Exploring Physical Activity Levels in Patients with Cardiovascular Disease-A Preliminary Study.

Increased physical activity may prevent disease onset and severity in individuals with cardiovascular disease. However, studies evaluating physical activity in people with cardiovascular disease are limited. This prospective observational study aimed to objectively assess the level of physical activity in patients with cardiovascular disease and determine the actual extent of physical activity in their daily lives. Participants aged 20 years or older with cardiovascular disease at a cardiology clinic were included. Physical activity was measured using an activity meter with a three-axis acceleration sensor. Overall, 58 patients were included in the study. Household activities were found to be more frequent sources of physical activity. The step count was related to age and housework, while total physical activity and household activity were related to age and work. Locomotive activity was related to sex and housework. Total physical and household activities tended to decrease with age. These findings indicate the influence of work and household chores on physical activity and suggest that physical activity may be underestimated if household activity is not also assessed. These fundamental findings may provide clinical evidence to underpin physical activity for patients with cardiovascular disease.

Development of artificial intelligence-based slow-motion echocardiography and clinical usefulness for evaluating regional wall motion abnormalities.

The diagnostic accuracy of exercise stress echocardiography (ESE) for myocardial ischemia requires improvement, given that it currently depends on the physicians' experience and image quality. To address this issue, we aimed to develop artificial intelligence (AI)-based slow-motion echocardiography using inter-image interpolation. The clinical usefulness of this method was evaluated for detecting regional wall-motion abnormalities (RWMAs). In this study, an AI-based echocardiographic image-interpolation pipeline was developed using optical flow calculation and prediction for in-between images. The accuracy for detecting RWMAs and image readability among 25 patients with RWMA and 25 healthy volunteers was compared between four cardiologists using slow-motion and conventional ESE. Slow-motion echocardiography was successfully developed for arbitrary time-steps (e.g., 0.125×, and 0.5×) using 1,334 videos. The RWMA detection accuracy showed a numerical improvement, but it was not statistically significant (87.5% in slow-motion echocardiography vs. 81.0% in conventional ESE; odds ratio: 1.43 [95% CI: 0.78-2.62], p = 0.25). Interreader agreement analysis (Fleiss's Kappa) for detecting RWMAs among the four cardiologists were 0.66 (95%CI: 0.55-0.77) for slow-motion ESE and 0.53 (95%CI: 0.42-0.65) for conventional ESE. Additionally, subjective evaluations of image readability using a four-point scale showed a significant improvement for slow-motion echocardiography (2.11 ± 0.73 vs. 1.70 ± 0.78, p < 0.001).In conclusion, we successfully developed slow-motion echocardiography using in-between echocardiographic image interpolation. Although the accuracy for detecting RWMAs did not show a significant improvement with this method, we observed enhanced image readability and interreader agreement. This AI-based approach holds promise in supporting physicians' evaluations.

Sitting maneuver to uncover latent left ventricular outflow tract obstruction in patients without hypertrophic cardiomyopathy.

BACKGROUND: Left ventricular outflow tract obstruction [LVOTO; pressure gradient (PG) ≥30 mmHg] is observed in some patients without hypertrophic cardiomyopathy (HCM), and it may develop especially in older patients without HCM (non-HCM). The aim of this study is to investigate if the Valsalva or an upright sitting maneuver can unveil latent LVOTO in patients with non-HCM. METHODS: A total of 33 non-HCM patients with a late peaking or dagger-shaped pulsed Doppler waveform of the LVOT and PG <30 mmHg were included. The Doppler flow velocity of the LVOT was measured at rest, after the Valsalva and a sitting maneuver. Peak PG of ≥30 mmHg after either maneuver was defined as latent LVOTO. The angle between the left ventricular septum and the aorta in the parasternal long-axis view and the apical three-chamber view was measured. RESULTS: Twenty (61 %) of the 33 patients (mean age 74 ±â€¯9 years) were diagnosed with latent LVOTO. Of these, five (25 %) patients were diagnosed after both the Valsalva and sitting maneuver, and 15 (75 %) were diagnosed only after the sitting maneuver. The latent LVOTO group had a significantly smaller angle than the no-LVOTO group between the ventricular septum and the aorta in the parasternal long axis views (107 ±â€¯8° vs. 117 ±â€¯8°, p < 0.01). CONCLUSION: The sitting maneuver is better than the Valsalva maneuver in unveiling latent LVOTO in older, non-HCM patients.

