Site-Selective Atrial Septal Puncture. Atrial transseptal puncture is a technique that provides pervenous access to the left heart. The aim of this technique is to provide catheter access to the left atrium and ventricle for mapping, as well as stable electrode-endocardial contact for ablation energy application. In the present report, "site-selective" atrial septal puncture is described and illustrated using case reports.