The Power-Pulse Spray Technique
A novel simultaneous combination therapy allows rapid revascularization in critical limb ischemia.
Acute lower extremity arterial thrombotic occlusive disease can lead to critical limb ischemia (CLI) with impending limb loss if rapid revascularization is not provided. Open surgical thrombectomy, percutaneous chemical thrombolysis (CT), and percutaneous rheolytic thrombectomy (RT) are accepted CLI treatments, but the mortality, morbidity, and limb-loss rates have remained alarmingly high.1-3 Recently, RT and CT have demonstrated improved outcomes, yet both approaches possess limitations including long infusion and procedure times, incomplete thrombus removal, embolic complications, bleeding, and increased hospital resource utilization and costs.4-6 The novel Power-Pulse Spray (P-PS) technique was developed at the Cardiovascular Institute of the South (CIS), in concept, to simultaneously maximize the advantages and benefits of both RT and CT while minimizing their disadvantages and limitations. The P-PS technique aims to rapidly reperfuse the ischemic limb, lessen risks and complications, decrease ICU and hospital resource utilization, and improve clinical outcomes.
An 81-year-old white male with a history of diabetes, stroke, MI, PVD, hypertension, and a prior CABG presented with an acute onset of right leg pain, coolness, and weakness of 4-hour duration. Physical examination revealed a cool, pulseless, ischemic right foot (Figure 1). An urgent contralateral approach peripheral angiogram revealed a total occlusion of the proximal right common iliac artery below the aortic bifurcation. The thrombotic occlusion was crossed using a .035-inch guidewire, and the CIS P-PS protocol was used for revascularization. A discrete culprit lesion was unmasked after the pulsed tenecteplase (TNK) (Genentech, San Francisco, CA) was allowed to “lyse” for 20 minutes. A single balloon-expandable stent was deployed, providing revascularization in a total procedural time of 55 minutes. ICU monitoring was not required, limb salvage was achieved, and the patient was asymptomatic at 36-hour discharge and at 30-day follow-up, when a postprocedural angiogram revealed excellent results (Figure 2[ please refer to the print version of our March issue, page 26 to view this figure]).
RHEOLYTIC THROMBECTOMY: Angiojet
The AngioJet RT system (Possis Medical, Inc., Minneapolis, MN) includes a drive unit console, pulsatile jets, and various specifically tailored RT catheters. The device uses a complex mixture of rapid fluid streaming and hydrodynamic forces (1,000 psi to 2,000 psi) to fracture thrombus, allowing extraction at the distal catheter tip using negative pressure (Bernoulli/Venturi effect) (Figure 3).5,6 The AngioJet system is approved for use in hemodialysis grafts, infrainguinal arteries, and coronary artery and saphenous vein bypass grafts. We used the recently introduced 6F Xpeedior RT catheter with six high-velocity jets and improved cross-streaming hydrodynamics.
CHEMICAL THROMBOLYSIS: TENECTEPLASE
We selected TNK, a third-generation, bioengineered, plasminogen-activator thrombolytic. Our choice was based on the lytic agent’s superior safety and efficacy profile; rapid, single-bolus enhanced lytic capacity and potency; longer plasma half-life; and increased fibrin affinity and specificity when compared to alteplase (r-TPA) and other second- and third-generation plasminogen activators.4,7,8 These superior pharmacodynamic characteristics were accomplished by three amino acid alterations at the T, N, and K domains of the rt-PA molecule.4,8 We initially chose an empiric lytic dose of 10 to 20 mg of TNK in 50 cc of normal saline (the ?lytic bag?), with 10 mg of TNK in 50 cc of saline being the current protocol recommendation. Recently, after Urokinase (UK) (Abbott Laboratories, Abbott Park, IL) was made available again, three patients were successfully treated with 1 million units of UK in 50 cc of saline as the lytic bag.
THE GOAL OF SIMULTANEOUS COMBINATION THERAPY
Both RT and CT are accepted stand-alone treatments for CLI, but each poses significant limitations. As many as 40% to 50% of cases require repeat, prolonged, or creative adjunctive combinations of both treatments for more complete thrombus resolution.5,6,9,10 The CIS P-PS technique was designed to minimize these limitations and maximize the advantages of both CT and RT with the following points as goals:
Goal No. 1
Decrease bleeding and distal embolic complications by delivering a potent, high-dose, fibrin-specific lytic directly into the thrombus thereby minimizing any systemic lytic effect and decreasing hemorrhagic complications. Distal embolic complications have been reported in as many as 20% of CT and RT cases, with a 5% to 8% incidence considered acceptable.4,6,8 Using multiple passes of the RT catheter through insoluble thrombus has been theorized to push emboli downstream. During CT, the melting of thrombus and reinstitution of flow through the thrombosed segment is theorized to wash emboli downstream. The CIS P-PS technique minimizes the risk of embolic complications by avoiding these two potential mechanisms.
Goal No. 2
Facilitate thrombus removal capacity by delivering the lytic under high pressure (1,000 psi to 2,000 psi) directly into this rich clot-bound fibrin environment. This approach enhances TNK-thrombus penetration and mixing, therefore maximizing the superior pharmacological lytic effects of TNK. Occluding the AngioJet outflow with a stopcock removes the Bernoulli/Venturi effect from the RT system, converting it to a high-pressure lytic delivery system (Figure 4). In theory, this would allow softening of the thrombus, making relatively insoluble thrombus more soluble and facilitating extraction with the AngioJet RT catheter.
Goal No. 3
Rapid revascularization of the ischemic limb with minimal or no ICU requirement, decreased hospital resource utilization, and improved patient outcomes.
THE CIS P-PS TECHNIQUE
Table 1 outlines the steps involved in the simultaneous combination CIS P-PS approach. The total or subtotal iliofemoral or bypass graft thrombotic occlusion is crossed using standard techniques with a .035-inch guidewire. This step is often facilitated with a 5F Terumo glide-catheter (distributed by Boston Scientific Corporation, Minneapolis, MN). Initially, the AngioJet RT system is set up and primed in its thrombectomy mode with normal saline. A lytic bag (10 mg of TNK in 50 mL of normal saline) is then exchanged for the saline prime and a stopcock is added to the outflow port RT catheter manifold, thus converting the RT system to its P-PS mode.
It is important to advance the RT catheter slowly at 0.5 to 1.0 mm increments through the entire thrombosed segment using a single foot pedal pump/pulse per advanced increment. The RT system is set to deliver 0.6 mL volume of lytic solution (0.2 mg of TNK in each 0.6 mL of saline) per each pedal pump/pulse. The infused volume meter on the device unit console is set at zero at the initiation of the P-PS mode, allowing calculation of the total lytic volume and dose. A single antegrade and retrograde pass in the P-PS mode is recommended; the RT catheter is then removed. The concentrated pulsed lytic is allowed to “lyse” for 20 minutes as the RT system is converted back to its thrombectomy mode. It is important to evacuate the residual 12 mL of TNK outside the patient to avoid infusing additional lytic. The AngioJet RT catheter is then reintroduced with a single antegrade and retrograde pass followed by immediate angiography.
RAPID REVASCULARIZATION IS POSSIBLE
Our initial results in 18 patients have recently been reported.11 The immediate procedural success and 30-day limb salvage rates were 100%, with each patient experiencing significant thrombus resolution and a percutaneous revascularization option (PTA and/or stenting) without bleeding or embolic complications. The CIS P-PS technique potentially allows clinicians to achieve rapid revascularization of the critically ischemic limb in terms of minutes, not hours or days, and provides a way to treat the acutely ischemic limb like the acutely ischemic LAD.
David E. Allie, MD, is Director of Cardiothoracic and Vascular Surgery at the Cardiovascular Institute of the South in Lafayette, Louisiana. He holds no financial interest in any of the products mentioned herein. Dr. Allie may be reached at (800) 582-2435; David.Allie@cardio.com.
Chris J. Hebert, RT, RCIS, is Director of Technology at the Cardiovascular Institute of the South in Lafayette, Louisiana. He holds no financial interest in any of the products mentioned herein. Mr. Hebert may be reached at (800) 582-2435; Chris.Hebert@cardio.com.
Mohamed H. Khan, MD, is Director of Cardiology at the Cardiovascular Institute of the South in Opelousas, Louisiana. He holds no financial interest in any of the products mentioned herein. Dr. Khan may be reached at (800) 553-2394; Mohamed.Khan@cardio.com.
Craig M. Walker, MD, is Medical Director of the Cardiovascular Institute of the South in Houma, Louisiana. He holds no financial interest in any of the products mentioned herein. Dr. Walker may be reached at (800) 445-9676; Craig.Walker@cardio.com.
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Figure 1. This 81-year-old white male presented with a pale, painful, pulseless, paresthetic, paretic right foot, demonstrating the classic “five P’s” of acute critical limb ischemia.
Figure 3. The Xpeedior RT catheter uses high-velocity saline jets to create a localized low-pressure zone at the catheter tip for thrombus aspiration, breakup, and extraction.
Figure 4. This illustration shows the Xpeedior catheter being used for P-PS lytic infusion in a thrombosed blood vessel. The cutaway shows the internal stainless steel hypotube and distal loop with exiting saline jets. The catheter outflow lumen is occluded using a stopcock; lytic solution exits from the distal windows, sending a high-pressure, penetrating infusion into nearby thrombus without extraction.