William Emmanuib

J.

Drasler, PhD I. Protonotarios,

Rheolytic Removal

#{149} Mark

MS

L. Jenson, #{149} Robert

Catheter for of Thrombus’

The authors present a percutaneous thrombectomy system (rheolytic thrombectomy catheter [RTCJ) in which high-velocity jets of saline solution are used to lyse and remove thrombus. The catheters (4-6 F) direct a 10,000-15,000-psi (0.7-1.05 x 10kPa) jet of saline solution onto an exhaust port from orifices at the end of the catheter. The jet entrains clot and resulting fragments and brings them into the high-velocity region for lysis and removal. Whole blood clots (10-15 cm) placed in 6-9-mm-diameter tubing were completely dissolved and removed with the RTC in less than 1 minute. In vivo use in a canine model resulted in lysis and removal of clots from a femoral artery, without vessel damage. The small caliber, flexibility, and effective lysis of this system suggest its potential usefulness in large central vessels that are difficult to access surgically and in small-diameter vessels that require more rapid removal of thrombus than can be achieved with thrombolytic therapy. Index terms: Catheters technology #{149} Thrombolysis, bosis, experimental Radiology

1992;

and

catheterization, 9*12992

#{149} Throm-

182:263-267

R

J.

BS #{149} Gregory G. Dutcher, MS

Wilson,

MD, FRCPC #{149} Joseph C. Possis, BMechE

#{149} Zinon

Percutaneous

EMOVAL

veins,

of thrombus and vascular

creasingly common acute ischemia and

venous outflow five to balloon bytic therapy tomy, alone angioplasty,

from arteries, grafts is in-

for treatment reestablishment

of of

and is often adjuncangioplasty. Thrombo-

on mechanical or in combination anticoagubation,

thrombecwith or other

procedures, is becoming more cepted as a treatment for acute nary being

accoro-

and peripheral ischemia examined as treatment

vein thrombosis and bolism. Thrombobytic streptokinase,

and is for deep

pulmonary therapy

urokinase,

emwith

or another

plasminogen activator is the most common form of such treatment but the risk of hemorrhagic complications, along with the length of treatment time, limits the use of thrombobytic

drugs

(1).

Various

mechanical

thrombectomy methods are also used, including the time-honored Foganty balloon embolectomy procedure and other newer catheter systems. Several mechanical systems ablate thnombus but and

do not others

bus

with

remove attempt suction

the debris to remove

due

to size

We developed small,

(2-4), throm-

or mechanical

(5-8). Some of these devices ited in the channel size that necanabized or are otherwise some

or stiffness

a method

high-velocity

jets

means

are limcan be cumben-

of saline

same From neapolis,

Possis Medical, 8325 10th MN 55427 (W.J.D., M.L.J.,

R.G.D.,

Z.C.P.),

and Toronto

General

Ave N, MmJ.M.T., E.I.P.,

Hospital

and Hospital for Sick Children, Toronto (G.J.W.). Received January 14, 1991; revision requested February 25; final revision received July 22; accepted August 12. Address reprint requests to W.J.D. W.J.D. is vice president of research and development for Possis Medical, the company that developed and will manufacture the thrombectomy device described in this article. 2 9* indicates generalized vein and artery involvement. ,,

RSNA,

1992

percutaneous

catheter.

The

sobu-

apart. The fragments of thrombus rccirculate in this region and repeatedly pass near the jets until they are bro-

into

smaller

and

smaller

remnant

pass

into

particles.

thrombus an

particles

exhaust

lumen

then

near

the

catheter tip and are removed through the catheter. An additional jet impinges on the exhaust lumen and provides a barge stagnation pressure to aid in the evacuation of the thrombus debris and to further break up any fragments that may be too large to pass

into

the

lumen.

The jets are oriented such that direct close-range impingement onto the vessel wall is avoided; thrombus removed from the vessel wall primariby by

the

fluid

tion.

A balloon

helps

to center

mixing

and

at the

catheter

the

tip

ments.

