referring to fig1 and 5 , the main body 10 of the assembly consists of ten individual wires 12 , each individually insulated at 14 ( see fig6 ) and held together in this embodiment with heat shrink tubing 16 . the distal and proximal ends d and p respectively of the main body 10 terminate in four limbs or legs 30 , 31 , 32 , 33 and 40 , 41 , 42 and 43 , respectively . two legs of each set ( 30 , 32 ; 40 , 42 ) each has two wires and two legs of each set ( 31 , 33 ; 41 , 43 ) each has three wires . each group is held together in this embodiment with smaller shrink tubing 18 . all wires at the distal end terminate with an electrode ferrule 19 ( stainless steel band ) connected onto a bare end of a wire 14 . a two wire and a three wire leg ( 30 , 31 ) has one size of electrode ( short electrodes 20 ) and a two wire and a three wire leg ( 32 , 33 ) has electrodes about twice the size of the first set , ( long electrodes 22 ). in this embodiment , the short electrodes are 3 mm . in length and the long electrode . 5 mm . the electrode ferrules on each leg are spaced in this embodiment equally , 1 cm . from each other and are staggered in relation to the ferrules of a neighboring leg ( see projection lines , fig5 ), to reduce lateral clumping , such that they will fit a small inner diameter of a conventional cardiac catheter 50 ( fig1 ) of about 0 . 060 inch diameter when collapsed . the proximal legs hook up to electrical connector box 52 ( fig8 ) which plugs into a stimulation and recording system 54 for mapping of electrical activity when the electrodes lie in the ventricle . referring to fig8 and 10 , the electrode assembly is introduced subcutaneously with the help of a conventional cardiac placement catheter . it is correctly positioned by advancing the catheter 50 ( which contains the electrode assembly ) to the apex a , fig1 , of the ventricle , at which point the catheter 50 is retracted to the position of fig1 a , allowing the release of the spring legs . this may be used for either left or right ventricular studies . by use of a catheter 50 with torsional stiffness , the array of electrodes may be rotated within the ventricle to a series of successive positions , and may be partially withdrawn , see fig1 b , for further contact with upper portions of the ventricular wall , all with the aid of the distinctive patterns that extend to the distal ends of the legs . in the alternative embodiment of fig1 the connecting shrink tubing 18a at the distal end does not extend to the entire length of the electrodes , rather it stops to allow each electrode a small flare from the others (&# 34 ; flare - on - flare &# 34 ;). the connector ( proximal ) end is constructed so that all wires in the group terminate at the same end point and are electrically connected to stainless steel ferrules of deliberate by different numbers in correlation with the different numbers of electrodes on the distal ends of the legs , as an important identification aid to the caridologist . the significant features of this mapping electrode system include the fluoroscopically identifiable legs having three and two electrodes of one size and three and two electrodes of another size , the termination points of each electrode enabling individual flare on flare where desired , the spacing of the electrodes being such that they fit together when collapsed to reduce overall diameter ( a feature known per se for individual electrodes , from halvorsen u . s . pat . no . 4 , 289 , 138 ). the present invention significantly extends the practical capabilities of electrodes to map the area within the ventricle . because the presently preferred embodiment includes two different sizes of electrodes and two different numbers of each size , each limb presents a distinguishable linear pattern from the other upon fluoroscopy , see fig9 . the numerous , identifiable electrodes allow more recordable electrograms with accuracy of localizaton . the multiple arms allow for simultaneous recording and / or stimulation of multiple three - dimensional spaced points on the walls of the endocardium . in a typical assembly procedure according to the invention , the individual conductors 12 are stainless steel spring wire of 0 . 007 to 0 . 009 inch diameter , coated with urethane insulation 14 of e . g ., 0 . 001 inch thickness . the selected number of wires is cut to appropriately different lengths and the insulation 14 is stripped from the ends to provide bare connection wire ends 15 . a shrink tubing 18 , e . g . high shrink polyethylene of 0 . 002 inches wall thickness , is slipped over each set of conductors to the nodal point n . this tubing is then skived at appropriate points and the ends 15 of the wires are then led out of the registering openings 17 and bent back , as shown in fig6 . the tubing is then heat shrunk , and electrode ferrules 19 are applied over the bare wire ends , and swagged down to correspond with the outer diameter of the shrink tubing 18 , see fig7 . the proximal end connectors are similarly applied . each leg is bent to the desired shape as shown in fig3 with the leg bending concavely outwardly from the nodal point n with radium r 1 of about 1 centimeter , and then bent convexly back with larger radius r 2 , thus to form an s curve , terminating on a line approximately parallel with but off - set from axis x . care is taken , with reference to the chosen material of the legs and the size of the introducer catheter , not to exceed the elastic limit of the wires during bending and during insertion into the catheter . referring to fig4 two of such legs are joined together back to back in a pane at an adhesive joint in the nodal region n , then with the aid of an appropriate jig , two such sets are joined at 90 ° to each other , again with adhesive being applied in the nodal region , to set the angles of the legs with respect to one another . the proximal portions of these conductors are then aligned with one another and are let through a further length of shrink tubing 16 up to nodal point n , tubing 16 being sized to allow protrusion of the proximal end portions of the various conductors . thereupon , the introducing catheter 50 sheath can be slipped over the assembly , and , if not done previously , the proximal connecter ferrules can be attached in mating numbers on the legs , to match the numbers on the proximal ends of the respective legs . these proximal connectors may be marked &# 34 ; long &# 34 ; and &# 34 ; short &# 34 ; to correspond with respective distal electrodes , or the proximal connectors themselves can be correspondingly long or short in dimension for ease of identification . referring to fig7 a , to achieve a &# 34 ; flare - on - flare &# 34 ; the tubing 18a may terminate at the first elecrode , leaving the protruding portions 12a , 12b and 12c of the insulated wires to freely protrude at varying distances . if desired , bends can be introduced to these flaring portions to achieve further distribution of the electrode contact points . referring to fig7 b , as an alternative to the assembly procedure of fig6 and 7 , each wire 12 extends for the full length of the respective wire . the wires are stripped at different points , the overlying shrink tube is correspondingly skived and conductive adhesive 8 is introduced to effect electrical contact between the respective wires and their connectors . the advantage of such construction is that the full length of the leg may be strengthened by the full extension of each wire , despite the fact that the electrodes for some of the wires are placed further up the assembly . variations in the details of the implementation of the invention are possible in numerous ways , e . g ., in respect of the selection of tubing , wire , wire insulation , connecting ferrules , electrodes , adhesive and possible use of a transition piece between the body and electrode limbs to maintain desired angular relationship of the legs . alternate methods of connecting the electrodes , ferrules , and grouping of wires can be acceptably employed . design changes that may occur include number of limbs , number of electrodes , size of electrodes and the shape of the usable end . the limbs may be preformed to a variety of shapes such as a basket , tulip or even reverse flare . for example , fig1 - 14 illustrate variations within the general concept of the invention , in this case employing four free - ended limbs , with mating electrode placement ( see projection lines ) between pairs of limbs to reduce lateral clumping .
an endocardial electrode assembly of three or more spring legs to be inserted into the heart , sets of electrodes on respective spring legs comprising distinctive geometrical patterns , over the ventricle - contacting span of the legs , such that the active sets of electrodes provide recognizable patterns when within a ventricle of the heart and viewed with a fluoroscope , the respective locations of at least some of the electrodes of these patterns being staggered relative to electrodes on other legs in the manner to reduce lateral clumping , thus to permit the numerous electrodes to be housed in a catheter sized to be conveniently introduced into the heart .