The anatomy of interatrial communications - what does the interventionist need to know?

Increasingly the interventional cardiologist is seeking to close interatria l communications by inserting devices by means of catheterisation. So as to optimise these procedures, it is advantageous to have a firm grasp of the anatomy of the normal atrial septal structures, this then providing the bas is to understand the morphology of the holes which can exist between the ch ambers, not all of which are true septal defects. ri true septal structure can be removed without exiting from the cavities of the heart. It is the fl ap valve of the oval fossa, along with the anterior rim of the fossa, which fulfill this criterion. The remainder of the extensive rim of the normal f ossa is no more than an infolding between the walls of the right and left a triums and their venous tributaries, and has different dimensions at variou s points around the circumference. The so-called muscular atrioventricular "septum" is a sandwich incorporating a layer of epicardial fibro-adipose ti ssue. True defects of the atrial septum, therefore, exist because of defici ency, perforation, or absence of the flap valve. Most of these defects will prove suitable for interventional closure, but potential caveats include m ultiple defects, aneurysm of the flap valve, or adjacency of the fossa to t he venous orifices. The other interatrial communications, namely the sinus venosus, coronary sinus, and "ostium primum" defects are outside the confin es of the oval fossa. Recognition of this feature is the key to their diagn osis, and their differentiation from true atrial septal defects. Of these d efects, only the coronary sinus defect is likely to be suitable for device closure, and then only in the very rare circumstances when it is seen in is olation.