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

Phase dependent sympathetic dysinnervation in Takotsubo syndrome revealed with transparent heart

Takotsubo syndrome (TTS) is an acute cardiac syndrome characterized by transient left ventricular dysfunction. Although the wall motion abnormality resolves completely, the prognosis is poor. Defect of 123I-metaiodobenzylguanidine uptake, interpreted as sympathetic impairment, persisted in TTS patients, but the mechanism is not fully understood. We aimed to elucidate morphological sympathetic nerve change in a TTS model mouse using three-dimensional imaging techniques, with a particular focus on the role of factors in these alterations. The TTS model was induced by a single intraperitoneal injection of 2.0 mg/kg adrenaline to C57BL/6 mice, resulting in transient akinesis localized to the inferior apical region of the heart. Three-dimensional morphological assessment revealed that sympathetic nerve length within the inferior apical area of TTS mice reduced during the chronic phase compared with the sham mice. Notably, the study observed a pattern of denervation during the acute phase, followed by re-innervation and subsequent denervation in the chronic phase. The neurotrophic factors expressions changed in a time-dependent manner, corresponding to the phase-specific damage both to cardiomyocytes and sympathetic neurons. The bimodal change in sympathetic nerves and altered neurotrophic factors in TTS mice provide novel insights into the pathophysiological mechanism of TTS to establish therapeutic strategies for TTS.

Transient Left Ventricular Dysfunction from Cardiomyopathies to Myocardial Viability: When and Why Cardiac Function Recovers

Transient left ventricular dysfunction (TLVD), a temporary condition marked by reversible impairment of ventricular function, remains an underdiagnosed yet significant contributor to morbidity and mortality in clinical practice. Unlike the well-explored atherosclerotic disease of the epicardial coronary arteries, the diverse etiologies of TLVD require greater attention for proper diagnosis and management. The spectrum of disorders associated with TLVD includes stress-induced cardiomyopathy, central nervous system injuries, histaminergic syndromes, various inflammatory diseases, pregnancy-related conditions, and genetically determined syndromes. Furthermore, myocardial infarction with non-obstructive coronary arteries (MINOCA) origins such as coronary artery spasm, coronary thromboembolism, and spontaneous coronary artery dissection (SCAD) may also manifest as TLVD, eventually showing recovery. This review highlights the range of ischemic and non-ischemic clinical situations that lead to TLVD, gathering conditions like Tako-Tsubo Syndrome (TTS), Kounis syndrome (KS), Myocarditis, Peripartum Cardiomyopathy (PPCM), and Tachycardia-induced cardiomyopathy (TIC). Differentiation amongst these causes is crucial, as they involve distinct clinical, instrumental, and genetic predictors that bode different outcomes and recovery potential for left ventricular function. The purpose of this review is to improve everyday clinical approaches to treating these diseases by providing an extensive survey of conditions linked with TLVD and the elements impacting prognosis and outcomes.

A Review of Nuclear Imaging in Takotsubo Cardiomyopathy

Takotsubo cardiomyopathy or Takotsubo Syndrome (TTS) is a reversible left ventricular dysfunction syndrome that is increasingly being recognized. Recent advances in nuclear imaging have allowed us to study TTS in greater detail. We searched the PubMed and Medline databases and identified 53 publications with 221 patients reporting nuclear imaging findings in TTS. The age of the patients ranged from 17 to 87 years and were predominantly women (88.2%). The TTS variant was apical (typical) in 170 (76.9%), mid-ventricular in 23 (10.4%), and basal (reverse TTS) in 2 (0.9%). Cardiac perfusion was assessed using 99mTc sestamibi (MIBI) SPECT, 99mTc tetrofosmin SPECT, 201Tl SPECT, 82Rb PET, 201Tl SPECT, and 13N ammonia PET. Additional studies used were 123I MIBG SPECT, 123I BMIPP SPECT, 18F FDG PET, 67Ga citrate, and 11C hydroxy-ephedrine. A perfusion defect was seen in 69 (31.2%), and an inverse perfusion-metabolism mismatch (normal or near-normal perfusion with absent myocardial metabolic activity) was seen in 183 (82.8%) patients. Nuclear imaging has a significant role in evaluating, diagnosing, and prognosticating patients with TTS. As nuclear imaging technology evolves, we will surely gain more insights into this fascinating disorder.

Cardiac 123I-mIBG Imaging in Heart Failure

Cardiac sympathetic upregulation is one of the neurohormonal compensation mechanisms that play an important role in the pathogenesis of chronic heart failure (CHF). In the past decades, cardiac 123I-mIBG scintigraphy has been established as a feasible technique to evaluate the global and regional cardiac sympathetic innervation. Although cardiac 123I-mIBG imaging has been studied in many cardiac and neurological diseases, it has extensively been studied in ischemic and non-ischemic CHF. Therefore, this review will focus on the role of 123I-mIBG imaging in CHF. This non-invasive, widely available technique has been established to evaluate the prognosis in CHF. Standardization, especially among various combinations of gamma camera and collimator, is important for identifying appropriate thresholds for adequate risk stratification. Interestingly, in contrast to the linear relationship between 123I-mIBG-derived parameters and overall prognosis, there seems to be a "bell-shape" curve for 123I-mIBG-derived parameters in relation to ventricular arrhythmia or appropriate implantable cardioverter defibrillator (ICD) therapy in patients with ischemic CHF. In addition, there is a potential clinical role for cardiac 123I-mIBG imaging in optimizing patient selection for implantation of expensive devices such as ICD and cardiac resynchronization therapy (CRT). Based on cardiac 123I-mIBG data risk models and machine learning, models have been developed for appropriate risk assessment in CHF.

