CA1300449C

CA1300449C - Diagnostic catheter for monitoring cardiac output

Info

Publication number: CA1300449C
Application number: CA000518885A
Authority: CA
Inventors: Robert C. Owens
Original assignee: Cardiac Pacemakers Inc
Current assignee: Cardiac Pacemakers Inc
Priority date: 1986-02-27
Filing date: 1986-09-23
Publication date: 1992-05-12
Anticipated expiration: 2009-05-12
Also published as: US4721115A; JPS62201138A; GB2187100A; DE3704500A1; GB8623656D0; GB2187100B; JPH0331050B2; DE3704500C2; FR2594681A1; FR2594681B1

Abstract

DIAGNOSTIC CATHETER FOR MONITORING CARDIAC OUTPUT
ABSTRACT OF THE DISCLOSURE
An elongated flexible plastic tubular member having a plurality (five) lumens extending along the length dimension thereof has a balloon-like expander located at the distal end portion thereof, the balloon surrounding a port communicating with one of the plural lumens so that a fluid introduced at the proximal end of the catheter can be made to inflate the balloon. Starting a first predetermined distance proximal of the distal end of the catheter is a zone in which a series of surface electrodes are axially spaced over the zone of the catheter body.
extending through another lumen of the catheter are the electrical conductors which connect each of the surface electrodes to an electrical connector at the proximal end of the catheter. In still another of the catheter's lumens are a pair of stiffener members, one being co-extensive with the zone of the catheter bearing the axially spaced surface electrodes and the other being spaced a short predetermined distance proximally of the first stiffener member. The gap between the two stiffener members allows the catheter to bend without kinking the lumen so that when used, the most proximal ring electrode will be disposed near the apex of the right ventricle with the portion distal of the bend extending upward through the outflow tract of the right ventricle. The distal end portion bearing the balloon is located in the pulmonary outflow tract leading to the lungs. Further lumens and ports communicating therewith may be added to permit the catheter to be used to take thermal dilution measurements of cardiac outputs so that they can be compared with measurements taken using impedance plethysmography.

Description

13(~ 4 1 9 DIAGNOSTIC CATHETER FOR MONITORING CARDIAC OUTPUT
~ACKGROUND OF THE lNVeNTlON
Pleld o~ the Inventlons Thls Inventlon relates gonorally to medical apparatus for measuring characteristics of an anlmal heart, and 5 more partlcularly to a diagnostic catheter to be used wlth approprlate equipment whereby cardiac outputs can be monltored on B beat-by-beat basis over a prolonged period of time.
Discussion of the Prior Art: In assessing cardlac performance and in diagnosing heart abnormalltles, an Important parameter to be 10 observed is cardiac output, which is generaJly measured In terms of llters-por-mlnute and whlch corresponds to the heart s stroko volume multlpllod by heart rate. Por example, followlng the occurronco of a cardlac Infarct, the attendlng cardiologist may want to assess the amount of dama8e In terms of the heart s ability to pump blood. Also, when certaln 15 drugs are administered, the attending physician will want to monitor the effects of such drugs on cardiac performance.
Varlous methods are known In the art for measuring cardlac output . A common approach has been the use of a thorm al dllutlon technlque In which a catheter is wed to inject cold sallne solution Into the 20 heart and further means are provided on the catheter for senslng temperature at a point exterlor to the heart, usually In the pulmonary outflow tract. By Its very nature, the procedure can only be used on an Intermittent bads at relatively wldely spaced lntervals. The thermal dilution technlque Is not capable of provlding real-time data on a beat-by 25 beat basis.
More recently, researchers have found a way to measure stroko volume through the use of a technlque calJed impedance pleythsmography.
Here, a catheter havlng a plurallty of surface electrodes Is Inserted Into the rlght ventrlcb and an AC voltage is appllcd across one palr of spaced-30 apart surface electrodes, whlch may be referred to as tho drlve palr. At ,~ .

