Structural and Functional Brain Changes in Acute Takotsubo Syndrome

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T akotsubo syndrome is an acute heart failure cardiomyopathy mimicking an acute myocardial infarction in its presentation. 1Typically, it occurs in the aftermath of intense psychologic or physical stress, affecting women in more than 90% of cases.The mechanism by which emotional processing in the context of stress leads to significant cardiac injury and acute left ventricular dysfunction has yet to be elucidated.Therefore, a full exploration of the brain structure and function in takotsubo syndrome merits investigation.
A recent retrospective analysis using 18 F-fluorodeoxyglucose positron emission tomographiccomputed tomographic examination of a patient cohort investigated for cancer showed higher amygdala activity (an area involved in the experiencing of emotions) in subjects who subsequently developed takotsubo syndrome after 2 years, 2 suggesting the possibility of a premorbid state affecting the brains of patients with takotsubo syndrome.4][5] All of these studies, except one, 5 included patients at variable later stages after the acute presentation, possibly masking phasic variations that occur thereafter that may be important markers of recovery or sustained predisposing risk.Furthermore, a large international registry reported a significant stroke outcome in takotsubo patients, 6 and recently white matter hyperintensities (which reflect small vessel disease) have been linked to an increased risk of developing future stroke. 7 the present study, we explored a whole-brain magnetic resonance imaging (MRI) investigation of acute changes in takotsubo presenters.Specifically, we examined the cortical surface areas, cortical thickness, and white matter hyperintensity volumes as well as gray matter volumes, the structural connectivity network of gray matter centers (tractography) by means of diffusion tensor imaging, and their resting state connectivity with the use of functional magnetic resonance imaging (fMRI), compared with a matched control population.LGA requires T1 and FLAIR images and outputs lesion probability maps and total lesion volume and number.An initial binary lesion map obtained by imposing a predetermined initial threshold (0.5) on the independent maps is then grown along hyperintense voxels in the FLAIR image.

METHODS
Total lesion volume was calculated from the lesion probability maps with a threshold of 0.5.

VOLUMETRIC, SURFACE AREA, AND CORTICAL THICKNESS ANALYSIS FOR TOTAL AND INDIVIDUAL
BRAIN CENTER AREAS.Cortical reconstruction and volumetric segmentation were performed with the FreeSurfer image analysis suite v7.1.1,which is freely available online. 13This involves several postprocessing steps to output volume measurements that are well validated in the published reports.Once the cortical models were complete, several deformable procedures were performed for further data processing and analysis and creation of a variety of surface-based data, including surface area measurements.Cortical thickness was calculated from both intensity and continuity information from the entire 3-dimensional MRI volume in segmentation and deformation to produce representations of cortical thickness.Procedures for the measurement of cortical thickness have been validated against histologic analysis and manual measurements. 14NCTIONAL CONNECTIVITY.Resting state fMRI was analyzed using the CONN (Functional Connectivity Toolbox), which allowed takotsubo patients to be compared with matched control subjects for differences in functional connectivity with a bandpass filter of 0.008-0.090Hz.Six motion-corrected parameters were included in the generalized linear model.An region of interest-region of interest based analysis was performed on all brain regions included in CONN.All results were corrected for age and sex.
Pearson's correlation between clusters was calculated across all regions.The r value acquired for the Pearson correlation between every 2 regions was z transformed and group differences were calculated on the z-transformed values with a 2-sample Student's t-test.False discovery rate correction was used to correct for multiple comparisons at the cluster level, and corrected P < 0.05 was considered to be significant.

STRUCTURAL CONNECTIVITY (TRACTOGRAPHY).
Diffusion tensor images were preprocessed using the FMRIB (Functional Magnetic Resonance Imaging of the Brain) Diffusion Toolbox.We corrected for motion and geometric distortion caused by eddy currents with the eddy correct tool in FMRIB Diffusion Toolbox, taking the average of the 8 b0 volumes as the reference image.Nonbrain tissue from the average b0 image was removed with the use of the FMRIB Diffusion Toolbox.False discovery rate correction was used to correct for multiple comparisons with the use of CONN at the cluster level, and corrected P < 0.05 was considered to be significant.

