Wake-up stroke-Amendable for thrombolysis-like stroke with known onset time?

Patients suffering an acute ischemic stroke can be treated with intravenous thrombolysis in the absence of contraindications. A known onset time is a prerequisite as treatment, according to guidelines, has to be started within 4.5 hours. In patients awakening with a stroke, the last time they were seen without a neurological deficit is assumed to be the time of onset. Thus, despite of lack of contraindications on initial brain imaging, these patients are largely excluded from therapy. This review discusses the underlying pathophysiological, clinical, and radiological evidence surrounding wake-up stroke and its consequences for making treatment decisions.

Radiological imaging in acute ischaemic stroke.

Patients who suffer acute ischaemic stroke can be treated with thrombolysis if therapy is initiated early. Radiological evaluation of the intracranial tissue before such therapy can be given is mandatory. In this review current radiological diagnostic strategies are discussed for this patient group. Beyond non-enhanced computed tomography (CT), the standard imaging method for many years, more sophisticated CT stroke protocols including CT angiography and CT perfusion have been developed, and additionally an increasing number of patients are examined with magnetic resonance imaging as the first imaging method used. Advantages and challenges of the different methods are discussed.

Evaluation of the recombinant tissue plasminogen activator pretreatment in acute stroke patients with large vessel occlusions treated with the direct bridging approach. Is it worth the effort?

BACKGROUND AND PURPOSE: The direct bridging concept in acute stroke treatment combines intravenous thrombolysis (IVT) and endovascular treatment (EVT). The frequency and extent of reperfusion obtained already due to IVT were evaluated. Additionally undesired events and the clinical outcome were analysed. METHODS: Fifty-seven acute stroke patients treated with direct bridging were analysed for this study. The response to IVT was evaluated according to the modified Thrombolysis in Cerebral Infarction scale (m-TICI). IVT responders (m-TICI ≥2B in digital subtraction angiography) were compared with IVT non-responders (m-TICI <2B in digital subtraction angiography) with respect to clinical outcome and occurrence of undesired events. RESULTS: Fourteen patients (25%) got a change from TICI 0 to ≥2B due to IVT alone. There were otherwise no differences between the IVT responders and IVT non-responders. CONCLUSIONS: Intravenous thrombolysis pretreatment in the context of the bridging approach contributes substantially to revascularization.

Acute ischemic stroke--from symptom recognition to thrombolysis.

OBJECTIVES: The understanding of stroke has changed in the recent years from rehabilitation to an emergency approach. We review existing data from symptom recognition to thrombolysis and identify challenges in the different phases of patient treatment. RESULTS: Implementation of treatment in dedicated stroke units with a multidisciplinary team exclusively treating stroke patients has led to significant reduction of stroke morbidity and mortality. Yet, first the introduction of treatment with intravenous rtPA (IVT) has led to the 'time is brain' concept where stroke is conceived as an emergency. As neuronal death in stroke is time dependent, all effort should be laid on immediate symptom recognition, rapid transport to the nearest hospital with a stroke treatment facility and diagnosis and treatment as soon as possible. The main cause of prehospital delay is that patients do not recognize that they suffered a stroke or out of other reasons do not call the Emergency Medical Services immediately. Educational stroke awareness campaigns may have an impact in increasing the number of patients eligible for rtPA treatment and can decrease the prehospital times if they are directed both to the public and to the medical divisions treating stroke. Stroke transport times can be shortened by the use of helicopter and a stroke mobile--an ambulance equipped with a CT scanner--may be helpful to decrease time from onset to treatment start in the future. Yet, IVT has several limitations such as a narrow time window and a weak effect in ischemic strokes caused by large vessel occlusions. In these cases, interventional procedures and the concept of bridging therapy, a combined approach of IVT and intraarterial thrombolysis or mechanical thrombectomy, might improve recanalization rates and patient outcome. CONCLUSIONS: As neuronal death in stroke patients occurs in a time-dependent fashion, all effort should be made to decrease time from symptom onset to treatment start with rtPA: major challenges are stroke recognition in the public, transport times to hospital and an efficient stroke triage in the hospital.

Ischemic stroke--novel therapeutic strategies.