The

source

pressure

(2.1

x i0

device

tip

to keep

can

the

be used

of at least

kPa)

and

can

is

necircula-

away from the vessel walls, and lates the region, thus minimizing potential for escape of thrombus

jets

isothe fragat a

30,000

cut

psi,

a variety

of materials at the higher pressures. Because high pressures arc not necessary to break apart thrombus and because

they

could

be dangerous

to the

vessel wall, the RTC is used at up to approximately 15,000 psi (1.05 x 10 kPa) for thrombectomy. This RTC system has shown promisc in initial

in vitro

iments

may

and oven

present testing of the

other

report of the possible

and

offer

in vivo

clinical

methods.

exper-

advanThe

describes the initial RTC and suggests some applications of this

system.

mul-

tiple small-diameter jets at the tip of a rheobytic thrombectomy catheter (RTC) are directed into a thrombus. These high-velocity jets have sufficient energy to cut into the thrombus and create a region of intense fluid mixing in the region of the thrombus, which helps to break the thrombus

ken

The

tages

(5,7).

in which

tion from a catheter tip are used to break up thrombus and allow withdrawal of the resulting debris via the I

M. Thielen

MATERIALS Device

AND

METHODS

Construction were

fabricated

of 4-6-F

2.0-mm

outer

diameter)

dual-lumen

ing

1). The

RTCs (Fig

the inflation

Abbreviations: rafluonoethylene, tomy catheter.

smaller

lumen

ePTFE RTC

lumen

for a latex

= =

expanded rheolytic

(1.3tub-

was

used

balloon

as

(to

polytetthrombec-

263

RHEOLYTIC THROMBECTOMY

SYSTEM

Figure 1. RTC is 2 mm in diameter and contains seven jet orifices at the tip. Six equally spaced jets form a conical pattern around the catheter and provide the necessary circulalion patterns for clot lysis, and one jet impinges on the exhaust lumen to aid in debris withdrawal. The guide wire and exhaust lumen (the same lumen) can be seen; no centening balloon is shown.

Rheolytic center

the

also

catheter

coaxially

contained

stainless-steel larger lumen debris lumen.

tip in the vessel) high-pressure

tubing provided

to supply the jets. A for the exhaust of

and was also The catheter

eight

jet orifices

(0.001-0.002

that

were

inches)

impinged debris

used as the tip contained

guide-wire four

25-50

evacuation;

the

to

One

lumen

RTC

system

remaining

is shown

supplied

to the

catheter

jets

were

in Figure

pressurized and

was

saline activated

was

with

minor

capable

of providing

saline solution to 30,000 psi in the present

of the

to the

per

passed through of exhaust woubd

sion. Although exhaust lumen exhaust

vent

and

sufficient

flow

flow,

exhaust

a roller equal

pump that

of

catheter at up The catheters used 50 mL

port so the of saline

the

pump

flow

was

through

used

atrate infu-

to pre-

the exhaust

lumen.

In Vitro

Testing

eter,

264

(ePTFE)

6 mm)

vascular

and

#{149} Radiology

to obtain

at one the pores

better

was advanced functioning

was

grafts

allowed

clot,

in the The

inflated

so they

some each

would

pressure to) tube or graft,

ten was The

used

catheter

procedures

same materials embolectomy

four farther

advanced

In cathe-

times.

used

through

the whole length. The was opened longitudinally

approximately

two

more

through

the it was times

tubing or and pho-

tographed.

which and guidepump

debris;

Small arteries,

were

distal

(inner

diam-

sd branches bosis in the

to clot.

The

were

used

placed

to the

graft,

grafts femoral anThe grafts in diameter.

on the and

femorab

nearby

yes-

were ligated to ensure thromgraft and vessels. No additives to aid

clamps

was

inserted

the femorab

artery

artery

and

the

in thrombus

formation.

were either

or graft into

the

or fem-

oral artery by advancement with a guide catheter under fluoroscopic guidance. Aften the thrombus was reached, the RTC was advanced through the vessel with the jets functioning; the thrombus was lysed and removed by using the RTC at 10,00015,000 psi (0.7-1.05 x io kPa). Heparin was not used in the saline solution supplied to the RTC, but was administered intravenously thrombosis

after

ing balloon

was

to avoid any thrombobysis.

inflated

artifactual The

during

ation, and cane was taken inflation, so that the chance

from

bnis

passage

saline

center-

RTC

open-

to avoid ovenof vessel

the centering

balloon

be minimized. The centering served to isolate the debris

would

balloon and block

also de-

the vessel; the infused mixed with the debris and

along

solution

carried it out the exhaust lumen. A balloon embolectomy-thrombectomy

was

performed

in the

crab vessel as a control; artery on the graft was

Testing

clamps

distal

RTC

a carotid

procedure

In Vivo

the an

into

damage

each

passed through or graft, and

then graft

apply

material walls. embolectomy

approximately

it could be length of tubing

used as were

(and

was

until

whole

touch

the the

per-

were balloons

days,

and

directly

through the and the centering

embolectomy

formed a control.

