Concomitant Heparin Administration Research Articles

Safety of tirofiban and dual antiplatelet therapy in treating intracranial aneurysms

BackgroundEndovascular treatment of intracranial aneurysms usually involves stent-assisted coiling (SAC) and flow diverters. Glycoprotein IIb/IIIa inhibitors such as tirofiban and dual antiplatelet therapy (DAPT) are required to prevent thromboembolic complications...

Antithrombin Supplementation and Mortality in Sepsis-Induced Disseminated Intravascular Coagulation: A Multicenter Retrospective Observational Study.

Supplemental doses of antithrombin (AT) are widely used to treat sepsis-induced disseminated intravascular coagulation (DIC) in Japan. However, evidence on the benefits of AT supplementation for DIC is insufficient. This multicenter retrospective observational study aimed to clarify the effect of AT supplementation on sepsis-induced DIC using propensity score analyses. Data from 3,195 consecutive adult patients admitted to 42 intensive care units for severe sepsis treatment were retrospectively analyzed; 1,784 patients were diagnosed with DIC (n = 715, AT group; n = 1,069, control group). Inverse probability of treatment-weighted propensity score analysis indicated a statistically significant association between AT supplementation and lower in-hospital all-cause mortality (n = 1,784, odds ratio [95% confidence intervals]: 0.748 [0.572-0.978], P = 0.034). However, quintile-stratified propensity score analysis (n = 1,784, odds ratio: 0.823 [0.646-1.050], P = 0.117) and propensity score matching analysis (461 matching pairs, odds ratio: 0.855 [0.649-1.125], P = 0.263) did not show this association. In the early days after intensive care unit admission, the survival rate was statistically higher in the propensity score-matched AT group than in the propensity score-matched control group (P = 0.007). In DIC patients without concomitant heparin administration, similar results were observed. In conclusion, AT supplementation may be associated with reduced in-hospital all-cause mortality in patients with sepsis-induced DIC. However, the statistical robustness of this connection was not strong. In addition, although the number of transfusions needed in patients with AT supplementation increased, severe bleeding complications did not.

Efficacy and bleeding risk of antithrombin supplementation in septic disseminated intravascular coagulation: A prospective multicenter survey

IntroductionAlthough supplementation with antithrombin (AT) concentrates has been widely accepted for the treatment of disseminated intravascular coagulation (DIC) in Japan, the effects and adverse effects have not been investigated. Materials and MethodsWe conducted a nonrandomized multi-institutional survey. A total of 729 septic DIC patients with AT activity levels of 70% or lower, who had undergone AT substitution at either 1500IU/day or 3000IU/day for consecutive 3days were analyzed. Of these, 650 and 79 patients had received 1500IU/day (AT1500 group) and 3000IU/day (AT3000 group), respectively. ResultsBleeding events were observed in 6.52% of patients (severe bleeding, 1.71%). A significant decrease in initial AT level (below 50%) was observed in 69.6% of patients in AT3000 group and 48.2% in AT1500 group, and this difference was significant (P<0.01). A logistic-regression analysis conducted using age, gender, body weight, initial AT activity, and supplemented AT dose, revealed that higher initial AT activity (odds ratio (OR), 1.032; P<0.001), AT dose of 3000IU/day (OR, 1.912; P=0.026), and age (OR, 0.985; P=0.023) were significant factors for improved survival. ConclusionThe risk of severe bleeding is less than 2%, and concomitant administration of heparin did not increase the risk. The survival in AT1500 group was 65.2%, while that in AT3000 group was 74.7%.

Nécroses cutanées tardives sous fluindione révélant un déficit en protéine C

Cutaneous necrosis is a rare complication of vitamin K antagonist therapy. It presents as cutaneous hemorrhagic necrosis and usually occurs at the start of treatment. We describe an atypical case of recurrent skin necrosis after two years of treatment with fluindione. A 70-year old woman with a history of venous thromboembolism and obesity presented with a large haemorrhagic necrosis of the abdominal wall. She had been treated with fluindione for two years. Genetic protein C deficiency was discovered. Resumption of vitamin K antagonist therapy was followed by recurrence of skin necrosis despite concomitant administration of heparin. Treatment with vitamin K antagonists could not be continued. This observation is unusual due to the late onset of skin necrosis. The condition usually begins shortly after initiation of vitamin K antagonist therapy, generally between the third and the sixth day of treatment. It is due to a transient hypercoagulable state in patients with protein C deficiency or, in rare cases, protein S deficiency. This late-onset skin necrosis, occurring many years after initiation of anticoagulant therapy, may be explained by a sudden worsening of pre-existing protein C deficiency due to infectious and iatrogenic factors.