OBJECTIVES: Treatment of acute, ischemic stroke has changed markedly during the last two decades. We review existing data for optimizing modern stroke care. RESULTS: Implementation of stroke units, giving systematic treatment and observation to stroke patients, has lead to a significant reduction in death and dependency. Introduction of intravenous rt-PA (IVT) within 3 h for selected stroke patients and recent extension of the time window to 4.5 h improved the outcome even further. Still, one must consider that IVT has several limitations, such as a narrow time window and several contraindications, and the effect is modest, particularly in strokes with a large vessel occlusion. Recanalization of the occluded vessel is a major predictor for good outcome and should be set as a goal. Intra-arterial rt-PA (IAT) and the concept of bridging therapy (IVT prior to IAT or thrombectomy with a mechanical device) may improve recanalization rates and outcome. Randomized controlled trials (RCT) are available for IAT, but not for thrombectomy with devices, and we mostly have retrospective non-controlled data. The Merci- and Penumbra system are the most studied devices, for which recent studies report acceptable safety and efficacy. CONCLUSIONS: Sufficiently powered RCTs to evaluate the effect of thrombectomy with mechanical devices are warranted, but as the natural course of a large vessel stroke carries a devastating prognosis, a proactive recanalization approach is justified based on today's knowledge.

Renal transplant failure due to urologic complications: Comparison of static fluid with contrast-enhanced magnetic resonance urography.

PURPOSE: Postrenal reasons of renal transplant failure can be assessed by magnetic resonance urography. This study was designed to retrospectively compare the diagnostic accuracy of static fluid (T2-)MRU compared to contrast enhanced (CE-)MRU in patients with renal transplant failure. MATERIAL AND METHODS: Thirty-five consecutive patients (14 female, 21 men; mean age 48.6 years) with renal transplant failure and sonographically detected hydronephrosis were examined both with T2-MRU as well as CE-MRU resulting in 39 MRU examinations. MRU was performed both using T2-weighted HASTE-sequence (T2-MRU) as well as Gadolinium-enhanced 3D-FLASH-sequence (CE-MRU) on a 1.5-T clinical MRI scanner (Magnetom Vision, Siemens Medical Solutions). Subjective image quality of resulting maximum intensity projection was assessed in consensus by two readers blinded to the final diagnosis, using a five point scale. MRU findings were correlated to sonography, operative results or clinical follow up. RESULTS: CE-MRU yielded a sensitivity of 85.7% (T2-MRU 76.2%), and a specificity of 83.3% (T2-MRU: 73.7%), however statistical significance was not reached. The subjective image quality was significantly better in CE-MRU. CONCLUSIONS: Only concerning subjective image quality CE-MRU proved superior to T2-MRU. Yet, there was no significant difference in diagnostic accuracy between T2- and CE-MRU. Thinking of incipient nephrogenic systemic fibrosis, T2-MRU can be used as reliable alternative in patients with decreased renal transplant function due to urological complications.

Assessment of three different software systems in the evaluation of dynamic MRI of the breast.

OBJECTIVE: The aim was to compare the diagnostic performance and handling of dynamic contrast-enhanced MRI of the breast with two commercial software solutions ("CADstream" and "3TP") and one self-developed software system ("Mammatool"). MATERIALS AND METHODS: Identical data sets of dynamic breast MRI from 21 patients were evaluated retrospectively with all three software systems. The exams were classified according to the BI-RADS classification. The number of lesions in the parametric mapping was compared to histology or follow-up of more than 2 years. In addition, 25 quality criteria were judged by 3 independent investigators with a score from 0 to 5. Statistical analysis was performed to document the quality ranking of the different software systems. RESULTS: There were 9 invasive carcinomas, one pure DCIS, one papilloma, one radial scar, three histologically proven changes due to mastopathy, one adenosis and two fibroadenomas. Additionally two patients with enhancing parenchyma followed with MRI for more than 3 years and one scar after breast conserving therapy were included. All malignant lesions were classified as BI-RADS 4 or 5 using all software systems and showed significant enhancement in the parametric mapping. "CADstream" showed the best score on subjective quality criteria. "3TP" showed the lowest number of false-positive results. "Mammatool" produced the lowest number of benign tissues indicated with parametric overlay. CONCLUSION: All three software programs tested were adequate for sensitive and efficient assessment of dynamic MRI of the breast. Improvements in specificity may be achievable.

