Coronary thrombolysis with facilitated absorption of intramuscularly injected tissue-type plasminogen activator

Conventional activators of the fibrinolytic system used for coronary thrombolysis entail unavoidable delay, risk of bleeding, or both in contrast to tissue-type plasminogen activator (t-PA). Because the potential benefit of coronary thrombolysis is inversely related to the duration of antecedent ischemia, this study was performed to develop an approach for facilitated absorption of intramuscularly injected t-PA potentially adaptable for prompt, self-medication. In rabbits, absorption was markedly potentiated by hydroxylamine hydrochloride and electrical stimulation at the injection site. Intramuscular administration of t-PA in doses of 1 mg/kg of body weight, comparable to amounts given intravenously to patients (0.5-0.75 mg/kg), elicited peak blood levels of 431 +/- 52 (SEM) ng/ml 5 min after injection, well within the therapeutic range. In dogs, absorption facilitated by hydroxylamine promptly elicited angiographically documented coronary thrombolysis as well. The approach developed should ultimately permit prompt coronary thrombolysis and enhanced salvage of jeopardized ischemic myocardium in patients with life-threatening coronary thrombi.

Coronary thrombolysis and infarct size reduction after intravenous infusion of recombinant tissue-type plasminogen activator in nonhuman primates

Occlusive thrombus was produced by thrombin-induced coagulation in the left anterior descending coronary artery (LAD) of 16 open-chest baboons. In six control animals, occlusive thrombosis persisting over a period of 4 h as evidenced by coronary arteriography resulted in large transmural infarction (63.1 +/- 3.5% of the perfusion area). In 10 animals, tissue-type plasminogen activator obtained by recombinant DNA technology (rt-PA) was infused systemically at a rate of 1,000 IU (10 micrograms)/kg per min for 30 min after 30-80 min of coronary thrombosis. Reperfusion occurred within 30 min in nine animals. In one animal, intravenous infusion was followed by an intracoronary infusion at the same rate, which resulted in thrombolysis within 8 min. In the rt-PA group, mean duration of occlusion before reperfusion was 77 +/- 24 min. Reocclusion occurred in one animal. Recanalization resulted in an overall reduction of infarct size (37.8 +/- 5.9%, P less than 0.05 versus controls). Residual infarction was related to the duration of occlusion (r = 0.80, P less than 0.01). Reperfusion was associated with reduced reflow. Myocardial blood flow in the perfusion area of the LAD was only 70% of normal after 4 h despite perfect angiographic refilling. The infusion of rt-PA was not associated with systemic activation of the fibrinolytic system, fibrinogen breakdown, or clinically evident bleeding. It is concluded that intravenous infusion of rt-PA may recanalize thrombosed coronary vessels without inducing systemic lysis. The extent of residual infarction is closely related to the duration of coronary artery occlusion before thrombolysis.

Thrombolysis with recombinant tissue plasminogen activator in atherosclerotic thrombotic occlusion

Human tissue plasminogen activator holds promise for the dissolution of coronary thrombi by intravenous administration and without systemic anticoagulation. Prior animal experiments have been conducted only in vessels without disease. To test the thrombolytic efficacy of recombinant tissue plasminogen activator in the presence of diseased intima, an established model of atherosclerosis was utilized. The aorta of 16 New Zealand white rabbits (2 to 3 kg) was made atherosclerotic by balloon endothelial denudation and concurrent 1% cholesterol feeding for 8 weeks. An aged (24 hour) heterologous (human) clot, labeled with I-125 fibrinogen was injected into the distal aorta and produced thrombotic occlusion. After 1 hour of thrombosis (control period), recombinant tissue plasminogen activator (100,000 IU approximately equal to 1 mg protein, n = 6) or streptokinase (100,000 IU, n = 5) or saline solution (n = 5) was systemically infused over 30 minutes. Serial blood samples, obtained to determine fractional change in blood radioactivity over time, showed a fourfold increase of blood radioactivity after tissue plasminogen activator and streptokinase infusion compared with the control period (47,400 +/- 3,300 [mean +/- standard error] versus 11,800 +/- 300 counts/min, p less than 0.001). Time to 50% of maximal thrombolysis was 41 +/- 14 minutes (+/- standard deviation) for tissue plasminogen activator versus 63 +/- 16 minutes for streptokinase (p less than 0.01). In six of six rabbits receiving tissue plasminogen activator and four of five rabbits receiving streptokinase, reestablishment of distal aortic flow was detected via the indwelling catheter within 25 minutes of drug infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary thrombolysis with recombinant human tissue-type plasminogen activator: a prospective, randomized, placebo-controlled trial

