Introduction: Cerebral mechanical thrombectomy for acute stroke has become more efficient but is still not successful in 100% of cases.[1] One strategy to increase clot removal was ultrasonic cerebral clot lysis, which utilized high-frequency, low amplitude oscillation as a destructive force on the thrombus but has met with limited clinical success.[2] More powerful ultrasound caries the risk of increased heat, threatening cerebral tissue.[3] It is possible that applying significantly higher amplitude mechanical oscillation with concurrent aspiration could break up and clear a thrombus, using the same principles of high-power ultrasonic destruction without increased heat.

Methods: An oscillating mechanical impact aspiration device was created with a Penumbra Aspiration System. A Penumbra 5Max catheter was placed in a flow model and attached to a Penumbra aspiration pump with a 4-way stop-cock and primed to 25mmHg. A 2mm x 3mm artificial clot that was too large to fit through the 5Max with syringe suction was placed at the catheter tip. 1 Hz oscillation between 25mmHg and 0 was then applied for 5 minutes. This was repeated 7 times.

Results: The clot was removed from the flow model in all trials within 5 minutes.

Conclusions: An oscillating mechanical impact aspiration device utilizing the Penumbra Aspiration System can destroy and remove clots too large to fit through a 5Max catheter. Further study will involve experimentation with rate and amplitude to find the most effective combination.

Patient Care: Our research has the potential to increase the rate of revascularization for cerebral thrombectomy and therefore decrease the number of patients who suffer a cerebral infarction

Learning Objectives: Understand the principles of ultrasound clot lysis and how they can be manipulated to create a more effective device

References: 1: Nogueira RG, Lutsep HL, Gupta R, Jovin TG, Albers GW, Walker GA, Liebeskind DS, Smith WS; TREVO 2 Trialists. Trevo versus Merci retrievers for thrombectomy revascularisation of large vessel occlusions in acute ischaemic stroke (TREVO 2): a randomised trial. Lancet. 2012 Oct 6;380(9849):1231-40. doi: 10.1016/S0140-6736(12)61299-9. Epub 2012 Aug 26. Erratum in: Lancet. 2012 Oct 6;380(9849):1230. 2: Mahon BR, Nesbit GM, Barnwell SL, Clark W, Marotta TR, Weill A, Teal PA, Qureshi AI. North American clinical experience with the EKOS MicroLysUS infusion catheter for the treatment of embolic stroke. AJNR Am J Neuroradiol. 2003 Mar;24(3):534-8. 3: Harnof S, Zibly Z, Cohen Z, Shaw A, Schlaff C, Kassel N. Cranial nerve threshold for thermal injury induced by MRI-guided high-intensity focused ultrasound (MRgHIFU): preliminary results on an optic nerve model. IEEE Trans Ultrason Ferroelectr Freq Control. 2013 Apr;60(4):702-5.