Direct Aspiration of Large Thrombi in Acute Myocardial Infarction Using a Standard 6 Fr Guide Catheter Via the Transradial Approach

ABSTRACT: A large thrombus load on the culprit coronary artery of patients with acute myocardial infarction (MI) is associated with increased procedural complications and adverse coronary events following angioplasty. This case series describes effective removal of large, occlusive thrombi in acute MI via direct aspiration using a standard 6 Fr guide catheter, following failed conventional catheter aspiration. This procedure is a simple and rapid alternative for challenging thrombi-containing coronary lesions when current thrombectomy catheters fail.

J INVASIVE CARDIOL 2012;24(11):E283-E288

Key words: thrombus aspiration, transradial approach

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Acute myocardial infarction (MI) results from sudden thrombotic occlusion of a coronary artery at a fissured atherosclerotic plaque. Reperfusion therapy by percutaneous coronary intervention (PCI) with ballooning and/or stenting is the optimal approach for reducing morbidity and mortality in acute MI. However, a large thrombus load on the culprit lesion remains a predictor of unfavorable PCI results and long-term outcome because of increased distal embolism risk and/or the no-reflow phenomenon.¹ Implementing the optimal intervention for lesions with occlusive thrombi is technically and therapeutically challenging. Published reports² highlight the advantages of systematically planned manual thrombus aspiration devices as an initial approach to improve myocardial perfusion and clinical outcome. Although various thrombus aspiration devices are available, their working internal diameter is limited, and their aspiration capacities might be insufficient to remove large thrombi.

A 6 Fr guide catheter is the current standard for PCI and has a 0.071" internal diameter, potentially sufficient for effective thrombus aspiration. In this report, we describe 3 patients with acute MI who underwent primary PCI following the failure of conventional catheter aspiration, in whom direct aspiration using a standard 6 Fr guide catheter successfully removed their large thrombus burden.

Case Report 1. An 82-year-old female with diabetes was admitted to our hospital having experienced chest pain for 12 H. Electrocardiography (ECG) on arrival revealed ST-segment elevation and Q waves in leads II, III, and aVF. She underwent emergency coronary angiography (CAG). At our institution, patients are usually catheterized via the right radial artery and administered 5,000 units of heparin intravenously. Her initial CAG demonstrated total occlusion of the proximal right coronary artery (RCA) (Figure 1A). Percutaneous coronary intervention (PCI) was performed via the right transradial artery using a 6 Fr Ikari-Curve Right guide catheter (IR-1.0, HeartRail II, Terumo Corporation). After crossing the lesion with a guidewire (Neo’s Rinato, Asahi Intecc, Co., Ltd.), thrombectomy was attempted several times using an aspiration catheter (TVAC-S6; Nipro Corporation) (Figure 1B). However, a significant amount of thrombus remained, extending from the proximal to mid segment of RCA (Figure 1C). The 6 Fr Ikari-Curve Right guide catheter was inserted deep into the distal RCA for manual thrombus aspiration. A 30-cc syringe was attached to the Y-connector, maintaining constant negative suction, and the guide catheter was slowly withdrawn from the distal to proximal RCA while the guidewire remained in RCA to maintain access to the distal vasculature of the occluded artery (Figure 2A). We aspirated several times to ensure there was no aspirate left in the guide catheter. This procedure led to successful retrieval of a large, cylindrical, red–white thrombus (Figure 2B). Angiography revealed a significantly improved RCA appearance with no residual thrombus or distal embolization (Figure 2C). It also showed ulceration of the proximal RCA (Figure 3A). Based on the angiographic appearance, this ulceration was considered the culprit (plaque rupture) site. Therefore, a 3.5 mm × 23 mm coronary stent (S-Stent™; Biosensors International Group, Ltd.) was deployed into the proximal RCA. An excellent final angiographic result with no distal embolization was achieved (Figure 3B).

