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C H A P T E R 143

MECHANICAL INTERVENTIONS IN ARTERIAL AND

VENOUS THROMBOSIS

Steven Sauk and Suresh Vedantham

Arterial and venous thromboses are common medical conditions that Catheter-Directed Intrathrombus Thrombolysis
are associated with significant morbidity. Patients who suffer from
acute occlusions of the peripheral arteries may present with ischemic Catheter-directed intrathrombus thrombolysis (CDT) refers to the
extremities, culminating in limb loss or death if left untreated. Those infusion of a fibrinolytic drug directly into the thrombosed vessel via a
who suffer from venous thrombosis are not only at significant risk catheter that has been inserted into that vessel using imaging guidance.
for recurrent thrombotic episodes and pulmonary embolism (PE), The rationale for CDT is to improve the efficacy of thrombus dissolu-
but are also at risk for the postthrombotic syndrome (PTS), which tion by achieving a higher intrathrombus concentration of fibrinolytic
can cause significant impairment of their long-term quality of life drug, and to reduce the risk of hemorrhage by enabling the use of lower
(QOL). total fibrinolytic drug doses than those required for systemic fibrinolysis.
For many patients with symptomatic arterial or venous occlusions, Although several catheters and devices have been approved by the US
surgical therapies are required in addition to standard medical treat- Food and Drug Administration (FDA) for this purpose, none of the
ments to provide optimal patient outcomes. Spurred by advances in currently available fibrinolytic drugs is FDA approved for the specific
vascular imaging and catheter/device technology, and driven by the indication of peripheral arterial or venous thrombosis.
clinical needs of the large number of vascular patients with concomi- Although the procedural details are beyond the scope of this chapter,
1
tant comorbidities, many patients are now referred for nonsurgical, the principles of CDT are reviewed here (Fig. 143.1). First, a vascular
imaging-guided endovascular interventions to eliminate thrombi and access site is selected based upon the thrombus location and extent,
to treat associated vascular lesions. In this chapter, we discuss the use and needle access into the vessel is obtained. With ultrasound-guided
of catheter-based interventions in the management of arterial and venipuncture, access site bleeding is rare. Under fluoroscopic guidance,
venous thromboses. the needle is exchanged over a guidewire for an angiographic catheter
and iodinated contrast is injected to delineate the location, extent, and
OVERVIEW OF CATHETER-BASED THROMBOLYTIC morphology of the thrombus and the status of other relevant vessels in
the limb. The angiographic catheter is then exchanged for a specially
INTERVENTIONS designed infusion catheter with multiple side holes (akin to a soaking
garden hose) that is positioned such that the side holes are embedded
Systemic thrombolysis, which refers to the dissolution of thrombus within the thrombus-containing vascular segment. Fibrinolytic drug is
via the administration of a fibrinolytic drug into an intravenous line then infused. The drugs and doses commonly used for this purpose
distant from the affected site, can be a valuable treatment option for include rt-PA (0.01 mg/kg/hour up to 1.0 mg/hour), and rt-PA vari-
acute myocardial infarction (MI), massive PE, and acute ischemic ants such as reteplase (0.25–0.75 units/hour), and tenecteplase
1,2
stroke. A primary advantage of the systemic administration route is (0.25–0.50 mg/hour). The procedure is done under conscious seda-
the ability to rapidly initiate therapy in almost any clinical setting, tion and with local anesthesia, and the heart rate, blood pressure, and
without the need for specialized technical expertise or hospital oxygen saturation are continuously monitored.
resources. However, only a fraction of systemically administered drug Patients are then transferred to an observation unit, usually an
reaches the target vessel. This problem is compounded when there is intensive care or step-down unit, for monitoring during the fibrino-
complete occlusion of blood flow in the target vessel such that access lytic drug infusion. Typically a concomitant infusion of unfraction-
of the fibrinolytic drug to the interior of the thrombus is precluded. ated heparin at subtherapeutic doses is administered and the
For acute MI and stroke, this limitation is overcome by the use of hemoglobin, activated partial thromboplastin time (aPTT), and in
relatively high concentrations of fibrinolytic drugs (e.g., 50–100 mg some centers, the fibrinogen level are measured every 6–8 hours while
of recombinant tissue plasminogen activator [rt-PA]) and the ability the fibrinolytic drug is given. Patients are monitored closely for evi-
of arterial pulsations to force sufficient amounts of the drug into the dence of bleeding and for changes in limb status, and the drug
fresh thrombus that occludes a small (2–4 mm) coronary or cerebral infusion rate is adjusted (or stopped entirely) as necessary. After 6–18
artery to effect fibrinolysis. However, with these high doses of fibri- hours, patients return to the procedure room for a follow-up veno-
nolytic drugs, there is a small but significantly increased risk of major gram or angiogram to assess the extent of thrombus dissolution. The
bleeding, a price that physicians are willing to pay given the poten- infusion catheter may be repositioned and the infusion continued if
tially fatal consequences of ongoing vascular occlusion in these there is residual thrombus. Once thrombolysis is nearly complete, the
critical sites. fibrinolytic drug infusion is stopped and, based on the results of the
For occlusions in the peripheral arteries and veins, however, sys- venogram or angiogram, a decision is made as to whether adjunctive
temic fibrinolysis is not sufficiently effective to justify the attendant treatment with balloon angioplasty or stent placement is needed—if
risks, presumably because of the larger vessel size, greater thrombus so, this is performed, usually through the same vascular access site
burden, and the presence of mature thrombus that is less susceptible during the same procedure session. The catheter and sheath are then
to dissolution. For these reasons, catheter-directed fibrinolysis and removed and systemic anticoagulation at fully therapeutic levels is
mechanical methods for thrombus extraction and dissolution have reinstituted. The treated limb is closely monitored for improvement
been developed. in pain, perfusion abnormalities (arterial), and/or swelling (venous).

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