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.