Case Report 2. A 56-year-old male was admitted to our hospital with acute central chest pain lasting 1 H. He had a history of hypertension, hypercholesterolemia, and cigarette smoking. ECG on arrival showed negative T waves in leads II, III, and aVF, and he was diagnosed with non-ST-segment elevation acute MI. He received 200 mg of aspirin orally and 5,000 units of heparin intravenously, and he underwent emergency CAG. Initial CAG demonstrated an acute large thrombus in the distal RCA with distal flow delay (Figure 4A). PCI was performed via the right transradial artery using a 6 Fr Judkins Right GC (JR-4.0, HeartRail II, Terumo Corporation). Thrombectomy was attempted several times with an aspiration catheter (ASPREY Plus; Kawasumi Laboratories, Inc.) (Figure 4B). Scant red thrombus was collected in several aspirations, but the angiographic appearance differed little (Figure 4C). We passed the Judkins Right guide catheter into the distal RCA over the guidewire and performed manual aspiration (Figure 5A). A large, red thrombus was successfully aspirated from the culprit lesion. Subsequent injection revealed significantly improved angiographic appearance, no haziness of the distal RCA lesion, and good flow recovery (Figure 5B). Because of the vessel size discrepancy proximally and distally to the culprit lesion and no signs of residual thrombus or distal embolization, no additional intervention (such as balloon angioplasty or stenting) was performed. His subsequent clinical course was uneventful with no further elevation of cardiac enzyme levels.

Case Report 3. A 66-year-old male heavy smoker with no specific medical history visited a local clinic with chest discomfort and nausea lasting >12 H. Blood tests demonstrated elevated cardiac enzymes, and his ECG revealed ST-segment elevation and Q waves in leads II, III, and aVF. He was diagnosed with ST-segment elevation acute MI and was transferred to our hospital. He underwent emergency CAG via the right transradial artery, which demonstrated severe narrowing and ulceration in the proximal RCA and total occlusion in the distal RCA (Figure 6A). Based on the angiographic appearance, the proximal lesion was considered the culprit segment, and the distal lesion was to be embolized by a mobile thrombus from the proximal lesion. After passage of a 0.014" guidewire (Neo’s Rinato; Asahi Intecc) through the occlusion, thrombectomy was attempted with an aspiration catheter (ASPREY Plus; Kawasumi Laboratories, Inc.) (Figure 6B). This achieved partial restoration of the coronary flow; however, a large thrombus remained extending to the distal bifurcation of the posterior descending and atrioventricular nodal arteries (Figure 6C). Following dilatation at the proximal lesion using a 3 mm balloon angioplasty catheter (SIGNET Plus; St. Jude Medical, Inc.), the Judkins Right guide catheter (JR-4.0, Profit; Goodman Co. Ltd.) was inserted deep into the distal lesion for manual thrombus aspiration (Figure 7A). This procedure led to the successful retrieval of a red, cylindrical thrombus (Figure 7B). Subsequent injection revealed a significantly improved angiographic appearance of the distal RCA lesion (Figure 8A). A 3.5 mm × 28 mm coronary stent (MULTI-LINK VISION; Abbott Vascular) was deployed at the proximal RCA lesion; no further intervention was performed at the distal lesion. Final angiography demonstrated TIMI 3 distal flow without residual thrombus at the distal lesion (Figure 8B).

Discussion. A large thrombus load on the infarct-related arteries poses technical and therapeutic challenges during PCI for acute MI. Intracoronary thrombi are associated with adverse procedural outcomes, including persistent or transient no-reflow, distal embolization, abrupt closure, and increased incidence of in-hospital major adverse cardiac events. Despite recent improvements in coronary intervention strategies, CAG detects distal embolization in 15% of patients with acute MI following successful primary angioplasty,³ a macroscopic phenomenon associated with poor long-term prognosis.³