13(~4 ~9 the sa~e t~ne. ~-o~a~e s~gr.als are sensed at l~.er~er.~e ~)al--s o~ sensing electrodes ar.d i-t is found that these s gnals are proportional to t~e impedance between the sensing e:lectrodes, which impedance is a runction of the quantit~ of ~'ood con~aln.ed ln the heart chamber between the sensing elect~odes in question.
The beating action of the heart thus modulates the appli~d AC
carrie~ signal and, using available signal processing techniques, the modulating signal can be removed from the carrier and it ls found to be proportional to stroke volume.
Those readers desiring more inrormation on t~.e impedance ple~hysmography technique are referred to the United States patent of Rodney Salo et al, United States patent No.
4,686,g8~ which is assigned to the assignee of the instant application, as well as to the published references cited therein.
The present invention is concerned with the design of a special-purpose catheter which has been developed to facilitate the real-time monitoring of stroke volume and, therefore, cardiac outputs using the impedance plethysmography technique.
Specifically, the catheter has been designed to facilitate the positioning of the driving and sensing electrode pairs within the ventricular chamber of the heart in such an orientation that accurate readings can be insured. The catheter is deslgned so that it will be disposed in the right ventricle with a drive electrode located in the apex and with another drive electrode being located near the pulmonic valve and with the intermediate sensing electrodes space away from the endocardial tissue improving the quality of the intracardiac impedance signals and minimizing cardiac induced PVCs. The construction thus reduces the risk of catheter-induced arrhythmias and allows thee catheter to remain in place for prolonged periods while providir.g the physical placement of electrodes necessary for accurate cardiac ~utput determinations by impedance plethysmography.

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SUMMARY OF THE INVENTION
The catheter of the present invention comprises an elongated plastic tubular member having a plurality of lumens runnlng the length thereof, the catheter body beJng sufficiently flexible that It may be 5 routed through the vascular system and into the rlght ventrlcle of tho heart. To assist in the catheter placement, a floatatlon devlce in the form of a balJoon is located near the distal end of the catheter and may be inflated by a suitable fluid via one of the plural lumens and an appropriately positioned port extending through the wall of the catheter 10 in the zone occupied by the balloon. Located a predetermlned distance or length proximal from the distal cnd of the catheter are a serles of surface eîectrodes in the form of conductive rings mounted on the exterlor surface of the catheter body and extending in an axlally spaced manner over a second predetermined length of the cathetcr. Each of the surface 15 electrodes is connected to an appropriate electrical connector located at the proxlmal end of the catheter by way of wires whlch pass through a second lumen.
To provide an independent measure of forward flow, both to permit the verification of cardiac outputs determlned by Impedance 20 plethysmography and for the quantitation of valvular regurgitatlon, thermal dilutlon capability may be included In the catheter. In order to accompllsh this, a port Is formed throu8h the side wall of the cathetcr body proxlmally of the balloon, this port contalnlng a thermistor-type sensor whose electrical leads extend the length of the catheter body vla a 25 further lumen. The thermistor can also be used for dcterminlng blood temperature upon demand. A still further port is located proxlmally of the most proximal one of the rin8 electrodes and communlcates wlth yet another lumen, the proximal lumen. This lumen Is used to measure ri8ht atriaJ pressure and for drug delivery. Also, cold saline may be injected at 30 the proximal end of the catheter through this proximal lumen and out the 004 ~9 port so as to be ejected into the right atrial chamber. Then, on the next contraction, a ten~perature change may be detected by the thermistor and by noting the temperature change, the cardiac output can be inferred, all as is weJI known in the art.
5Located in the same lumen through which the cold saJlno 15 introduced, but dlstally to the proximal ejectlon port In tho catheter slde wall, are first and second stlffener members whlch are longltudlnally spaced from one another by a short predetermined distance, with one such stiffener member bein8 in the zone of the catheter spanned by the surface 10electrodes and the other stiffener member being proximal thereto. The spacing between the stiffener members allows the catheter to bend at an acute angle with the most proxlmal surface electrode belng located In the apex of the right ventricle and the segment of the catheter bearlng the more dlstal surface electrodes projectlng upward through the right 1~ventricle whcn the flow-dlrectlng balloon portlon o~ the catheter Is located wlthln the pulmonary outflow tract of the heart. Furthermorc, ehe spaclng b~twecn the stlffener members contained wlthln tho samo lumen In the cathcter permlts the catheter to bend at an acute angle wlthout kinklng and occluding the catheter's plural lumens. Moreover, the 20routlng of the catheter into and out from the right ventricle is such that there is minimal contact between the catheter body and excitable tlssue.
Hence, the occurrence of catheter-lnduced PVCs may be reduced.
OBJeCTS
It is accordlngly a principal object of the present Invention to ;~5provlde a new and Improved catheter for use In monltorlng stroke volume.
Another object of the invention is to provlde a catheter for use with stroke volume monltorlng equipment that facllltates the measurements of cardiac output on a beat-by-beat basis.
Stiil another object of the invention Is to provlde, In a single 3Ucatheter structure, means for conductlng stroke volume measurements ~` 13~