Effective management of intracranial haemorrhage with continuous infusion of highly purified von Willebrand factor/factor VIII complex concentrate in an adult with severe haemophilia A.

Effective management of intracranial haemorrhage with continuous infusion of highly purified von Willebrand factor/factor VIII complex concentrate in an adult with severe haemophilia A.

Influence of concomitant heparin administration on pregnancy-associated plasma protein-A levels in acute coronary syndrome with ST segment elevation

IntroductionThe time course of pregnancy-associated plasma protein-A (PAPP-A) levels was studied at admission, immediately after percutaneous coronary intervention (PCI) and 1, 2, 4, 6, 12, 24 and 48 h after PCI in acute coronary syndrome with ST segment elevation (ACS-STE) to determine the impact of PCI, concomitant clinical complications and heparin administration.Material and methodsPregnancy-associated plasma protein-A serum levels, examined by the KryptorTM system, were studied in 30 heparinized PCI ACS-STE patients, in 10 elective PCIs and 12 coronary angiographies with heparin, and in 5 patients with normal coronary angiogram without heparin.ResultsHeparin caused a high PAPP-A increase in ACS-STE patients, in all patients with heparin without ACS and angiographic signs of significant atherosclerosis. This increase was directly associated with heparin dosage and activated clotting time (ACT) (r = 0.71, p = 0.0001) and inversely with the interval between heparin applications and time of serum sampling. It was followed by a rapid decrease within 1 to 2 h and return to normal levels in 10 to 12 h. In ACS-STE patients the decrease was significantly slower than in heparinized elective PCI and angiography patients. The PAPP-A increase was not significantly dependent on the length of PCI. Persistent increase after 24 h was associated in 4/7 patients with concomitant clinical complications.ConclusionsThe diagnostic validity of PAPP-A can be verified only within the 1st h after clinical onset of ACS before heparin administration, the prognostic value in heparinized patients not earlier than 12 h after the last heparin application, if ACT is normal and serious clinical concomitant complications are eliminated.

Development of mPF4/Heparin Antibodies in a Murine Platelet Activation Model

Heparin-Induced Thrombocytopenia (HIT) is an immune-mediated thrombotic disorder caused by antibodies that recognize complexes of Platelet Factor 4 (PF4) and heparin. We have previously shown that exogenous administration of murine PF4 (mPF4) and heparin (mP+H) daily for five days into mice leads to development of high titer PF4/heparin autoantibodies (anti-mP+H; Suvarna Blood, 2007). While this experimental model has been extremely useful for understanding various biological aspects of heparin sensitization, this murine model requires extremely high-doses of mP+H to elicit antibody production. To circumvent this non-physiologic approach, we studied effects of in vivo platelet activation in mice with or without concomitant heparin administration. After receiving approval from our Institutional Animal Care and Use Committee, we initially performed dose-finding studies of various platelet agonists {arachidonic acid (AA), ADP, collagen and PAR-4} to identify the maximal tolerated dose associated with in vivo platelet activation (assays of circulating PF4 levels) and associated with increased morbidity. Once optimal doses of platelet agonists were identified, we injected agonists in the presence or absence of heparin daily for five days and monitored for development of PF4/heparin antibodies as previously described (Suvarna, Blood, 2005). Of the various agonists tested, we noted development of anti-mP+H in mice injected with collagen (coll), but not in mice injected with AA, ADP and PAR-4. Moreover, anti-mP+H responses in mice injected with collagen showed heparin dependence, as shown in the Table below.Mean A450nmCollagen (coll) alone (n=5)0.04 ± 0.01coll + 0.25 U/mL hep (n=5)0.1 ± 0.04coll + 0.5 U/mL hep (n=5)0.1 ± 0.02coll + 1 U/mL hep (n=5)0.32 ± 0.27* (P<0.05 v collagen alone)Additional cohorts injected with coll + 1U/mL heparin showed significantly higher rates of seroconversion (mean A450nm= 0.25 ± 0.06, n=15) as compared to mice injected with coll alone (mean A450nm= 0.07 ± 0.02, n=15; p=0.007 for coll+hep v. coll alone, See Figure). In mice treated with coll+ 1U/mL Hep, anti-mP+H were specific for mP+H (mean A450nm= 0.358 ± 0.133) as compared to mPF4 alone (mean A450nm= 0.06±0.007). Anti-mP+H did not recognize rat albumin (mean A450nm= 0.015 ±0.006) or ELISA wells coated with PBS (mean A450nm=0.019 ±0.003). In summary, these studies indicate that anti-mP+H can be elicited in mice after platelet activation and heparin exposure. Further refinements of this model will be important in advancing our understanding the physiologic basis of heparin sensitization. [Display omitted]

