27 Thrombectomy and Protection Systems

Aspiration Catheter

Aspiration catheters basically consist of a catheter with a terminal opening and distal side holes (Fig. 27.1). All aspiration catheters are 6F-compatible with an external diameter of 0.066 to 0.07 in. Larger catheters impede the pressure measurement via the guiding catheter. The systems usually have an internal diameter of 1.0 to 1.1 mm.

All catheters are advanced as monorail systems via a 0.014-in. wire. Aspiration is done with a syringe that is connected to the end of the catheter and used to generate suction. The most frequently used catheters are summarized in Table 27.1.

Fig. 27.1 Tip of an aspiration catheter.

Screw on the aspiration syringe with the stopcock in the locked position, apply suction, and lock the syringe.

For fresh thrombi and atheromas this is a very efficacious, fast, and uncomplicated intervention (Fig. 27.2).

Clinical studies have shown that aspiration catheters improve the perfusion in acute coronary syndromes.

Fig. 27.2 Thrombus material aspirated during an intervention for acute coronary syndrome (ischemia time < 12 hours).

Mechanical Thrombectomy

The ThromCat system (Spectranetics, Colorado Springs, CO, USA) is single-use and consists of a catheter, a control and drive unit, a collection bag, an infusion system, and a power cord with connection to a power supply (Fig. 27.3). Its function is based on the principle of the Archimedes’ screw (Fig. 27.4). The system contains two helices: one infusion helix and one extraction helix. The control unit drives the helices, so that the infusion helix pumps saline from the saline bag into the catheter and the extraction helix generates a vacuum of −700 mm Hg. The helix rotates at 95,000 rpm. The vacuum aspirates the thrombus into the openings of the catheter, macerates it inside the catheter, and transports it to the collection bag.

The catheter has a profile of 5.5F and a working length of 150 cm. The infusion rate is 15 mL/min and ~45 mL/min is extracted. The system has a flexible, atraumatic tip. The helix is completely encapsulated, thus there is no direct contact with the vessel wall.

Fig. 27.3 Individual components of the ThromCat system.

1 Catheter

2 Drive unit

3 Collection bag for the aspirate

4 Connection for flush

5 Electrical connection

Fig. 27.4 Tip of the ThromCat catheter.

Indications and Contraindications

The system consists of the individual components mentioned above (Fig. 27.3) plus:

1. Guiding catheter: size 7F (≥ 0.078 in.) or sheath: size 6F (≥ 0.078 in.)

2. Standard guidewire: 0.014 in.

3. Y-connector to be connected to the guiding catheter

Procedure

Preparation of the System

Connect saline to the designated line.

Connect the power cable.

Flush the system and remove any air.

Place the catheter tip in a saline bath and switch on the system at the control unit for an extracorporeal test run.

Procedure for Thrombectomy

Use only if the vessel diameter is > 2.5 mm.

The guiding catheter is seated. Then, the thrombus is crossed with the guidewire, and the wire tip is positioned as distally as possible.

The catheter is advanced up to the end of the guiding catheter.

After switching on the drive unit and opening the flush solution, the catheter is advanced through the lesion carefully and very slowly (~1 cm/5 seconds).

The procedure is repeated several times.

The system should be moved within the vessel only with the system running, if possible.

Withdraw the catheter into the guiding catheter and angiographically evaluate the procedure’s success.

Summary and Evaluation

The disadvantages of the technique are the equipment required and the associated costs. An advantage is the potential to completely remove older thrombi.

X-Sizer

The X-Sizer system (EndiCOR Medical Inc., San Clemente, CA, USA) consists of a helical rotating cutting system housed in the distal tip of a flexible double-lumen catheter. This system also works according to the principle of the Archimedes’ screw. The double-lumen catheter is connected to a hand-held, battery-powered control module that rotates the cutter at 2,100 rpm. The generated vacuum entraps the thrombus, the Archimedes’ screw draws in material and shears it, and then the material is removed by the vacuum lumen into the connected collection bottle (Figs. 27.5, 27.6, 27.7).

The system is available in two sizes: 1.5 mm and 2.0 mm cutting diameter. The procedure can be performed with 7F to 8F standard guiding catheters and 300 cm long 0.014-in. standard guidewires. There is no specific atraumatic, flexible tip at the catheter end (Fig. 27.7).

Fig. 27.5 Components of the X-Sizer system with catheter and control module.

Fig. 27.6 Mechanism of action of the X-Sizer system according to the principle of the Archimedes’ screw.

Fig. 27.7 Cutting system of the X-Sizer system with 0.014-in. wire.

The system (Fig. 27.5) consists of a pre-assembled system in two sizes (diameters of 1.5 mm [4.5F] and 2.0 mm [5.5F]) with a drive unit and two vacuum collection bottles.

Procedure

Preparation of the System

Removal of the lock wire from the control module

Flushing of the system with heparinized saline

Connection to the vacuum collecting bottle after occluding the tubing clamp

The system is held under water and the tubing clamp is opened to test whether the catheter is aspirating; then the tubing is clamped again and kept occluded until the system has been deployed.

Procedure of Thrombectomy

Premedicate with heparin and a GP IIb/IIIa inhibitor.

Place the guiding catheter.

The lesion is crossed with a 300 cm long 0.014-in. guidewire.

Advance the system via the wire to the distal end of the catheter and carefully position it before the lesion or occlusion.

Open the clamp that occludes the tubing to the vacuum collection bottle.

After switching on the drive unit, advance the catheter very slowly (≤ 1 mm/s) across the entire lesion.

Avoid known dissections.

Ablated material and blood appear in the vacuum bottle.

Repeat the cutting procedure several times.

Withdraw the X-Sizer catheter in the guiding catheter and undertake angiographic evaluation of the procedural success.

Summary and Evaluation

Disadvantages:

A stiff catheter tip with little flexibility

Risk of aspiration of dissection tissue

High cost

Advantages:

Standard guiding catheters and guidewires can be used.

The system is technically easier than the AngioJet catheter (see below)—no special drive console, etc. is required.

AngioJet

The AngioJet thrombectomy catheter (MEDRAD, Inc., Warrendale, PA, USA; Fig. 27.8) was developed to remove thrombi safely from the coronary arteries without embolization. From the catheter tip, six high-velocity saline jets are directed into a specially designed catheter, so that a vacuum is generated according to the Bernoulli principle. The thrombotic material is broken up and removed through the catheter.

To achieve this effect, a pressure of 6,000 atm (608 MPa) is applied to the catheter, which due to the decrease in pressure within the catheter is reduced to 170 atm (17 MPa) at the catheter tip. The six saline jets at the catheter tip can achieve speeds of up to 500 km/h (300 miles per hour) (Fig. 27.9). Before the procedure, the catheter is connected to a specific console and filled. The heparinized saline introduced into the catheter is directed on its return into a special collection container for later examination. Thus, in addition to thrombectomy, an effective thrombolysis is also done.

Due to the size of the catheter only vessels with a diameter of > 2 mm can be treated. The intervention can be performed with 6F standard guiding catheters and 190 cm long 0.014-in. standard guidewires.

Indications and Contraindications

The most important indications for thrombolysis and thrombectomy with the AngioJet system are

Coronary thrombi (filling defects) on angiography in unstable angina, acute infarction, or occluded vein graft

Thrombotic stent occlusion

The use of the AngioJet system is not indicated for

Atherectomy indications

Extensive, untreated dissections

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