Field of the Invention

This invention pertains to catheters for use in the blood vessels of humans, as well as in aminals generally. More particularly, it pertains to a blood pumping retroperfusion catheter featuring an improved balloon support structure enabling blood to be used effectively as a balloon inflation fluid without damage to the blood for such purpose.

Background of the Invention

A new medical technique for heart attack patients involves the pulsatile retroperfusion of oxygenated blood into the myocardium from the coronary sinus. The procedure comprises advancing a autoinflatable catheter into the coronary sinus. During diastole, oxygenated blood is pumped through the catheter into the coronary sinus. The blood flowing through the catheter is under sufficient pressure to inflate the balloon which is also positioned in the sinus. Inflation of the balloon blocks a portion of the sinus which results in the unidirectional retroperfusion of oxygenated blood from the catheter through coronary veins into the myocardium. During systole, no blood is pumped through the catheter which, as a result, deflates the balloon and allows coronary

venous blood to drain past the collasped balloon.

Oxygenated blood is continuously pumped to the myocardium by this method until such time as the coronary arteries can be repaired. For this procedure to operate efficiently, the balloon of the catheter must be inflatable and deflatable in a very short period of time. Typical inflation times are on the order of 50 milliseconds. This requires the free flow of blood into and out of the balloon chamber. Some conventional autoinflatable catheters utilize holes in the catheter tube to form passages into the balloon chamber formed between the balloon and the catheter tube through which the blood flows for inflating and deflating the balloon. The number and size of the holes are sufficiently small to not significantly weaken the catheter tube. However, the small size of the holes may cause significant damage to the blood. This is because a portion of the blood flowing through the holes and contacting the catheter wall may be damaged by the contact. The amount of damage to the blood is related to the amount of blood contacting the catheter wall as it flows into the balloon chamber, which in turn is dependent on the size of the holes.

In addition, the small size of the holes tends to restrict the free flow of blood into and out of the balloon chamber resulting in undesirably slow inflation and deflation of the balloon. To compensate, increased pressure may be used, resulting in faster inflation of the balloon, but may further damage the blood as it passes through the holes. Furthermore, a small number of holes create regions in the balloon chamber where blood tends to stagnate arid possibly clot.

There are other catheters which utilize an axial rod between two catheter tube sections as a balloon support.

One end of the balloon is attached to each catheter tube section. This catheter design enables free flow of a liquid within the interior of the balloon but results in obstructions in each catheter tube section at the positions where the axial rod is attached to the catheter tube sections. These obstructions restrict the amount of the liquid flowing through the catheter tube to inflate the balloon. As such, catheters having an axial rod as a balloon support are not suitable for applications such as the retroperfusion of blood to the myocardium.

Summary of the Invention

In accordance with the invention, there is provided a balloon support suitable for allowing rapid inflation and deflation of the balloon of an autoinflatable catheter. The balloon support is attachable between two sections of a catheter tube and comprises a rigid cage having open anterior and posterior ends and a continuous hollow interior. The anterior end of the cage is attachable to the posterior end of one catheter tube section and the posterior end of the cage is attachable to the anterior end of the other catheter tube section. The cage has open ends and thereby forms an unobstructed pathway between the two catheter tube sections. The cage further comprises openings for forming passages between the interior, of the cage and a balloon chamber formed between the cage and a balloon positioned surrounding the cage. The openings are sufficiently large not to significantly restrict the flow of a liquid, such as blood, through the openings. The openings are also sufficiently large to substantially prevent pooling of liquid in the balloon chamber.

In a preferred embodiment, the cage comprises a plurality of spaced generally-parallel rods. The rods are connected at each end to rings which are attachable

about the ends of the catheter tube sections. The spaces between adjacent rods form openings which are sufficiently large not to significantly restrict the flow of a liquid through the openings and to substantially prevent pooling of a liquid in the balloon chamber. It is particularly preferred that the cage be constructed from stainless steel wire.

