Radio frequency pulmonary vein isolation

A system for tissue ablate, comprising: means for providing a coil (34; 92; 102; 122; 123) is constructed from a shape memory alloy; means (10) for introducing said coil into a hollow viscus (56); means (22; 100, 108, 114, 118; 124; 125) for circumferentially connecting said coil with an inner wall of said viscus to define a circumferential region of contact between said coil and said inner wall; and means (42) for conducting radiofrequency energy from said coil to said circumferential region of contact while said circumferential region of contact is maintained to ablate tissue therein, wherein said means for connecting (22; 100; 108, 114, 118, 124; 125) is adapted to circumferentially connected to said coil (34; 92; 102; 122; 123) by radially expanding said coil. characterized in that the system further comprises means (100; 108, 114, 118, 124, 125, 132, 134) for varying the temperature of said coil (92; 102; 122; 123) to alter a configuration thereof, wherein adapted the system so that while said means (100; 108, 114, 118, 124; 125, 132, 134) for varying said temperature is operating, said coil (92; 102; 122; 123) expands radially in response to a shape memory thereof, and the system further includes means (100, 108, 114, 118; 124; 125) for differentially heating segments (30, 32; 96, 98; 104, 106) of said coil to expand said coil (92; 102; 122; 123).