Neurointerventional tools and techniques for coronary thrombus removal. A case-based review

Abstract

Due to the negative results of randomized aspiration thrombectomy studies, its role in myocardial infarction has been limited to high thrombus burden and/or failed vessel recanalization, with little technological advancement over the last years. In contrast, there has been rapid progress in mechanical thrombectomy in stroke, which is understandable as most ischemic cerebrovascular accidents have an embolic etiology.

We present three transradial procedures wherein neurointerventional catheters were used as a first-line device for en bloc removal of large clots lodged distally in tortuous coronary anatomy. First-pass reperfusion was achieved in all the cases, without dissection, distal embolization, or the no reflow phenomenon.

Learning objective

In the case of large clots, where coronary aspiration devices fail, neurointerventional catheters may be considered as a rescue strategy. They provide large aspiration lumen and excellent trackability with atraumatic design. Many other neurointerventional techniques can be easily adopted into the coronary armamentarium, possibly increasing the safety and efficacy of thrombus aspiration.

Introduction

Considering the difference in the results of large clinical trials and thus the recommendation level for mechanical thrombectomy in stroke versus routine thrombus aspiration in myocardial infarction (class IA vs class IIIA, respectively), unsurprisingly, it is neurointervention where the finest developments in technology and techniques take place [1], [2], [3], [4].

Currently available rapid exchange devices used for coronary aspiration are often unable to evacuate large clots, although it is the large thrombus scenario where thrombectomy is most needed and still performed [5]. This has become particularly important in the era of coronavirus disease 2019 (Covid-19) pandemic, when cases with high thrombotic burden were repeatedly described. Having established mechanical thrombectomy in a stroke program based on our cardiac catheterization laboratory team, we started using neurovascular catheters for rescue clot extraction in ST-segment elevation myocardial infarction (STEMI), when coronary monorail aspiration catheters and/or guide extension catheters failed. Additionally, we have introduced several techniques employed in endovascular stroke treatment to prevent distal embolization. Consequently, we decided to test neurointerventional catheters as first-line tools when a large thrombus was located distally and/or in a tortuous coronary artery, i.e. when conventional aspiration devices were expected to fail and prolong the time to reperfusion.

In the presented cases, a rapid first-pass reperfusion was achieved. To further minimize the risk of the no reflow phenomenon, three strategies were used: no stent, deferred stenting, and deferred stent postdilation. All cases were performed with our default right radial access and a 6-F (French) Judkins Right 4.0 Launcher (Medtronic, Minneapolis, MN, USA) guiding catheter.

Patient 1

A 68-year-old man with hypertension and type 2 diabetes mellitus was admitted with inferior STEMI. In angiography, mid-right coronary artery (RCA) occlusion was revealed (Fig. 1A, Video 1). After eptifibatide (GP IIb/IIIa inhibitor) intracoronary injection and balloon predilation, a large thrombus was revealed (Fig. 1B, Video 2). A 5-F Sofia catheter (MicroVention Terumo, Tustin, CA, USA) was advanced over the wire, with aspiration and withdrawal performed wireless (Fig. 1C). The clot was completely removed with Thrombolysis In Myocardial Infarction (TIMI) Grade 3 flow restored (Fig. 1D, Video 3). The lesion was covered with a drug-eluting stent (5.0 × 26 mm) deployed at nominal pressure to avoid the no reflow phenomenon, with a deferred non-compliant postdilation performed two days later (Fig. 1E, Video 4, Video 5).

Fig. 1.

Patient 1. (A) Occlusion of the right coronary artery. (B) Large thrombus (arrow) revealed after balloon inflation. (C) Sofia catheter tip (arrow) advanced to the clot. (D) Initial result of thromboaspiration (arrow). (E) Final result of deferred stent postdilation (arrow).

Patient 2

A 44-year-old man, with a history of anterior STEMI and the left anterior descending artery stenting, was admitted due to inferior STEMI. Critical stenosis of the mid-RCA was found in angiography, with a massive thrombus and distal embolization of the right posterolateral branch (Fig. 2A). Eptifibatide was administered intracoronarily. Due to the S-shape of the proximal RCA and the large thrombus, a 5-F Sofia was chosen and advanced wireless to avoid further distal embolization (Fig. 2B, Video 6). The large clot was almost completely evacuated with the residual thrombus left for treatment with eptifibatide and low-molecular weight heparin (Fig. 2C). One-month follow-up angiography revealed excellent result, with spontaneous recanalization of the right posterolateral branch (Fig. 2D).