using two different techniques so that comparison and/or callbration can be performed.
Yet another object of the invention is to provlde a rlght ventrlcular, flow-directed cathcter having a serles o~ axlally allgned 5 surface electrodes extending over a predetermlned Icngth proxlmally of the balloon such that when the balloon is guided into the pulmonary outflow tract, the portion of the catheter bearing the surface eJectrodes extends substantially the entire length of the right ventricle and remains substantially straight.
A yet further object of the invention Is to provlde a flow-directed catheter havlng spaced-apart stiffening members contained In the lumen thcreof for causing the catheter to bend in a predetermlned fashion proximate the apex of the right ventricle.
These and othcr objects and advantages of thc Inventlon wlll 15 becomc apparent to those skilled In the art from the iollowlng detalled descrlption of a prcferred embodiment, especially when consldered In conjunctJon with the accompanying drawings in which llke numerals in the sevcral vlews refer to corresponding parts.
DESCRIPTION OF THE DRAWINGS
Pigure 1 is 8 drawing showing the preferred embodiment of the present invention;
Figure 2 is a cross-sectional view taken along the llne 2-2 In Flgure 1~
Flgure 3 Is a cross-sectional view taken along the line 3-3 In 25 Flgure l;
Figure 4 is a longitudinal cross-section view of the distal end portion of the catheter of Figure l;
Figure S is a further longitudinal sectlonal vlew showing the manner In whlch a typical surface electrode is conflguredt S
.
!

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Figure 6 Is a cross-sectional view showlng the manner In whlch the thermistor-type temperature sensor Is dlsposed In the lumen of Figure 1~
Flgure 7 Is a drawlng showlng the constructlon of ~tlffenor S members used in the embodlment of Plgure l;
Fi~ure 8 is an alternative stiffener member used In the embodiment of Figure l;
Figure 9 shows the manner in which the stiffener of Figure 7 is installed in the proximal lumen of the catheter of Figure l; and Figure 10 is a sectioned view of the heart showlng the catheter of this invention installed in the right ventricle.
DESCRIPTION OF THe PREFERReD eMBODIMENT
Referrlng to Flgure 1, the dlagnostic catheter of the present I-lnventlon 18 seen to comprl# an elongated tubular member 10 whlch Is lS extruded so as to have a predetermined outer diametor whlch, for purposes of example only, may be about 2.28 mm and whlch is preferably formed from sllicone rubber, polyurethane or some other suitable plastlc whlch tends to be non-thrombogenic. With reference to the cros~
sectlonal vlew of Flgure 2, there are a plurallty o~ separate lumens 14, 16, 18, 20 and 22 extendlng the length thereof. For reasons whlch wlll become apparent from a continued reading of the speciflcation, the lumen 14 i5 referred to as the inflatJon lumen, 16 the dlstal lumen, 18 the sensing electrode lumen, 20 the thermistor lumen, and 22 the proximal lumen. For a catheter 10 of the typical size set forth above, the Inflatlon lumen 1~ may ~e about 0.37 mm ~n diameter. The lumens 16 and 22 may each be approximately 0.81 mm in diameter. The thermlstor lumen 20 may also be 0.Sl mm, while lumen 18 is about 0.71 mm in diametcr.
l~onded to the proximal end 24 of the extruded catheter 101s a yoke member 26 whlch provides a means whereby varlow devlcos may be connected to the several lumens runnlng through the c theter body 10.

