82 or the inner tube 78 or both cover the distal ends of the needles 79 in the pre deployment condition inflation of the balloon 76 would pull the needles 79 in the proximal direction out from under such an elastic band such an elastic band would prevent the needles 79 from catching on the inside of the guiding catheter as the cas 70 is advanced into the body for this embodiment of the cas 70 the method of use would be the following steps 1 remove the sterilized cas 70 from its packaging in a sterile field 2 flush the guide wire lumen 85 with saline solution 3 access to the left atrium via a large peripheral vein such as the femoral vein typically with the insertion of a sheath 4 use a transseptal approach to get into the left atrium via the vein to the right atrium to enter the left atrium this approach is a well known procedure 5 advance a guide wire and guiding catheter across the inter atrial septum into the left atrium 6 using a guiding catheter or guiding sheath with a shaped distal end engage the first targeted pulmonary vein this can be confirmed with contrast injections as needed 7 advance.