Radial loops can be simple and complex. The incidence of simple loop is 10 -15 in 1000 individuals and that of complex loop is 2-3 in 1000 individuals. Simple Loops can be easily crossed with 0.25 terrumo wire. The 360° complex loop requires PTCA guides were to cross. Over the PTCA wire micircatheter is advanced over the loop and little traction will straighten the loop. Now the  catheter can be introduced easily over the loop