The yoke 26 Is preferably molded from a thermosetting, medical 8rade .
plastic. Wlth the ald of the cross-sectlonal vlew of Flgure 3 and the vlew of Figure 1, there is shown a length of PVC tubing 28 whlch Is adheslvoly bonded withln the yoke 26 and a Luer lock 30 is afflxed to the othor end 5 of the tube 28. Thus, fluid communication Is establlshcd between the Luer lock 30 and the proximal lumen 22 (Figure 2) of the catheter 10. As shown In Pigure 1 and as better seen in the enlarged view of Flgure 9, extending through the side wall of the tubular catheter 10 and communicating with the proximal lumen is a port 32. Thus, fluid 10 communication is established from the Luer lock 30, through the tube 28 and the yoke 26, and through the proximal lumen 22 out through the port 32.
In a ~ornewhat slmilar fashlon, a tube 34, preterably formed from PVC, is termlnated at its proxlmal end wlth a Luer lock 36. The other end lS i5 adheslvcly bondcd into a borc in the yoke 26 leadlng to the distal lumcn 16 (Flgure 2) which extends the entire length of the catheter body 10 and termlnates In a distal port 38. Thus, fluld such as radlopaque dyes, drugs, ctc. may be Introduced through the Luer connector 36 and will flow through the tubing 34, the yoke 26 and the dlttal 16 to exit the 20 distal port 38.
As can best be seen In the enlarged vlew of Plgure 4, the distal end portlon of the catheter 10 Is formed to a reduced dlamcter. Pltted over that end portlon ls a plece of expandable balloon tu~lng 40. It Is bonded to the catheter body 10 at locations 42 and 44 wlth a sultable 25 adhesive. Formed through the side wall of the cathetcr 10 In the zone spanned by the balloon member 40 Is a port 46 whlch communlcates wlth the inflation lumen 14. The inflation lumen runs the entlre length of the catheter body and extends through the yoke 26 where a PVC tube 48 jolns it to a Luer valve S0. Thus, when a fluld, under pressure, is Introduced 30 through the opened Luer valve S0, it flows through the tube 48, the 1~()` (:) 4 L~ 9 yoke 26, the inflation lumen 14 and out the port 46 to inflate the balloon 40 By then closing the valve S0, the balloon can be retalned In lts Inflated state.
Ncxt, wlth rcference to Flguros 1 and 5, It can bo soon that there are afflxed to the outer surface of the tubular catheter 10, a plurality of rlng-type surfacc electrodes S2, the most proxlmal rlng belng Identlfied by numeral S2P and the most distal rlng bclng identlflcd by numeral S2D. For a catheter to be used wlth an adult heart, the rin8 electrode 52D may typically be disposed approximately 80 mm from the 10 distal end of the catheter 10. The spacing between adjacent surface electrodes may typlcally be 10 mm, but It to be understood that an alternatlvc spaclng may be used, especially In pedlatrlc operatlon~.
Wlth reference to Figure 5, independently connected to each of the ~urface clectrodes 52, ~2D and S2P are Insulated conductors, as at 54, 15 which extend proxlmally through the senslng electrode lumen 18 and through a length of PVC tubing S6 to the indivldual connector plns (not shown) contalned wlthin the connector houslng S8. Thls connector is adapted to be jolned to the electronic circuitry used In the measurement of stroke volume using impedance pleysthmography.
Next, wlth reference to Flgures I and 6, formed through the slde wall of the tubular catheter 10 is an openlng 60, and just below the openlng 60 Is a thermistor element 62 whlch Is disposed wlthln the thermi~tor lumen 20. Its electrical leads 64 extend down thls lumen and through the yoke 26 and the PVC tubing 66 to a further electrlcal 25 connector 68. A plug formed from silicone rubber adhesive is identlfied by numeral 70. lhen, a plastic, such as polyurethane, havlng good heat conducting properties, is made to cover the opening 60 to prevent the ingress of blood and other body fluids.
Referring now to Figure 9, it can be #en that a polyurethane 30 potting adhesive plu~ 72 is injected into the proximal lumen at a locatlon , ' ' - .'' . .