STATISTICAL ANALYSIS OF BRAIN VOLUME, SURFACE
AREA, AND CORTICAL THICKNESS.SPSS v27 was used to analyze the differences in volumetric data with the use of the general linear model, and multivariate analyses of the brain volumes were corrected for total brain volume, age, sex, and photoperiod.Surface area was corrected for age, sex, and total brain volume.
Cortical thickness was corrected for age, sex, and whole-brain cortical thickness.Multiple correction testing was performed for brain volume, surface area, and cortical thickness using the Bonferroni correction.A value of P < 0.05 after Bonferroni adjustment was considered to be statistically significant.

RESULTS
Baseline demographics and the validated questionnaire scores of the 50 participants recruited for the study are presented in Table 1.The median age was 65 years in the control group and 68 years in the takotsubo syndrome group (P ¼ 0.809).There were 24 women and 1 man in each group (P ¼ 1.00)There was no significant difference in comorbidities, including psychiatric illnesses, apart from a small number of patients with chronic obstructive pulmonary disease in the takotsubo group (n ¼ 5; P ¼ 0.018).There were 40% of takotsubo patients with an emotional trigger, 28% with a physical trigger, and 32% with no obvious identifiable trigger.The median time to MRI scanning was 5 days in the takotsubo syndrome group.The mean left ventricular ejection fraction in the takotsubo syndrome group was 45.0% AE 8.3%.The JACC: HEART FAILURE VOL.11, NO. 3, 2023  Hospital Anxiety and Depression Scale score was significantly higher in the patient group compared with control subjects (P < 0.001).See Supplemental  2 and Supplemental Table 5, acute takotsubo patients had significantly smaller white matter and subcortical gray matter volumes, whereas their cortical gray matter was larger.In addition, there were numerous significant differences in many of the limbic center brain volumes between acute takotsubo syndrome patients and matched control subjects, notably, left, right, and total hippocampus and the brainstem were all significantly smaller in acute takotsubo patients.Conversely, left, right, and total thalamus and insula were larger in patients with takotsubo syndrome compared with matched control subjects (P < 0.001).
FUNCTIONAL CONNECTIVITY.As shown in Figure 1, there were multiple significantly increased (red lines) and decreased (blue lines) functional connectivity networks in takotsubo patients vs matched control subjects (all P < 0.05).Specifically, there was increased connectivity between either the right thalamus or the left thalamus and the left caudate and left nucleus accumbens, between the anterior cingulate cortex and the right cerebral cortex, or between the left thalamus and the posterior cerebellum.
Conversely, there was significantly decreased functional connectivity between the right thalamus and the right inferior frontal gyrus, between the entire thalamus and the left amygdala, left insula, visual lateral and visual medial lobes, orbitofrontal cortex, and inferior frontal gyrus, or between the left insula and the left caudate and thalamus.

STRUCTURAL CONNECTIVITY (TRACTOGRAPHY).
As shown in Figure 2, there was a significant increase in all structural connectivity connections in takotsubo syndrome compared with matched control subjects, notably with absence of any reduced structural connections in takotsubo patients.Specifically, the right and left thalamus showed significantly increased structural connectivity to the temporal regions.The left insula had significantly increased structural    cortical surface area appears to be regulated by unique developmental factors. 16,17Therefore, both a genetic difference as well as an adaptive cortical reorganization could be responsible for the findings seen in the brain of takotsubo patients compared with control subjects.
Smaller cortical surface area and greater cortical thickness as noticed in takotsubo patients in the present study is also seen in patients with major psychiatric disease, such as major depression. 18In addition, smaller brain gray matter volumes, especially hippocampal volumes, that we observed in patients with takotsubo syndrome are also seen in patients with elevated levels of inflammation 19 and have been previously reported in the amygdala by Hiestand et al, 20 albeit at a later time after the index presentation.The reduction in gray matter volumes was also shown by Dichtl et al, 5 confirming the involvement of the gray matter in patients who develop takotsubo syndrome.Hiestand et al 20 showed reduced cortical thickness in a cohort of takotsubo patients 1 year after the acute event, which is contrary to our results and may be explained by the timeframe when scanning was performed in that Only enhanced structural connections were seen in takotsubo patients (all P < 0.05).
JACC: HEART FAILURE VOL.11, NO. 3, 2023 study.Both depression and anxiety disorders are associated with elevated levels of inflammation. 21stemic and myocardial inflammation is a wellrecognized feature of takotsubo syndrome, 22,23 which raises the possibility that the changes we observed in the brain of takotsubo syndrome patients are potentially adaptive and related to inflammation.
White matter hyperintensity findings in this cohort would suggest that takotsubo patients have a similar risk of cognitive impairment, dementia and stroke as a matched control population. 24If the increased risk of stroke suggested by the international takotsubo registry 6 was assigned to the significant premorbid incidence of neurologic disease of the patients included in this registry, it could mean that in the absence of preexistent neurologic disease, the risk of subsequent stroke for takotsubo patients may not be as high as suggested by registries.