Temporal Course of Pregnancy-Associated Plasma Protein-A in Angioplasty-Treated ST-Elevation Myocardial Infarction Patients and Potential Significance of Concomitant Heparin Administration

Pregnancy-associated plasma protein-A (PAPP-A) is a putative plaque instability marker. In acute coronary syndromes, the disrupted culprit plaque contains abundant PAPP-A, and circulating PAPP-A levels predict clinical outcomes. Determinants of circulating PAPP-A levels, however, are not fully understood, and the potential role of concomitant heparin administration has not previously been evaluated. The purposes of the present study were to evaluate in-hospital levels of PAPP-A compared with other circulating biomarkers in patients with acute myocardial infarctions and to explore the potential impact of concomitant heparin administration on PAPP-A levels in an animal experiment. Group A comprised 84 patients with ST elevation myocardial infarctions (STEMIs) who were treated with heparin and transferred for primary percutaneous coronary intervention. Plasma samples were obtained at the time of primary percutaneous coronary intervention, twice within the next 24 hours, and subsequently daily during hospitalization. Levels of PAPP-A, troponin T, soluble cluster of differentiation 163, N-terminal-pro-brain natriuretic peptide, and high-sensitivity C-reactive protein were determined. PAPP-A levels were also determined in 2 historical cohorts not given heparin: 14 patients with STEMIs (group B) and 56 patients with non-ST elevation myocardial infarctions (group C). The impact of concomitant heparin administration on the clearance of PAPP-A from the circulation was also explored in mice. In group A, PAPP-A levels were increased in the initial plasma sample in 95% of patients presenting within 3 hours of symptom onset, whereas increased levels of troponin T, soluble cluster of differentiation 163, N-terminal-pro-brain natriuretic peptide, and high-sensitivity C-reactive protein were detectable in 45%, 15%, 50%, and 35% of patients, respectively. Compared with group A, lower levels of PAPP-A were observed in the initial plasma samples drawn in groups B (p = 0.07) and C (p <0.001) not given heparin. In the animal experiment, concomitant heparin administration resulted in increased levels of PAPP-A and delayed clearance of PAPP-A from the circulation. In conclusion, PAPP-A is markedly elevated in the earliest hours after the onset of symptoms in patients with STEMIs treated with heparin and primary percutaneous coronary intervention, and in animal studies, heparin administration is associated with a significant increase in PAPP-A levels, presumably because of the detachment of PAPP-A from the vessel wall. If future studies confirm that concomitant heparin administration also increases PAPP-A levels in humans, the prognostic role of PAPP-A in patients with STEMIs needs to be reevaluated.

Anticoagulant and Anti-Inflammatory Effects of Recombinant Human Antithrombin in Man after LPS Challenge.

