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Success of stroke treatment with rt-PA depends on rapid vessel recanalization. Enzymatic thrombolysis may be enhanced by additional transcranial application of ultrasound (US). We investigated this novel technique using a 185-kHz probe and compared it to standard diagnostic US. In vitro studies were performed in a continuous pressure tubing system. Clots were placed in a postmortem skull and treated with rt-PA together with or without transtemporal 185-kHz US insonation (2W/cm(2)) and in comparison to 1-MHz diagnostic US (0.5 W/cm(2)). Recanalization time was significantly (p0.01) shorter in the 185-kHz (14.1 min) and 1-MHz (17.1 min) US rt-PA treatment group compared to rt-PA treatment alone (29.3 min.). Flow rate was significantly higher (p0.025) and increased faster in the combined treatment group with rt-PA + 185-kHz US compared to rt-PA + 1-MHz US. We investigated the blood-brain barrier in rats after 90-min exposure time of the brain with 185-kHz US, but no damage was observed. Results suggest efficacy and safety of the 185-kHz transducer, which is superior to diagnostic US. Such a novel US probe may be able to optimize thrombolytic stroke treatment.

Increased platelet reactivity may contribute to the development of coronary artery disease and myocardial infarction. The aim of the present study was to assess platelet adhesiveness in different stages of coronary artery disease using the platelet adhesion assay (PADA). In addition, the acute effect of coronary angiography and stent implantation on platelet adhesiveness was examined.85 patients with stable coronary artery disease (SAP - stable angina pectoris) and 19 patients with acute myocardial infarction (AMI) were enrolled in the study. 35 volunteers served as controls. Blood sampling in SAP and AMI patients was done before coronary angiography to measure the adhesion index (AI) using the PADA. In 33 patients additional blood was drawn at the end of coronary angiography. In 6 patients blood samples were drawn also after stent implantation.In blood samples from patients with an AMI the AI was significantly higher than in blood samples from the SAP group (p0.01) and the control group (p0.01). Coronary angiography and stent implantation did not result in significant acute changes in mean AI however results show an interindividual variability in initial values as well as in AI changes during procedures.This is the first study to show that PADA, a quick and simple laboratory method for the quantitative determination of platelet adhesiveness, is able to detect platelet hyper-adhesiveness in patients with AMI.

Thrombolysis is an efficient therapy for hyperacute stroke within a limited time window. Neurological outcome depends on the recanalization time of the occluded vessel. Nonthermal effects of low-frequency ultrasound (US) accelerate enzymatic fibrinolysis in vitro. We examined the effects of transcranially applied US on recombinant tissue plasminogen activator (rt-PA)-mediated thrombolysis in a flow model in vitro. Pure fibrin clots were placed in a continuous-pressure flow model and treated with rt-PA during 1-MHz US exposure (0.5 W/cm2; spatial peak, temporal peak intensity). Transcranial and direct US application in combination with rt-PA significantly (p < 0.001) shortened recanalization time, increased perfusion flow and reperfusion rate in comparison with rt-PA-mediated thrombolysis alone. Recanalization rate within 30 min was 90–100% in the US-exposed clots vs. 30% in the clots treated only with rt-PA. Our results suggest that transcranial application of 1-MHz US may accelerate reperfusion and recanalization rate of occluded intracerebral vessels by enhancing rt-PA-mediated thrombolysis. Shortening of recanalization time could contribute to optimizing effects of acute thrombolytic stroke therapy.