In another preferred embodiment, the cage comprises a rigid slotted tube. The anterior end of the cage is attachable about the posterior end of one catheter tube section and the posterior end of the cylinder is attachable about the anterior end of the other tube section. The cage has open anterior and posterior ends and slots in the cage wall forming openings which are sufficiently large not to significantly restrict the flow of a liquid through the openings and to substantially prevent pooling of liquid in the balloon chamber.

A preferred autoinflatable catheter comprising a balloon support constructed according to the principles of the invention comprises an elongated first catheter tube section that forms a main catheter body. The main catheter body is connected by the balloon support to a short second catheter tube section that forms a catheter tip. A balloon surrounds the balloon support forming a ^' balloon chamber between the balloon and the balloon support and is sealed at one end around the catheter tip and at the other end around the main catheter body. Free flow of a liquid, such as blood, into and out of the balloon chamber through the ballon support enables rapid inflation and deflation of the balloon. Furthermore, the openings of the balloon support substantially eliminate pooling of the liquid in the balloon chamber. In the case of liquids such as blood which may be damaged, the openings are sufficiently large to minimize the damage to such liquids due to contact with the cage wall.

Brief Description of the Drawings

These and other features and advantages of the present invention will be better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:

FIG. 1 is a fragmentary, partially cutaway, sectional view of a autoinflatable catheter showing a preferred embodiment of a balloon support; and

FIG. 2 is a fragmentary, partially cutaway, sectional view of a autoin latable catheter showing another preferred embodiment of a balloon support.

_ _. O PI /ty ^■ .iro

Detailed Description _ _^

The present invention is particularly suited to a process for the pulsatile retroperfusion of oxygenated blood into the myocardium of a heart attack patient from the venous side.

In such a process, a puncture is made into a large artery, e.g., the brachial artery in the patient's arm, using a hypodermic needle. A tube connects the hypodermic needle to a pulsatile pump which is driven by air pressure, The anterior end of an autoinflatable catheter constructed according to principles of this invention is inserted into a vein, e.g., the exterior jugular vein, and advanced into the coronary sinus part of the heart so that the catheter balloon is positioned in the coronary sinus. The posterior end of the catheter is attached to the pulsatile pump.

Oxygenated blood flows from the punctured artery through the hypodermic needle and tube to the pulsatile pump and is then delivered pulsatilely during diastole through the catheter to the coronary sinus. A portion of the blood flowing through the catheter inflates the balloon, thereby blocking a portion of the coronary sinus. The remainder of the oxygenated blood flows through the catheter into the coronary sinus where it retroperfuses into the myocardium, thereby providing at least a portion of the oxygen supply that has been cut off from the coronary arteries. During systole, blood is not pumped through the catheter and the balloon deflates, thus allowing deoxygenated venous blood to drain through the coronary sinus.

A preferred embodiment of an autoinflatable catheter, used in the retroperfusion of blood to the myocardium, constructed according to principles of the present invention, is shown in FIG. 1. The catheter 10 comprises an elongated flexible catheter tube section forming a

main catheter body 11 and a short flexible catheter tube section forming a hollow catheter tip 12 which is connecte to the main catheter body by a balloon support 13. The main catheter body and the catheter tip have generally circular cross-sections and substantially the same outer diameter ranging from about 0.080 inch to about 0.120 inch.

The inner diameter of the catheter tip is smaller at the anterior end than at the posterior end. The differenc in the inner diameter between the anterior and posterior ends of the catheter tip is sufficient to create a pressur drop in a liquid flowing through the catheter. The magnitude of the pressure drop is sufficient to cause the balloon to inflate when a liquid is pumped through the catheter at a select pressure. In this application, blood is pumped through the catheter at about 2 psi (about 100 m Hg). The catheter tip creates a pressure drop of about 1 psi (about 50 mm Hg) which is sufficient to inflate the balloon. The anterior end of catheter tip 12 is open for the flow of blood into the coronary sinus.

To minimize the increase in the diameter of the catheter due to the thickness of the balloon support and balloon at the junctures where they are mounted to the main catheter body and \he catheter tip, the thickness of the wall of the anterior end 19 of the main catheter body and the posterior end 17 of the catheter tip may be reduced as shown in FIG. 1.

