Anatomic definition of the defect

The choice of the right prosthesis

The stretching of the right atrium observed with P-O syndrome leads to a very difficult echocardiographic evaluation of the anatomy, in particular, of the real shape of defect and of septum primum characteristics. This is a major tool because a faulty intraprocedural echocardiographic evaluation may lead to a mismatch between the delivered prosthesis and the atrial septum, and a significant residual shunt may persist. Figure 23.2 shows how 2D imaging techniques may properly provide either the degree of PFO opening evaluated by the distance between the two septa or the degree of overlapping between septum primum and septum secundum but do not provide a correct estimation of the width of the PFO slit that, on the contrary, can be assessed by 3D technology. Rana et al. [9] highlighted how 3D rather than 2D echocardiography allowed a detailed understanding of the different PFO anatomies and of its neighboring structures and how these knowledge can be considered the main determinant for the choice of device and procedural success during percutaneous closure.

In this case, the residual shunt persisting behind the first implanted prosthesis suggests that the width of the slit between septum primum and septum secundum had been underestimated. So additional information obtained by 3D echo might have been helpful in guiding the procedure. When 3D echo is not available, a possible effective alternative is to perform a balloon sizing of the PFO to select the device to deploy, based on the dimension of the waist of the inflated balloon across the PFO, measured at fluoroscopy [10].

In this particular clinical context, the choice of the proper device to implant is mandatory to obtain symptom relief and to reduce the risk of paradoxical embolism that is higher in case of persistent rather than transient right-to-left shunt.