Advances in antithrombotic therapy of acute myocardial infarction

Magnetic resonance perfusion imaging in patients with coronary artery disease: a qualitative approach

Although contrast-enhanced first pass magnetic resonance imaging (MRI) has potential to quantify blood flow through extensive image post-processing, clinical utility is likely to depend on rapid qualitative analysis.

AIMS

To investigate use of an on-line analytical approach for detection of coronary artery disease (CAD).

METHODS AND RESULTS

Thirty subjects with CAD underwent contrast-enhanced rest/adenosine stress MRI with basal, mid-papillary and apical short-axis image acquisition. Each short axis was divided into eight regions of interest (ROI). Regional perfusion was visually classified as normal or impaired according to transmural distribution and defect reversibility. MRI and angiographic data were compared. Qualitative MRI reporting was possible for 98% ROI. Eighty-six coronary artery (CA) territories were assessed of which 71 (83%) had stenoses. Sensitivity and specificity for detection of stenoses were 93 and 60%, respectively. The proportion of hypoperfused ROI rose from 31% with < 50% stenosis to 65% with occlusion. More transmural defects were seen in infarction-related territories (75 vs. 54%, p < 0.05). More ROI demonstrated defect reversibility in occluded rather than in stenosed infarction-related vessels (89 vs. 58%, p < 0.05). Occluded vessels with grade 2-3 collaterals contained a higher proportion of normal ROI (44 vs. 25%, p < 0.05).

CONCLUSIONS

Qualitative MRI analysis had high sensitivity and moderate specificity for detecting CA stenoses. Additional information was obtained relating to lesion severity, previous infarction, myocardial viability and impact of collateral circulation. The technique has potential for de novo diagnosis of CAD and as a complementary modality to angiography to assess the significance of given angiographic lesions.

Prevention of experimental carotid and coronary artery thrombosis by the glycoprotein IIb/IIIa receptor antagonist CRL42796

1. The antithrombotic effect of the glycoprotein IIb/IIIa receptor antagonist, CRL42796, was examined in canine models of carotid and coronary artery thrombosis. 2. In the carotid artery thrombosis model, occlusion occurred in all control vessels (time to thrombosis 47.6+/-8.9 min). After treatment with low dose CRL42796 (15 microg kg(-1) loading dose +0.31 microg kg(-1) min(-1) i.v.), two of five vessels occluded. Time to thrombosis increased significantly to 155.2+/-23.1 min. When the drug infusion was increased (0.69 microg kg(-1) min(-1)), each of five vessels remained patent. 3. Ex vivo platelet aggregation in response to arachidonic acid (AA) and ADP was examined in platelet rich plasma (PRP) prepared from citrate or heparin anticoagulated blood. CRL42796 reduced platelet reactivity at low and high doses in PRP from citrate anticoagulated blood. However, in PRP from heparin anticoagulated blood, only the higher infusion dose produced a significant reduction in ex vivo platelet responses. 4. A combination of oral aspirin (4.6 mg kg(-1) -41, -17 h) and the low infusion dose of CRL42796 did not produce an additional benefit beyond that provided by CRL42796 alone. 5. Coronary artery thrombosis was inhibited in four of five vessels treated with the lower infusion dose of CRL42796 and in five of five vessels treated with the higher infusion. Time to thrombosis increased with both doses (Control, 90.8+/-10.4 min; low dose, 165.8+/-14.2 min; high dose, >180.0+/-0 min). 6. The results indicate that CRL42796 is an effective in vivo antithrombotic agent against experimentally-induced carotid and coronary artery thrombosis.

Cardiovascular drug utilization and its determinants in unselected medical patients with ischemic heart disease

Background: In patients with ischemic heart disease (IHD), secondary preventive drug therapy improves overall prognosis. Therefore, this study evaluated cardiovascular drug utilization in patients suffering from IHD, identified factors influencing drug utilization, and determined the prevalence of shortfalls of antithrombotic, beta-blocker, and lipid-lowering drug use. Methods: This study is based on data recorded prospectively between 1996 and 1998 in two Swiss teaching hospitals for the SAS/CHDM pharmacoepidemiologic database project. Drug utilization was evaluated in all 987 monitored medical inpatients with IHD. Results: At discharge, only 64% of patients with IHD received platelet aggregation inhibitors, 42% beta-blockers, and 26% lipid-lowering drugs. Secondary preventive drugs were more frequently administered to patients with acute myocardial infarction and less frequently in the elderly. After including other co-factors, no gender difference could be detected. Shortfalls of antithrombotic therapy occurred in 6.5--8.3% of patients and shortfalls in beta-blocker use in 9.9--23.3%. Only about half of all patients with IHD and elevated cholesterol received lipid-lowering drugs. Conclusions: Drugs for secondary prevention are prescribed to the majority of patients with IHD. However, their use could be further increased, especially in the elderly and in patients with IHD who are admitted to the hospital for reasons other than acute myocardial infarction. Lipid-lowering drugs should also be prescribed more often for patients with hypercholesterolemia.

Argatroban: a direct thrombin inhibitor for heparin-induced thrombocytopenia and other clinical applications

Argatroban, a direct thrombin inhibitor derived from arginine, is an effective anticoagulant indicated for prophylaxis or treatment of thrombosis in patients with heparin-induced thrombocytopenia (HIT). Argatroban has been used as an alternative anticoagulant in patients with HIT in various clinical conditions including interventional cardiovascular procedures that require anticoagulation. Satisfactory clinical outcomes with acceptable complications have been reported in these patients. Whether argatroban offers additional clinical advantage over conventional heparin therapy in patients without HIT remains unclear. Argatroban has been evaluated as an alternative anticoagulant to replace heparin in various clinical studies, especially in patients with coronary artery disease or cerebral vascular disease. To date, it remains unclear if argatroban is more effective than heparin, although the agent seems to cause less bleeding complications. This article reviews the pharmacology of argatroban and its clinical application beyond the management of HIT, with particular emphasis on interventional cardiology procedure, acute myocardial infarction, unstable angina pectoris, cerebral thrombosis or ischemic stroke, peripheral obstructive arterial disease, and extracorporeal circulation.