13004 ~9 just distal o~ the proxlrnal port 32 so as to block that lumen agalnst any fluid flow therebeyond. The proximal lumen 22 continues distally of the plug 72, however, and disposed in this lumen are first and second stiffening members of the type shown in Figure 7 of the drawlngs. The 5 stiffenJn6 members are indlcated generally by numeral 74 and comprl e a stainless steel coil 76 surrounding a s~ainle~s steel cor~ wlro 78. The core wire 78 Is welded at each end (80 and 82) to the surroundlng coll wlre 76.
In the case of a catheter made in accordance wlth thc preferrcd embodiment being described herein, the coil may be made f rom a 10 O.lSO mm wire wound as a unifiler coil and preferably i5 fabricated from Type 304 stainless steel. The core wire may typically have a diameter of 0.3SS mm and aJso may be Type 304 stainless steel. ay welding the core wire to the coll on each end thereof, unravellng of thc coll Is precluded when the stiffener Is subjected to tensile forces. The weldod core wlre 15 also prccludes penetration of the lumen walls.
As shown in Flgure 8, It Is also contemplated that one end of the corc wlre 78 may be tapered as shown at end 80 thereof to thereby Increase the relative flcxibility of the stiffener member at that end. Thc purpose ol thls will become more apparent as the descrlption proceeds.
20 lrrespective of the type of stiffener mcmber used, they may be approximately 0.81S mm in diameter and may have an overall Icngth of approximately lO cm.
Referring a~ain to Figures 1 and 9, a llrst stlffener member 74 may be fed down the proxlmal lumen untll positloned In the zone occupled 25 by the spaced-apart surface electrodes S2 and Identlfled by the bracket 84. Spaced proxlmally from the above-mentloned dlstal stlffener member ls a second stiffener member which extends distally from the end of the potting adhesive plug 72 near the proximal port 32 (Flgure 9) In the zone identified by bracket 86. These two stlffener members, beJng 0 located in the proximal lumen of the catheter 10 and spaced apart from 13~04.~9 ,~
one another ~y a snort dis~ance glves the catheter a ~endencl ~;o berd ~n the ~one ~etween the two, but in such a manner that tre catheter does not ~lnk so as tc occlude the lumen.
~ he surface electrodes 5~ are crimped in place only after the stiffener member 74 has been fitted into zone 84, and the crimping opera~ion not only secures the right electrodes to the outer sur~ace of the catheter, but also tends to hold the stiffener member 7~ in place.
OPE~ATION
Referring to E'igure 10, there is shown a se~tioned view of a heart with a catheter of the present invention nstalled so as to facilitate the monitoring of the patient's stroke volume using right ventricular impedance pleysthmosgraphy. The Catheter is installed by entering the patient's subclavean vein or brachial vein and routing it through the superior vena cava into the right atrium and from there through the tricuspid valve into the right ven~ricle. At this point, and inflating fluid is applied under pressure to the inflation lumen, via the valve 50, and the fluid exits the port 46 (Figure 4) to inflate the expander (balloon) 40. As blood is pumped from the right ventrlcle, the balloon 40 tends to be carried by the flow into the pulmonary outflow tract. Because of the first and second stiffener members, which are disposed in the proximal lumen downstream distally of the proximal port 32 and the relat~ve dimensions of those stiffener members and the spacing therebetween, the catheter tends to bend at a point proximate the apex of the right ventricle, as illustrated in Figure lo, with the segment 84 on which the surface electrodes are arrayed ; ~ extending upwardly through the right ventricle. The proximal -~ right electrode 52P is located in the apex of the heart while the distal surface electrode 52~ is at the entrance to the ~` pulmonary outflow tract.

-. Once the catheter is so installed, stroke volume measurements can be taken using the technique set out in the Salo ~, 10 : ~, "

l3no4~
J~lted States patent ~o. ~ Li enti'led "~ J ~J~ A~'UA'~ALU5 FOR MEASURING VENTRlC,ULAR VOLUME." ~ecause the present invention ~s concerned With physlcaï constructlon of the catheter, it ~s deemed unnecessary to explain in detail how the strohe ~701ume measurements are obtained. Those desiring an ex31an.ation ol the lmpedance pleysthmography technique for measurin~ stroke volume can refer to the aforementioned application and to the publications referenced therein.
To be able to calibrate the stroke volume measurements~
the catheter of the present invention also permits a measurement of cardiac output using the thermal dilution tecnnique. As is well known to practitioners in the field, a cold saline solution may be injected through the proximal lumen via Luer lock 30 whereupon it exits the proximal port 32 which, as seen in Figure 10, will be located in the right atrium. The temperature chanse occasioned by the flow of the cold saline diluted blood will be picked up by the thermistor element 60 exposed through the port 60 in the pulmonary outflow tract, and suitable instrumentation coupled to the electrlcal termi~al 68 is used to convert that temperature changed information to a stroke volume value for comparison with the stroke volume obtained using the impedance pleysthmography technique.
In using a catheter of the type described herein to measure relative stroke volume, a fewer number of sensing electrodes, e.g., four, positioned along the catheter body from the apex of the right ventrical to the pulmonic valve would be sufficient. Where absolute stroke volume is being assessed, however, an increased number of sensing electrodes, e.g. ten, is more appropriate. Furthermore, with the catheter designed for measuring absolute stroke volume, it is not re~uired that provision be made for conducting thermal dilution measurements such that the thermistor sensor can be eliminated.

