Changes in blood flow velocity in the radial artery during 1‐hour ultrasound monitoring with a 2‐MHz transcranial probe—A pilot study

Abstract

One-hour sonographic Doppler monitoring using a 2-MHz diagnostic transcranial PW Doppler probe may induce peripheral vasorelaxation in humans.

The Role of Sonolysis and Sonothrombolysis in Acute Ischemic Stroke: A Systematic Review and Meta‐analysis of Randomized Controlled Trials and Case‐Control Studies

“…64 In addition, continuous TCD monitoring may lead to peripheral (capillary) vasodilatation probably due to the increase of the nitric oxide synthase activity resulting in a temporal vasodilation which ameliorates local tissue perfusion. 65,66 Finally, several mechanical effects of ultrasound such as radiation force, and acoustic cavitation also have been implicated in the mechanism of sonothrombolysis. 15 In experimental models, ultrasound has been shown to facilitate the activity of fibrinolytic agents within minutes of its exposure to a thrombus and to blood that contains t-PA. [10][11][12][13][14][15][16][17]60 The mechanisms of ultrasound-enhanced thrombolysis include improved drug transport, reversible alteration of the fibrin structure, and increased binding of t-PA to fibrin 12,13 when ultrasound frequencies ranging from kilohertz to those used in diagnostic ultrasonography are used.…”

“…Although the underlying mechanisms of sonothrombolysis are not fully understood, it has been proposed that the ultrasound wave accelerates enzymatic fibrinolysis, primarily through nonthermal mechanisms, by increasing transport of drug molecules into the clot . In addition, continuous TCD monitoring may lead to peripheral (capillary) vasodilatation probably due to the increase of the nitric oxide synthase activity resulting in a temporal vasodilation which ameliorates local tissue perfusion . Finally, several mechanical effects of ultrasound such as radiation force, and acoustic cavitation also have been implicated in the mechanism of sonothrombolysis …”

Safety and efficacy of sonothrombolysis using bilateral TCD monitoring by diagnostic 2 MHz probes - a pilot study

“…Firstly, mechanical effect caused by the thrombus vibration may lead to the acceleration of the penetration of fibrinolytics 3 . Secondly, non-thermal mechanisms -increasing the transport of fibrinolytic agents into the thrombus by mechanical disruption of its structure 24 , direct activation of fibrinolytic enzymes 14,15 , transient peripheral vasodilatation caused probably by increased production of nitrite oxide in the endothelium 21,26 also play a role in clot dissolution. However, confirmation of different effects on thrombus dissolution using various ultrasound frequencies and intensities are still missing.…”

Safety and Efficacy of Endovascular Sonolysis Using the EkoSonic Endovascular System in Patients with Acute Stroke

“…Mechanisms that have been postulated include the following: increasing the transport of fibrinolytic agents into the thrombus by mechanical disruption of its structure 36 ; direct activation of fibrinolytic enzymes (either mechanical dissociation of the complex molecules, in which fibrinolytic enzymes are inactivated by binding to their inhibitors, or irrita- tion of the endothelium with increased production of fibrinolytic enzymes 37,38 ); and transient peripheral (capillary) vasodilation caused probably by increased production of nitric oxide in the endothelium. 39,40 Radiation force and acoustic cavitation are mechanical effects of sonography that have also been postulated to be a potential mechanism. 41 Several clinical studies have tested the feasibility and safety of other mechanical devices, especially of the Merci Retrieval System, Penumbra System, Solitaire stents, and direct placement of stents.…”