A review of thrombectomy devices

Suction force rather than aspiration flow correlates with recanalization in hard clots: an in vitro study model

BACKGROUND

ANA Advanced Neurovascular Access provides a novel funnel component designed to reduce clot fragmentation and facilitate retrieval in combination with stent-retrievers (SRs) in stroke patients by restricting flow and limiting clot shaving. In previous publications ANA presented excellent in vitro/in vivo efficacy data, especially with fibrin-rich hard clots. We aimed to determine the main physical property responsible for these results, namely suction force versus aspiration flow.

METHODS

We evaluated in a bench model the suction force and flow generated by ANA and compared them to other neurovascular catheters combined with a SR (Solitaire). Aspiration flow was evaluated with a flow rate sensor while applying vacuum pressure with a pump. Suction force was determined using a tensile strength testing machine and a purposely designed tool that completely seals the device tip simulating complete occlusion by a hard clot. Suction force was defined as the force needed to separate the device from the clot under aspiration. All experiments were repeated five times, and mean values used for comparisons.

RESULTS

Aspiration flow increased with the inner diameter of the device: ANA 1.85±0.04 mL/s, ACE68 3.74±0.05 mL/s, and 8F-Flowgate2 5.96±0.30 mL/s (P<0.001). After introducing the SR, the flow was reduced by an average of 0.57±0.12 mL/s. Due to its larger distal surface, ANA suction force (1.69±0.40 N) was significantly higher than ACE68 (0.26±0.04 N) and 8F-Flowgate2 (0.42±0.06 N) (P<0.001). After introducing the SR, suction force variation was not relevant except for ANA that increased to 2.64±0.41 N.

CONCLUSION

Despite lower in vitro aspiration flow, the ANA design showed a substantially higher suction force than other thrombectomy devices.

Novel aspiration catheter design for acute stroke thrombectomy

Background

Navigable, large diameter aspiration catheters demonstrate markedly improved recanalization rates over smaller lumen devices in suction embolectomy. We evaluated the performance of a novel aspiration catheter system designed to maximize lumen size, and compare it to other commercially available aspiration catheters.

Methods

The 6F R⁴Q aspiration catheter system comprises a proximal pusher wire of 117 cm length connected to a distal catheter of 25 cm length. When placed through standard guide catheters and into the cerebral circulation, the proximal catheter makes a tight seal between its outer surface and the guide catheter’s inner surface. During aspiration, in vitro flow rates and tip suction force under gentle retraction were compared among 10 commercially available aspiration catheters and the R⁴Q system.

Results

The R⁴Q 6F, 5F, 4F, and 3F catheters achieved flow rates at least 21.9%, 24.7%, 61.9%, and 244.7% greater than the other catheters tested respectively and the R⁴Q 6F produced a 140.2% higher tip force than a catheter of similar size. Fluid flow rate in the R⁴Q 6F increased on retraction into the guide catheter, delivering a 58.2% increase from fully extended to fully retracted.

Conclusion

The R⁴Q design demonstrates a substantial increase in aspirated flow rate and suction force due to an increased effective diameter than standard tubular catheter designs tested. The prominent increase in the aspiration parameters measured in vitro supports the potential for improved clinical results during stroke thrombectomy procedures.

Manual aspiration thrombectomy devices use in coronary interventions in 2016

Percutaneous coronary intervention is a highly effective therapy of acute myocardial infarction. Restoration of microcirculation is however often sub-optimal with negative impact on patient outcome. Distal thrombus embolization may contribute to this issue. Simple manual aspiration thrombectomy catheters were developed with aim of thrombus extraction. There are several of these devices with very similar design. Thrombotic or atheromatous tissue is successfully retrieved in over 70% of patients. The initial results of small, often single center studies have provided encouraging results. Unfortunately, three further studies clearly demonstrated lack of any clinical benefit and routine use of manual aspiration thrombectomy cannot be recommended. Small but statistically significant increase in stroke rate is the major safety issue. Selective use in patients with large thrombus burden or suboptimal flow or perfusion is likely to continue and needs to be scientifically studied.