Structure-based design of potent, amidine-derived inhibitors of factor Xa: evaluation of selectivity, anticoagulant activity, and antithrombotic activity.

To enhance the potency of 1,2-dibenzamidobenzene-derived inhibitors of factor Xa (fXa), an amidine substituent was incorporated on one of the benzoyl side chains to interact with Asp189 in the S1 specificity pocket. Lead molecule 1 was docked into the active site of fXa to facilitate inhibitor design. Subsequently, iterative SAR studies and molecular modeling led to a 1000-fold increase in fXa affinity and a refined model of the new inhibitors in the fXa active site. Strong support for the computational model was achieved through the acquisition of an X-ray crystal structure using thrombin as a surrogate protein. The amidines in this series show high levels of selectivity for the inhibition of fXa relative to other trypsin-like serine proteases. Furthermore, the fXa affinity of compounds in this series (K(ass) = 50-500 x 10(6) L/mol) translates effectively into both anticoagulant activity in vitro and antithrombotic activity in vivo.

Antithrombotic efficacy in the guinea pig of a derivative of human protein C with enhanced activation by thrombin.

Conversion by alpha-thrombin of the zymogen human protein C (HPC) to activated protein C (aPC) is an important physiologic feedback control mechanism for the coagulation cascade. Although activation of HPC by thrombomodulin-bound thrombin is relatively rapid, activation by free thrombin occurs at a significantly slower rate. Previously, we generated a "hyper-activatable" derivative of HPC (FLIN-Q3) with an increased activation rate by free alpha-thrombin in vitro. In this study, the antithrombotic efficacy of FLIN-Q3 was compared with both native zymogen and aPC in an arteriovenous shunt model of thrombosis in the guinea pig. Recombinant proteins were infused 15 minutes before and throughout a 15-minute period while blood was circulated from carotid to jugular through tubing that enclosed a thread on which fibrin was deposited. Parallel dose-dependent antithrombotic responses were observed. Under these non-steady-state conditions, the calculated infusion doses associated with a 50% reduction of thrombus mass were 2.7, 24, and 250 mg/kg/h for aPC, FLIN-Q3, and HPC, respectively. Thrombus weight correlated inversely with plasma concentration of aPC, measured amidolytically, from either direct infusion of aPC or that generated from the zymogens in the animal, and similarly correlated inversely with anticoagulant activity measured by whole blood aPTT. Neither zymogen form showed significant aPC activity before shunt circulation, suggesting a requirement for exposure to thrombin. After the infusion was discontinued for 15 minutes, a second period of thrombus formation in the shunt demonstrated the ability of zymogen forms of PC, unlike aPC, to provide "on-demand" anticoagulant responses to repeated thrombotic stimuli. Thus, a "hyper-activatable" PC molecule such as FLIN-Q3 may represent a superior form of anticoagulant therapy than either the native zymogen or aPC.

A family of arginal thrombin inhibitors related to efegatran.

Three new tripeptide arginal thrombin inhibitors were shown to have potent anticoagulant and antithrombotic activity: D-MePhg-Pro-Arg-H (LY287045), D-1-Tiq-Pro-Arg-H (LY294291), and D-MePhe-Pro-Arg-H (Efegatran). Efegatran and the related arginals differ mechanistically from old and from new anticoagulant agents. As illustrated with x-ray diffraction analysis of crystals of the LY294291 complex with human thrombin, the family of arginals binds thrombin with the P3, P2, and P1 residues interacting with the putative S3, S2, and S1 fibrinogen-binding sites. A hemi-acetal bond at Ser 195 was shown to contribute to the tight-binding reversible competitive thrombin inhibition properties observed with the arginal family. Tight-binding Kass values from thrombin inhibition studies correlated with thrombin clottin inhibition potency. The thrombin time (TT) assay was prolonged twofold with 33 nM Efegatran, which demonstrated an apparent Kass value of 0.8 x 10(8) L/mol (for comparison, 17 nM hirudin was required to prolong the TT assay two-fold). There are empirical anticoagulant selectivity differences between Efegatran and hirudin, manifested by large activated partial thromboplastin time (aPTT)/TT effect ratios (30 to 55) found with the arginals, as compared to the small aPTT/TT effect ratio (2 to 3) found with hirudin. The underlying anticoagulant mechanism differences between the arginals and hirudin appear to be confined to the aPTT pathway and, therefore, might involve different effects toward thrombin feedback activation of factor VIII. The arginals did not substantially inhibit other coagulation factor serine proteases. Antithrombotic effects of Efegatran and the arginal family occur at low infusion doses in dogs and appear to correlate with effects on TT without requiring perturbation of the aPTT. Selectivity properties regarding the fibrinolytic enzymes were shown to be important for successful use of the arginals in vivo as adjunctive agents during tissue plasminogen activator (t-PA) thrombolysis. The data suggest that LY287045, LY294291, and Efegatran should be expected to be useful as antithrombotic adjuncts to thrombolytic therapy with t-PA, urokinase, or streptokinase and should be expected to spare endogenous fibrinolysis. Efegatran has been evaluated in phase I clinical studies and is currently under clinical investigation in phase II protocols as a new cardiovascular anticoagulant.

