an intra - cardiac mapping system is based on locating the ports through which blood flows in or out the heart chambers . for many procedures , such as ablation to cure atrial fibrillation , locating the pulmonary veins and the mitral valve accurately allows to perform a maze procedure . the location of the ports and valves is based on using the convective cooling effect of the blood flow . the mapping can be performed by a catheter - deployed expandable net or a scanning catheter . the same net or catheter can also perform the ablation procedure .