Takotsubo Cardiomyopathy- Pathogenesis and clinical findings emotional physical stresses other neurologic endocrine drug brain natriuretic peptide coronary artery disease takotsubo catecholamine release stimulation Beta receptors ionotropic effect alpha receptors coronary vessels metabolic contraction band necrosis edema inflammatory cell infiltration localized fibrosis coronary vasospasm microvascular dysfunction decrease oxygen supply relative to demand hypo-contraction ballooning left ventricular apex chest pain troponin BNP elevation ST ECG changes absence of obstructive CAD transient left ventricle systolic dysfunction dyskinetic apex Mitral regurgitation ventricular thrombus cardiac output low dyspnea syncope heart failure cardiogenic shock echocardiogram apex Gu gagnon Ryznar Waechter