Patent claim: The catheter of claim 1 wherein the at least one electrode includes at least one ring electrode mounted in surrounding relation to the nonconductive covering.

Related passage: In accordance with a feature of the invention each spine 14 has a generally Lshaped configuration supported by the support arm 24.In the illustrated embodiment of FIGS.1 and 6 the generally Lshaped configuration of each spine is defined by a generally straight proximal portion 60 a generally straight distal portion 64 that extends at a generally orthogonal angle from the proximal portion 60.When the distal assembly 18 is initially deployed in a tubular cavity 71 as illustrated in FIG.6A the spines 14 are in their generally neutral and relaxed Lshaped configuration.As the distal assembly enters the tubular cavity as illustrated in FIG.6B the distal ends of the spines come into contact with an opening or ostium 70 of the tubular cavity where the Lshaped configuration of the spines 14 starts to change under a contact force applied to the distal ends of the spines by the ostium.When the distal assembly 18 is advanced the proximal portions 60 of the spines are pushed deeper into the tubular cavity and the distal ends of the spines 14 come into contact with tissue lining the tubular cavity 71.The distal assembly 18 is further advanced so that the distal portions 64 increasingly bend over the distal ends until moreof the distal portions 64 also come into contact with deeper tissue in the tubular cavity 71 whereupon the spines 14 are in a generally Ushaped configuration as shown in FIG.6C.Depending on various parameters the distal end or tip electrode 20 of the spine in the generally Ushaped configuration defines an anglewith the proximal end of the spine.The angleranges between about 45 and 135 degrees preferably between about 80 and 100 degrees and preferably about 90 degrees as illustrated in FIG.6D.Where the angleis less than 90 degrees the tip electrode 20 is distal of the proximal end of the spine 14 at the spine mounting assembly 31.Where the angleis about 90 degrees the tip electrode 20 is about even with the proximal end of the spine 14.Where the angleis greater than 90 degrees the tip electrode 20 is proximal of the proximal end of the spine 14.However regardless of the angle 0 the generally Ushaped configuration of the support member 24 and hence the spine 14 provides that the distal portion 64 is nearly parallel with the generally straight proximal portion 60 and that the ring electrodes 28 are consistently positioned deeper in the tubular structure than the tip electrode 20.As illustrated in FIG.6D the length andor curvature of each portion 60 and 64 can be varied as desired or appropriate.Moreover the length curvature andor angleneed not be uniform for each spine throughout the distal assembly.For example a first set of spines may have one length curvature andor angleand a second set of spines may have another length curvature andor angle.Although the spines are equally radially spaced from each other in the illustrated embodiments the radial spacing can also be varied as desired or appropriate.In the illustrated embodiment of FIG.6C the catheter is illustrated as it appears when pushed into a tubular cavity.The change in configuration of the spine from a relaxed state Lshaped in FIG.6A to a confined state Ushaped in FIB.6C reflects how the anglegrows when the distal assembly 18 is pushed into the tubular cavity.The length of the spine 14 extending between the exposed proximal end of the covering 26 to the distal tip end of the spine can range between about 1.0 cm and 5.0 cm.