Comparative 5-HT2-receptor antagonist activity of amesergide and its active metabolite 4-hydroxyamesergide in rats and rabbits.

Amesergide is an orally active ergoline amide, 5-HT2-receptor antagonist with a long duration of action. Since a major metabolite of amesergide is 4-hydroxyamesergide, we questioned whether the formation of this metabolite might contribute to the pharmacological activity and long duration of action observed after oral administration of amesergide. 4-Hydroxyamesergide was a potent 5-HT2-receptor antagonist with an affinity equal to or greater than amesergide under in-vitro conditions as measured by blockade of vascular 5-HT2 receptors, and 5-hydroxytryptamine (5-HT)-amplified ADP-induced rabbit platelet aggregation. Furthermore, 4-hydroxyamesergide, like amesergide, inhibited the pressor response to 5-HT after its intravenous administration to rats and was about 3-fold more potent than amesergide in this regard. 4-Hydroxyamesergide was also a potent inhibitor of vascular 5-HT2 receptors after oral administration to rats. After oral administration, 4-hydroxyamesergide had a similar or slightly greater duration of activity than the parent molecule. 4-Hydroxyamesergide, again like amesergide, also blocked central 5-HT2 receptors after its in-vivo administration to rats as measured by its ability to inhibit quipazine-induced increases in serum corticosterone. Thus, the formation of 4-hydroxyamesergide after oral administration of amesergide to animals and man may contribute to the potency and long duration of action of amesergide as a 5-HT2-receptor antagonist.

Preclinical studies on LY237733, a potent and selective serotonergic antagonist.

8B-N-cyclohexyl-6-methyl-1(1-methylethyl)ergoline-8-carboxamide (LY237733) is an ergoline with potent and highly selective 5-hydroxytryptamine (5-HT) antagonist activity. The in vitro radioligand displacement studies showed that LY237733 has a preferential affinity for 5-HT1c and 5-HT2 receptors compared to other monoaminergic receptors. This characteristic is shared with other previously described ergoline 5-HT antagonists, such as LY53857 and sergolexole. In parallel ligand displacement assays, LY237733 had a similar potency to sergolexole. LY237733 was equipotent to sergolexole, but slightly less potent than LY53857 in the antagonism of 5-HT-induced elevation in blood pressure and quipazine-induced elevation in corticosterone levels, which are considered to be measures of 5-HT2 and possibly 5-HT1c antagonist activity. LY237733 failed to antagonize pergolide or 8-hydroxy-2-(di-n-propylamino)tetralin-induced elevations in serum corticosterone levels, indicating selectivity for the 5-HT1c/2 receptor, relative to 5-HT1a and D2 dopaminergic receptors. The only in vivo response that could be detected after administration of LY237733 alone in doses less than 1 mg/kg was the amplification of male rat sexual behavior. LY237733 was 10 to 100 times more potent than LY53857 or sergolexole in augmenting sexual responses of male rats with different levels of sexual response capacity. LY237733 has a much longer serum half-life than sergolexole. These studies have provided the pre-clinical rationale to evaluate the effects of this compound in the treatment of sexual disorders such as psychogenic erectile dysfunction, and other therapeutic indications for a 5-HT2 antagonist, including depression, anxiety, schizophrenia and migraine.

