# Cardiac Nuclear Imaging Findings in Atypical Variants of Takotsubo Cardiomyopathy
###### Abstract
However, complications including lethal ventricular arrhythmia, pump failure, outflow tract obstruction, cardiac rupture, and systemic embolization may occur in the acute phase and cause morbidity and mortality. The overlapping of clinical features between TTC and ACS makes particularly critical the early distinction of the two entities, which is of primary importance due to their completely different management. Several diagnostic criteria have been developed following the first proposal by [PERSON] et al. in 2003 [38], but no consensus has yet been reached. The diagnostic criteria issued by the Takotsubo Cardiomyopathy Study Group (TCSG) are commonly followed in Japan [39]. Internationally, the 2008 Revised Mayo Clinic Criteria, based on the presence of transient left ventricle systolic dysfunction, absence of obstructive coronary disease, new electrocardiographic abnormalities or modest elevation in troponin, and absence of pheochromocytoma or myocarditis, are the most widely used [5]. However, certain limitations to the above-mentioned criteria have been recently addressed in the International Takotsubo diagnostic criteria [40]. Specifically, a diagnosis of TTC should not be excluded in the presence of significant CAD, in line with data from the International Takotsubo Registry reporting a rate of coexistence of CAD higher than expected (15.3%) [9]; in the presence of pheochromocytoma, as it can cause TC-like syndrome via catecholamine storm, being a secondary cause of TC [41]; and in the presence of wall motion abnormalities in the distribution of a single coronary artery, considering that rarely a focal subtype of TTC may involve only single coronary artery distribution, typically the anterolateral wall [42]. To predict the probability of diagnosing TTC and to differentiate it from ACS in the acute setting, the Inter Tak Diagnostic Score has been developed [43]. Based on this score, patients with non-ST elevation and a high score (>70 points), reflecting a high probability of TTC, should undergo an echocardiogram to provide an immediate assessment of the regional wall motion abnormalities, to assess right ventricle involvement and to evaluate TTC complications [44; 45; 46]. In clinical practice, an early coronary angiography is generally performed without delay within 48 h of the onset of symptoms [47] in patients with acute chest pain, ST-segment elevation, and elevated cardiac enzymes [48]. Left ventriculography, performed simultaneously with coronary angiography, helps confirm the diagnosis and identify the subtype of TTC [49]. Among non-invasive imaging techniques, both cardiovascular magnetic resonance (CMR) imaging and coronary computed tomography (CT) angiography have been proposed in TTC diagnostic algorithms [50]. In this scenario, cardiac nuclear imaging may represent a further non-invasive diagnostic and prognostic option able to provide additional pathophysiological details thanks to its functional nature. In a recent systematic review, [PERSON] et al. summarized the current literature, from perfusion and metabolic studies to sympathetic innervation imaging, underlining their role in improving diagnostic accuracy, providing prognostic information, and appreciating TTC pathophysiology [51]. However, at present, cardiac nuclear imaging is not included in the main diagnostic criteria [39]. To date, the term 'takotsubo' is widely used in recognition of [PERSON] et al., who first described it in 1990 [52; 53], but a consensus has not been reached, leading to variable nomenclature in the literature including acute stress-induced cardiomyopathy, broken-heart syndrome [54], apical ballooning syndrome, or ampulla cardiomyopathy [55], with no term properly describing the heterogeneous ventricular appearance of this syndrome [56].