Background: Antithrombin (AT) had beneficial effects on mortality of septic patients in an a priori defined subpopulation of the Kypersept trial, which received no concomitant administration of heparin.Objectives: We hypothesized that recombinant human (rh)AT (without concomitant heparin) has anticoagulant properties and may decrease cytokine production in a well standardized model of human endotoxemia.Methods: This study was randomized, double-blind, placebo-controlled in parallel groups in 30 healthy male volunteers. The active treatment groups received bolus primed continuous infusion of rhAT (recombinant human Antithrombin) to increase AT-levels to 200% and 500% iv. before infusion of 2ng/kg endotoxinResults: Infusion of rhAT rapidly decreased neutrophil (p<0.01) and monocyte counts (p<0.05) before LPS-challenge, demonstrating that rhAT directly interacts with these leukocyte subsets. rhAT exhibited intrinsic anticoagulant efficacy ex vivo as shown by thrombelastography ((p<0.01). More importantly, in vivo thrombin formation decreased in a dose dependent fashion as measured by prothrombin fragment (F1+2) and thrombin antithrombin complexes (TAT). rhAT significantly decreased interleukin-6 (IL-6) release by 40%.Conclusion: rhAT exhibited intrinsic anticoagulant effects, which are stronger than the minor effects of drotrecogin alfa (rhAPC; Blood 2003; 102:2093ff) in this model of tissue factor triggered coagulation. Effects of rhAT on leukocytes and inhibition of IL-6 release were not previously observed with various different synthetic or natural anticoagulants in this model and therefore represent specific pharmacodynamic properties of rhAT. The demonstrated anticoagulant and anti-inflammatory properties of rhAT may have beneficial effects in critically ill patients, and may explain the efficacy of rhAT in septic patients without concomitant heparin administration.

New anticoagulants for treatment of venous thromboembolism.

Treatment of venous thromboembolism (VTE) usually starts with concomitant administration of heparin or low-molecular-weight heparin (LMWH) and a vitamin K antagonist. The parenteral anticoagulant, which is given for at least 5 days, is stopped once the vitamin K antagonist produces a therapeutic level of anticoagulation. Although the introduction of LMWH has simplified the initial treatment of VTE, problems remain. LMWH must be given by daily subcutaneous (SC) injection and vitamin K antagonists require routine coagulation monitoring, which is inconvenient for patients and physicians. Recently, 3 new anticoagulants have been introduced in an attempt to overcome these limitations. These include fondaparinux and idraparinux, synthetic analogs of the pentasaccharide sequence that mediates the interaction of heparin and LMWH with antithrombin, and ximelagatran, an orally active inhibitor of thrombin. These agents produce a predictable anticoagulant response; thus, routine coagulation monitoring is unnecessary. Because they do not bind to platelets or platelet factor 4, fondaparinux and idraparinux do not cause heparin-induced thrombocytopenia (HIT). Unlike vitamin K antagonists, ximelagatran has a rapid onset of action, thereby obviating the need for concomitant administration of a parenteral anticoagulant when starting treatment. The lack of an antidote for these new agents is a drawback, particularly for idraparinux, which has a long half-life.

Clinical correlates and course of thrombocytopenia during percutaneous coronary intervention in the era of abciximab platelet glycoprotein IIb/IIIa blockade

Background Thrombocytopenia is infrequently associated with abciximab therapy but may contribute to hemorrhagic risk. Factors associated with development of thrombocytopenia, the role of weight-adjustment in concomitant heparin administration, and clinical outcomes in patients with thrombocytopenia are not well defined. Methods and Results Pooled data from 3 placebo-controlled, randomized trials (EPIC, EPILOG, and EPISTENT) of abciximab therapy during percutaneous coronary intervention identified 178 patients (2.4% of 7290 patients) in whom thrombocytopenia (platelet count <100 × 109/L) developed after enrollment. Multivariate regression analysis identified age (>65 years; P <.001), weight (<90 kg; P =.023), baseline platelet count (<200 × 109/L; P <.001), abciximab therapy (P =.002), and enrollment into the EPIC trial (P <.001) to be associated with development of thrombocytopenia. Major and minor nonsurgical hemorrhage and transfusion were more frequent (all P <.001) in thrombocytopenic patients. Although the primary composite clinical end point of these trials (death, myocardial infarction, or urgent revascularization to 30 days) was observed with similar frequency in patients with (11.2%) and those without (7.9%; P =.114) thrombocytopenia, 30-day mortality rate was higher in thrombocytopenic patients (8.4% vs 0.6%, respectively; P <.001). This excess mortality rate persisted after excluding patients in whom thrombocytopenia was first noted after the performance of coronary bypass surgery (4.8% vs 0.6%; P <.001). Among patients in whom thrombocytopenia developed during these trials, those who received prophylactic abciximab had fewer primary end point events (7.1% vs 23.1%; P =.056) and had a lower 30-day mortality rate (3.5% vs 15.4%; P =.048) than patients with thrombocytopenia who had received prophylactic placebo. Conclusions Thrombocytopenia associated with abciximab therapy for percutaneous coronary intervention was more frequent in older, lighter-weight patients, those with lower baseline platelet counts, and in those patients who were enrolled into the EPIC trial. Both bleeding and transfusion events occur more frequently in patients with thrombocytopenia. Patients in whom thrombocytopenia developed during these trials had increased mortality rates to 30 days not attributable to the performance of coronary bypass surgery. Among patients with thrombocytopenia, those who received prophylactic abciximab had better clinical outcomes including survival than those who did not. (Am Heart J 2000;140:74-80.)