Infective endocarditis with Osler's nodule in a patient with Osler's disease: a case report and review of the literature.

BACKGROUND: Hereditary hemorrhagic telangiectasia, also known as Osler-Weber-Rendu disease, induces arteriovenous malformations in visceral organs. Arteriovenous malformations increase the risk of severe infections and are a common complication associated with hemorrhagic telangiectasia. However, cases of endocarditis associated with hemorrhagic telangiectasia are rarely reported. Although hemorrhagic telangiectasia causes erythematous macules on the extremities, these macules are usually painless. We encountered a rare case of infective endocarditis in a patient with Osler-Weber-Rendu disease. CASE PRESENTATION: A 52-year-old Japanese woman who was diagnosed with hemorrhagic telangiectasia 5 years prior presented to our hospital with fever and muscular pain. She had erythematous nodules and tenderness on the finger, heel, and toe, suggestive of Osler's nodes. A physical examination revealed tachycardia with a 3/6 pansystolic murmur. A transesophageal echocardiogram showed vegetations along the atrial side of the mitral valve and mild mitral regurgitation because of prolapse of the anterior commissure. Methicillin-sensitive Staphylococcus aureus was identified in the blood cultures. Detection of distinctive skin lesions, so-called Osler's nodes, was the symptomatic key to early diagnosis, and the patient was treated without surgery. She was discharged with negative blood cultures after a 6-week intravenous antibiotic administration. CONCLUSIONS: Our report highlights the importance of considering the risk of extracerebral infections including endocarditis in hemorrhagic telangiectasia. This rare case effectively demonstrates the importance of proper diagnosis of skin lesions.

The Feasibility of a Newly Developed Local Network System for Cardiac Rehabilitation (the CR-GNet) in Disease Management and Physical Fitness after Acute Coronary Syndrome.

OBJECTIVE: To examine the Cardiac Rehabilitation Gifu Network (CR-GNet) feasibility in managing diseases and assisting patients in attaining physical fitness, and its impact on long-term outcomes after acute coronary syndrome (ACS). METHODS: In this prospective observational study, we enrolled 47 patients with ACS registered in the CR-GNet between February 2016 and September 2019. 37, 29, and 21 patients underwent follow-up assessments for exercise capacity (peak oxygen uptake) at 3 months, 6 months, and 1 year after discharge, respectively. Major adverse cardiac events (MACE) were compared with controls not registered in the CR-GNet. RESULTS: The coronary risk factors, except blood pressure, improved at 3 and 6 months, and 1 year after discharge. These risk factors in each patient significantly reduced from 2.9 at admission to 1.6, 1.4, and 1.9 at 3 months, 6 months, and 1 year after discharge (p<0.05), respectively. Peak oxygen uptake was significantly higher at 3 months (17.5±4.9 ml/kg/min), 6 months (17.9±5.1 ml/kg/min), and 1 year (17.5±5.5 ml/kg/min) after discharge than that at discharge (14.7±3.6 ml/kg/min) (p<0.05). During follow-up, there was no significant difference; MACE did not occur in any patients in the CR-GNet but occurred in controls. CONCLUSION: CR-GNet is a feasible option for the long-term management of ACS patients.

Impact of Autophagy on Prognosis of Patients With Dilated Cardiomyopathy.

BACKGROUND: Autophagy is a cellular process that degrades a cell's own cytoplasmic components for energy provision and to maintain a proper intracellular environment. Left ventricular reverse remodeling (LVRR) promises a better prognosis for patients with dilated cardiomyopathy (DCM). OBJECTIVES: The authors tested the hypothesis that autophagy is involved in LVRR and has prognostic value in the human failing heart. METHODS: Using left ventricular endomyocardial biopsy specimens from 42 patients with DCM (21 LVRR-positive and 21 LVRR-negative) and 7 patients with normal cardiac function (control), the authors performed immunohistochemistry and immunofluorescent labeling of LC3 and cathepsin D and electron microscopic observation in addition to general morphometry under light microscopy. RESULTS: The clinical characteristics of LVRR-positive patients were similar to those of the LVRR-negative patients, except for pulmonary artery pressure and left atrial dimension. Morphometry under light microscopy did not differ among specimens from DCM patients, regardless of their LVRR status. Electron microscopy revealed that autophagic vacuoles (autophagosomes and autolysosomes) and lysosomes were abundant within cardiomyocytes from DCM patients. Moreover, cardiomyocytes from LVRR-positive patients contained significantly more autophagic vacuoles with higher autolysosome ratios and cathepsin D expression levels than cardiomyocytes from LVRR-negative patients. Logistic regression analysis adjusted for age showed that increases in autophagic vacuole number and cathepsin D expression were predictive of LVRR. DCM patients who achieved LVRR experienced fewer cardiovascular events during the follow-up period. CONCLUSIONS: The authors show that autophagy is a useful marker predictive of LVRR in DCM patients. This provides novel pathologic insight into a strategy for treating the failing DCM heart.

