Coronary thrombosis treatment

Indications for treatment with streptokinase include acute occlusion of arteries, deep vein thrombosis, and pulmonary embolism. Streptokinase therapy in coronary thrombosis, which is the usual cause of myocardial infarction (54,71,72), has proved to be valuable. In this frequently fatal condition, the enzyme is adrninistered intravenously at a dose of 1.5 million units over 60 min, or given by intracoronary infusion at a 20,000- to 50,000-unit bolus dose followed by 2000 to 4000 units/min for 60 min therapy must be instituted as soon as practicable after the diagnosis of heart attack is made. For deep vein thrombosis, pulmonary embolism, or arterial occlusion, streptokinase is infused at a loading dose of 250,000 units given over 30 min, followed by a maintenance dose of 100,000 units over a 60-min period. 

SuccessM treatment of PEA and asystole depends almost entirely on diagnosis of the underlying cause. Potentially reversible causes include (1) hypovolemia, (2) hypoxia, (3) preexisting acidosis, (4) hyperkalemia, (5) hypothermia, (6) hypoglycemia, (7) drug overdose, (8) cardiac tamponade, (9) tension pneumothorax, (10) coronary thrombosis, (11) pulmonary thrombosis, and (12) trauma. 

New small molecule FXa inhibitors currently in development are able to enter the clot/prothrombinase complex and inhibit free and bound factor Xa regarded as the key enzyme in ACS. Although direct FXa inhibitors do not inhibit platelet aggregation, they abolish platelet-dependent thrombus formation in canine coronary thrombosis. Thus, direct inhibition of FXa may have higher efficacy and better risk/benefit profile than existing antithrombotic therapies in the treatment and prevention of ACS. 

Because of its powerfiil vasodilator action sodium nitroprusside is often used to treat vascular emergencies associated with hypertensive crisis. Since this compound shows some anti-platelet activity both in vitro and in vivo (Levin et al 1982, Hines and Barash 1989) its acute clinical effects may also be mediated, in part, through inhibition of platelet function. Recently, sodium nitroprusside was administered intrapericardially to treat experimentally induced coronary Arombosis in dogs (Willerson et al 1996). As this route of administration of sodium nitroprusside produced less vasodilatation than systemic one, localized administration of this dmg may offer new therapeutic possibilities for the treatment of the coronary thrombosis. 

An increased risk of thrombotic events, especially coronary thrombosis, has been reported in elderly patients taking retinoids (33). Two patients with acute promyelocytic leukemia developed thrombus in the right ventricle during induction treatment with tretinoin plus idarubicin (34). 

When it is suspected that there may only be small differences between active treatments, and when placebo controls are unavailable for clinical or ethical reasons, then it is often necessary to resort to large-scale studies ( mega-trials ). A good, famous example was the clinical trial known by the acronym GUSTO, where streptokinase and recombinant tissue plasminogen activator (t-PA) were compared for acute coronary thrombosis (for a commentary, see Hampton, 1996). 

Aspirin has been remarkably successful in the treatment of the pain and swelling of inflammatory disease and in fact, an estimated 45,000 tons of aspirin are still consumed each year. This success resulted in the syntheses of many other aspirin-like drugs , now referred to as NSAIDs. Aspirin, however, continues to have a unique use in the prevention of thrombosis. Since it produces irreversible inhibition of COX-1 by acetylation of serine at position 530 in the active site, a daily low dose of aspirin will cause a cumulative inhibition of COX-1 in platelets, in the portal circulation. A gradual inhibition of platelet aggregation occurs, reducing the possibility of occlusion of coronary or cerebral vessels by platelet thrombi. However, there are no systemic... 

Organic anticoagulants are used in vivo in the treatment of numerons conditions where blood coagulation can be dangerous, as in cerebral thrombosis and coronary heart disease, among others which will be described later. The main anticoagulants used are heparin and coumarin compounds, such as warfarin. 

Tissue plasminogen activator has been used successfully to treat acute myocardial infarction, and the benefits of this treatment are well documented.102,116 This drug, however, does not seem to be superior to other thrombolytics when treating coronary artery thrombosis, and streptokinase may be a more cost-effective method of treating myocardial infarction. Alternatively, t-PA may be more effective than other thrombolytics in its ability to initially reopen cerebral vessels this drug is often used preferentially during ischemic stroke.4,44 Hence, the added cost of t-PA may be justified in this situation. 

Mattsson C, Bjorkman JA, Abrahamsson T et al. Local proCPU (TAFI) activation during thrombolytic treatment in a dog model of coronary artery thrombosis can be inhibited with a direct, small molecule thrombin inhibitor (melagatran). Thromb Haemost 2002 87 557-562. 

In contrast to unfractionated heparin, the factor Xa inhibitor tick anticoagulant peptide (TAP) effectively inhibited coronary arterial thrombosis in a canine electrolytic injury model (57). TAP was also effective in inhibition of the procoagulant properties of whole blood clots in vitro however, it was stated that TAP might be not optimal due to its slow binding kinetics (54). Meanwhile, several low molecular weight direct factor Xa inhibitors are in clinical development (Table I), some of them specifically for the treatment and secondary prevention of ACS. DX-9065a, ZK-807834 and otamixaban have been intensively characterized in vitro and in vivo and are in clinical investigations for the treatment of acute arterial thrombosis. 

Urokinase is intended for intravenous use only and indicated for the treatment of pulmonary embolism, coronary artery thrombosis, and intravenous catheter clearance. Typical dosages in peripheral arterial disease consist of an infusion at a rate ranging from 60,000 lU/hr to 240,000 lU/hr infused directly into the thrombus. 

Thrombosis in stenosed human coronary arteries is one of the most common thrombotic diseases leading to unstable angina, acute myocardial infarction or sudden death. Treatment with angioplasty, thrombolysis, or bypass grafts can expose new thrombogenic surfaces and re-thrombosis may occur. The mechanisms responsible for this process include interactions of platelets with the damaged arterial wall and platelet aggregation. 

There is an association between the rare inborn recessive condition of homocystinemia and arterial and venous thrombosis, and observational data link coronary heart disease, stroke, and venous thromboembolism with increasing plasma homocysteine (Wald et al. 2002, 2004). This led to trials of foUc acid and pyridoxine supplementation to lower homocysteine levels (Hankey 2002 Hankey and Eikelboom 2005). Results from such trials have so far been disappointing the Vitamin Intervention for Stroke Prevention Study (VISP) and the Norwegian Vitamin Trial (NORVIT) (Toole et al. 2004 Bonaa et al. 2006) trials showed no treatment effect on recurrent stroke, coronary events or deaths. Preliminary results from the Study of Vitamins to Prevent Stroke (VITATOPS) trial have shown no evidence of reduced levels of iirflammation, endothelial dysfunction, or the hypercoagulability postulated to be increased by elevated homocysteine levels in patients with previous TIA or stroke treated with foUc acid, vitamin B12 and vitamin Bs... 

These drugs appear to be very useful adjxmcts for the treatment of unstable angina, and in the prevention of thrombosis following percutaneous revascularisation procedures such as angioplasty and coronary artery stenting. Their role in preventing infarction in patients with acutely compromised myocardium is likely to expand rapidly. 

---