FUNCTIONAL AND STRUCTURAL CONNECTIVITY
CHANGES IN TAKOTSUBO SYNDROME.Brain activity and functional connectivity networks are intricately linked to their structural connectivity patterns, such that brain regions with high structural connectivity normally exhibit high functional connectivity, whereas the converse is not necessarily true. 25 In this study, we showed that both thalamic and insulae nuclei were greater in size and had increased structural connections.Some of these findings overlap with those seen in other conditions, such as greater thalamic volumes seen in patients with major depression and suicidal ideation 26 or increased functional connectivity between thalamus and nucleus accumbens linked to emotional processing regulating the pain response 27 as well as involved in attenuating cardiac injury during ischemic damage. 28 have previously noted that there are increased proinflammatory cytokines and inflammatory markers, such C-reactive protein, in patients with takotsubo syndrome. 29Again, increased inflammation has been associated with reduced functional activation of the thalamus and insular cortex, 30 such as we observed here.
It is therefore intriguing to see a reduction in functional connectivity in the context of enhanced structural connections, which implies that the reduction in functional connectivity is not caused by abnormal structural connections.An inflammatory substrate hypothesis makes it easier to reconcile observations such as reduced functional connectivity from the right thalamus to the right inferior frontal gyrus (language center) or to the visual lateral cortex in takotsubo patients in this study.The first is also observed in schizophrenia and linked to aberrant encoding of semantic memory (abnormal processing of auditory stimuli, fixity of thinking with low flexibility, and high emotional distress), 31 and the latter is also seen in patients with anorexia nervosa and linked to abnormal processing of visual stimuli and overvalued ideation. 32noteworthy finding in the present study is the reduced functional connectivity between the left thalamus and the left insular cortex.Lesions in the left amygdala or left insular cortex are associated with a 5-fold increased risk of sudden cardiac death in patients with schizophrenia. 33In patients with left insular lesions, there is loss of parasympathetic control and sympathetic overactivity with an increased risk of cardiac injury and arrythmia. 34Stroke patients with left insular lesions had poorer cardiac outcomes and were more likely to have cardiac wall motion abnormalities on echocardiography in the absence of obstructive coronary artery disease. 35Left insular lesions induced in mice resulted in cardiac injury and elevated serum levels of noradrenaline.The extent of the insular injury corresponded with the degree of cardiac injury. 36A previous study of patients with takotsubo syndrome 2 years after the acute event, however, noticed increased functional connectivity in the left insular cortex.A biphasic response with initial reduced insular functional connectivity leading to loss of parasympathetic control followed by increased insular connectivity thereafter is a plausible explanation of maladaptive autonomic response in these patients. 37Dichtl et al 5 showed similar findings, with reduced functional connectivity of the insula during the acute period, in keeping with the results seen in our study.Templin et al 3 showed similar findings with reduced functional connectivity in the insular region.
This recurring finding of abnormal insular function strongly suggests a role for this region in the pathogenesis of takotsubo syndrome.
Another interesting finding in takotsubo patients in this study is the reduced functional connectivity in the caudate, putamen, and pallidum with increased functional connectivity in the nucleus accumbens.
These together form key parts of the basal ganglia.
Abnormalities in the basal ganglia have been associated with altered vagal nerve function and an increased risk of both bradyarrhythmias and atrial fibrillation. 38,39Altered functioning in this area may contribute to arrhythmic presentations seen in acute takotsubo syndrome or in the development of subsequent atrial fibrillation. 40e also observed reduced functional connectivity in the amygdala of patients with acute takotsubo similarly to patients with a tendency to catastrophize events. 41Previous observations showed reduction in functional connectivity in the amygdala years after the acute event.Together these findings would imply that this area of emotional processing is abnormal during both the acute phase and long term. 3ese findings would support the nitrosative stress theory of takotsubo syndrome whereby maladaptive brain responses to stress involving the thalamusamygdala-insular pathways lead to loss of autonomic control over the nervous system, leading to sympathetic overactivity, nitrosative stress, and cardiac injury, which contributes to the acute and chronic heart failure phenotype seen in takotsubo syndrome (Central Illustration). 22,29,42,43 in white matter hyperintensities compared with control subjects, implying absence of small vessel disease; 2) show areas of functional hypoconnectivity in key brain regions involving the thalamus-amygdalainsula axis and basal ganglia, which are responsible for higher-level functions (emotion, reasoning, language, perception) as well as autonomic regulation of the brain-heart axis; and 3) have increased structural tractography connections compared with control subjects, suggesting that the abnormalities in functional connectivity are not caused by abnormalities in structural connections.
TRANSLATIONAL OUTLOOK: The abnormalities in the thalamus-amygdala-insula and basal ganglia support the concept of involvement of higher-level function centers in takotsubo syndrome, and interventions aimed at modulating these may be of benefit.
photoperiod of the scanning center was determined by using the United States Naval Observatory online data repository and calculated by subtracting the time of sunset from the time of sunrise on the day of scanning for each participant. 12BRAIN MRI PROTOCOL.Brain MRI was performed on a 3-T Philips Achieva TX-series MRI system (Philips Healthcare) based in the biomedical imaging center at Aberdeen Royal Infirmary with a 32-channel phasedarray head coil.T1-weighted fast gradient echo images (160 sagittal slices, repetition time [TR] 8.2 ms, echo time [TE] 3.8 ms, inversion time [TI] 1,031 ms, fractional anisotropy [FA] 8 , field of view [FOV] JACC: HEART FAILURE VOL.11, NO. 3, 2023 connectivity to the right amygdala, right putamen, right posterior cingulate gyrus, and right rostral anterior cingulate gyrus.DISCUSSION This is the largest cohort of takotsubo syndrome patients whose acute brain phenotype has been investigated.All cases were examined during the acute phase (within 5 days of presentation) to allow benchmarking of any changes that may have occurred before or during the subsequent convalescent phase because of medications or other interventions.We found no evidence of cerebral small vessel disease, as evidenced by similar number and volume of white matter hyperintensities compared with control subjects.In this study, takotsubo patients had greater cortical thickness but smaller cortical surface areas and smaller total white matter, total subcortical gray matter volume, and all individual gray matter brain centers except for the thalamus and insula, which were larger, in either hemisphere or combined.Distinct bidirectional changes in functional connectivity were seen compared with matched control subjects, and this occurred in the context of all structural tractography connections being significantly increased in takotsubo patients.

