Background The failure to deliver a stent across the target lesion during transradial coronary intervention, especially in arteries with calcified tortuous anatomy, is often due to insufficient back-up support from the guiding catheter.Deep-vessel intubation with the guiding catheter may overcome this problem, but risks coronary dissection.The Heartrail "five-in-six catheter system" (or "mother-and-child" catheter) comprises a flexible-tipped long 5 Fr catheter advanced through a standard 6 Fr guiding catheter to deeply intubate the target vessel, thus providing enough back-up support to enable stent delivery.