3-7

After removed,

adhesion.

Bilateral ePTFE intcrpositionab were placed in the superficial teries of six 28-38-kg canines. were 3-5 cm long and 5 mm

Fresh animal blood was placed in woyen polyester tubing (inner diameter, 8 mm) and expanded polytetrafluoroethylene

RTC jets

time,

was

clamped through

the clot was allowed to age for 1-7 the RTC was used to lyse the clot.

Balloon

the jet impingement on the was sufficient to drive the

excessive

used to limit the flow of exhausted thrombus the catheter to a disposable collection bag.

balloon inflated, and the exhausted debris was collected. The clamps were left in place to ensure that the catheter did not simply push the clot.

a

The steady

minute at 10,000x i0 kPa). Tubing

catheter

days, The with

grafts were was forced

material

After

solution

variation

to supply the (2.1 x 10 kPa). study typically

of saline solution 15,000 psi (0.7-1.05

tached

cyclic

and also drives the roller pump thrombus debris is carried from

tubing and end; blood

2. A

with

footswitch by the catheter operator. pump provided an approximately pressure

A bag of sterile saline solution supplies a disposable pump, and supplies the RTC. The centering balloon inflation port shown. A nondisposable unit drives the disposable high-pressure

jet

standard saline solution bag was used for the supply, and a similar empty bag was used to coblect the exhausted thrombus debris. A disposable positive-displacement pump

RTC system. the solution access are

to aid in

oriented at a retrograde angle to avoid direct contact with the vessel wall while providing the necessary mixing and recircubation for effective clot lysis. The

Figure 2. pressurizes wine lumen

im

in diameter.

on the exhaust

Thrombectomy Catheter

and

Radiographic suits were

and

After

explanted,

the

femoral access.

procedures

procedure,

stained

collected during was examined

animal,

for

contrabat-

of the ne-

control

and examined with electron microscopy.

one

the

documentation

of study

obtained.

either used

RTC

with

was

the vessels Evans

blue,

bight and scanning Distal effluent was use

in

two

cases

and

for particulate matter. In the RTC was passed at 10,000

January

1992

dispensed, thrombus

diffuse residual mural was apparent on radio-

graphs

obtained

after

the

balloon

cedure; back of fluonoscopic and evaluation during the may

have

contributed

thrombus.

Figure

graphic

a.

b.

Figure 3. Radiographs documenting thrombectomy performed with the (a) Left femonal stump indicates occluded femoral artery and ePTFE graft; seen distally verify that an adequate amount of contrast medium has been diate results show patent artery and graft. Graft anastomoses can be seen.

All

experiments

animal

care

RTC in a dog. small branches infused. (b) Imme-

complied

and

use

with

guidelines

(9).

in the polyester grafts resulted

in

bysis of the clot in each case. A typical 10-cm-long clot was lysed and removed at 10,000-13,000 psi (0.7Figure

4.

Femoral

artery and graft thrombectomy

planted 2 weeks after the RTC. The specimen Evans

blue

damage.

stain

was treated

to examine

The proximal

for

artery

cxwith

0.91

x i0

RTC

left very

with

bus, less than that left with the Fogarty procedure; the walls of even the 8-mm-diameter tubing were cleaned effectively with the 2-mm-diameter

endothelial

is at the left.

The 5-mm-diameter, 3-cm-long ePTFE graft indicates the size of the specimen. The nonendothelialized surface of the graft absorbed

the stain

and

served

as a positive

psi

(0.7

io

x

kPa)

without for graft

through

a manner

similar

bolysis, and immediately. was allowed

damage catheter

to that

the vessels In another to recover

used

ing.

Volume

182

#{149} Number

The reto

resulted from was passed in for

throm-

were explanted case, the animal for 2 weeks before

radiography was performed were explanted and stained nations of patency and the

1

minute.

The

remaining

throm-

and vessels for determiextent of heal-

Testing RTC

was

used

to byse and

rc-

move occlusive thrombi from eight vessels. The average age of the thrombus was 4 days (range, 3-7 days). The

average

pressure

used

was

12,000

psi

(0.84 x i0 kPa). The RTC was successfully used to remove thrombus and restore patency in all cases. The

RTC for

jets 1-2

were

typically

minutes

functioning

in each

loon

thrombectomy

used

to open

stain, whereas tery absorbed

four

vessel.

procedures vessels.

the

native

femonab

an-

of thrombus. attributable marks

seen

were

near

the

graft.

