beyond the distal tip of the catheter, the fold remains
SNARE-TYPE PROBE and inhibits the wire from expanding into a loop in the
absence of relative axial movement of one wire strand
FIELD OF THE INVENTION with respect to the other.
The present invention generally relates to devices 5 °nce a looP has been formed, the foreign body frag
used in medical procedures and has particular utility for ment may be ensnared within the loop. Repeated passes
retrieving items from cavities within the body. at a free end of the fragment frequently must be attempted before the loop passes over the fragment. Suc
BACKGROUND OF THE INVENTION cessfu] engagement is indicated by movement of the
During medical procedures which utilize catheters 10 fragment, usually viewed with fluoroscopic equipment and guide wires, a distal portion of the catheter or guide Once engagement has been accomplished, the foreign wire can sometimes accidentally detach from the rest of article is pinned between the loop and the distal tip of the article and be left within the patient. This fragment the catheter. This may be performed by either (1) remay then travel, e.g., within the vascular system until it tracting one strand of the folded wire, making the loop comes to rest either within a vein or artery, usually at a '5 smaller, or (2) relative movement between the entire branching point, or in a body cavity, such as the heart. wire and the catheter, usually by advancing the catheter The results of leaving these foreign bodies within a over the wire until it closely contacts the ensnared patient can be quite harmful, and include septicemia, body. The entire system, including the item to be remultiple pulmonary emboli, perforation, and even sud- trieved, may then be retracted while engagement of the den death. 20 item against the catheter tip is maintained.
In the past, foreign articles were often left in place The snare technique is often rather difficult to utilize
despite these grave risks because the procedural options successfully, however. The wires used are commonly
for removal were highly traumatic. The risks associated standard guide wires formed of stainless steel or like
with open heart surgery to remove items lodged in the metalS; which have a te„dency to kink, particularly if
heart, for example, may well outweigh the problems 25 ... diameter wjres are used Such thin wires are
inherent in allowing the article to remain. necessary in many applications, however, because a
Safer techniques were then developed to remove double tnickness of the wire must ^ passed through the
foreign objects from the body. These techniques use a innw lumen of the ... ^ the diameter of the
grasping mechanism earned within a catheter to grip ... js fe the sJze Qf ^ ... tfa h
he foreign object and retract it to a more accessible 30 ^.^ h d requirement of small diameter
location or even out of the patient through the cathe- , ° j, . .. ..
. , .. c . r ° wires decreases stiffness, and hence controllable maneu
ters site of entry. .... , 'T .... .. .
Three basic configurations of grasping mechanisms verabihty, of the wire. Lower maneuverability limits
are most commonly employed: a modified urological utlhty m acces*lnJ remotely hxf^ fragments and
stone basket, rigid forceps, and a snare comprising a 35 makes it more difficult to control the loop when at
loop of wire extending from the forward end of a cathe- ^ptIfng t0 paSS the loop °VCr * pOTtl0n °f the f°relgn
ter. The stone basket technique utilizes an assembly of a body fragment.
plurality of wires within a sheath, the assembly being Snares known ln the ■« suffer MOther deficiency as
threaded through a catheter. The wires are all joined at welL The looP that IS formed at the llP necessarily lies
their distal end and, when the wires protrude beyond 40 m a plane parallel to the catheter. Unless a free end of
the tip of the sheath, the wires become spaced away the foreign body fragment happens to be substantially
from one another to define a wire "basket." The basket perpendicular to the plane of the loop, slipping the loop
is closed by retracting the wires within the sheath and over the fragment may require many passes at the item,
opened by advancing the wires through the tip of the If this is unsuccessful, the physician ma have to resort to
sheath 45 prodding the item to reorient the free end into a more
Forceps used in these types of operations are much acceptable position. While this may work in larger cavi
like those used in bronchoscopic procedures and com- ties where there is room to maneuver, the position of
prise a pair of rigid fingers which may be urged toward the loop may be problematic if the fragment has trav
one another to pinch the object therebetween. Use of eled to a remote site within a vessel where movement is
these devices is limited almost exclusively to items' 50 much more limited.
lodged in relatively large cavities such as the right Attempts have been made to avoid these problems,
atrium or venacava. Although this instrument has one The basket mentioned above has been suggested as
major advantage in that it may grasp the item to be superior in some instances because the multiplicity of
retrieved at any point, the rigidity of the instrument wires with slightly varying orientations ma increase the
limits maneuverability and creates a risk of perforation 55 chance of grabbing the fragment. At least one re
of the walls of the cavity or vessel. searcher has attempted to solve this by providing a loop
The third grasping mechanism, the snare, is probably which extends to the side of a central, straight guide
the most widely used. Commonly, a long wire is folded wire. (See Bloomfield, "The Non-Surgical Retrieval Of
in half and the folded end is passed through a catheter Intracardiac Foreign Bodies An Internationa] Survey,"
from its proximal end to its distal end adjacent the arti- 60 Catheterization And Cardiovascular Diagnosis, 4 (1978),
cle to be retrieved. Once the folded end portion of the 1-14.) This instrument incorporates a standard guide
wire extends beyond the distal tip of the catheter, one of wire and catheter with a loose nylon thread carried on
the two proximal ends of the wire is retracted to induce one side of the catheter. The thread is attached at two
formation of a loop in the distal end adjacent the end of points along the exterior of the catheter, forming a loop
the catheter. A suitable loop usually will not form with- 65 which hangs to the side of the apparatus. This device
out such relative movement of the two strands of the has rather limited use due to the lack of control over the
folded wire. A permanent bend or crease is necessarily slack nylon loop and the inability to cinch the loop to
formed in the wire when it is folded. When it protrudes tightly grip the fragment, which can severely hamper