Two treatment strategies for intracoronary thrombi are the pharmacologic approach and mechanical thrombectomy. Intracoronary infusion of thrombus solvents (eg, glycoprotein IIb/IIIa inhibitors, urokinase) or vasodilators (eg, nitroprusside, verapamil) reduces the amount of thrombus, preventing the slow- or no-reflow phenomenon. However, despite advances in such pharmacologic agents, this approach cannot completely remove thrombi, particularly the large ones, and may cause intramyocardial hemorrhage or systemic bleeding.^4-6 In addition, some agents such as glycoprotein IIb/IIIa inhibitors are not globally available. Conversely, thrombectomy using a dedicated thrombus aspiration catheter prior to primary coronary intervention has gained widespread acceptance following reports^2,7,8 that it effectively reduces the infarct size and mortality. The main advantage of thrombus aspiration is local removal of thrombi, avoiding distal embolization of atherothrombotic debris. This decreases macrovascular and microvascular obstruction, leading to improved perfusion and reduced infarct size.^7,9 Various adjunctive thrombectomy devices have been developed; however, their working diameter for thrombosuction is limited and might prove ineffective for large thrombi in acute MI.

We reported a case series of 3 patients with acute MI, treated with direct thrombus aspiration using a standard 6 Fr guide catheter combined with a routine angioplasty guidewire, following failure of conventional catheter aspiration to retrieve large, embolized thrombi. This technique proved to be a simple, easy, and useful alternative to the existing thrombectomy procedures and is suitable for both proximal and distal thrombus occlusions. Distal vessel patency and functionality were successfully restored in all 3 patients. Furthermore, additional balloon angioplasty, which incurs further risk of thrombus fragmentation and distal embolization, was avoided.

One explanation for the efficient aspiration of large thrombi in our cases is the internal diameter of the 6 Fr guide catheter. Rioufol et al¹⁰ reported that the key factor for successful thrombus aspiration is the catheter’s working internal diameter, not its area of contact. They showed that the catheter bore was inversely proportional to the vacuum pressure required to achieve complete thrombus aspiration, and the best results are obtained when the catheter bore is as large as possible. Because a large lumen size contradicts the current trend for smaller catheters, a compromise must be reached for aspiration capacity in conventional aspiration catheters, although they have a beveled tip. The internal diameter of a 6 Fr guide catheter is approximately double that of the 6 Fr guide catheter-compatible aspiration catheter. We believe that patients with a large thrombotic load will particularly benefit from our treatment.

Direct aspiration of large intracoronary thrombi using a guide catheter is desirable for several reasons. First, fewer patients treated with this technique require balloon dilatation as we reported here. Published studies¹¹ suggest that balloon dilatation mobilizes thrombi, inducing further distal embolization. In this study, post-procedure distal embolization was not observed in any patient. Optimizing coronary reperfusion improves myocardial tissue salvage and limits the myocardial infarction extent. Second, removing as much of the thrombus as possible might reduce the incidence of the slow- or no-reflow phenomenon. Third, patients treated with efficient thrombus aspiration might exhibit low rates of side branch occlusion.

Guide catheter use for intracoronary thrombus aspiration has been described in previous studies. Guide catheter aspiration was initially described using 9 Fr¹² and 8 Fr catheters¹³ for proximally located thrombi. Subsequently, Turkoglu et al¹⁴ demonstrated successful retrieval of a proximally located RCA thrombi with a 6 Fr guide catheter. Other techniques such as inserting a smaller guide catheter within a larger one¹⁵ (eg, 6 Fr in 8 Fr, the “mother and child technique”); the double wire technique, exchanging a larger guide catheter for a smaller one;¹⁶ or guide catheter aspiration combined with a filter-based distal embolic protection device¹⁷ have also been described for retrieving more distally located intracoronary thrombi. Compared to these techniques, our method of deep passage of a single 6 Fr guide catheter to the distal segment of native coronary arteries over a single guidewire is a very simple and practical technique for successful retrieval of both proximally and distally located embolized thrombi and restoration of coronary flow without additional ballooning or intracoronary lytic administration. Unlike earlier models, the current-generation 6 Fr guide catheter is reasonably soft and flexible, facilitating deep insertion over a guidewire down native coronary arteries. Furthermore, the inner lumen size is considerably larger than that of the dedicated aspiration catheters, while the external size is sufficient in many cases to wedge the guide catheter in the coronary arteries, thereby maximizing the suction applied downstream to extract thrombi in a manner akin to proximal occlusion vascular protection devices. In addition, contrary to previous reports, our patients were successfully treated via the transradial artery approach. Softness and flexibility of the current-generation 6 Fr guide catheter might contribute to its deep insertion into the distal coronary bed, even with the poor support offered by the transradial approach. This might be of great clinical significance because transradial coronary interventions with a 6 Fr guide catheter have become increasingly popular, particularly for treating patients with acute MI. Our method can be simply applied in addition to routine practice when conventional dedicated aspiration catheters fail, without the need for additional artery puncture to insert a larger guide catheter such as a 7 Fr or 8 Fr.