Serum syndecan-1 concentration in hospitalized patients with heart failure may predict readmission-free survival.

Syndecan-1 is found in the endothelial glycocalyx and is released into the bloodstream during stressed conditions, including severe diseases such as acute kidney injury, chronic kidney disease, and cardiovascular disease. This study investigated the prognostic value of serum syndecan-1 concentration in patients with heart failure upon admission. Serum syndecan-1 concentration was analyzed in 152 patients who were hospitalized for worsening heart failure from September 2017 to June 2018. The primary outcome of the study was readmission-free survival, defined as the time from the first admission to readmission for worsened heart failure or death from any cause, which was assessed at 30 months after discharge from the hospital. The secondary outcome of the study was survival time. Blood samples and echocardiogram data were analyzed. Univariate and multivariable time-dependent Cox regression analyses adjusted for age, creatinine levels, and use of antibiotics were conducted. The serum syndecan-1 concentration was significantly associated with readmission-free survival. Subsequently, the syndecan-1 concentration may have gradually decreased with treatment. The administration of human atrial natriuretic peptide and antibiotics may have modified the relationship between readmission-free survival and serum syndecan-1 concentration (p = 0.01 and 0.008, respectively). Serum syndecan-1 concentrations, which may indicate injury to the endothelial glycocalyx, predict readmission-free survival in patients with heart failure.

Endothelial Glycocalyx Disorders May Be Associated With Extended Inflammation During Endotoxemia in a Diabetic Mouse Model.

In diabetes mellitus (DM) patients, the morbidity of infectious disease is increased, and these infections can easily progress from local to systemic infection. Sepsis is a characteristic of organ failure related to microcirculation disorders resulting from endothelial cell injury, whose most frequent comorbidity in patients is DM. The aim of the present study was to evaluate the influence of infection on DM-induced microvascular damage on inflammation and pulmonary endothelial structure using an experimental endotoxemia model. Lipopolysaccharide (LPS; 15 mg/kg) was injected intraperitoneally into 10-week-old male C57BLKS/J Iar- + lepr db /lepr db (db/db) mice and into C57BLKS/J Iar-m + / + lepr db (db/ +) mice, which served as the littermate non-diabetic control. At 48 h after LPS administration, the survival rate of db/db mice (0%, 0/10) was markedly lower (P < 0.05) than that of the db/ + mice (75%, 18/24), whereas the survival rate was 100% in both groups 24 h after LPS administration. In control mice, CD11b-positive cells increased at 6 h after LPS administration; by comparison, the number of CD11b-positive cells increased gradually in db/db mice until 12 h after LPS injection. In the control group, the number of Iba-1-positive cells did not significantly increase before and at 6, 12, and 24 h after LPS injection. Conversely, Iba-1-positive cells continued to increase until 24 h after LPS administration, and this increase was significantly greater than that in the control mice. Expression of Ext1, Csgalnact1, and Vcan related to endothelial glycocalyx synthesis was significantly lower in db/db mice than in the control mice before LPS administration, indicating that endothelial glycocalyx synthesis is attenuated in db/db/mice. In addition, ultrastructural analysis revealed that endothelial glycocalyx was thinner in db/db mice before LPS injection. In conclusion, in db/db mice, the endothelial glycocalyx is already injured before LPS administration, and migration of inflammatory cells is both delayed and expanded. This extended inflammation may be involved in endothelial glycocalyx damage due to the attenuation of endothelial glycocalyx synthesis.

A novel device for detecting anaerobic threshold using sweat lactate during exercise.

