Thrombolysis in Acute Limb Ischemia

Surgery versus Catheter Intervention

The debate between surgical revascularization and endovascular thrombolysis has been ongoing since the 1990s, with two randomized control trials (RCTs) serving as the foundation. Post hoc analysis of one of the RCTs—the Surgery versus Thrombolysis for Ischemia of the Lower Extremity (STILE) trial—concluded that in patients with symptoms of ischemia of 14 days or less had better amputation-free survival at 6 months with thrombolysis over surgery. In the Thrombolysis or Peripheral Arterial Surgery (TOPAS) trial, the rates of limb salvage and death were comparable. In both trials, the rates of hemorrhage and complications were higher in the thrombolysis groups. Despite no clear superiority in 30-day limb salvage or mortality, surgery continues to be performed 3–5 times more often than CDT, based on European and United States national registry data, and are likely secondary to the feared complications that will be discussed later in this chapter.

Catheter-Directed Lysis

The principle behind CDT is the dissolution of clots to uncover the underlying lesion that caused thrombosis. Additionally, it offers the advantage of lysing both large and small arteries, potentially providing better run-off. The likelihood of successful reperfusion with CDT increases when the occlusion is less than 14 days old, the thrombus is easily crossed by a wire, the graft being lysed has been patent for at least 1 year, and if a culprit lesion is found and can be treated ( Fig. 31.2 ). In fact, one study reported a 2-year native vessel patency rate after lysis of 79% if a lesion was found and treated versus 9.8% if no lesion was found.

The authors’ practice is to access the contralateral femoral artery with a single puncture in a retrograde fashion, typically under ultrasound guidance in order to minimize the likelihood of puncture site hematomas. Diagnostic images are obtained to evaluate the extent of thrombosis and the quality of the outflow. After the extent of thrombosis is defined, a 4- or 5-French Cragg-McNamara (Covidien, Mansfield, Massachusetts) multi-side-hole catheter is embedded in the thrombus. If the clot extends into the tibial vessels, a ProStream (Covidien, Mansfield, Massachusetts) infusion wire is used in a coaxial manner ( Fig. 31.3 ). Although there is controversy over the dose and rate of thrombolytic delivery, the author uses a 2–4-mg bolus of rtPA followed by an infusion rate of 0.25–1.00 mg/h through each catheter. UFH at 500 units/h is infused through the sheath to prevent pericatheter thrombosis. Follow-up angiography is performed 6–12 hours later. During the follow-up angiogram, depending on the rate of clot clearance, the operator may opt to continue lysis by repositioning the catheters or finalize the procedure by ballooning or stenting uncovered lesions as needed.

While infusion catheters are in place and lytic agents are actively being administered, ICU management is commonly advocated. Continuous monitoring of vitals and neurologic status are essential. Any change in neurologic exam or sudden headache should be treated like a hemorrhagic stroke until ruled out by CT scan. The ICU can also provide hourly access site surveillance to ensure no growing hematomas and to perform regular neurovascular checks to evaluate the progress of lysis. Controversy exists on whether laboratory monitoring is essential. It is the authors’ practice to check hemoglobin and fibrinogen levels every 6 hours and to titrate the infusion rate with precipitous drops in fibrinogen. If levels decrease by 50%, the infusion rate is generally halved. At fibrinogen levels below 100 mg/dL, the infusion rate is decreased to 0.25 mg/h or paused entirely.

Patients are routinely kept on either clear liquid diets or no food at all. They are maintained on bedrest while the femoral sheath is in place, with the leg kept straight to decrease risk of puncture site hematoma. A Foley catheter can be utilized, which will also help with urine output monitoring.

Intravenous hydration while restoring flow to an acutely ischemic limb is essential. Reperfusion of the ischemic limb leads to release of acidic metabolites and myoglobin and can lead to metabolic derangement and/or renal failure. Patient education is also tantamount. Patients undergoing CDT should be informed that their pain may wax and wane with microembolization and then subsequent lysis of emboli. If PMT is used, tea-colored urine may result from red blood cell lysis. This is especially true with the AngioJet device discussed in the following section.

Pharmacomechanical Thrombectomy

One of the limitations of CDT is the time to reperfusion may not be rapid enough to prevent irreversible neuromuscular injury. This is precisely why Rutherford IIB ischemic patients generally undergo open surgery rather than lysis. However, since the advent of CDT, innovation has introduced endovascular mechanical clot removal devices that can be considered in conjunction with pharmacologic thrombolytics to accelerate clot dissolution and, in turn, decrease the dose of lytic agent given. Below are the three most widely used catheters for PMT in ALI.