Occlusion length is a crucial determinant of efficiency and complication rate in thrombectomy for acute ischemic stroke

Abstract

Background and purpose: Although mechanical thrombectomy (MT) has an encouragingly high recanalization rate in treating stroke, it is associated with severe complications of which the underlying factors have yet to be identified. Because MT is a mechanical approach, the mechanical properties of the thrombus might be crucial for its success. The present study assesses the effect of thrombus length on the in vivo effectiveness and complication rate of MT.

Materials and methods: Angiography and embolization of 21 cranial vessels with radiopaque whole-blood thrombi 10, 20, and 40 mm in length (7 occlusions each) were performed in 7 swine. MT was carried out using a distal snarelike device (BCR Roadsaver) with proximal balloon occlusion. A total of 61 retrievals were attempted.

Results: In the group of 10-mm occlusions, 77.8% of the attempts achieved complete recanalisation. For longer occlusions, the success rates decreased significantly to 20% of attempts for 20-mm occlusions (odds ratio [OR], 14; 95% confidence interval [CI], 2.2-89.2) and 11.1% for 40-mm occlusions (OR, 28; 95% CI, 3.9-202.2; P < .005). The low success rates were largely due to complications associated with thrombus compaction during retrieval. Similarly, the rate of thromboembolic events increased from 0% in 10-mm occlusions to 14.8% in 40-mm occlusions.

Conclusions: MT using a distal device proved to be a fast, effective, and safe procedure for recanalizing short (10-mm) occlusions in the animal model. However, occlusion length emerged as a crucial determinant for MT with a significant decrease in recanalization success per attempt and increased complication rates. These findings suggest limitations of MT in the clinical application.

Fig 1.

Comparison of distal devices. The Merci device (A) has a coil-like shape; the Catch device (B) has significantly more filaments forming its basketlike shape than the BCR Roadsaver device (C) with its complex snarelike shape. D, The device is delivered using a microcatheter and is unsheathed behind the clot, where force is applied to the distal base of the thrombus.

Fig 2.

Magnified image of initial 10-mm thrombus; the microcatheter (*) is positioned proximal to the thrombus (]) with the device unsheathed (upper and lower markers >) distal to the thrombus (A). B–D, During initial retrieval, the device partially catches the thrombus without significant elongation of the vessel. C and F, Minor dislocation of thrombus and device is visible at the junction of the lingual and maxillary arteries. E, Elongation of the thrombus in proximity to the balloon catheter (open arrow) illustrates the effect of the additional proximal aspiration. Total retrieval was achieved.

Fig 3.

Retrieval of the 10-mm thrombus. A, The distal device (upper and lower markers <) enters the thrombus. B and C, Approximately half of the thrombotic material is carried within the device; the other half is either pushed sideways to the microcatheter (*) or proximal to the device and is prone to collateral flow (D). E, The supplementary proximal aspiration sucks the entire thrombus from the device into the balloon catheter (open arrow) to achieve total recanalization.

Fig 4.

A, During the retrieval attempt of the 40-mm thrombus, the device is unsheathed distal to the thrombus. B, The device (upper and lower markers <) enters the thrombus. C–E, The thrombotic material is progressively compressed between the device and the microcatheter (*).

Fig 5.

The 40-mm thrombus (]) is initially mobilized within the carrying vessel (A) and partially compressed sideways to the microcatheter (B). C, The thrombus enters the balloon catheter (open arrow); compression of the thrombus causes the distal part to stick at the tip of the balloon catheter. The thrombus is elongated (D) and finally fractures with consequent thromboembolization (→) into other major vessels (E). A major potion of the thrombus is retrieved to the balloon catheter.

Fig 6.

A, The device (upper and lower markers <) is unsheathed distal to the 40-mm thrombus. B and C, During the retrieval attempt, the device enters the compressed thrombus, and the pulling force causes marked elongation of the carrying vessel. The device finally slips through the thrombus catching only a minor fragment (D), which is retrieved together with the microcatheter (*) to the balloon catheter (open arrow; E).