Rat model of arterial thrombosis induced by ferric chloride.

The purposes of these studies were to produce a small animal model of arterial thrombosis for study of novel antithrombotic agents, to validate a simple temperature index of occlusive thrombosis, and to describe the composition of the thrombus. Small thermocouple transducers were fabricated from readily available materials. A thermocouple was inserted under a carotid artery of the anesthetized rat and vessel temperature was recorded continuously. Arterial injury was induced by FeCl3 solution applied topically to the artery above the thermocouple. To validate the relationship between thrombotic occlusion and vessel temperature, blood flow velocity, proximal to the injury, and temperature were recorded simultaneously. Temperature decreased rapidly when velocity averaged 24 +/- 12 percent of control and velocity did not differ from zero within 20 sec. In normal vessels, average flow velocity did not decrease significantly from control until a fixed stenosis decreased diameter by 78 percent. Average time to occlusion (TTO), signaled by the abrupt temperature inflection, ranged from 56 +/- 4 min to 14 +/- 1 min after 10 and 65 percent FeCl3 application respectively. Vessel segments were fixed at various times after FeCl3 exposure and examined by scanning electron microscopy. Endothelial damage was observed and was associated with thrombus composed of activated platelets, fibrin strands and entrapped erythrocytes. The results demonstrate that FeCl3 dose-dependently induced formation of an occlusive mixed thrombus that was indexed by monitoring the time between FeCl3 application and a rapid temperature decrease in the carotid artery of the rat.

Preclinical pharmacology of a new serotonergic receptor antagonist, LY281067.

The preclinical pharmacologic activity of LY281067 shows it to be a potent and highly selective serotonergic (5-HT2) receptor antagonist. Based upon binding studies with 5-HT2 receptors in brain cortical membranes and block of 5-HT-induced contractions in the rat jugular vein, LY281067 showed high affinity at 5-HT2 receptors with a dissociation constant of approximately 1 nM. Furthermore, LY281067 was a highly selective 5-HT2 receptor antagonist without appreciably binding to 5-HT1, D1 or D2 receptors or interacting with histamine (H1), cholinergic, beta adrenergic or alpha-1 adrenergic receptors in smooth muscle. LY281067 had modest affinity at alpha-2 receptors with a dissociation constant of approximately 100 nM. Oral bioavailability of LY281067 in spontaneously hypertensive rats was excellent with an oral to i.v. dose ratio approximating 4, based upon blockade of pressor responses to 5-HT as an in vivo estimate of 5-HT2 receptor antagonist activity. Furthermore, LY281067 blocked quipazine-induced increase in serum corticosterone concentration, an increase thought to be mediated by activation of central 5-HT receptors. After oral administration to rats, LY281067 antagonized vascular 5-HT2 receptors with a relatively long duration of action (greater than 6 hr), an observation likely to be related to plasma concentrations of both the parent and an active metabolite. Lastly, LY281067 was relatively nontoxic, possessing a therapeutic index of approximately 1000 after oral administration to rats. In summary, LY281067 is a potent and highly selective, orally active 5-HT2 receptor antagonist with a relatively long duration and wide margin of therapeutic safety.

Pinacidil-induced vascular relaxation: comparison to other vasodilators and to classical mechanisms of vasodilation.

Pinacidil is a potent antihypertensive agent in animals and humans. In conscious spontaneously hypertensive rats after oral administration, pinacidil was approximately 3- and 10-fold more potent than hydralazine and minoxidil, respectively. Likewise, under in vitro conditions, pinacidil (ED50 = 0.3 microM) was more potent in relaxing serotonin-contracted rat aortic strips than either minoxidil (ED50 = 0.1 mM) or hydralazine (ED50 = 0.2 mM). These data are consistent with the contention that pinacidil is a direct-acting vasodilator whereas minoxidil and hydralazine may be converted in vivo to active moieties and/or exert indirect effects more apparent under in vivo than in vitro conditions. The pharmacology of pinacidil appears unrelated to classical mechanism of vasodilation. Pinacidil does not interact with alpha, beta, cholinergic, or histaminergic receptors. Pinacidil does not produce vasodilation via an indirect effect mediated by adenosine, prostaglandin, or endothelial-derived relaxant factor (EDRF) release. Pinacidil does not alter cAMP or cGMP levels and, based on numerous approaches, does not resemble conventional calcium channel antagonists in its vasodilating activity. Thus, a review of the literature presented herein supports the contention that pinacidil-induced vascular relaxation is a direct effect mediated by a novel mechanism.

