Abstract
Atypical anatomy may be encountered unexpectedly and undiagnosed in clinical practice, and this is especially important during the performance of interventional procedures such as transvenous implantation of cardiac electronic devices. The body of the first rib can be absent. If this not noticed, pneumo-/haemothroax may be induced during subclavian vein puncture as the needle may enter the first intercostal space rather than the costo-clavicular angle. The cephalic vein may pursue a supraclavicular course, the axillary vein may drain into an intercostal vein rather than the axillary vein, and the entire length of the axillary-subclavian-brachio-cephalic vein may be absent. Device implanters should be vigilant about the possibility of these anatomical variations, and be equipped with the knowledge and spectrum of alternative techniques needed to deal with them.