Stepwise approach for diagnosis and management of Takotsubo syndrome with cardiac imaging tools

Takotsubo syndrome is featured by transient left ventricle dysfunction in the absence of significant coronary artery disease, mainly triggered by emotional or physical stress. Its clinical presentation is similar to acute coronary syndrome; therefore, cardiac imaging tools have a crucial role. Coronary angiography is mandatory for exclusion of pathological stenosis. On the other side, transthoracic echocardiography is the first non-invasive imaging modality for an early evaluation of left ventricle systolic and diastolic function. Left ventricle morphologic patterns could be identified according to the localization of wall motion abnormalities. Moreover, an early identification of potential mechanical and electrical complications such as left ventricle outflow tract obstruction, mitral regurgitation, thrombus formation, right ventricular involvement, cardiac rupture, and cardiac rhythm disorders could provide additional information for clinical management and therapy. Because of the dynamic evolution of the syndrome, comprehensive serial echocardiographic examinations should be systematically performed. Advanced techniques, including speckle-tracking echocardiography, cardiac magnetic resonance, and nuclear imaging can provide mechanistic and pathophysiologic insights into this syndrome. This review focuses on these aspects and provide a stepwise approach of all cardiac imaging tools for the diagnosis and the management of Takotsubo syndrome.

Alteration of β-Adrenoceptor Signaling in Left Ventricle of Acute Phase Takotsubo Syndrome: a Human Study

Accumulating evidence indicates alteration of the β-adrenoceptor (AR), such as desensitization and subtype switching of its coupling G protein, plays a role in the protection against catecholamine toxicity in heart failure. However, in human takotsubo syndrome (TTS), which is associated with a surge of circulating catecholamine in the acute phase, there is no histologic evidence of β-AR alteration. The purpose of this study was to investigate the involvement of alteration of β-AR signaling in the mechanism of TTS development. Left ventricular (LV) biopsied samples from 26 patients with TTS, 19 with normal LV function, and 26 with dilated cardiomyopathy (DCM) were studied. G protein-coupled receptor kinase 2 (GRK2) and β-arrestin2, which initiate the alteration of β-AR signaling, were more abundantly expressed in the myocardium in acute-phase TTS than in those of DCM and normal control as indicated by immunohistochemistry. The percentage of cardiomyocytes that showed positive membrane staining for GRK2 and β-arrestin2 was also significantly higher in acute-phase TTS. Sequential biopsies in the recovery-phase for two patients with TTS revealed that membrane expression of GRK2 and β-arrestin2 faded over time. This study provided the first histologic evidence of the involvement of alteration of β-ARs in the development of TTS.

Gaze Palsy, Sleep and Gait Disorder, as Well as Tako-Tsubo Syndrome in a Patient with IgLON5 Antibodies

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Sympathoneural and adrenomedullary responses to mental stress

This concept-based review provides historical perspectives and updates about sympathetic noradrenergic and sympathetic adrenergic responses to mental stress. The topic of this review has incited perennial debate, because of disagreements over definitions, controversial inferences, and limited availability of relevant measurement tools. The discussion begins appropriately with Cannon's "homeostasis" and his pioneering work in the area. This is followed by mental stress as a scientific idea and the relatively new notions of allostasis and allostatic load. Experimental models of mental stress in rodents and humans are discussed, with particular attention to ethical constraints in humans. Sections follow on sympathoneural responses to mental stress, reactivity of catecholamine systems, clinical pathophysiologic states, and the cardiovascular reactivity hypothesis. Future advancement of the field will require integrative approaches and coordinated efforts between physiologists and psychologists on this interdisciplinary topic.

Cardiac sympathetic activity in hypertrophic cardiomyopathy and Tako-tsubo cardiomyopathy

¹²³I-meta-iodobenzylguanidine (¹²³I-mIBG) scintigraphy has been established as an important technique to evaluate cardiac sympathetic function and it has been shown to be of clinical value, especially for the assessment of prognosis, in many cardiac diseases. The majority of ¹²³I-mIBG scintigraphy studies have focused on patients with cardiac dysfunction due to hypertension, ischemic heart disease, or valvular disease. However less is known about the role of ¹²³I-mIBG scintigraphy in primary cardiomyopathies. This overview shows the clinical value of ¹²³I-mIBG scintigraphy in two types of primary cardiomyopathy: The genetic hypertrophic cardiomyopathy (HCM) and the acquired Tako-tsubo cardiomyopathy (TCM). Cardiac sympathetic activity is increased in HCM and correlates to the septal wall thickness and consequently to the LVOT obstruction. Moreover, increased cardiac sympathetic activity correlates with impaired diastolic and systolic LV function. In addition, ¹²³I-mIBG scintigraphy may be useful for determining the risk of developing congestive heart failure and ventricular tachycardia in these patients. In TCM ¹²³I-mIBG scintigraphy can be used to assess cardiac sympathetic hyperactivity. In addition, ¹²³I-mIBG scintigraphy may identify those patients who are prone to TCM recurrence and may help to identify responders to individual (pharmacological) therapy.