The lactate threshold (LT1), which is defined as the first rise in lactate concentration during incremental exercise, has not been non-invasively and conveniently determined in a clinical setting. We aimed to visualize changes in lactate concentration in sweat during exercise using our wearable lactate sensor and investigate the relationship between the lactate threshold (LT1) and ventilatory threshold (VT1). Twenty-three healthy subjects and 42 patients with cardiovascular diseases (CVDs) were enrolled. During exercise, the dynamic changes in lactate values in sweat were visualized in real-time with a sharp continuous increase up to volitional exhaustion and a gradual decrease during the recovery period. The LT1 in sweat was well correlated with the LT1 in blood and the VT1 (r = 0.92 and 0.71, respectively). In addition, the Bland-Altman plot described no bias between the mean values (mean differences: - 4.5 and 2.5 W, respectively). Continuous monitoring of lactate concentrations during exercise can provide additional information for detecting the VT1.

Morphological characteristics in diabetic cardiomyopathy associated with autophagy.

Diabetic cardiomyopathy, clinically diagnosed as ventricular dysfunction in the absence of coronary atherosclerosis or hypertension in diabetic patients, is a cardiac muscle-specific disease that increases the risk of heart failure and mortality. Its clinical course is characterized initially by diastolic dysfunction, later by systolic dysfunction, and eventually by clinical heart failure from an uncertain mechanism. Light microscopic features such as interstitial fibrosis, inflammation, and cardiomyocyte hypertrophy are observed in diabetic cardiomyopathy, but are common to failing hearts generally and are not specific to diabetic cardiomyopathy. Electron microscopic studies of biopsy samples from diabetic patients with heart failure have revealed that the essential mechanism underlying diabetic cardiomyopathy involves thickening of the capillary basement membrane, accumulation of lipid droplets, and glycogen as well as increased numbers of autophagic vacuoles within cardiomyocytes. Autophagy is a conserved mechanism that contributes to maintaining intracellular homeostasis by degrading long-lived proteins and damaged organelles and is observed more often in cardiomyocytes within failing hearts. Diabetes mellitus (DM) impairs cardiac metabolism and leads to dysregulation of energy substrates that contribute to cardiac autophagy. However, a "snapshot" showing greater numbers of autophagic vacuoles within cardiomyocytes may indicate that autophagy is activated into phagophore formation or is suppressed due to impairment of the lysosomal degradation step. Recent in vivo studies have shed light on the underlying molecular mechanism governing autophagy and its essential meaning in the diabetic heart. Autophagic responses to diabetic cardiomyopathy differ between diabetic types: they are enhanced in type 1 DM, but are suppressed in type 2 DM. This difference provides important insight into the pathophysiology of diabetic cardiomyopathy. Here, we review recent advances in our understanding of the pathophysiology of diabetic cardiomyopathy, paying particular attention to autophagy in the heart, and discuss the therapeutic potential of interventions modulating autophagy in diabetic cardiomyopathy.

Recombinant thrombomodulin protects against LPS-induced acute respiratory distress syndrome via preservation of pulmonary endothelial glycocalyx.

BACKGROUND AND PURPOSE: Disruption of the endothelial glycocalyx is causally related to microvascular endothelial dysfunction, a characteristic of sepsis-induced acute respiratory distress syndrome (ARDS). Recombinant human thrombomodulin (rhTM) attenuates vascular endothelial injuries, but the underlying mechanism remains elusive. Here, we investigated the structural basis and molecular mechanisms of rhTM effects on vascular endothelial injury in a model of sepsis. EXPERIMENTAL APPROACH: LPS (20 mg·kg-1 ) was intraperitoneally injected into 10-week-old male C57BL6 mice, and saline or rhTM was intraperitoneally injected 3 and 24 h after LPS injection. Using serum and/or lung tissue, histological, ultrastructural, and microarray analyses were performed. KEY RESULTS: Survival rate of rhTM-treated mice was significantly higher than that of control mice 48 h after LPS injection. Serum concentrations of IL-6 and high-mobility group box 1 were lower in the rhTM-treated group than in the control. Injury to the endothelial glycocalyx in pulmonary capillaries was attenuated by rhTM treatment. Gene set enrichment analysis revealed up-regulation of gene sets corresponding to cell proliferation/differentiation and anti-inflammation, such as the TGF-ß pathway, and negative regulation of IL-6, upon rhTM treatment. Gene expression of heparan sulfate 6-O-sulfotransferase 1 and endothelial cell-specific molecule 1 (components of the endothelial glycocalyx) was significantly preserved by rhTM treatment, and their protein expression levels were maintained in endothelial cells. CONCLUSION AND IMPLICATIONS: Our findings show that rhTM treatment affected inflammation, cell proliferation/differentiation, and glycocalyx synthesis in serum and lung tissue, subsequently attenuating ARDS caused by endothelial injury.