The

pattern

Bal-

were

of damage

that

was

consistent shearing Histologic

with the stretching and forces imposed by a balloon. and scanning electron mi-

croscopy

examination

strate

significant

in the vessels used. Figure vessel use.

did

damage in which 5 shows

not

intact

intima

the RTC was a small focal fi-

in an otherwise

with

demon-

to the

elastica

normal after

RTC

For most of the procedures, the RTC was contained in a guide catheten that helped to position the device and allowed for contrast medium delivery. In a few cases, the RTC was manipulated over a 0.014-inch guide wire, which demonstrated that the device can be used over a wire if neccssary. Debris

lumen clumps cells.

collected

from

the

exhaust

of the catheter consisted of of platelets and red blood Effluent

downstream ing

A randomly

initial

little stain and was free No vessel trauma was to RTC use, but clamp

brim deposit

RTC.

undisturbed

the manipulations placement on clotting,

determine whether the procedure. The

in one

little

control.

In Vivo

arteries, quired

kPa)

radio-

of the

occlusion and the immediate results of successful thrombectomy with the RTC; the graft anastomoses can be seen in Figure 3b. After the control balloon thrombectomy procedure was performed in the contrabateral vessels of several animals, the procedure was abandoned because of excessive bleeding, swelling, and other complications, which were possibly due to the procedure being performed in the area without sufficient time being allowed for healing after graft implantation. Explanted vessels after thrombectomy with the RTC showed little damage; the explanted graft and vessel obtamed from an animal 2 weeks after thnombectomy are shown in Figure 4. The nonendothebiabized surface of the ePTFE graft absorbed the Evans blue

stress

Testing

Use of the RTC tubes and cPTFE

residual

the

RTC was capable of removing 1-weekold thrombus from both the ePTFE graft and the native vessel. The vessels in which balloon thrombectomy was used showed a

standard

RESULTS In Vitro

to this

3 shows

demonstration

pro-

guidance procedure

the

blood

from RTC

procedure

that

the

was

collected

thrombus consisted

dunpri-

many of individual red blood cells with occasional platelet and red cell clumping (Fig 6). Radiology

#{149} 265

Figure

5.

Histologic

tery shows inner focal

elastic fibnin

wise

normal

of the

section

of femoral

ar-

intact

vessel wall and undamaged lamina after RTC use. A small deposit can be seen in the other-

figure

vessel.

The lumen

(original

is at the top

magnification,

x200). Figure 6. Light photomicnognaphs of exhausted debris RTC use. (a) Debris collected from the catheter exhaust seen, which indicates the scale (original magnification, downstream from the thrombus during thrombectomy blood cells (original magnification, x500).

DISCUSSION The potential for an effective

clinical applications thrombectomy system

are many. The ability of the RTC to lyse thrombi that were at least one

week ness

old in vivo in a variety

ability

to use

ously

offers

indicates

its useful-

of situations.

the

device

reduced

The

pencutane-

time

and

cost

of

treatment and less surgical trauma. The RTC may result in less vessel trauma than do Foganty-type balloon embolectomy procedures, which can produce various vessel injuries (10,1 1), and percutaneous access through an easily accessible periphcrab vessel combined with fluonoscopic

guidance

may

allow

the

treat-

ment of thrombi that are not easily treated with balloon embobectomy. Removal of thrombotic debris rather than fragmentation of the thrombus and creation of multiple small emboli seems

desirable.

Although

controlled

studies of distal embobization to verify the benefit of debris evacuation with the RTC have not been performed, the exhaust of debris from the catheten tip combined with the breaking of thrombus into small fragments seems preferable to balloon embobectomy procedures. Further testing is under way to abten the

angle

of the

retrograde

jets

that generate the necincubation pattern. Jets that direct the flow radially without an axial component tend to restrict any axial particulate embolization reflux proximal to the catheter tip. The centering balloon on the catheten shaft aids in restricting proximal and distal embolization. Additional research to evaluate the need for an 266

#{149} Radiology

and effluent blood collected during lumen. Single red blood cells can be x200). (b) Effluent blood collected consisted primarily of individual red

isolation catheter through which the RTC would be delivered is currently under way. This isolation catheter would contain an inflatable balloon affixed to its tip and could be positioned to protect side branches from possible embobization and to isolate the vessel from arterial blood flow during the rheolytic procedure. Although heparin anticoagulation would likely be used perioperativeby, the occurrence of bleeding complications

may

be less

lytic agents, due the RTC. Indeed, useful in patients lytic

drug

avoided risk

than

treatment

because

with

thrombo-

to the local action the RTC may be in whom thromboshould

be

of its associated

of hemorrhagic

of

high

complications.

