Critical stenosis of the main stem of the left coronary artery is one of the most serious findings which we might detect in a patient with acute coronary syndrome. This finding is according the current recommendations indicated for early revascularization - optimally surgical. If risks of an operation exceed a potential benefit - as in the first report, it is necessary to consider an alternative approach - percutaneous coronary intervention. As a benefit of a successful intervention, serious pulmonary hypertension disappeared (which paradoxically was one of the reasons of the operation contraindication). Another reason for interventional solution of serious stenosis of the main stem of left coronary artery is time. The patient with a very high risk according to the TIMI risk score with reccurent chest pain on full pharmacologie treatment should be solved according to present recommendations as in the regimen of acute myocardial infarction with elevation ST segment (STEMI) – i.e. with revascularisation within 2 hours since the diagnosis, as the patient in the second case.