McConnell's sign — An insight into the pathogenesis of Takotsubo syndrome?

Takotsubo syndrome (TTS), also known as stress-induced cardiomyopathy, is an acute cardiac syndrome. The unique characteristics of TTS are that one or more circumferential cardiac segments are stunned out of contraction in the absence of an explanatory coronary lesion [1]. Although the peculiar myocardial akinesia can affect any part of the ventricular wall, two common patterns of TTS are apical akinesis (the typical TTS) and basal akinesis (the inverted pattern) [2]. The pathogenesis underlying Takotsubo syndrome is incompletely understood. Several mechanisms have been proposed for the development of TTS, including overstimulation of the β2-adrenoceptor-Gi pathway [3], acute coronary microvascular and endothelial dysfunction [4], aborted myocardial infarction with spontaneous recanalisation [5], acute metabolic stunning [6], lipotoxicity [1,7], acute left ventricular outflow tract obstruction (LVOTO) and abnormal ventriculo-arterial coupling [8]. One critical shortcoming of some of these proposed mechanisms is that they are not able to elucidate why myocardial akinesia in TTS is usually segmental and circumferential. Although the gradient distribution of β-adrenoceptors or sympathetic nerves in the heart may explain why catecholamine-induced myocardial akinesia can be apical or basal, such physiological properties, including genetic profiles, currently fail to