Aspiration and First Pass - Ep.2/2 - SLICE WorldWide 2022

Aspiration technology: it’s not just about luminal diameter, although diameter is the most important!

Introduction:

As mentioned in a previous analysis – first-line aspiration technology is rapidly evolving and provides promising first-pass effect rates of 70-80%[1,2]. These improvements are expected to be available for routine clinical use in the following years. They are mainly obtained by increasing the device’s size, which provides subsequent, direct improvements in aspiration force and facilitates complete clot ingestion, thereby limiting distal emboli. However, several other enhancements may involve “aspiration” making future pump aspiration much more efficacious than it is now.

Future aspiration force improvements:

• Convincing previous work showed that using an aspiration pump does not provide any additional benefit while aspirating with a 0.070 catheter compared to manual aspiration. Although counterintuitive –the vacuum created by the pump must be maintained in a 1.5 L canister and a 2.7-meter tubing and thus is not superior to that produced by manually aspirating with a 60 ml syringe. These results must be remembered each time a costly at least 200-300 euro pump is constantly used in clinical practice[3].
• However, several improvements in pump engineering, AI, and design may (if they finally show superiority in third third-party testing) create a significant advantage for pump aspiration: notably cyclical aspiration and intermittent aspiration.
• There are several reports in the literature showing that initial results with cyclical aspiration are promising. Kalousek et al. report first-pass reperfusion rates of as high as 68.4% with 76.3% with a novel system of cyclical aspiration in a pioneer study[4]. This compares very favorably with historic first-pass effects of 24-30%. However, further validation of the efficacy of cyclic aspiration in a randomized patient population with outsourcing of imaging adjudication to people blinded to initial aspiration type is mandatory to obtain valid results – as comparisons of otherwise selected patients to historical data are always expected to favor the current technique.
• The reasons for the improvement of the first-pass effect with cyclical aspiration are related to the following[4–6]:
  1. Improving Dimensional Fit: cyclical aspiration may allow for dynamic stretching of the clot, which can decrease the outer diameter of the clot facilitating the ingestion. Moreover, this may reduce clot fragmentation by keeping it within its elastic limits.
  2. Reducing friction force. Once the clot is trapped in the catheter tip – continuous aspiration may not overcome the friction between the clot and the catheter. It may remain stuck there – leading to fragmentation and distal emboli upon retrieval. Cyclic aspiration may help to stretch the clot dynamically and thus ingest it.
  3. Improving lubrication via micro-fluid flow.  There are microfluid channels of retrograde blood that enter the catheter once the clot enters the catheter tip – this may facilitate aspiration, which is increased by a cyclical aspiration pattern and act as a sort of lubrication. 
• Intermittent aspiration. While probably not providing a big advantage in terms of first-pass effect – intermittent aspiration (aspiration stops when the clot is not engaged) has already proven useful for sinus venous thrombosis in several reports. Adapting this kind of technology to the neurovascular field will probably enhance these results[7].

Conclusion

The technological evolution driving acute ischemic stroke reperfusion therapies is extraordinary and unprecedented in the field of neurointervention. While we are not there yet – future aspiration technology promises 70% first pass effect as compared to less than 40% with currently available devices. Due to its simplicity and provided its cost will further decrease – we might expect a thrombectomy revolution to be implemented world-wide with no discrepancy between developed and less developed countries.

Further reading:

1. Fitzgerald S, Ryan D, Thornton J, et al. Preclinical evaluation of Millipede 088 intracranial aspiration catheter in cadaver and in vitro thrombectomy models. J Neurointerv Surg 2021;13:447–52. doi:10.1136/neurintsurg-2020-016218

2. Caldwell J, McGuinness B, Lee SS, et al. Aspiration thrombectomy using a novel 088 catheter and specialized delivery catheter. J Neurointerv Surg 2022;14:1239–43. doi:10.1136/neurintsurg-2021-018318

3. Gross BA, Jadhav AP, Jovin TG, et al. Dump the pump: Manual aspiration thrombectomy (MAT) with a syringe is technically effective, expeditious, and cost-efficient. J Neurointerv Surg 2018;10:354–7. doi:10.1136/neurintsurg-2017-013520

4. Kalousek V, Yoo AJ, Sheth SA, et al. Cyclical aspiration using a novel mechanical thrombectomy device is associated with a high TICI 3 first pass effect in large‐vessel strokes. Journal of Neuroimaging 2021;31:912–24. doi:10.1111/jon.12889

5. Arslanian RA, Marosfoi M, Caroff J, et al. Complete clot ingestion with cyclical ADAPT increases first-pass recanalization and reduces distal embolization. J Neurointerv Surg 2019;11:931–6. doi:10.1136/neurintsurg-2018-014625

6. Marosfoi M, Strittmatter L, Arslanian R, et al. E-112 How do clots respond to direct aspiration during interventional treatment of acute ischemic stroke. In: Journal of NeuroInterventional Surgery. BMJ 2019. A109.2-A110. doi:10.1136/neurintsurg-2019-snis.187

7. Kothari S, Morsi RZ, Thind S, et al. Endovascular thrombectomy for cerebral venous sinus thrombosis using the Penumbra Indigo ® Aspiration System. Interventional Neuroradiology 2023;:159101992311526. doi:10.1177/15910199231152692