PROSPECT is a multi-center prospective registry of Acute Coronary Syndromes (ACS) patients with single or double vessel coronary artery disease. Approximately 700 patients with ACS will be enrolled into the study at sites in the United States and European Union.

To identify in patients presenting with ACS imaging modalities and/or serologic markers of inflammation which may aid in the identification of non-flow obstructing lesions with an increased risk for future acute coronary events. This study will ascertain the prevalence and clinical significance of non-flow obstructing lesions, which subsequently result in acute coronary events - defined as vulnerable plaque. The safety of regional imaging of non-culprit lesions in ACS patients will also be assessed.

Inclusion Criteria:

1. Acute cardiac pain, or angina equivalent, consistent with unstable angina or myocardial infarction, lasting greater than 10 minutes duration within the past 72 hours.

2. Patient must have evidence of an ACS requiring catheterization documented by the presence of any one of the following conditions:

   1. Elevated enzymes (CK-MB or troponin I or troponin T greater than upper limits of normal).
   2. ST depression of >1 mm in 2 or more contiguous leads measured at 40 ms after the J point, in the absence of left ventricular hypertrophy, bundle branch block, paced rhythms, pre-excitation or other ECG artifacts or confounding conditions.
   3. Transient ST elevation of >1 mm in 2 or more contiguous leads lasting <30 minutes (otherwise same criteria as above).
   4. ST elevation myocardial infarction with onset >24 hours previously, diagnosed with the typical triad of nitrate unresponsive chest pain lasting >30 minutes, ST elevation of >1 mm in 2 or more contiguous leads or new left bundle branch block, and rise and fall of CK-MB isoenzymes.

Key Clinical Exclusion Criteria:

1. Patient has had a documented acute ST-segment elevation myocardial infarction within the past 24 hours.
2. Known serum creatinine > 2.5 mg/dl.
3. Decompensated hypotension or heart failure requiring intubation, inotropes, intravenous diuretics or intraaortic balloon counterpulsation.
4. Patient has a known hypersensitivity, allergy or contraindication to any of the following: aspirin, heparin, clopidogrel, and ticlopidine or to contrast that cannot be adequately pre-medicated.
5. Presence of cardiac implants (i.e. implantable defibrillators); however, prior implantation of pacemaker or biventricular pacemaker is permitted.
6. Presence of cardiogenic shock.
7. Patient has a known left ventricular ejection fraction <30%.
8. Refractory ventricular arrhythmia requiring either intravenous pharmacologic treatment or defibrillator therapy (e.g. ventricular tachycardia or fibrillation).
9. Acute conduction system disease requiring temporary pacemaker insertion.
10. Patient has had a recent (within 6 months) PCI unless the patient is undergoing a staged procedure for dual vessel treatment.
11. Patient has other medical illness (i.e., cancer or congestive heart failure) or recent history of substance abuse that may cause non-compliance with the Investigational Plan, confound the data interpretation or is associated with an anticipated limited life expectancy less than one year..
12. Prior participation in this study or patient is currently enrolled in another investigational use device or drug study that has not reached its primary endpoint. If the patient is enrolled in another study that is not investigational, required visits for that trial must not interfere with the conduct of this trial.

Patients presenting with an Acute Coronary Syndrome that require catheterization and interventional treatment of a culprit lesion(s).