Vacuolated cardiomyocytes in human endomyocardial biopsy specimens.

We encountered an unfamiliar finding during electron microscopic examination of an endomyocardial biopsy obtained from a 55-year-old woman suffering from heart failure due to dilated phase hypertrophic cardiomyopathy. Many cardiomyocytes contained large vacuoles that were mainly empty except for small amounts of amorphous substrate. These were not autophagic vacuoles, as they lacked limiting membranes. Six years later, we encountered similar histological findings in three successive biopsies sourced from another hospital. They were obtained from a 77-year-old man with hypertrophic cardiomyopathy, a 28-year-old woman with endocardial fibrosis, and a 33-year-old man with dilated cardiomyopathy. This biopsy was the second for the endocardial fibrosis patient, and her first biopsy showed no vacuoles within cardiomyocytes. Close inspection of the procedures revealed that in all of these cases the fixed biopsy specimens were carried to the hospital from other institutes using a refrigerated courier service. We then fixed rat heart tissues, froze them once, and processed them for electron microscopy. In that experiment, we were able to reproduce the vacuolar cardiomyocytes, thereby demonstrating it to be a laboratory artifact. We therefore want to emphasize to physicians not to freeze biopsy specimens and not to use a refrigerated courier service for their transport. .

In situ nuclear DNA methylation in dilated cardiomyopathy: an endomyocardial biopsy study.

AIMS: Although distinct DNA methylation patterns have been reported, its localization and roles remain to be defined in heart failure. We investigated the cellular and subcellular localization of DNA methylation and its pathophysiological significance in human failing hearts. METHODS AND RESULTS: Using left ventricular (LV) endomyocardial biopsy specimens from 75 patients with dilated cardiomyopathy (DCM; age: 58 ± 14 years old, %female: 32%) and 20 patients without heart failure (controls; age: 56 ± 17 years old, %female: 45%), we performed immunohistochemistry and immunoelectron microscopy for methylated DNA, 5-methylcytosine (5-mC). We next investigated possible relations of the incidence of 5-mC-positive (%5-mC+ ) cardiomyocytes with clinicopathological parameters. Immunopositivity for 5-mC was detected in the cardiomyocytes and other cell types. The %5-mC+ cardiomyocytes was significantly greater in DCM hearts than in controls (57 ± 13% in DCM vs. 25 ± 12% in controls, P < 0.0001). The localization of 5-mC immunopositivity in cardiomyocyte nuclei coincided well with that of heterochromatin, as confirmed by immunoelectron microscopy. Substantial DNA methylation was also observed in interstitial non-cardiomyocytes, but the incidences did not differ between control and DCM hearts (39 ± 7.9% in DCM vs. 41 ± 10% in controls, P = 0.4099). In DCM patients, the %5-mC+ cardiomyocytes showed a significant inverse correlation with LV functional parameters such as heart rate (r = 0.2391, P = 0.0388), end-diastolic pressure (r = 0.2397, P = 0.0397), and ejection fraction (r = -0.2917, P = 0.0111) and a positive correlation with LV dilatation (volume index at diastole; r = 0.2442, P = 0.0347; and volume index at systole; r = 0.3136, P = 0.0062) and LV hypertrophy (mass index; r = 0.2287, P = 0.0484)-that is, LV remodelling parameters. No significant correlations between DNA methylation and the histological parameters of the biopsies, including cardiomyocyte hypertrophy, fibrosis, and inflammatory cell infiltration, were noted. CONCLUSIONS: The present study revealed increased nuclear DNA methylation in cardiomyocytes, but not other cell types, from DCM hearts, with predominant localization in the heterochromatin. Its significant relations with LV functional and remodelling parameters imply a pathophysiological significance of DNA methylation in heart failure.

Neutrophil Elastase Inhibition Ameliorates Endotoxin-induced Myocardial Injury Accompanying Degradation of Cardiac Capillary Glycocalyx.

