THESIS
2017
1 volume (various pages) : illustrations ; 30 cm
Abstract
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...[
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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.
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