FIGURE 1
FIGURE 1 Altered Functional Connectivity in Takotsubo Syndrome

FIGURE 2
FIGURE 2 Structural Connectivity of Regions of Interest Based on Diffusion Tensor Imaging Differences Between Acute Takotsubo Syndrome and Matched Control Subjects

Table 1
for detailed case description of patients.As seen in Table2and Supplemental Table3, acute takotsubo patients had significantly smaller surface areas of several brain regions, such as the left rostral anterior cingulate and the right and left insula.
SURFACE AREA OF INDIVIDUAL BRAIN REGIONS.

TABLE 1
Baseline Characteristic In Patients With Takotsubo Syndrome and Matched Hospital Anxiety and Depression Scale; LVEF ¼ left ventricular ejection fraction; MRI ¼ magnetic resonance imaging.

TABLE 2
Brain Parameters Values are mean AE SD.P values were obtained after correction for total brain volume, age, sex, and photoperiod.Corrected P values are after Bonferroni correction.NS ¼ not significant.
This work was supported by National Health Service GrampianEndowment EA9667/ES868.The authors have reported that they have no relationships relevant to the contents of this paper to disclose.ADDRESS FOR CORRESPONDENCE: Dr Hilal Khan, Aberdeen Cardiovascular and Diabetes Centre, Room 1:03 Ashgrove House, Foresterhill, University of Aberdeen, King's College, Aberdeen AB24 3FX, United Kingdom.E-mail: hilal.khan@abdn.ac.uk.
PERSPECTIVES COMPETENCY IN MEDICAL KNOWLEDGE: In the acute phase of illness, takotsubo syndrome patients demonstrate overall increased cortical thickness but smaller cortical surface areas, smaller white and gray matter volumes, and smaller individual brain center volumes, except thalamus and insula.Patients with takotsubo syndrome: 1) have no significant difference : HEART FAILURE VOL.11, NO. 3, 2023 Brain Changes in Acute Takotsubo Syndrome M A R C H 2 0 2 3 : 3 0 7 -3 1 7 JACC