authors approved the final version.