Fig. 2.

Patient 2. (A) Large thrombus in the right coronary artery and distal embolization of the posterolateral branch (arrow). (B) Sofia catheter introduced wireless (arrow points to its tip). (C) Result of thromboaspiration with a small residual clot. (D) 1-month control angiography with spontaneous recanalization of the posterolateral branch (arrow).

Patient 3

A 57-year-old man with hypertension was admitted due to inferior STEMI. Angiography showed distal occlusion of RCA. Eptifibatide was administered intracoronarily and a guidewire advanced, with TIMI 1 flow restored in the right posterolateral branch and a large thrombus revealed before the crux. A 5-F Sofia was introduced in a wireless fashion without the Y-connector to reach the distally located thrombus (Video 7). The clot was evacuated with TIMI 3 flow restored in all distal branches and a residual stenosis present before the RCA bifurcation. The lesion was not stented immediately to avoid the no reflow. Four days later, tight stenosis was stented without flow impairment.

Discussion

Advances in coronary aspiration technology have been stalled after the publication of negative results of randomized studies, with new devices differing only slightly in the catheter tip shape. Recently, however, there has been some revival in the field with inspiration coming from endovascular stroke treatment. Given the embolic etiology behind most ischemic strokes (and intracranial stents used only as a bailout strategy), neurointervention is naturally the leader of innovation in thrombectomy.

It is usually the dominant RCA, where the largest clots are found, reaching 4–4.5 mm in diameter even at the crux. This calls for a special device that is extremely trackable (flexible and atraumatic), and still quite bulky (large aspiration lumen). The 5-F Sofia (Soft torqueable catheter Optimized For Intracranial Access), a 125 cm long, single lumen catheter, offers both, obviating the use of 7 or 8-F coronary aspiration devices, which require bigger size guides and usually femoral crossover (Fig. 3A). The catheter's working length is 9.5 cm and even 18 cm without a Y-connector (Fig. 3B, C). Due to its highly hydrophilic soft tip plus hybrid braid and coil reinforcement, Sofia can easily cross moderate coronary stenoses. When a large thrombus dwells distal to a tight lesion, predilation should be considered.

Fig. 3.

Sofia's output and variants of the setup. (A) Clots retrieved during aspiration with Sofia. (B) Sofia's working length of 9.5 cm with a Y-connector. Two syringes attached to Sofia (vertical arrow) for continuous vacuum with another syringe connected directly to a guide (horizontal arrow). (C) Sofia's working length of 18 cm without a Y-connector. (D) Simulation of over-the-wire retrieval of an aspiration catheter showing the risk of clot dislodgement.

Studies have shown that bigger aspiration lumen accommodates larger clots and generates greater aspiration force. Sofia's internal lumen is 1.5 times bigger than that of the largest 6-F guide-compatible coronary aspiration catheters (Sofia: 1.52 mm² vs 1.06 mm² Thrombuster III GR, Kaneka, Osaka, Japan), and comparable to 6-F guide extension catheters (e.g. 1.55 mm² with guidewire for Guidezilla, Boston Scientific, Marlborough, MA, USA), and 8-F coronary aspiration devices (1.58 mm² for Eliminate, Terumo, Tokyo, Japan). The 120 cm long, 5-F ST01 catheter by Terumo, also used for coronary thrombectomy, offers somewhat bigger lumen (1.67 mm² with wire) but at the cost of poor deliverability to distal coronary segments due to stiff distal part, as expected for a catheter used to increase support in the mother-and-child technique. Inferior trackability is also a disadvantage of guide extension catheters, which, although thinner, are stiffer than Sofia, having been designed for guide backup. The distal 17 cm of Sofia is soft and highly flexible with good shape retention, and much more hydrophilic than conventional coronary aspiration devices. In stroke interventions, catheters are sometimes introduced with the coaxial technique (with the microcatheter support); however, Sofia is often advanced wireless. With this approach in the coronary vessels, there is less friction over a thrombus inside Sofia upon its retrieval, which, at least theoretically, may minimize the risk of clot loss (Fig. 3D). The wireless technique may be used in large, even tortuous vessels by slowly pushing the catheter, with gentle rotation used. When resistance is encountered, a guidewire should be used.

