Meta-analysis of all available published clinical trials (1958–1990) on thrombolytic therapy for AMI: Relative efficacy of different therapeutic strategies

Loco-regional thrombolysis for deep vein thrombosis: fact or fiction? A study of hemostatic parameters

Loco-regional thrombolysis for deep-vein thrombosis (DVT) has been claimed to be equally effective and safe compared with systemic thrombolysis. It is not known whether a loco-regional thrombolytic effect exists and of what it might consist. To investigate this issue, we studied eight patients with DVT undergoing loco-regional thrombolysis with 20 mg alteplase infused over 4 h in a dorsal foot-vein of the affected leg, while the leg was kept tightly bandaged; alteplase infusions were repeated every 24 h, the number of therapy cycles (TC) was seven, and full-dose heparin was given. For coagulation analyses, 'loco-regional' blood samples were taken from a vein of the affected leg and 'systemic' samples were taken from an antecubital vein. After a median number of six TC, good partial reperfusion was achieved in 4/8 patients, moderate partial reperfusion in 2/8, major bleedings occurred in 2/8, and minor bleedings in 1/8 patients. During the first TC, recombinant tissue-type plasminogen activator (rtPA) activity and antigen, as well as FgDPs and d-dimers, were elevated significantly loco-regionally over systemic values, and a complete breakdown of plasmin-inhibitor activity occurred with only a slight systemic reduction; no other differences were found. During successive TC, differences in rtPA-activity and -antigen levels decreased, and no significant differences were found for all other parameters. Thus, a local fibrinolytic effect was demonstrable during loco-regional thrombolysis for DVT; the magnitude of this effect diminished during successive TC, giving rise to the hypothesis that the fibrinolytic efficacy may be decreased due to growing, antifibrinolytic activity. The preserved, loco-regional plasmin-inhibitor activities during the later TC, in contrast to the complete breakdown during the first TC, suggest that part of the enhanced antifibrinolytic activity is due to loco-regionally increased plasmin-inhibitor activity. The ultimate goal of loco-regional thrombolysis, the induction of local fibrinolysis without systemic effects, has not, however, been achieved.

A recombinant antibody-targeted plasminogen activator with high affinity for activated platelets increases thrombolytic potency in vitro and in vivo

To increase thrombolytic specificity of urokinase (uPA), we engineered a recombinant chimeric plasminogen activator SZ51Hu-scuPA, which consists of a humanized monoclonal antibody (SZ-51Hu) specifically against P-selectin on activated human platelet and a single-chain urokinase (scuPA). The cDNA, encoding scuPA amino acids 1-411, was inserted in 5' end to 3' end orientation immediately after the CH3 of SZ-51Hu heavy-chain sequence in the expression vector alphaLys30. The resulting construct alphaLys30-SZ51VH/Hu-scuPA was used to transfect into SP2/0 murine myeloma cell line, which was pretransfected with SZ51Hu light chain. The fusion protein SZ51Hu-scuPA was expressed at 5 mg/L in the supernatant of cell culture. The fusion protein purified by affinity chromatography had a molecular weight of 160 kDa with fibrinolytic activity of 39,000 IU/mg and its affinity to activated human platelet was 67% of the parent murine mAb SZ-51. The thrombolytic property of the fusion protein was first characterized in an in vitro system, which consists of a 125I-fibrin-labeled human plasma clot containing different concentrations of human platelets suspended in citrated human plasma. Fifty percent lysis was reached with SZ51Hu-scuPA in 1 hour at a concentration of 20 IU/mL or in 2 hours at a concentration of 10 IU/ mL, which was much faster than uPA at the same concentration. The maximal lysis of the clots by SZ51Hu-scuPA was 4.1 to 8.4 times more potent than that by uPA. The fusion protein was further characterized in the hamster pulmonary embolism model with clots prepared from fresh platelet-rich human plasma containing 125I-labeled fibrinogen. The thrombolytic activity of SZ51-scuPA was 3.9 times more potent than that of uPA at 2,000 IU/kg in this model. Almost no significant fibrinogen breakdown was observed either in vitro and in vivo.

Cost-effectiveness of thrombolytic therapy for acute myocardial infarction

OBJECTIVE

To estimate the cost-effectiveness of thrombolytic therapy versus no thrombolytic therapy for patients following acute myocardial infarction, focusing on the impact of time to treatment on outcome.

METHODS

A decision model was developed to assess the benefits, risks, and costs associated with thrombolytic therapy for treatment of acute myocardial infarction compared with standard nonthrombolytic therapy. The model used pooled data from a recent study of nine large randomized, controlled clinical trials and 12-month outcome data from a recently published meta-analysis of thrombolytic therapy trial data. Outcomes were expressed in terms of survival to hospital discharge and survival to 1 year after discharge. The risks of treatment that led to death, morbidity, or added costs were estimated. The model determined excess and marginal costs per death averted to hospital discharge and at 1 year. Results were also estimated in terms of cost per year of life saved. Sensitivity analyses included variations in time to treatment and drug cost.

RESULTS

The marginal cost of thrombolytic therapy per death averted at 1 year was $222,344, or $14,438 per year of life saved. For patients treated within 6 hours of acute myocardial infarction, the marginal cost per death averted was $181,536 at 1 year, or $11,788 per year of life saved.

CONCLUSIONS

Thrombolytic therapy is significantly more cost-effective than many other cardiovascular interventions and compares favorably with other forms of medical therapy. Results suggest that shortening the time to treatment has a critical impact on the cost-effectiveness of thrombolytic therapy.