Efficacy of abciximab readministration in coronary intervention

Abciximab, an Fab monoclonal antibody fragment that blocks the platelet glycoprotein IIb/IIIa receptor, is increasingly used as an adjunct to coronary intervention. Little is known, however, about the efficacy and safety of readministration of abciximab. This study examined and characterized outcomes of patients receiving abciximab for a second time. From April 1995 to June 1997, 164 consecutive patients were readministered abciximab at our 3 institutions. We retrospectively examined and analyzed in-hospital outcomes in this cohort. The median time to readministration was 95 days. The angiographic success rate of percutaneous intervention was 99.5%. Rates and 95% confidence intervals of in-hospital events were death 2% (0.7% to 6.1%), myocardial infarction 3% (1% to 7%), coronary bypass surgery 0% (0% to 2.2%), and intracranial hemorrhage 2% (0.4% to 5.3%). Severe thrombocytopenia was observed in 4% of patients (1.4% to 7.8%) after readministration. Allergic or anaphylactic reactions were not observed. Major bleeding was associated with excessive concomitant antithrombotic therapy. Patients undergoing readministration of abciximab within 2 weeks of first administration experienced a higher incidence of severe thrombocytopenia (12% vs 2%, p = 0.046). Thus, abciximab remains clinically efficacious when readministered as an adjunct to percutaneous coronary intervention. However, concomitant heparin administration must be carefully monitored and warfarin therapy should be avoided. Vigilant surveillance for thrombocytopenia should be employed. Reduced dosing may be necessary when abciximab is readministered within days of the initial administration.

Lamifiban.

Lamifiban is an intravenously administered, selective, reversible, nonpeptide glycoprotein IIb/IIIa receptor antagonist which inhibits platelet aggregation and thrombus formation by preventing the binding of fibrinogen to platelets. In trials in patients with non-Q wave myocardial infarction (MI) or unstable angina pectoris (PARAGON A and the Canadian Lamifiban Study), the incidence of clinical events at 30 days in patients receiving lamifiban (1 to 5 microg/min) was not significantly different from that in patients receiving aspirin plus heparin or aspirin alone. In PARAGON A, the incidence of clinical events at 6 months was significantly lower after lamifiban (with or without heparin) and aspirin therapy than after standard heparin and aspirin therapy. A large phase III trial (PARAGON B) is under way comparing lamifiban plus aspirin and heparin with standard aspirin and heparin therapy in patients with non-Q wave MI or unstable angina pectoris. In clinical trials, the most common adverse events associated with lamifiban were bleeding complications which were increased by the concomitant administration of heparin.

Thrombolysis in Newborns and Infants

This review analyses literature reports from 1970 to 1998 assessing the use of streptokinase (SK), urokinase (UK) or recombinant tissue-type plasminogen activator (rt-PA) for thrombolytic therapy in neonates and infants. From 1970 to 1998 182 infants were reported to have received SK (n = 54; 29.5%), UK (n = 41; 22.5%) or rt-PA (n = 87; 48%). During thrombolytic therapy no concomitant heparin administration or low dose heparin therapy (5 U/kg/h) were recorded. To perform reocclusion prophylactics heparin was reinitiated at the end of thrombolytic therapy usually in the recommended dosage of 20 U/ kg/h. The overall thrombolytic patency rate in neonates varied from 39% to 86%. Besides bleeding from local puncture sites or recent catheterisation sites (10.4%), pulmonary embolism was reported in 1.1% of the 182 infants. Major bleeding complications, i.e. pulmonary bleeding (0.6%), gastrointestinal bleeding (0.6%) or intraventricular haemorrhage (IVH 2.7%) are rarely reported side effects and only 2 thrombolysis related deaths due to haemorrhage were mentioned. Bleedings reported in the central nervous system (n = 4) mainly occurred in preterm infants (n = 3). In conclusion, data of this preliminary analysis suggest that there is no big difference (p = 0.09; chi2-test) in the efficacy rate between the 3 thrombolytic agents used in the first year of life. In each case an assessment must be made with respect to the relative benefit conferred by thrombolytic therapy in preventing organ or limb damage versus the potential side effects, costs and inconvenience for the childhood patient. Controlled prospective multicentre studies on thrombolytic therapy in neonates and infants are recommended to evaluate patency rates and adverse effects for the different thrombolytic agents used.

