Stroke is a leading cause of death worldwide. The majority (85%) of the cases occur when a cerebral artery is occluded by a thrombus, resulting in ischemic stroke. The occluded vessel can be recanalised by mechanical thrombectomy. In mechanical thrombectomy, a device is guided along the vessel to reach, engage and retrieve the occluding thrombus. While a high recanalisation rate (92%) has been achieved, shortcomings (such as distal embolisation and stroke recurrence) are reported.

The major causes of these shortcomings are thrombus disengagement, thrombus fragmentation and vascular damage, which result from poor thrombus-device binding, thrombus maceration and device dragging along the vessel. To improve the treatment outcomes, a better thrombectomy device that (1) enhances the...[ Read more ]

Stroke is a leading cause of death worldwide. The majority (85%) of the cases occur when a cerebral artery is occluded by a thrombus, resulting in ischemic stroke. The occluded vessel can be recanalised by mechanical thrombectomy. In mechanical thrombectomy, a device is guided along the vessel to reach, engage and retrieve the occluding thrombus. While a high recanalisation rate (92%) has been achieved, shortcomings (such as distal embolisation and stroke recurrence) are reported.

The major causes of these shortcomings are thrombus disengagement, thrombus fragmentation and vascular damage, which result from poor thrombus-device binding, thrombus maceration and device dragging along the vessel. To improve the treatment outcomes, a better thrombectomy device that (1) enhances the thrombus engagement, (2) minimises the thrombus fragmentation, and (3) induces minimal vascular damage is needed.

Radio frequency (rf) electric current is commonly used in surgery to coagulate tissue. While the literature has shown that coagulation could induce tissue binding and increase the tissue fracture resistance, the effects of rf on a thrombus remain unknown. In this theis, the application of rf for thrombectomy has been developed and in-vitro and in-vivo (rabbit model) tested. Wire pull testing has been used to examine the effects of rf on a thrombus and to determine the optimal rf-setting. Test results showed that the optimal rf enhances the thrombus-device binding by 40x (detailed in Chapter 2) and increases the thrombus stiffness by 30x (detailed in Chapter 4) (as a result of the 1.8x increase in thrombus cross-linking) (detailed in Chapter 3). The significant increases in thrombus-device binding and thrombus stiffness suggest that the rf enhances the thrombus engagement and minimises thrombus fragmentation, which will reduce the distal embolisation.

In-vitro tests results showed that the rf-thrombectomy achieves a 100% recanalisation rate with an 85% reduction in the retrieval force (correlated with the vascular damage) in comparison with a conventional device (detailed in Chapter 5). The dramatic reduction in retrieval force suggests that the rf-thrombectomy induces minimal damage to the vessel, which will minimise the stroke recurrence. In-vivo tests results showed normal physiological and vascular conditions in a rabbit model after rf-thrombectomy (detailed in Chapter 6). This suggests that rf-thrombectomy is clinically safe, which will satisfy the clinical requirements.

rf-thrombectomy can (1) enhance the thrombus engagement, (2) reduce the thrombus fragmentation, and (3) minimise the vascular damage, making this a promising stroke treatment with improved outcomes.