Forty-five patients with acute transmural myocardial infarction and angiographically confirmed complete coronary occlusion were prospectively randomized, two for one, to treatment of acute coronary thrombosis with intravenous recombinant human tissue-type plasminogen activator (rt-PA) or placebo. Each of five additional consecutive patients was treated with a high dose of rt-PA for 2 hr. Twenty-five of 33 patients (75%) receiving 0.5 to 0.75 mg/kg of rt-PA over 30 to 120 min had angiographically proven recanalization within 90 min of initiation of therapy. Only one of 14 patients given placebo had spontaneous recanalization within 45 min (p less than .001). Thirteen placebo-treated patients were crossed over to the intracoronary rt-PA group. Nine (69%) exhibited subsequent recanalization within 45 min. Levels of circulating fibrinogen decreased after treatment with rt-PA by an average of only 8% of baseline values. None of the patients manifested a depletion of fibrinogen level to below 100 mg/dl. Six patients who were completely unresponsive to rt-PA were subsequently treated with intracoronary streptokinase and none responded. Thus, either intravenous or intracoronary rt-PA induced coronary thrombolysis without eliciting clinically significant fibrinogenolysis in patients with evolving myocardial infarction due to thrombotic coronary occlusion.

Comparison of the hypotensive effects of streptokinase-(human) plasmin activator complex and BRL 26921 (p-anisoylated streptokinase-plasminogen activator complex) in the dog after high dose, bolus administration

In view of current interest in the possibility of rapid, high-dose administration of thrombolytic agents by the intravenous route in patients with coronary thrombosis (AMI), a study of this technique was carried out in the dog. Streptokinase-(human) plasmin activator complex (SK-Pm) and BRL 26921 (p-anisoylated streptokinase-(human) plasminogen activator complex) were each given at equivalent doses (28,500 IU/kg and 800 micrograms/kg respectively) to groups of beagle dogs by rapid injection over 10 sec and their effects on blood pressure, plasmin formation and kallikrein production were compared over the next 3h. SK-Pm produced, within 1-3 min, a pronounced hypotensive effect that was kinetically related to a rapid and steep rise in systemic plasmin and kallikrein concentrations. BRL 26921 had no hypotensive effect, the rise in plasmin production was slower and the rate and extent of kallikrein formation was significantly less than in the SK-Pm group.

In vivo metabolism of human tissue-type plasminogen activator

The turnover of human tissue-type plasminogen activator (t-PA), purified from cell culture fluids and radiolabelled with 125I, was studied in 2 healthy males. After injection, the plasma radioactivity initially disappeared with a half-life of about 3 min, but after 30 min reached a plateau level which persisted for several hours. The radioactive material had then already been converted to forms soluble in 10% trichloroacetic acid (TCA). Surface counting rates indicated a rapid uptake in the liver during the first 10 min after injection, followed by a rapid release from the liver, beginning already at 25 min, which coincided with the appearance of the TCA-soluble radioactive material. After 18 h, about 80% of the injected dose had already been excreted in the urine. We conclude that, in humans, injected t-PA is rapidly cleared from the circulation, mainly by the liver, and within 30 min metabolized to low molecular weight forms which ultimately (within 1 d) appear in the urine.

Coronary thrombolysis with tissue-type plasminogen activator in patients with evolving myocardial infarction

Tissue-type plasminogen activator is a naturally occurring, clot-selective activator of fibrinolysis. We recently reported that human tissue-type plasminogen activator isolated from a Bowes-melanoma-tissue-culture supernate lysed coronary thrombi in dogs without depleting circulating fibrinogen or alpha 2-antiplasmin, in contrast to the case with streptokinase and urokinase. In the present study coronary thrombolysis, confirmed angiographically, was induced within 19 to 50 minutes with intravenous or intracoronary tissue-type plasminogen activator in six of seven patients with evolving myocardial infarction. Circulating fibrinogen, plasminogen, and alpha 2-antiplasmin were not depleted by this agent, in contrast to the case in the two patients subsequently given streptokinase. In the one patient in whom lysis was not inducible with tissue-type plasminogen activator, it was also not inducible with streptokinase. These observations indicate that clot-selective coronary thrombolysis can be induced in patients with evolving myocardial infarction by means of tissue-type plasminogen activator, without concomitant induction of a systemic lytic state. Definition of its therapeutic benefit must await greater availability of the agent and the performance of appropriate clinical trials.