In our patients, the culprit vessel was the RCA. Because the RCA exhibits low vessel tapering,¹⁸ relatively large diameter, low flow velocity, and increased flow turbulence, it frequently contains larger thrombi in patients with acute MI compared with the left anterior descending and left circumflex coronary arteries. Moreover, big vessels have a high plaque load that, in cases of rupture or erosion, can cause more severe platelet activation and thrombus formation. It was reported¹⁹ that RCA occlusion is often found in fatal pre-hospital acute MI. Greater susceptibility of the RCA to large thrombus development makes successful reperfusion harder to achieve with standard aspiration catheters as reported in previous studies.^12-17 Although our report does not include any left-sided coronary occlusion, the effectiveness of direct aspiration using a 6 Fr guide catheter might be better emphasized in the RCA in patients with acute MI.

Because of the small number of cases reported in this study, some theoretical and practical disadvantages of our technique have yet to be determined. First, even though the current-generation 6 Fr guide catheter is soft and flexible, it is less trackable and maneuverable than conventional thrombus aspiration catheters. In addition, delivery of a 6 Fr guide catheter as distally as required might be challenging, especially in tortuous or calcified coronary arteries. Therefore, our procedure depends on the physician’s experience and anatomic considerations. Second, the passage of a 6 Fr guide catheter through the distal lesion risks damaging the endothelium and the vessel wall. Although the risk might be lower than that of balloon dilatation, the long-term effect on the vessel wall remains unknown. Third, with massive thrombi, withdrawal of distal thrombi proximally for retraction carries a risk of distal or catastrophic systemic embolization.

We meticulously avoided thrombus release in the aorta by maintaining continuous negative suction on the syringe while pulling the guide catheter. We combined this maneuver with very deep guide engagement of the coronary artery to lessen the chance of accidental thrombus dislodgement and repeated aspiration several times until there was no aspirate left in the guide catheter to prevent distal or aortic embolization. However, given its potential risks, we believe that our technique should be applied only when other approaches for thrombus aspiration, such as aspiration by standard dedicated devices, fail.

In conclusion, we successfully performed direct aspiration using a standard 6 Fr guide catheter for a large thrombus load in 3 patients with acute MI. The procedure was a simple and viable alternative, particularly in patients unresponsive to conventional thrombectomy interventions. Although limited comparisons and conclusions regarding the long-term effects of our procedure can be drawn from our small number of cases, we believe that our experiences provide compelling evidence that this technique is advantageous and convincing for thrombus reduction in primary PCI.

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From the Cardiovascular Center, Shiroyama Hospital, Habikino City, Osaka, Japan.
The authorshave completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.
Manuscript submitted April 10, 2012, provisional acceptance given June 11, 2012, final version accepted July 27, 2012.
Address for correspondence: Yoshihisa Shimada, MD, PhD, Cardiovascular Center, Shiroyama Hospital, 2-8-1 Habikino, Habikino City, Osaka, Japan 583-0872. E-mail: shimada@shiroyama-hsp.or.jp