Fibrinolytic Mechanism, Biochemistry, and Preclinical Pharmacology of Recombinant Prourokinase

The purpose of this review is to provide a biochemical characterization of recombinant prourokinase (r-ProUK [ABT-187]), including a description of its clot-specific fibrinolytic mechanism. In addition, the preclinical data will be briefly reviewed, demonstrating the efficacy of r-ProUK as a potent therapeutic plasminogen activator. r-ProUK was purified to homogeneity from the culture medium of SP2/0 mouse hybridoma cells. The fibrinolytic potency of r-ProUK was characterized by both in vitro clot lysis experiments in human plasma and a canine femoral artery thrombosis model. In the in vitro clot lysis system, with use of clots prepared from fresh frozen human plasma, r-ProUK exhibits a lag phase to the onset of lysis and a concentration-dependent threshold effect due to the presence of the inhibitors alpha 2-antiplasmin and plasminogen activator inhibitor (PAI-1). Effective clot lysis can be achieved without degradation of the fibrinogen in the surrounding plasma. Over a dose range of 50,000-220,000 IU, the canine femoral artery thrombosis model shows a dose-dependent relationship for r-ProUK and effective clot lysis. The lytic activity of r-ProUK is significantly enhanced in this model by the concomitant administration of heparin as an adjunctive agent for thrombolytic treatment. Fibrinogen, plasminogen, and alpha 2-antiplasmin levels in the systemic circulation were unaltered during the 30-minute infusion period and a 4-hour observation period, in which 85% lysis was achieved with r-ProUK (100,000 IU) and heparin. Moreover, restoration of blood flow in the previously fully occluded femoral artery was achieved within minutes of the start of the r-ProUK infusion. The experimental findings presented here are consistent with the clot-specific fibrinolytic mechanism of r-ProUK. Effective clot lysis can be achieved without alteration of the systemic coagulation and fibrinolytic parameters.

Activation of the Hemostatic Mechanism During Thrombolysis in Patients With Unstable Angina Pectoris

In patients with myocardial infarction, thrombolytic therapy induces a paradoxical activation of the hemostatic mechanism. In patients with unstable angina, the effect of thrombolysis on the coagulation cascade is unknown. We prospectively measured the plasma concentrations of prothrombin fragment 1 + 2 and fibrinopeptide A in consecutive patients with unstable angina randomized to receive placebo alone (n = 23), streptokinase 1,500,000 IU over 1 hour followed by a 48-hour placebo infusion (n = 21), or streptokinase 250,000 over 1 hour followed by a continuous infusion of 100,000 IU per hour over 48 hours (n = 20). All the patients received intravenous heparin for 72 hours. The plasma levels of the different markers were measured at baseline, 90 minutes, 24 hours, and 48 hours after the start of therapy. The median baseline plasma concentrations of prothrombin fragment 1 + 2 and fibrinopeptide A were similar in the three treatment groups. In comparison with placebo, an increase in plasma prothrombin fragment 1 + 2 and fibrinopeptide A, was observed after 90 minutes in the two groups receiving thrombolysis. After 24 and 48 hours, the prothrombin fragment 1 + 2 levels remained significantly higher only in the patients receiving the 48-hour streptokinase infusion. In patients with unstable angina, thrombolytic therapy induces an activation of the hemostatic mechanism, despite concomitant heparin administration; in those receiving a prolonged streptokinase infusion, the activation of coagulation persists for as long as the drug is administered.