Large lumen catheters may be the right tool for aspiration of older, bulkier, more organized, and less compressible clots. Some studies showed that while the reperfusion rate decreased with time, such a trend was not reported for thromboaspiration [6]. In future studies of coronary thrombectomy, clot age (based on total ischemic time) and thus its composition and consistency will probably become more important [7].

There is also room for simple innovations in coronary thrombus extraction based on stroke management. Experiments have shown a rapid drop in negative pressure in a syringe during aspiration; therefore, the double syringe technique (two 60 cm³ vacuum locking syringes connected to an aspiration catheter through a 3-way stopcock) is utilized in stroke. To reduce the risk of clot embolization, we have introduced this technique in STEMI (Fig. 3B). Moreover, given that embolization in new territory is the second most dreaded complication of stroke thrombectomy, both the guide and the aspiration catheter are kept under negative pressure. We use this approach with Sofia in coronary procedures, considering that stroke was one of the negative findings of thromboaspiration studies in STEMI (Fig. 3B) [5]. We have also adopted the contact aspiration technique, in which the catheter is advanced under continuous vacuum only until blood inflow into a syringe is blocked due to the contact with a clot. It is then ‘parked’ there for thrombus ‘ingestion’ and removed with continuous suction.

Yet another example of neurointervention-inspired coronary technology is the stent-retriever NeVa (Vesalio, Nashville, TN, USA), which has undergone first-in-human studies [8]. Other ‘extra-coronary’ techniques of thrombectomy are currently studied in STEMI. One such example is the CAT Rx catheter (Penumbra, Alameda, CA, USA), engineered on the basis of the intracranial experience [9]. In the system, movements of a clot separator, positively tested in pulmonary and peripheral embolism, enable thrombus fragmentation, with suction provided by the Penumbra engine.

Interestingly, mutual inspiration of cardiology and neurointervention has led not only to the reinvention and redesign of endovascular devices, but also allows for simultaneous management of concurrent pathologies (stroke and STEMI), or immediate treatment of ‘multidisciplinary complications’ [10].

The refinement of neurointerventional aspiration catheters makes them a safe tool, yet reserved for experienced interventionists. For ethical and medico-legal reasons, their use should be decided individually, considering their possible life-saving role in failed recanalization and the risk of catheter-induced complications. The ethics committee approval should be obtained in advance and the patient informed about the intention and necessity to use equipment dedicated for another vascular bed.

Conclusions

The unique softness and atraumatic design of devices dedicated to the thin-walled and tortuous intracranial arteries makes them a useful supplement to the coronary thrombectomy portfolio with the possibility of increasing its effectiveness and safety. However, neurointerventional devices are used in STEMI off-label; therefore, their application should be limited to bailout situations.

Unsurprisingly, in fear of stroke, the inspiration for safe clot aspiration in STEMI comes precisely from neurointerventional stroke treatment.

The following are the supplementary data related to this article.

Video 1

Patient 1. First angiogram after vessel wiring showing the occlusion of the mid- right coronary artery.

Video 2

Patient 1. Large thrombus revealed in the mid-right coronary artery after balloon predilation.

Video 3

Patient 1. Result of clot aspiration with the Sofia catheter.

Video 4

Patient 1. Control angiography 2 days later showing residual stenosis in stent deployed in the mid-right coronary artery during primary angioplasty.

Video 5

Patient 1. Final result of deferred non-compliant stent postdilation performed with a 5.0-mm balloon.

Video 6

Patient 2. Wireless advancement of the Sofia catheter through the S-shaped proximal right coronary artery.

Video 7

Patient 3. Wireless passage of the Sofia catheter for the aspiration of a distally lodged clot.

Declaration of competing interest

The authors declare no conflict of interest regarding this publication.