Pathophysiology and therapy of Takotsubo syndrome. Letter regarding the article 'Pathophysiology of Takotsubo syndrome - a joint scientific statement from the Heart Failure Association Takotsubo Syndrome Study Group and Myocardial Function Working Group of the European Society of Cardiology - Part 1: overview and the central role for catecholamines and sympathetic nervous system'

QT interval prolongation in Takotsubo syndrome: a frightening feature with no major prognostic impact

Despite the frequent and often severe repolarization abnormalities seen in Takotsubo syndrome (TTS), the underlying mechanism of life-threatening arrhythmias is incompletely understood, and the risk remains uncertain. TTS is considered a potential cause of acquired long QT syndrome; however, there is no robust evidence that QT prolongation has a major prognostic impact on these patients' outcomes. Our aim was to assess the prevalence and clinical implications of acquired long QT during TTS events and compare in-hospital and long-term outcomes between patients with and without corrected QT interval (QTc) prolongation. This is a retrospective cohort study that included 113 patients admitted to our tertiary care hospital with a diagnosis of TTS. The cohort was divided into two groups: a long QTc group (QTc≥460 milliseconds in any electrocardiogram at admission or during hospitalization) and a normal QTc group. Baseline characteristics, occurrences during hospitalization, and outcome data were obtained from the revision of medical registries and hospital visits. Of the 113 patients, 107 (94.7%) were female. The mean age was 67.6±11.7 years. QTc prolongation was found in 38%. Demographic characteristics, relevant chronic medication, prevalence of cardiovascular risk factors, and other comorbidities were similar between the groups, except for history of atrial fibrillation, which was more common in the long QTc group. Syncope was more prevalent in the long QTc group. In-hospital complications were not statistically different between patients with long and normal QTc (48.8% versus 44.2%, p=0.637), including ventricular arrhythmias and complete atrioventricular block (both 4.7% versus 1.4%, p=0.556). In-hospital mortality was 0.9%, corresponding to one patient in the long QTc group. The mean follow-up time was 4.8±3.8 years. 5-year all-cause mortality and the occurrence of the composite endpoint of major adverse cardiac and cerebrovascular events did not differ between the groups (p=0.511 and p=0.538, respectively). Our study found no association between prolonged QTc interval during TTS events and adverse prognosis, since in-hospital and long-term outcomes were similar between the groups. Our findings suggest that, although QT prolongation is usually a frightening feature on ECG, this repolarization abnormality during the acute phase has no major prognostic implications in the TTS population.

Orexin/hypocretin system dysfunction in patients with Takotsubo syndrome: A novel pathophysiological explanation

Takotsubo syndrome (TTS) is an acute heart failure syndrome. Emotional or physical stressors are believed to precipitate TTS, while the pathophysiological mechanism is not yet completely understood. During the coronavirus disease (COVID-19) pandemic, an increased incidence of TTS has been reported in some countries; however, the precise pathophysiological mechanism for developing TTS with acute COVID-19 infection is unknown. Nevertheless, observing the symptoms of COVID-19 might lead to new perspectives in understanding TTS pathophysiology, as some of the symptoms of the COVID-19 infection could be assessed in the context of an orexin/hypocretin-system dysfunction. Orexin/hypocretin is a cardiorespiratory neuromodulator that acts on two orexin receptors widely distributed in the brain and peripheral tissues. In COVID-19 patients, autoantibodies against one of these orexin receptors have been reported. Orexin-system dysfunction affects a variety of systems in an organism. Here, we review the influence of orexin-system dysfunction on the cardiovascular system to propose its connection with TTS. We propose that orexin-system dysfunction is a potential novel explanation for the pathophysiology of TTS due to direct or indirect dynamics of orexin signaling, which could influence cardiac contractility. This is in line with the conceptualization of TTS as a cardiovascular syndrome rather than merely a cardiac abnormality or cardiomyopathy. To the best of our knowledge, this is the first publication to present a plausible connection between TTS and orexin-system dysfunction. We hope that this novel hypothesis will inspire comprehensive studies regarding orexin's role in TTS pathophysiology. Furthermore, confirmation of this plausible pathophysiological mechanism could contribute to the development of orexin-based therapeutics in the treatment and prevention of TTS.