Tako-tsubo cardiomyopathy: how to understand possible pathophysiological mechanism and the role of (123)I-MIBG imaging.

Tako-tsubo cardiomyopathy (TCM) is an increasingly recognized clinical syndrome characterized by acute reversible apical ventricular dysfunction, commonly preceded by exposure to severe physical or emotional stress. In this review, we give a short overview on clinical presentation and treatment of TCM and discuss the possible pathophysiological mechanisms of TCM and the role of various non-invasive imaging modalities in TCM with a focus on the potential role of (123)I-meta-iodobenzylguanidine (MIBG) scintigraphy. Currently, the dominating hypothesis on the pathophysiology of TCM postulates that high levels of the neurotransmitter epinephrine may trigger a change in intracellular signaling in ventricular myocytes. More specific, epinephrine stimulates G-protein coupled β2 adenoreceptors (β2AR) which are located on ventricular myocytes. Normal levels of this neurotransmitter predominantly stimulate the intracellular G-protein, and induce a positive inotropic effect. However, with significant increasing levels of epinephrine, the predominance of stimulation is shifted from G-stimulating to the G-inhibitor protein coupling, which leads to a negative inotropic effect. Interestingly, this negative inotropic effect is the largest in the apical myocardium where the β2AR:β1AR ratio is the highest within the heart. Echocardiography and ventriculography are essential to diagnose TCM, but new imaging tools are promising to diagnose TCM and to evaluate therapeutic efficacy. Cardiovascular magnetic resonance can be used to differentiate TCM from other myocardial diseases, such as myocarditis. (123)I-meta-iodobenzylguanidine ((123)I-MIBG) scintigraphy can be used to assess ventricular adrenergic activity and may guide optimization of individual (pharmacological) therapy. These new insights into the possible pathophysiological mechanisms and novel diagnostic imaging modalities can be used as starting point for the development of international guidelines of TCM which may increase the awareness, and optimize the treatment of TCM.