In

addition, whereas thrombobytic drugs often require many hours to induce complete thrombolysis (1,12), treatment with the RTC may provide rapid symptomatic relief in a matter of a few minutes. The combination of thrombolytic drugs and the RTC is theoretically appealing. The RTC can serve to quickly

break

up

and

remove

barge

thrombi, and thrombolytic drugs would be effective on any remaining smaller thrombi, including debris that may not have been removed through the catheter and thrombi in distal yessels

that

are

too

small

for

access

with

the RTC. The addition of thrombolytic on anticoagulant drugs to the saline solution used with RTC may be a convenient means of delivering the drugs

and achieving tions at the

Other

appear

may

system. vessels

diameter is more

local concentrasite.

mechanical

devices

that

high treatment

thrombectomy

to have

shortcomings

be addressed The much

may useful

with

ability larger

of the than

indicate than

the

RTC

RTC to clear the catheter

that other

the

system

devices

that

produce channels of a size only simibar to that of the catheter (2,3,5-7). Treatment of an entire lesion with a single insertion of the RTC may be possible

due

to the

breaking

up

and

removal of thrombus through the catheter, and would thus avoid the repeated withdrawal and reinsertion required with some aspiration devices (6,7). Preliminary research with rheobytic catheters of similar size and flexibility has

demonstrated

catheters vessels possible

moval arteries follow

to gain in animals,

the

ability

access which

application

of these

to coronary suggests

of the

RTC

the in re-

of thrombus from coronary (13). The ability of the RTC a guide wire provides access

distal vascubatune and in peripheral applications Early in vitro testing

to to

side

branches as webb. demonstrated

that when the jets were spaced closer together, fewer passes with the device were needed to effectively clean the tubing walls. The earlier four-jet prototype

rheobytic

catheters

were

there-

fore replaced with catheters with up to seven jets. The present study did not attempt to quantify any differJanuary

1992

ences between the prototypes either in vitro or in vivo. The exhaust ability of the catheters is affected by the cxhaust lumen size, but other factors such

as jet

size

and

position

are

also

important. Smaller catheter tubing allows the use of smaller guide cathetens and sheaths; a barge guide catheten was used with all RTC prototypes in this study, but this technique could be optimized with smaller guide catheters used with smaller RTC prototypes in future studies. The variation of catheter tubing diameter was more influenced by the availability of suitable tubing than by choice; the flexibibity, handling ease, and exhaust ca-

Acute pulmonary emboli that require treatment present a variety of undesirable choices. Open-vessel surgicab embolectomy is associated with great operative risk (14), and thrombolytic drug therapy is time-consuming and involves the risk of bleeding complications. Rapid treatment of barge pulmonary emboli by a percutaneous device has been advocated (5,14), and the RTC may offer fast, effective treatment and thus reduce

2.

mortality

6.

and

morbidity.

In addition,

may follow (13). The RTC may be useful for treatment of vascular graft thrombosis, including saphenous vein

immediate lysis of any large thrombi in the deep veins by using the RTC may be desirable, to reduce the likeihood of recurrent pulmonary emboli. The ability of the RTC to follow a guide wire and gain access to coronary vessels suggests its possible use in acute myocardial infarction, after sufficient preclinical and clinical testing has been performed. In conclusion, the RTC system is effective for percutaneous bysis and removal of thrombus. The ability of the RTC system to lyse thrombus up to 1 week old has been demonstrated both in vitro and in vivo in canine arteries and in vascular grafts. Initial vessel examinations from short-term in vivo studies were favorable, and follow-up in one animal demonstnated patent vessels and ePTFE vascuban graft 2 weeks after thrombectomy with this technique. The size and flexibility of the catheter and its ability to follow a guide wine suggest possible application to the treatment of acute coronary thrombosis. #{149}

or synthetic bypass venous hemodialysis

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tubing

in this study, but in this study sucdebris in each

case. Infusion of contrast material through the exhaust lumen of the RTC allows assessment of the vessel without the use of a separate catheter. Use of fluoroscopy with the RTC may provide for timely treatment of the underlying disease. In the case of an arterial atherosclerotic stenosis, the thrombus may be rapidly and safely removed with the RTC, providing initial relief and aiding in nadiobogic examination of the stenosis, and standard dilation balloon angioplasty or revasculanization or mechanical atherectomy

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