Myocardial injury in sepsis may be caused by a burst of several inflammatory mediators, leading to vascular endothelial injuries. However, the contribution of neutrophil elastase (NE) to myocardial injury in sepsis is still unknown. We aimed to evaluate whether endotoxemia-induced myocardial injury is associated with NE. Lipopolysaccharide (LPS) was injected intraperitoneally at a dose of 20 mg/kg into granulocyte-colony-stimulating-factor knockout mice (G-CSF-KO), which have few neutrophils, and littermate control mice. The survival rate of G-CSF-KO mice 48 hours after LPS injection was significantly greater than that of control mice. The serum level of troponin I in G-CSF-KO mice was significantly lower than that in control mice. In addition, the concentration of inflammatory cytokine interleukin-6 (IL-6) was significantly decreased 6 and 12 hours after LPS administration compared with that in control mice. Ultrastructural analysis revealed that vascular endothelial structures and the endothelial glycocalyx in G-CSF-KO mice were clearly preserved. Next, mice were injected with 0.2 mg/kg sivelestat (an NE inhibitor) after LPS administration. The survival rate was significantly higher and the serum level of troponin I was lower in sivelestat-injected mice than in control mice, respectively. Furthermore, IL-6 levels were significantly decreased 6 and 12 hours after LPS administration compared with those in control mice. Vascular endothelial structures and the endothelial glycocalyx in sivelestat-treated mice were clearly preserved at the ultrastructural level. In conclusion, NE is significantly associated with myocardial injury in endotoxemia. Inhibition of NE may be a useful tool for the management of endotoxemia.

Anterior early repolarization pattern and T-wave inversion in a healthy African-Japanese athlete.

Precordial lead T-wave inversion subsequent to early repolarization is thought to be a normal variant in African athletes and that additional testing is unnecessary. With the increasing number of foreign people living in and traveling to Asian countries, it is becoming crucial for Asian physicians to comprehend the abnormal ECG change in African athletes.

Factors Enhancing Serum Syndecan-1 Concentrations: A Large-Scale Comprehensive Medical Examination.

Endothelial disorders are related to various diseases. An initial endothelial injury is characterized by endothelial glycocalyx injury. We aimed to evaluate endothelial glycocalyx injury by measuring serum syndecan-1 concentrations in patients during comprehensive medical examinations. A single-center, prospective, observational study was conducted at Asahi University Hospital. The participants enrolled in this study were 1313 patients who underwent comprehensive medical examinations at Asahi University Hospital from January 2018 to June 2018. One patient undergoing hemodialysis was excluded from the study. At enrollment, blood samples were obtained, and study personnel collected demographic and clinical data. No treatments or exposures were conducted except for standard medical examinations and blood sample collection. Laboratory data were obtained by the collection of blood samples at the time of study enrolment. According to nonlinear regression, the concentrations of serum syndecan-1 were significantly related to age (p = 0.016), aspartic aminotransferase concentration (AST, p = 0.020), blood urea nitrogen concentration (BUN, p = 0.013), triglyceride concentration (p < 0.001), and hematocrit (p = 0.006). These relationships were independent associations. Endothelial glycocalyx injury, which is reflected by serum syndecan-1 concentrations, is related to age, hematocrit, AST concentration, BUN concentration, and triglyceride concentration.

Importance of over-reading ambulatory ECG-based microvolt T-wave alternans to eliminate three main sources of measurement error.

BACKGROUND: Ambulatory electrocardiogram (ECG)-based microvolt T-wave alternans values measured by the modified moving average method (MMA-TWA) can be disrupted by T-wave changes that mimic true repolarization alternans. METHODS: We investigated potential sources of measurement error by studying 19 healthy subjects (12 men; median age, 25) free of known heart disease with 36-month follow-up to establish freedom from significant arrhythmia or syncope. All participants underwent 24-hr continuous 12-lead ECG monitoring. Causes of automated MMA-TWA ≥42 µV episodes were classified based on visual inspection. RESULTS: A total of 2,189 episodes of automated MMA-TWA episodes ≥42 µV were observed in all subjects (peak MMA-TWA: median, 94 µV; interquartile range, 81-112 µV). All episodes included one or more beats with T-wave deformation which lacked "repeating ABAB pattern" and therefore were identified as TWA measurement error. Causes of such error were categorized as: (a) artifact [72.6% (1,589/2,189), observed in 19 (100%) subjects], more frequently in limb than precordial leads; (b) T-wave changes due to changes in heart/body position [25.5% (559/2,189), observed in 14 (73.7%) subjects], frequently observed in leads V1-2; and (c) postextrasystolic T-wave changes [1.9% (41/2,189), observed in 2 (10.5%) subjects]. CONCLUSIONS: Relying only on automated MMA-TWA values obtained during ambulatory ECG monitoring can lead to incorrect measurement of TWA. