Chasing the Two “C”s in Acute Limb Ischemia: The Clot and Catheter

VASCULAR DISEASE MANAGEMENT 2020;17(4):E55-E62

Abstract

Acute limb ischemia is an emergent limb- and life-threatening condition that needs to be treated quickly to decrease associated morbidity and mortality. Treatment strategies include a variety of endovascular techniques, which have been shown to be safe and effective to restore blood flow to the affected extremity. A thorough understanding of the advantages and disadvantages of available devices is paramount to the management of this disease. Herein, we present a case of an 82-year-old female presenting with acute arterial occlusion of her left leg, in which multiple endovascular techniques were utilized, each highlighting the risk of distal embolization, and an unsuspected subsequent cause of occlusion was encountered as well.  

Case

An 82-year-old female presented to the emergency department due to worsening pain and numbness affecting her left leg, which began seven days prior to her visit. She was found to be in rapid ventricular response due to newly diagnosed atrial fibrillation, in addition to her long-standing history of breast cancer, diabetes, stage IV chronic kidney disease, and hypertension.  

The patient was started on intravenous diltiazem and heparin, and an arterial duplex ultrasound demonstrated occlusion of the mid superficial femoral artery, with no significant flow seen within the infrapopliteal arteries, although the peroneal artery could not be seen (Figure 1). Interventional radiology, vascular surgery, and cardiology were immediately consulted to form a multidisciplinary approach for treatment. A computed tomography angiogram (CTA) of the aorta and lower extremities confirmed occlusion of the left superficial femoral artery, with reconstitution of the peroneal artery, the single runoff vessel to the foot. The distal aorta and iliac arteries were patent. An incidental arteriovenous fistula arising from the left superficial femoral artery was unknown in etiology.

On physical exam, the patient’s left foot was cool to the touch, and her toes were rubrous (Figure 2). Although she had difficulty moving her toes, she retained the ability to plantarflex and dorsiflex her foot. She complained of moderate tenderness within the calf and sensation remained intact to the level of the distal forefoot. A good, palpable femoral pulse could be appreciated on the left.  Pedal pulses were not palpable and not audible on doppler. 

The patient underwent lower extremity angiogram under moderate conscious sedation. A contralateral right groin access up-and-over approach was utilized in anticipation of performing thrombectomy and/or catheter-directed thrombolysis. Initial arteriography was performed from the distal aorta and then selectively within the left common femoral artery for the remainder of the lower extremity runoff study. 

Diagnostic angiography (Figure 3) revealed a long-segment occlusion of the femoropoliteal artery beginning approximately 10 cm from the origin of the superficial femoral artery, at the level of the arteriovenous fistula. Numerous collaterals from the profunda artery were seen through the thigh and knee. There was faint reconstitution of the proximal peroneal artery. No significant below-ankle pedal reconstitution was noted.

For support, a 55 cm, 6 French (Fr) Flexor Raabe sheath (Cook Medical) was advanced into the proximal left superficial femoral artery. An angled 5 Fr catheter and .035-inch Glidewire (Terumo) was easily advanced across the femoropopliteal occlusion, consistent with acute, soft thrombus. Once below the knee, the system was then downsized to an .018-inch support catheter and wire, which were carefully advanced into the reconstituted peroneal artery, confirmed with a gentle angiogram. There was some difficulty advancing the wire across the tibioperoneal trunk, presumably due to underlying chronic disease. At this time, ultrasound-assisted catheter-directed thrombolysis (CDT) with a 50 cm infusion length multi-sidehole catheter (EKOS, Boston Scientific) was initiated, beginning at the mid superficial femoral artery and extending to the proximal peroneal artery. Intra-arterial alteplase was begun at 0.5 mg/hour and intravenous heparin was maintained at a subtherapeutic dose (goal PTT 40-60).  

The patient was transferred and monitored in the intensive care unit. The calf pain improved overnight and the patient’s foot became warm, with concurrent improvement of toe discoloration. There were no signs of remote bleeding and fibrinogen levels were maintained greater than 100 mg/dL. After approximately 20 hours of CDT, the patient returned to the interventional radiology suite for a follow-up angiogram of the left lower extremity.  

The repeat angiogram demonstrated restoration of flow throughout the femoropopliteal segment, with direct inline flow to the peroneal artery (Figure 4). On this study, distal peroneal artery collaterals and perforators were seen reconstituting pedal arteries, not demonstrated previously, in keeping with the patient’s markedly improved physical exam. There was near resolution of the previously identified superficial femoral arteriovenous fistula. Despite the slightly ectatic appearance of the distal popliteal artery and tibioperoneal trunk, no true aneurysmal dilation was identified on the recent CTA. An approximate 80% stenosis was present within the tibioperoneal trunk, at the same location where difficulty was encountered in advancing the wire on the previous day. Angioplasty of this segment was performed with a 3.0 x 60 mm balloon in order to improve single-vessel inline flow to the foot.  

Following angioplasty, the repeat angiogram demonstrated resolution of the tibioperoneal stenosis, but with a new, nearly occlusive 5 mm filling defect in the proximal peroneal artery (Figure 5). Several therapeutic options were discussed and a decision to perform spot laser thrombolysis was made. Using a 0.9 mm Turbo-Elite laser atherectomy catheter (Philips), a total of two passes were performed across the proximal peroneal artery at low and moderate fluence and rate settings. The repeat angiogram demonstrated unsuccessful lysis, with the embolus now having migrated into the mid segment of the peroneal artery, resulting in complete occlusion. Fortunately, an .014-inch wire remained across the occlusion and a decision to perform long-segment angioplasty in order to macerate the lesion was made. The angioplasty was performed with slow and prolonged inflation of a 2.0 x 220 mm balloon, with the balloon tip in the distal peroneal artery. It also resulted in more distal migration of an occlusive filling defect, bringing complete occlusion of important, unnamed collaterals to the pedal arteries, as well as the perforating branch of the peroneal artery.

A third, final option was to perform embolectomy at this location, using an over-the-wire mechanical aspiration with a CAT3 catheter (Penumbra). After a single pass, there was flow restored to most of the distal peroneal artery, but a second pass was required in order to restore flow into the perforating branch of the peroneal artery (Figure 5). When the catheter was externalized from the groin sheath, physical exam demonstrated an unwound coil and no radiopaque marker band, consistent with shearing of the catheter tip (Figure 6). Although there was no significant resistance when removing the catheter, findings were confirmed on spot view of the ankle, which showed the radiopaque tip wedged within the perforating branch of the peroneal artery (Figure 7).  

Despite successful embolectomy, attention was now drawn to foreign body retrieval. Initial attempts were performed under the basis of threading a wire though the catheter tip containing the radiopaque marker band and using a small-diameter balloon to fixate the device for retrieval (a “thread the needle” approach). However, the .014-inch wire could not be advanced through the lumen of the radiopaque band, but instead, could only be advanced beside the marker band. A repeat angiogram was performed that revealed the underlying issue: a thin radiolucent defect was noted in the peroneal artery, consistent with a much longer segment than expected for the catheter fragment (Figure 7). Multiple angiograms were performed in a stepwise, cephalad fashion in order to determine the location of the proximal catheter fragment. However, once in the larger diameter popliteal artery, it was difficult to delineate the catheter. Multiple spot views and oblique digital subtraction angiograms still could not delineate the radiolucent catheter.

An astute team member brought up the idea of using ultrasound to identify the fluoroscopically radiolucent catheter. Therefore, intravascular ultrasound (Philips) was performed, and easily and accurately demonstrated the proximal tip to be within the mid superficial femoral artery, a few centimeters distal to the sheath (Figure 8). Using a 15 mm loop snare, the catheter fragment was successfully retrieved, completely intact (Figure 9). The final angiogram demonstrated completely restored flow through the personal artery, with reconstituted pedal arteries (Figure 10). The patient’s foot was warm and her pain had resolved. There were no signs of compartment syndrome after flow was restored.

Discussion

Acute limb ischemia (ALI) is defined as a defined as a sudden decrease in limb perfusion that threatens the viability of the limb, resulting in significant morbidity and mortality. The annual incidence of ALI in the United States is up to 2.6 cases per 10,000 patients. The key difference between acute and chronic limb ischemia is that in the acute setting, there is not enough time for collateral vessel growth to compensate for the loss of tissue perfusion, and thus, rapid treatment is required for limb preservation.^1–4 

The diagnosis of ALI is primarily clinical, and several signs and symptoms are often referred to as the 6 P’s: pain, paresthesia, paralysis, pallor, poikilothermia, and pulselessness. In this case, the patient demonstrated five of these conditions. Along with newly diagnosed atrial fibrillation, the diagnosis was straightforward, confirmed with imaging. Causes of ALI result from embolism or thrombosis, such as thrombosed bypass grafts or underlying severe atherosclerotic disease. Other cause of ALI can be from trauma, acute myocardial infarction, left ventricular dysfunction, prosthetic cardiac valves, thrombophilia, dissection, intimal hyperplasia, and vasculitis.^1–4  

The most appropriate treatment depends on the ischemic degree of the limb and location of occlusion. Treatment options include surgical embolectomy or bypass, as well as numerous endovascular options. Endovascular options include, but are not limited to, catheter-directed thrombolysis, pharmomechanical thrombolysis, and catheter-directed thrombus aspiration, all of which were utilized in this case. Despite these various options, there is still a high morbidity rate associated with ALI, with reports of up to 15% of amputations occurring during the acute hospital stay and mortality rates ranging from 15 to 40%.^5,6 Despite prompt reperfusion to the limb, a dreaded complication includes compartment syndrome, which requires fasciotomy and/or amputation.^1–4

In this case, the patient’s degree of ischemia was compatible with a threatened limb (Rutherford IIa-IIb) and immediate endovascular treatment was performed. At our institution, when there is a large burden of thrombus, we start with catheter-directed thrombolysis. There is some data to suggest that using ultrasound-assisted CDT in infrainguinal disease leads to shorter infusion times and decreased intervention.⁷ At times, CDT can resolve the entire burden of disease overnight, but, more frequently, endovascular treatment of critical lesions is performed the following day with additional techniques and devices. These options include angioplasty, mechanical aspiration, rheolytic aspiration, filter basket retrievals, snares, and laser thrombolysis.  

