An autoinflatable catheter is disclosed which comprises an elongated first catheter tube section forming a main catheter body, a short second catheter tube section forming a catheter tip, a balloon support extending between the posterior end of the catheter tip and the anterior end of the main catheter body and an inflatable balloon surrounding the balloon support. The balloon support comprises a rigid cage having a continuous hollow interior and openings for the flow of liquid through the cage to inflate the balloon. The openings are sufficiently large to not significantly restrict the flow of liquid through the openings and to prevent pooling of liquid in the chamber between the cage and the balloon.

FIELD OF THE INVENTION 
This invention pertains to catheters for use in the blood vessels of 
humans, as well as in animals 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 an 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 and 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.

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 connected 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 difference in the inner diameter between the 
anterior and posterior ends of the catheter tip is sufficient to create a 
pressure 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 mm 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 the 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 bag 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. The seals prevent leakage of liquid from the catheter. The seals may 
be made by conventional methods, e.g., tying with nylon thread 20 and then 
overlaying the juncture with a compatible adhesive 21 or by solvent 
evaporation techniques. The balloon forms a balloon chamber 22 between the 
balloon support and the balloon wall. 
The balloon support 13 comprises a generally cylindrical tubular cage of 
about 0.40 inch (about one centimeter) in length but may vary from about 
0.2 inch to about 0.6 inch. The cage has open anterior and posterior ends 
and a hollow interior, thereby forming an unobstructed pathway between the 
main catheter body and the catheter tip. The inner diameter of the cage 
ranges from about 0.060 inch to about 0.100 inch, depending on the outer 
diameters of the anterior end of the main catheter body and 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 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 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 and the anterior end of 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-catheter tip seal using adhesive compatible with the cage, the 
catheter tip and the patient's blood, e.g., a polyurethane adhesive. The 
posterior end 24 of the cage is attached in the same manner about the 
anterior end 19 of the main catheter body 11 and is positioned anterior to 
the balloon-main catheter body seal. This construction completely encloses 
the cage within the balloon. 
The cage comprises openings or slots 25 in the wall of the cage, forming 
passages between the interior of the cage 13 and the balloon chamber 22 
sufficiently large to not significantly restrict the flow of a liquid 
through the openings. In this application, the openings are large enough 
to enable blood to flow into the balloon chamber sufficiently rapidly to 
inflate the balloon and block the coronary sinus during diastole and to 
flow out of the balloon chamber sufficiently rapidly to deflate the 
balloon during systole, thereby allowing drainage of blood through the 
coronary sinus without significantly damaging the blood. The balloon is 
inflated in about 50 milliseconds to provide effective retroperfusion of 
oxygenated blood into the myocardium. 
The slots 25 extend lengthwise a distance sufficient to substantially 
prevent 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 comprises six slots. Each slot is about 0.280 inch in 
length and has a circumferential width of about 0.025 inch. 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 the 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 machining 
(EDM), followed by electrochemical machining to remove sharp edges. These 
processes do not alter the stainless steel metallurgy. The metallurgical 
properties of the cage are therefore controlled by selection of the 
appropriate grade of stainless steel tubing. 
Another preferred embodiment of an autoinflatable catheter applicable to 
such a procedure is shown in FIG. 2. In this embodiment, a main catheter 
body 11 and a catheter tip 12 of similar construction as previously 
described for the embodiment shown in FIG. 1 are connected by a balloon 
support 26. A balloon 14 is positioned surrounding the support balloon and 
is attached to the main catheter body and catheter tip also as described 
in the previous embodiment. 
The balloon support 26 comprises a plurality of spaced generally-parallel 
rods 27 defining a generally cylindrical shape. The rods are attached at 
their anterior ends to a first generally-circular ring 28 and at their 
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 made of stainless steel wire having an outer 
diameter about 0.010 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 weld. If the altered metallurgy is incompatible with the liquid, e.g., 
blood, flowing through the cathether, 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 body, generally from about 0.060 inch to about 0.100 
inch. The anterior ring 28 is attached about the posterior end 17 of the 
catheter tip 12 and the posterior ring 29 is attached about the anterior 
end 19 of the main catheter body 11. Attachment is made by a compatible 
adhesive. The thickness of the wall of the main catheter body at its 
anterior end and of the catheter tip at its posterior end may be reduced 
as shown to minimize the increase in catheter diameter at these positions. 
The rods are sufficiently strong to supply the stiffness required by the 
cage to prevent bending and crimping. The rods are spaced apart 
sufficiently to form openings 31 between the interior of the support cage 
26 and the balloon chamber 21 that do not significantly restrict passage 
of liquid into and out of the balloon chamber. In addition, the openings 
extend completely between the main catheter body and the catheter tip, 
thereby effectively preventing pooling of a liquid in the balloon chamber. 
The size of the openings is sufficient to minimize damage to liquids such 
as blood passing through the openings. 
For catheters having non-circular cross-sections, the embodiments shown in 
both FIG. 1 and FIG. 2 may be modified for use in such catheters. The 
cross-sectional configuration of the cage is formed into a configuration 
corresponding to the cross-sectional shape of the catheter tube sections. 
If the main catheter body has a different cross-sectional configuration 
than the catheter tip, the rod and ring cage construction as shown in FIG. 
2 is preferred 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 retroperfusion of blood to the 
myocardium, an autoinflatable catheter 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 invention shown in the accompanying 
drawings. Workers skilled in the art and technology to which this 
invention pertains will appreciate that alterations and changes in the 
described apparatus can be practiced without meaningfully departing from 
the principles, spirit and scope of this invention. Accordingly, the 
foregoing description should not be read as pertaining only to the precise 
structures described, but rather should be read consistent with and as 
support for the following claims which are to have their fullest fair 
scope.