NPPB and Aortic dissection: Similar to myocardial injury markers (cardiac troponin, cTn; and creatine kinase-MB, CK-MB) and cardiac function markers (brain natriuretic peptide, BNP; and pro-BNP) for MI, and D-dimer for pulmonary embolism, we hope to identify a biomarker specific to aortic dissection in the case of severe chest pain.