The purpose of this study is to compare the safety of two different dose regimens of unfractionated heparin (UFH) during a PCI procedure in patients with UA (unstable angina)/NSTEMI (non ST segment elevation myocardial infarction) who have been initially treated with fondaparinux.

Subjects presenting at hospital with suspected UA or NSTEMI and who are likely to undergo angiography (ideally within 72 hours) will be assessed for eligibility and consented. Suitable subjects will be enrolled and commence treatment with open-label fondaparinux, 2.5 mg, s.c., once daily. Following angiography subjects indicated for PCI and meeting the additional requirements for randomization will be randomised to receive one of two dose regimens of UFH either standard dose or low dose immediately prior to the PCI procedure. Post-PCI, therapy with fondaparinux (2.5 mg, s.c.) may be resumed at the investigator's discretion for up to a maximum of 8 days or hospital discharge, whichever is earlier.

Subjects not indicated for PCI, will continue treatment with fondaparinux, 2.5mg, s.c, once daily for up to 8 days or hospital discharge, whichever is earlier.

All subjects will be followed up for 30 days after randomization/angiography.

• Acute Coronary Syndrome
• Non ST Segment Elevation Myocardial Infarction
• Unstable Angina

• Standard dose UFH: Experimental
  • No planned GPIIb/IIIa use: 85 U/kg bolus with additional bolus (2,000 U - 4,000U) if needed to achieve a target ACT of 300 - 350 seconds (using the HEMOCHRON device) or ACT of 250 - 300 seconds (using the HEMOTECH device).
  • Planned GPIIb/IIIa use: 60 U/kg bolus with additional bolus of (2,000 U - 4,000U) if needed to achieve target ACT of ≥200 seconds (using the HEMOCHRON or HEMOTECH device)
  Intervention: Drug: Unfractioned heparin
• Low Dose UFH: Experimental
  - All subjects irrespective of planned GPIIb/IIIa use: 50 U/kg bolus
  Intervention: Drug: Unfractioned heparin

The following are inclusion and exclusion criteria for enrollment in the study:

Inclusion Criteria:

• Presenting or admitted to hospital with symptoms suspected to represent UA or NSTEMI, i.e., clinical history consistent with new onset, or a worsening pattern of, characteristic ischemic chest pain or ischemic symptoms occurring at rest or with minimal activity (lasting longer than 5 minutes or requiring sublingual nitro-glycerine for relief of the pain).
• Available to be enrolled within 48 hours of the onset of the most recent episode of symptoms.
• Planned coronary angiography, with PCI if indicated, within 72 hours of enrollment where possible.
• At least two of the three following additional criteria:
• Age greater than or equal to 60 years
• Troponin T or I or CK-MB above the upper limit of normal for the local institution;
• ECG changes compatible with ischemia, i.e., ST depression at least 1 mm in 2 contiguous leads or T wave inversion > 3 mm or any dynamic ST shift or transient ST elevation.
• Written informed consent dated and signed

Exclusion Criteria:

• Age < 21 years.
• Any contraindication to UFH or fondaparinux
• Contraindication for angiography or PCI at baseline
• Subjects requiring urgent (<120 minutes) coronary angiography as characterized by those with:
• refractory or recurrent angina associated with dynamic ST-deviation
• heart failure
• life-threatening arrhythmias
• hemodynamic instability
• Subjects already receiving treatment with enoxaparin (or other LMWH), bivalirudin or UFH for treatment of the qualifying events unless the last administered (i.v. or s.c.) dose was:
• ≥ 8 hours for LMWH
• ≥60 minutes for bivalirudin
• ≥90 minutes for UFH
• Hemorrhagic stroke within the last 12 months.
• Indication for anti-coagulation other than ACS during the index hospitalization.
• Pregnancy or women of childbearing potential who are not using an effective method of contraception.
• Co-morbid condition with life expectancy less than 6 months.
• Currently receiving an experimental pharmacological agent.
• Revascularization procedure already performed for the qualifying event.
• Severe renal insufficiency (i.e., estimated creatinine clearance <20 ml/min)

Following angiography and confirmation that the subject is to undergo PCI, the subject must also meet all of the following additional criteria in order to be randomised:

• Subjects will have received at least 1 dose of open-label fondaparinux
• The most recent dose of open-label fondaparinux will not have been more than 24 hours before the start of the PCI procedure.