The straightening of a sinuous proximal segment of a coronary artery using the stiffness of the guidewire has recently been recognized as likely to cause false coronary lesions. The accurate diagnosis between a true dissection and a pseudo-lesion is usually only done once all intra-coronary material has been removed into the guiding catheter. Such a manoeuvre may prove dangerous in case of dissection. We propose to demonstrate that it is possible to diagnose this phenomenon while leaving the guidewire within the coronary artery, and withdrawing it progressively until its floppy segment rests equally on either side of the suspect lesion.