5-HT2-receptor antagonists: alpha 1- vs. 5-HT2-receptor blocking properties in blood vessels.

LY53857, spiperone, ketanserin, and setoperone were potent and competitive 5-HT2-receptor antagonists in the rat jugular vein with equivalent affinities at 5-HT2 receptors. In the rat jugular vein, ritanserin blocked 5-HT2-mediated contractile responses with a depression of the maximum response in concentrations greater than 3 X 10(-10) M. Ketanserin, spiperone, ritanserin, and setoperone were also alpha 1-adrenergic receptor antagonists, although affinity at alpha 1-adrenergic receptors was less for ritanserin and setoperone than for ketanserin or spiperone. Of the 5-HT2-receptor antagonists examined, LY53857 was the most selective with respect to alpha 1-adrenergic receptor affinity, showing 250,000-fold selectivity as an antagonist at 5-HT2 receptors. The possibility that the dual properties of 5-HT2- and alpha 1-receptor blockade confer greater antihypertensive efficacy than alpha 1-receptor blockade alone was also examined in vivo. However, acute administration of LY53857 at doses sufficient to abolish 5-HT2-receptor activation did not enhance blood pressure reduction produced by the alpha-adrenergic receptor antagonist phentolamine in normotensive or spontaneously hypertensive rats. These data argue against an important role for 5-HT2 receptors in blood pressure regulation even in combination with alpha-adrenergic receptor blockade.

Effect of meta-chlorophenylpiperazine (mCPP), a central serotonin agonist and vascular serotonin receptor antagonist, on blood pressure in SHR.

mCPP (meta-chlorophenylpiperazine) has agonist activity at some central serotonin receptors and antagonist activity at peripheral vascular 5HT2 receptors, both effects that have been postulated to lower blood pressure. mCPP (10 and 30 mg/kg, i.p. 1 hr after administration) increased serotonin and decreased 5-hydroxy-indolacetic acid (5-HIAA) brain concentrations and elevated serum corticosterone and prolactin, indications of central serotonergic agonist activities. The same doses of mCPP also antagonized vascular 5HT2 receptors as measured by blockade of pressor responses to serotonin in pithed rats. Although mCPP could be demonstrated to activate central serotonergic receptors and block peripheral vascular 5HT2 receptors, mCPP (10 and 30 mg/kg, i.p.) produced little effect on blood pressure in either the anesthetized or conscious spontaneously hypertensive rat (SHR) up to 1 hr after intraperitoneal administration. The findings are consistent with initial studies in normotensive humans that have not demonstrated a reduction in blood pressure clinically after mCPP in doses that produce elevations in serum cortisol and prolactin levels.

Body fluid volumes in rats with mestranol-induced hypertension.

Because estrogens have been reported to produce sodium retention, this study investigated the possibility that hypertension in rats resulting from the ingestion of an estrogen used as an oral contraceptive could be due to increases in body fluid volumes. Female rats were given feed containing mestranol for 1, 3, and 6 mo; control rats were given the feed without mestranol. The mestranol-treated rats had higher arterial pressures than the controls only after 6 mo of treatment. Plasma volume, extracellular fluid volume, and total body water were measured in each rat by the distribution volumes of radioiodinated serum albumin, 35SO4, and tritiated water, respectively. Values for blood volume, interstitial fluid volume, and intracellular fluid volume were derived from these measurements. These body fluid volumes, expressed per 100 g of body weight, were not different between the mestranol-treated rats and their controls at any of the three treatment times. Due to differences in body weight and lean body mass between the mestranol-treated and the control rats, these volumes also were expressed per 100 g of lean body mass. Again, no differences were observed between the mestranol-treated rats and the control rats for any of these body fluid compartments at any of the treatment times. These studies, therefore, were unable to provide evidence that increases in body fluid volumes contributed to the elevated arterial pressure in this rat model of oral contraceptive hypertension.