An inflatable and deflatable balloon 14 surrounds the balloon support. The balloon may be a non-elastomeric b g or bladder or an elastomeric balloon. The anterior end 16 of the balloon is sealed about the outer circumference of the posterior end 17 of the catheter tip 12 and the posterior end 18 of the balloon is sealed about the anterior end 19 of the main catheter body 11.

CMPI

-S- i -Th*** seals prevent leakage of liquid from the catheter.. 2.____ seals may be made by conventional methods, e.g., tying with nylon thread 20 and then overlaying the juncture vrith a cofi-patibls adhesive 21 cr by solvent evaporation

5 -techniques _* The balloon forms a balloon cha&ber 22 between tr . b lloon support δrd the hallooi- v_._i.l_. 7 e be__loon su o t --.om rises a gen riHy cylindrical tubular cage of about 3.43 inch _-30out one centimeter in length but -sa vary from about 3 - 2 inch

10 to about »6 inch. The cage has open anterior ar_d posterior -*__ds and a hollow interior, thereby forming an un bs r cted pathway between the main catheter body and the catheter tip. The inner diameter of the cage ranges from about >_._060 inch to about 0.100 inch, depending on

1 the outer diaateters of the anterior end of t e s i catheter foody a d the posterior end of the catheter tip,

The cage is constructed of a rigid material which may be metallic or non-metallic. The material is compatible with the liquid, e.g., blood in this

20 application, flowing through the catheter. The material is also sufficiently strong to maintain a rigid shape under the conditions of use. This prevents crimping of the cage with a concomitant restriction of the blood flow through the cage. The presently preferred balloon

2 supports are constructed from "stainless steel. However, other compatible metals and rigid plastics are also suitable.

The inner diameter of the cage is about equal to the outer diameter of the posterior end of the catheter tip C- and the anterior end cf the main catheter body. The anterior end 23 of the cage is attached about the posterior end 17 of the catheter tip 12 at a position posterior to the balloon-ca hete tip seal using a si *. c^ .patibl with the cage, t_he catheter tip and the p t,te t's blood. 5 .g. _* a polyurethane adhesive. The poste io~ ^* end 24 of

C FI

__e oa-ge is attached i_s the same manner about the anterior •a?A«-. 19 f the stair- cs Jbefcer body 11 and is positioned _s-tsr£σr to *±_ ^~ . tsallooπ-main catheter body seal. ^T his compl& . ^~ ilγ encloses the cage within the * t-aιllocτt _* ϊ e cage openings or slots 25 in the wall of the ca e _* orni tg passages between the interior of the sag 13 and t e balloon chamber 22 sufficiently large to Λo slgαificantly restrict the flO'W f a liquid through th "i _p yin s- In this ap lication,, e openings are large enc-j-gh to es_abie blood to flow inzα the balloon chamber su ^f icien ly rapidly tfi. Inflate the balloon and block he coronary siϊias di3 i__g diastole and to f ow out of the balloon chamber sufficiently ra idly to deflate the _* -balloo-ϊ during syst le _* thereby allowing drainage of

^■ lood through the coron ry sinus without significantly 'a iaaging the blood _* the balloon is inflated in about 50 sailliseconds to .pro ___*s e ^' ffectxve retroperfusion of oxy ena e blood ^" i,*®,to the rayocardium. &ø The .3lots ^" 25 •e-rteft lengthwise a distance sufficient

&_o substantially presrβi-t pooling of the blood, i.e., the formation of stagnant regions of blood, in the balloon •chamber 21 _* In the preferred embodiment, as shown in FIG- 1 _* the cage comp ises six slots. Each slot is about 2 ₅ JO.230 inch iϊa length and has a circumferential width of about Q-025 i ^< nch„ This leaves about 0.060 inch on each end of the cage for bonding to the catheter tube sections. Thus approximately fifty percent of the circumferential .area between he main catheter body and the catheter tip defines openings into the balloon chamber.

The slots in the cage wall may be made by electron discharge _i.achi_.i__g (ED ), followed by electrochemical εtachining to r mote sharp edges. These processes do not alter the stainless steel metallurgy. The metallurgical 5

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-10- propertias of the cage are therefore controlled by selecti of the appropriate grade of stainless steel tubing.

