Optical Coherence Tomography in Acute Coronary Syndrome

Inclusion Criteria: 1. Men and Women (aim: consecutive) 2. Age 18 to 85 years old. 3. ACS as trigger event - (ESC guidelines) being: 1. Acute cardiac chest pain or angina equivalent consistent with moderate to high-risk unstable angina or myocardial infarction, lasting more than 10 minutes duration during 72 hours before invasive examination AND 2. Evidence for ACS requiring catheterization documented by a) elevated enzymes (CK-MB or hs-Troponin I/T \> 99th percentile or in-/decrease) AND/OR 3. ECG with ST-depression \>1mm in 2 or more contiguous leads after the J-point AND/OR transient ST-elevation \>1mm in 2 or more contiguous leads lasting \<30 min OR c) STE-ACS with onset \< 24 hours previously and chest pain \>30 min ST-elevation \>1mm in 2 or more contiguous leads or new left bundle block. 4. Written informed consent 5. Patients must have at least coronary one-vessel disease with one angiographically detectable "culprit lesion" (or in case of more \> 1 lesion all lesions have to be in one "culprit vessel") in a native coronary vessel requiring PCI. Identification of this lesion as the "culprit lesion" has to be in line with other non-invasive findings (ECG-leads; regional wall motion abnormalities in echocardiography). Other "non-culprit-lesions" are allowed to have significant stenosis requiring interventional revascularization in a staged procedure. Exclusion Criteria: 1. Active pregnancy. 2. Active sepsis. 3. Acute psychotic disease. 4. Known systolic heart failure with left-ventricular ejection fraction (LV-EF≤ 30 %). 5. Cardiogenic shock or heart failure requiring intubation, inotropes; diuretics or mechanical circulation support. 6. Refractory ventricular arrhythmia requiring pharmacologic or defibrillator therapy. 7. Patients who had received heart transplantation or any other organ transplant or are on waiting list. 8. Renal insufficiency with serum-creatinine ≥ 1.5 mg/dl. 9. Patients with other medical illness (i.e. cancer) 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. 10. Prior participation in this study or in other investigational studies, that have not reached its primary endpoint. 11. Unprotected left main- CAD with ≥ 50% stenosis. 12. ACS with culprit lesion in a bypass graft or ACS caused by stent-thrombosis. 13. Extent and severity of CAD is such that investigator believes it is likely that bypass surgery will be required within 1 year of enrollment. 14. No suitable anatomy of "culprit lesion" for OCT: * severe calcification or extreme tortuosity of "culprit lesion". * culprit lesion with very distal location. * infarct vessels with an diameter \> 4 mm or \< 2 mm. * STE-ACS: "No-reflow" (TIMI 0-I) after thrombus aspiration/slight pre- dilatation