Coronary thrombolysis with intravenously administered human tissue-type plasminogen activator produced by recombinant DNA technology

Coronary thrombolysis was induced by intravenous infusion of human tissue-type plasminogen activator (recombinant human t-PA or rt-PA) obtained by expression of the cloned gene in a mammalian cell system. Thrombolysis was detected by the appearance of reperfusion arrhythmia and confirmed by repeat angiography in anesthetized dogs with 1-hr-old thrombi of the left anterior descending coronary artery that were induced with a copper coil. Infusion of 1000 IU (10 micrograms)/kg/min intravenous rt-PA (n = 9) elicited reperfusion within 13.7 +/- 1.9 min (mean +/- SE) without producing systemic fibrinolysis or distal coronary embolization. Infusion of urokinase at the same rate elicited thrombolysis in seven of 10 dogs within an average of 19.3 +/- 2.2 min. However, distal coronary embolization occurred in two dogs and systemic fibrinolysis was observed in all. In three dogs treated with urokinase thrombolysis was obtained only with subsequent intracoronary infusion. Restoration of myocardial perfusion and metabolism assessed with positron-emission tomography was consistently noted in dogs treated with rt-PA. Thus, rt-PA, a clot-selective thrombolytic agent that does not activate the fibrinolytic system systemically and that is potentially available in large quantities, in view of its synthesis by recombinant DNA technology, offers a promising practical approach for coronary thrombolysis in patients with acute myocardial infarction.

[Effect of high doses of tissue plasminogen activator on the hemostatic and fibrinolytic systems]

Intravenous administration of tissue activator plasminogen (TAP), isolated from a frozen pig heart using the technique of Bachman et al., to white rats produced considerable fibrinolysis activation in the euglobulin fraction only. The clot lysis time of this fraction was reduced 2.4-fold within 10 minutes after TAP administration, and high levels of the activator were maintained for 60 minutes. The absence of changes in the fibrinolytic activity of undiluted plasma might be due to TAP binding with antiactivator as the latter's level dropped after 10 minutes. Successive administration of heparin after a therapeutic dose of TAP resulted in decreased heparin activity and inhibited TAP which may be due to the formation of a complex between the two whose specific activity is not manifested in the presence of excessive heparin.

Clot-selective coronary thrombolysis with tissue-type plasminogen activator

Coronary thrombolysis, an intervention that can abort the sequelae of acute myocardial infarction, was accomplished within 10 minutes in dogs by intravenous administration of clot-selective, tissue-type plasminogen activator. In addition to inducing clot lysis, this promising fibrinolytic agent restored intermediary metabolism and nutritional myocardial blood flow, detectable noninvasively with positron tomography, without inducing a systemic fibrinolytic state.

Changes of the fibrinolytic system of animals induced by injection of tissue plasminogen activator

The changes in the fibrinolytic system of rats induced by repeated injections of tissue plasminogen activator (TPA) have been studied. The euglobulin fraction fibrinolytic activity increases 10 min after the first injection of TPA. Repeated injections of TPA for one or more days do not stimulate the fibrinolytic activity or TPA accumulation in the blood. Apparently in the absence of fibrin clots in the blood flow of healthy animals TPA is incapable of activating plasminogen conversion into plasmin. TPA, in its turn, is rapidly bound to the antiactivator and is excreted from the organism.

Proteolysis of fibrinogen in healthy volunteers following major and minor vivo plasminogen activation

Changes in immunoreactive fibrinopeptide A, fragment B beta 1-42 and fragment E were followed after major and minor in vivo plasminogen activation, after infusion of streptokinase and acylated streptokinase-plasminogen complex respectively, in healthy male volunteers. Major activation resulted in a dramatic rise in all three peptides, fragment E persisting in the circulation longest. Fragment B beta 1-42 was also markedly increased after minor systemic plasminogen activation despite apparently adequate levels of immediate antiplasmin.

[Fibrinolytic system of animals repeatedly and chronically administered plasminogen tissue activator]

Fibrinolytic system was studied in rats under various conditions of intravenous administration of the plasminogen tissue activator (RTA). Two administrations of the activator with an interval of 10 min did not cause an additional activation of fibrinolysis as compared with single treatment. Increase in amount of administrations up to four times within a day (an interval for 30 min) as well as chronic administrations of PTA within 5 days did not cause also any significant and long-term action on the animal fibrinolytic system. Efficiency of blood plasma antiactivator was decreased after repeated and chronic PTA administrations. Insensitivity of the healthy animal fibrinolytic system to repeated and chronic administration of PTA depended apparently on binding of the activator to inhibitors and on its rapid excretion from circulation.

[Indoor treatment of involutional depressions in cerebro-vascular insufficiency (author's transl)]

In this study we are reporting about our results concerning a combined therapy of short-time hospitalized patients, who suffered from an involutional depression and a cerebro-vascular-insufficiency. All patients had been treated outdoor without sufficient results before this. We could see, that all patients who had suffered their acute state within the last 18 months had good or very good improvements. Patients suffering already for several years showed no improvement in spite of all our efforts to promote the cerebral blood flow, the metabolic situation and the environment situation. These results proved, that one should start with a proper therapy of infusions and workshop rehabilitation immediately after the first sign of an involutional depression and cerebro-vascular-insufficiency.