It is important, however, that it be .~

13Q~

Included where relatlve stroke volume measurements aro to be obtalncd so that periodic correlatlons can be made.
~ ecause of the inclusion of the stiffener members 74, the catheter does not tend to lay along excitable heart tlssue and, hence, 5 catheter-lnduced PVCs are minlmlzed.
By using a stiffener mernber of the type shown In Figure 8 wlth a tapered core wire 78 and by orlenting that stiffener in the prox~mal lumen so that the tapered end of the stlffener member Is pointlng toward the balloon 40 In the zone 84 of the catheter, the abillty of the catheter to 10 snake around turns Is enhanced. This is partlcularly advantageous In pedlatric UJO of the catheter.
Thus, therc has been Jhown and deacrlbed the doslgn o~ a ~1 diagnostic coronary catheter whlch can be left In place over a perlod of ~-hours and even days so that a varlety of medical procedures and 15 measurements may be carried out. One or more drugs may be injected into the heart cavity via the distal end port 38 and the effect of those drugs on cardiac performance can be monitored as previously descrlbed.
Thia inventlon has been descrlbed hereln In conslderable detall In order to comply wlth the Patent Statutes and to provlde those skllled in 2û the art with the Information needed to apply the novel prlnclplca and to con~truct and use such spoclallzed components aa are requlred. Howover, lt 1~ to be understood that the Inventlon can be carrled out by spoclflcally d}~ferent egulpment and devlces, and that varlous modl~lcstlons, both as to egulpment detalls and operatlng procedures, can bo accompllshod 25 wlthout departing from the scope of the invent.on Itself.
What is clalmed is:

Claims

1. A diagnostic catheter for use in measuring cardiac output in the right ventricular chamber comprising:
(a) an elongated, multi-lumen, flexible member having a distal end and a proximal end, a first lumen extending the entire length of said member and terminating in a distal port, a second lumen extending from said proximal end of said member to a second port extending through the side wall of said member at a location immediately proximate of said distal end of said flexible member;
(b) an expandable sleeve adhesively bonded about said member at each end of said sleeve and spanning said second port and inflatable by a fluid introduced into the proximal end of said second lumen;
(c) a plurality of ring electrodes secured to the outer surface of said member at predetermined axial spacing beginning a first predetermined distance proximal of said distal end of said flexible member and ending a second predetermined distance greater than said first predetermined distance from said distal end of said flexible member;
(d) a plurality of electrical conductors extending longitudinally through a third lumen in said flexible member from said proximal end of said flexible member and individually connected to separate ones of said plurality of ring electrodes;
(e) a first stiffening member disposed in a fourth lumen in said flexible member and extending from said first predetermined distance to said second predetermined distance; and (f) a second stiffening member disposed in said fourth lumen in said flexible member and extending from a location proximal of the proximal end of said first stiffening member to a location which is a third predetermined distance, the spacing between said opposed ends of said first and second stiffening members creating a zone in which said flexible member can bend without kinking the lumens of said multi-lumen flexible member.

2. The diagnostic catheter as in Claim 1 wherein said first, second and third predetermined distances are such that when the proximal ring electrode is disposed at the apex of the right ventricle of a heart, the distal ring electrode approaches the pulmonic valve with said first predetermined distance extending into the right atrium.

3. The diagnostic catheter as in Claim 1 and further including a fifth lumen extending from said proximal end of said flexible member and terminating in a third port formed through the side wall of said flexible member and located within said first predetermined distance; and a thermistor element exposed to heat conduction through said third port and having conductor means extending therefrom through said fifth lumen to the proximal end of said flexible member.

4. The diagnostic catheter as in Claim 1 and further including a fourth port extending through the side wall of said flexible member and communicating with said fourth lumen at a location proximal of the proximal end of said second stiffening member.

5. The diagnostic catheter as in Claim 1 wherein said first and second stiffening members each comprise a helical stainless steel coil having a strand of stainless steel disposed within the lumen of said coil, said strand being welded at each end to the opposed ends of said coil.

6. The diagnostic catheter as in Claim 1 and further including a multi-terminal electrical connector connected to said plurality of electrical connectors.

7. The diagnostic catheter as in Claim 3 wherein said third port containing said thermistor is sealingly covered with a plastic having a predetermined thermal conductivity for allowing said thermistor to detect a small temperature change rapidly.

8. The diagnostic catheter as in Claim 1 and further including valve means connected to the proximal end of said second lumen of said flexible member.