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Warfarin After Anterior ST-Elevation Myocardial Infarction

2014-08-27 03:31:12 | BioPortfolio

Summary

Following severe heart attacks involving the front wall of the heart (anterior myocardial infarction), patients are at risk of developing blood clots in the main pumping chamber that can cause a stroke. In the past, studies have shown that a blood thinner (warfarin) can decrease the risk of stroke and clot formation if administered to patients after an anterior myocardial infarction.

However, in today's current practice, certain heart attack patients are commonly treated with two blood-thinning medications (aspirin and clopidogrel) to prevent recurrent heart attacks.

Thus, a clinical problem is created as physicians are not clear how to treat patients after an anterior myocardial infarction who are at risk of a clot but require aspirin and clopidogrel to keep their blood vessels open. Adding warfarin to the combination of aspirin and clopidogrel will possibly decrease the risk of stroke but increase the risk of bleeding. Currently, there is no good evidence to help guide physicians. As demonstrated by a survey done at the Hamilton Health Sciences, there is a fifty/fifty split between physicians who use dual (aspirin and clopidogrel) versus triple (aspirin, clopidogrel, and warfarin) therapy in the treatment of similar patients as described above.

The purpose of this study is to address the bleeding and stroke complications in patients after a severe anterior myocardial infarction. Half of the eligible patients will receive dual therapy and half will receive triple therapy. We will compare the incidence of stroke, blood clots, and bleeding complications between the two groups at 3 months.

Description

Rationale:

Left ventricular mural thrombus (LVT) remains a common complication after anterior ST-elevation myocardial infarction (STEMI) with a reported incidence ranging from 12- 17%. Previous studies from the pre-thrombolytic era have shown that warfarin therapy significantly reduces the incidence of LVT and embolic events in patients post anterior STEMI. However, the risk/benefit ratio of warfarin therapy in the setting of early revascularization and dual antiplatelet therapy with aspirin and clopidogrel remains unknown.

Purpose:

To compare the incidence of death, MI, stroke, embolic events, LVT, and bleeding complications at 3 months in patients with an anterior STEMI and ejection fraction less than 40% treated with ASA and clopidogrel alone versus those treated with aspirin, clopidogrel, and warfarin (triple therapy group).

Sample Size:

This is a pilot project to help establish the feasibility of conducting a full scale externally funded study. As such sample size calculations are not applicable. The primary aim of the study is to determine the safety and feasibility of conducting a large-scale trial, and this pilot project in not expected to reveal a statistically significant difference between the 2 groups.

Design/Methodology:

All patients will be randomized to either aspirin and clopidogrel alone or to triple therapy with aspirin, clopidogrel and warfarin. The randomization process will be centralized and computer generated. Patients with a clear indication for oral anticoagulation such as atrial fibrillation, LV thrombus, mechanical heart valve, or DVT/PE will not undergo randomization but will be followed as part of a registry of patients on triple therapy. All patients will remain on the allocated therapy for 3 months at which time outcomes will be determined.

Study interventions:

Patients will be treated with either ASA and clopidogrel alone (dual therapy) or with aspirin, clopidogrel and warfarin (triple therapy) in combination for 3 months. Patients in the triple therapy arm will be bridged with intravenous unfractionated heparin, low molecular weight heparin, or fondaparinux until their INR is therapeutic, and will be followed by the thrombosis service for the duration of the study.

Study Design

Allocation: Randomized, Control: Active Control, Endpoint Classification: Safety/Efficacy Study, Intervention Model: Parallel Assignment, Masking: Open Label, Primary Purpose: Treatment

Conditions

Myocardial Infarction

Intervention

aspirin + clopidogrel, aspirin + clopidogrel + warfarin

Location

Hamilton Health Sciences-Hamilton General Hopsital
Hamilton
Ontario
Canada
L8L 2X2

Status

Completed

Source

McMaster University

Results (where available)

View Results

Links

Published on BioPortfolio: 2014-08-27T03:31:12-0400

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Medical and Biotech [MESH] Definitions

A non-steroidal anti-inflammatory agent that is less effective than equal doses of ASPIRIN in relieving pain and reducing fever. However, individuals who are hypersensitive to ASPIRIN may tolerate sodium salicylate. In general, this salicylate produces the same adverse reactions as ASPIRIN, but there is less occult gastrointestinal bleeding. (From AMA Drug Evaluations Annual, 1992, p120)

Asthmatic adverse reaction (e.g., BRONCHOCONSTRICTION) to conventional NSAIDS including aspirin use.

A drug combination of aspirin and dipyridamole that functions as a PLATELET AGGREGATION INHIBITOR, used to prevent THROMBOSIS and STROKE in TRANSIENT ISCHEMIC ATTACK patients.

An anticoagulant that acts by inhibiting the synthesis of vitamin K-dependent coagulation factors. Warfarin is indicated for the prophylaxis and/or treatment of venous thrombosis and its extension, pulmonary embolism, and atrial fibrillation with embolization. It is also used as an adjunct in the prophylaxis of systemic embolism after myocardial infarction. Warfarin is also used as a rodenticide.

The prototypical analgesic used in the treatment of mild to moderate pain. It has anti-inflammatory and antipyretic properties and acts as an inhibitor of cyclooxygenase which results in the inhibition of the biosynthesis of prostaglandins. Aspirin also inhibits platelet aggregation and is used in the prevention of arterial and venous thrombosis. (From Martindale, The Extra Pharmacopoeia, 30th ed, p5)

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