Another preferred embodiment of an autoinflatable catheter ap licable to such a procedure is shown in FIG.

* _.- In this embodiment, a main catheter body 11 and a a. es e ti 12 of similar construction as previously ascribed f r the s_r_bodi-enfe shown in FI__ 1 are connected fey a balXocϊ, support 26 _* A balloon 14 is positioned surrounding ch-e supp t balloon and is attached to the

Z- main catheter body an catheter tip also as described in the previous e_ubo i__ie__t_

The balloon support 26 comprises a plurality of spaced generally-parallel rods 27 definite a generally cylindrical shape- e rods are attached at their anterior

___ ends to a first generally-circular ring 2 and at thsir posterior end to a second generally-circular ring 29. The rods and rings may be made of metal or non-metal material. It is presently preferred that the rods and rings are _sade of stainless steel wire having an outer

₂₀ diameter b-out Q- 1Q inch. Attachment of the ends of the rods to the rings is preferably made by welding to form a strong bond. However the welding may alter the metallurgy of the stainless steel in the immediate area of the vel . If the altered metallurgy s incompatible

25 with the liquid^ e.g_, blood, flowing through the cathether _r this method of attachment would be unsuitable.

The rings have an inner diameter substantially the same as the outer diameter of the posterior end of the catheter tip and the anterior end of the main catheter

3 ₃ body, generally from about O.C€ø inch to about C.lδO inch _* The anterior ring 28 is attached afoσct the posterior and 17 of the catheter tip 12 and -the posterior ring 29 is attached about the anterior er. 19 of the ".sin catheter bo 11. Attachment is made by __ compatible adhesive. The

,-»__. thickness of the wall of the main catheter body at its

-11- aj. erior end and. of the catheter tip at its posterior end say be ed ce as shown to minimize the increase in catheter dxajaete., -at these positions. he rods a e sufficiently st o g to supply the _. stiffness required b* the cage to prevent bending and p impi g. ke o * »__ ^■ __ s ced apart suf iciently to for pehir-gs 31 b ween the interior of the s ppor cage 25 and t e balloon chambe 21 that do not signi icantly restrict p ssag of li uid into and u of e balloon ch mber. In addition,, the openings exten completely betwe n the sain catheter body an the catheter ip/ ineyeby e fectively reven ing poollag of a liquid is the balloon t- asibetr _* The size of the o enings is suf icient to _ai_.inize damage to liquids such as oloo 5 .passing th-cough the openings.

For catheters having non-oir uiar cross-sections, the ejsbodi-tients .-shown in both FIG _* 1 and FIG. 2 may be modified for -u.se in such catheters. The cross-sectiona configuration of the cage is formed into a configuration 0 corresponding t© -the cross-sec ional shape of the catheter tube sections.

If the main catheter body has a different cross- sectional con iguration than the catheter tip, the rod and ring cage construction as shown in FIG. 2 is preferred 5 because the anterior and posterior rings may be formed into different shapes to correspond to the catheter tube section to which they attach.

In addition to applications such as the retroperfusio of blood to the myocardium_■ an autoin latable catheter 0 constructed according to the present invention may be used in other applications such as the delivery of saline plus an intervention to a patient.

The preceding description has been presented with reference to the presently preferred embodiments of the 5 invention shown in the accompanying drawings. Workers

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-12- _. _, _* ;_. ^"* ' in t_ie art aπεi techology to which this invention ^* -__r s ^! »r_-_ will appreciate that alterations and changes i." t.J. desc ibed apparatus can be practiced without ,-.--__ -t .^St _^ ^' lly άe artinr. fron the principles, spirit and S, *t <~_ $z t is i venhioΛ, Accordingly, the foregoing

_._*__ ^• e ion sΞ*_- ^« _tia nc; o--? read as pertaining only to the ρ*_..*■_; ^{' •} _-* s uc ures des-i ise , but rather shoul he read •_ ^■ &"&_ ^' %-.- ^■ _- ^■ - with and as support for the following claims ^■ wffeicj* e to have their fullest, fair scope.

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