Long Eustachian valve interfering with the access to coronary sinus during biventricular pacemaker implantation

Early during embryonic life, the right valve of sinus venosus sepa- rates venous right atrium from the muscular right atrium and directs oxygenated blood preferentially from the inferior vena cava (IVC) through the foramen ovale into the left atrium. This structure begins to regress during the second trimester leaving four remnants: the Eustachian valve (EV), the Thebesian valve, Chiari network and the ter- minal crest. Depending on the degree of regression, EV may be totally absent or it may appear as a thin flap originating from the orifice of the IVC. Here we describe a long EV, which impeded access to the coro- nary sinus (CS) during biventricular pacemaker implantation.