Ultrasound-assisted CDT worked well to resolve most of the thrombosis burden in this patient and established inline flow to the peroneal artery. It is possible that no further endovascular treatment was needed following initial therapy (10 mg alteplase), given the improvement both clinically and angiographically. The critical stenosis in the tibioperoneal trunk was incorrectly identified as a completely chronic lesion due to the wire “feel” performed on the initial intervention. Instead, this underlying chronic lesion likely had residual thrombus that was displaced following balloon angioplasty, resulting in distal embolization and occlusion of the patient’s only outflow to the foot.

Treatment of short segment acute/subacute lesions with the excimer laser (laser embolysis) has been described previously.^8–10 The excimer laser ablates material by photochemical mechanisms that involve the breaking of molecular bonds without the generation of heat, achieving vaporization instantaneously and safely. The unique properties of photoacoustic ablation and favorable interaction with thrombus make the laser a valuable tool to treat diffuse thrombotic vascular disease in coronary and peripheral applications.^8,10 Unfortunately, attempted laser thrombolysis of the embolus was unable to eliminate the lesion, instead displacing the material distally, making treatment more difficult. One possible explanation of the failure mechanism in this case is the use of low and moderate energy settings for the two passes during the exam.  Since the smaller 0.9 mm Turbo-Elite laser atherectomy catheter (Philips) was used, higher energy settings are recommended, by increasing both the fluence and rate. In addition to higher energy settings, an intentionally slow crossing speed is recommended, particularly in the setting of organized thrombus. The approximate speed would be less than 1 mm per second, but even slower may yield improved results.¹¹

In the setting of organized thrombus or atheromatous emboli, hybrid therapies with balloon maceration have also been reported to result in recanalization of the vessel.¹² However, balloon maceration has a very high rate of distal migration and embolization, as seen in this case. No hybrid techniques were utilized (ie, filter basket or intraarterial alteplase) due to the small caliber of the vessel and complexity of the procedure. This technique is usually reserved as a last-resort option in acute, focal occlusions. 

Finally, mechanical aspiration has been shown to be very effective in distal embolization.^9,13 In retrospect, we recognize that catheter-directed mechanical aspiration should have been the first-line therapy once the initial embolus was identified on the follow-up angiogram. In fact, given the more proximal location of the embolus initially, a larger bore Indigo catheter could have been used, which would increase the effectiveness of thrombus aspiration (ie, a CAT5 or CAT6 [Penumbra]). Fortunately, the CAT3 catheter was successful in removing the embolus, despite its final distal location in the peroneal artery and within the perforating branch of the peroneal artery. 

This is the first time we have encountered a situation where this specific catheter (CAT3) sheared in vivo. Even though there was little to no resistance, we do not believe that this is related to an underlying weakness in the catheter itself. Instead, the failure mode was likely due to the tip of the catheter getting wedged within the small perforating branch of the peroneal artery. Forward pressure was placed on the catheter during the aspiration within the vessel could have resulted in more “wedging” and friction of the catheter in a very small, calcified artery. That friction within the calcified artery could not be overcome when removing the catheter, resulting in the catheter shearing and fragmentation. The new version of the catheter is now in a rapid-exchange platform (CAT RX [Penumbra]), allowing for a more robust catheter and a larger lumen for aspiration. The CAT RX catheter is especially helpful for treating disease in the distal tibial (as in this case) or in the pedal vasculature.

Intravascular or extravascular ultrasound serves as an extremely vital tool to any endovascular operator as several lesions (or in this case, a catheter) are radiolucent on fluoroscopy, but easily identified by their degree of echogenicity on sonography. Once the proximal fragment of the catheter was accurately identified, retrieval of the catheter was straightforward. Vascular ultrasound could have also been used initially when evaluating the tibioperoneal stenosis, which may have revealed residual or adherent thrombus, and may have prevented the distal embolization that occurred in this case.

An in-depth understanding as to the devices and techniques utilized in all kinds of endovascular interventions includes knowledge of the potential risks and pitfalls. This case exemplifies the dreaded risk of distal embolization and demonstrates multiple methods that can be used for treatment.

Disclosure: Dr Dhand reports no conflicts of interest regarding the content herein.

Manuscript submitted November 6, 2019, final version accepted February 21, 2020.

Address for correspondence: Sabeen Dhand, MD, PIH Health Hospital – Whittier, 12401 Washington Blvd., Whittier, California 90602. Email: sabeen.dhand@gmail.com

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