Therapeutische Ultraschallbehandlung des akuten Hirnarterienverschlusses

Combination of ultrasound and rtPA enhances fibrinolysis in an In Vitro clot system

BACKGROUND

Catheter-based lysis with recombinant tissue plasminogen activator (rtPA) is a well-established therapy for spontaneous intracerebral hemorrhage (ICH). The effectiveness of this therapy can be increased with ultrasound, but the optimal conditions are not yet clearly established. Using a novel in vitro system of blood clots previously developed by our group, we investigated various parameters of intralesional sonothrombolysis using an endosonography catheter in combination with rtPA.

METHODS

Standardized human blood clots were equipped with a drainage catheter and weighed before and after 4 treatments: control (drainage only), rtPA only, ultrasound only and the combination of rtPA+ultrasound. The effectiveness of ultrasound was further analysed in terms of optimal frequency, duration and distance to the probe. Temperature and acoustic peak rarefaction pressure (APRP) were assessed to analyse potential adverse effects and quantify lysis. Histo-morphological analysis of the treated clots was performed by H&E staining and confocal laser scanning microscopy using fluorescent fibrinogen.

RESULTS

The combined treatment rtPA+ultrasound achieved the highest lysis rates with a relative weight of 30.3%±5.5% (p≤0.0001) compared to all other groups. Similar results were observed when treating aged clots. Confocal fluorescent microscopy of the treated clots revealed a rarefied fibrin mesh without cavitations. No relevant temperature increase occurred (0.53±0.75°C). The optimal insonation treatment time was 1 hour. APRP measurements showed a lysis threshold of 515.5±113.4 kPa. Application of 10 MHz achieved optimal lysis and lysis radius, while simultaneously proving to be the best frequency for morphologic imaging of the clot and surrounding tissue.

CONCLUSIONS

These promising data provide the basis for an individualized minimal invasive ICH therapy by rtPA and sonothrombolysis independent of ICH age.

In Vitro Evaluation of Focused Ultrasound-Enhanced TNK-Tissue Plasminogen Activator-Mediated Thrombolysis

INTRODUCTION

The low and incomplete recanalization performance of thrombolytic therapy in patients with acute ischemic stroke has created the need to use focused ultrasound (FUS) energy as a way to enhance thrombolysis efficiency (sonothrombolysis). Using an in vitro flow model, the role of various parameters involved in FUS-enhanced tenecteplase (TNK-tPA [tissue plasminogen activator])-mediated thrombolysis was evaluated.

MATERIALS AND METHODS

Fully retracted porcine blood clots were used for the proposed parametric studies. A spherically FUS transducer (4 cm diameter), focusing at 10 cm and operating at 1 MHz, was used. Pulsed ultrasound protocols were applied that maintained temperature elevation at the focus that never exceeded 1°C. Thrombolysis efficiency was measured as the relative reduction in the mass of the clot.

RESULTS

The role of various properties on thrombolysis efficacy was examined. These various properties are the acoustic power, the TNK-tPA concentration, the flow rate, the exposure time, the pulse length, the pulse repetition frequency, the duty factor, the formation of standing waves, the acoustic medium, and the administration of microbubbles. Study results have demonstrated that the parameters examined influenced thrombolysis efficacy and the degree of thrombolysis achieved by each parameter was measured.

CONCLUSIONS

Study findings helped us to optimize the treatment protocol for 1 MHz pulsed FUS that maximizes the thrombolytic efficacy of TNK-tPA, which potentially could be applied for therapeutic purposes. The outcome of the study showed poor thrombolysis efficacy, as with 30 minutes of FUS treatment only 370 mg of clot was removed.

The role of sonolysis and sonothrombolysis in acute ischemic stroke: a systematic review and meta-analysis of randomized controlled trials and case-control studies

OBJECTIVES

To assess the evidence on the safety and efficacy of sonothrombolysis in acute stroke.

SEARCH METHODS

Electronic databases and grey literature were searched under different MeSH terms from 1970 to present.

SELECTION CRITERIA

Randomized control trials (RCTs) and case control studies (CCSs) on sonolysis and sonothrombolysis alone or with microsphere in acute stroke patients (>18 old). Outcome measures included complete recanalization (CR) at 1-2 and 24 hours, 3 months modified Rankin Scale (mRS), and symptomatic intracerebral hemorrhage (sICH). Data was extracted to Review Manager software.

RESULTS

Fifty-seven studies were retrieved and analyzed. Ten studies (7 RCTs and 3 CCSs) were included in our meta-analysis, which revealed that sonolysis and sonothrombolysis are safe (OR of sICH: 1.14; 95% confidence interval (CI): 0.56- 2.34;P=0.71) and effective (OR of CR at 1-2 hours: 2.95;95% CI: 1.81-4.81;P<0.00001) and have more than two-fold higher likelihood of favourable long-term outcome (3-month mRS 0-2; OR: 2.20; CI:1.52-3.19;P<0.0001). Further subgroup analysis based on the presence of microsphere revealed that it is safe (OR of sICH: 1.18; CI:0.433.24;P=0.75) and effective (OR of CR: 2.61; CI: 1.36-4.99;P=0.004). Subgroup analysis based on sonolysis revealed to be safe and effective.

CONCLUSIONS

This novel treatment appears safe and effective. The evidence of microsphere as an enhancement of sonothrombolysis is evolving.

[Sonographic diagnostics in neurological emergency and intensive care medicine]

BACKGROUND

This article gives an up-to-date overview of neurosonographic emergency and intensive care diagnostics.

METHODS

Selective literature research from 1984 with critical appraisal and including national and international guidelines.

RESULTS

Fast and valid diagnostics in acute stroke is the main field of application of neurosonography. Specific monitoring methods bear great advantages for intensive care patients, especially "as-often-as-wanted" repetitive imaging under real-time conditions. A number of new developments make neurosonography an interesting area of research.

CONCLUSIONS

Neurosonography has played a key role in neurological emergency and intensive care medicine for many years. It remains important to continuously support dissemination of the method.