Recombinant Tissue Plasminogen Activator for the Treatment of Lower Extremity Peripheral Vascular Occlusive Disease

Regional thrombolysis in the recanalization of peripheral vascular occlusive disease is an increasingly accepted therapeutic modality. Efficacy and complication rate are major issues in thrombolytic therapy. This prospective study was undertaken to determine if locally delivered recombinant tissue plasminogen activator (r-TPA) is safe and effective in clot lysis at non-weight-adjusted doses. Twenty patients (undergoing 21 infusions) from two centers underwent fibrinolytic therapy with use of r-TPA, at a dose rate of 2 mg/h. The mean duration of arterial occlusion was 27.2 days (range, 1-117 days). Concomitant intravenous heparin anticoagulation was administered to all patients. A coaxial infusion delivery system was employed. Hematologic parameters and angiographic follow-up were evaluated at 4-hour intervals during thrombolytic infusion. The chosen maximum r-TPA dose of 40 mg could be extended at investigator discretion. Complete clot lysis was achieved in 18 of 21 (85.7%) infusions at a mean total dose of 38.9 mg (range, 8-84 mg). The mean infusion duration was 19.7 hours. In 16 of 19 (84.2%) infusions, in which the nadir fibrinogen level was recorded, it remained greater than 65% of baseline. Three of 21 (14.3%) infusions resulted in three major bleeding complications, one of which resulted in death. In this two-center trial, catheter-directed r-TPA infusion at 2 mg/h is effective for clot lysis. When combined with concomitant heparin administration, this treatment may result in an unacceptably high frequency of bleeding complications.

Lack of Interference by Heparin With Thrombolysis or Binding of Tissue-Type Plasminogen Activator to Thrombi

Coronary thrombolysis with t-PA is generally implemented with concomitant administration of heparin. However, results of studies in vitro suggest that heparin competes with fibrin for binding of tissue-type plasminogen activator (t-PA), augments activation of free plasminogen, decreases fibrin specificity, and impairs thrombolysis. To define the biological implications of these observations, we characterized effects of therapeutic concentrations of heparin on the binding of t-PA to thrombi formed in whole blood, effects of heparin on activation of plasminogen by t-PA in plasma, and effects of heparin on thrombolysis induced by t-PA in a clot lysis system designed to simulate conditions in vivo. The amount of t-PA bound to thrombi was not affected by heparin (0, 0.5, 1.0, and 5.0 U/mL). When t-PA activity was selectively and irreversibly inhibited by D-Phe-Pro-Arg-chloromethyl ketone (PPACK) the amount of t-PA-PPACK bound was similarly unaffected by heparin. Thrombolysis measured by 125I-fibrin(ogen) release and by reduction of mass of thrombi were not altered by heparin. Heparin did not affect plasminogen consumption induced by t-PA. Plasma concentrations of alpha-2-antiplasmin after exposure of blood to t-PA were less depressed with increasing concentrations of heparin. Thus, heparin in therapeutic concentrations does not interfere with binding of t-PA to thrombi, augment activation of free plasminogen, or inhibit thrombolysis. Accordingly, it appears likely that concomitant administration of heparin will not impair thrombolysis with t-PA implemented clinically.

Lack of interference by heparin with thrombolysis or binding of tissue- type plasminogen activator to thrombi

Coronary thrombolysis with t-PA is generally implemented with concomitant administration of heparin. However, results of studies in vitro suggest that heparin competes with fibrin for binding of tissue- type plasminogen activator (t-PA), augments activation of free plasminogen, decreases fibrin specificity, and impairs thrombolysis. To define the biological implications of these observations, we characterized effects of therapeutic concentrations of heparin on the binding of t-PA to thrombi formed in whole blood, effects of heparin on activation of plasminogen by t-PA in plasma, and effects of heparin on thrombolysis induced by t-PA in a clot lysis system designed to simulate conditions in vivo. The amount of t-PA bound to thrombi was not affected by heparin (0, 0.5, 1.0, and 5.0 U/mL). When t-PA activity was selectively and irreversibly inhibited by D-Phe-Pro-Arg- chloromethyl ketone (PPACK) the amount of t-PA-PPACK bound was similarly unaffected by heparin. Thrombolysis measured by 125I- fibrin(ogen) release and by reduction of mass of thrombi were not altered by heparin. Heparin did not affect plasminogen consumption induced by t-PA. Plasma concentrations of alpha-2-antiplasmin after exposure of blood to t-PA were less depressed with increasing concentrations of heparin. Thus, heparin in therapeutic concentrations does not interfere with binding of t-PA to thrombi, augment activation of free plasminogen, or inhibit thrombolysis. Accordingly, it appears likely that concomitant administration of heparin will not impair thrombolysis with t-PA implemented clinically.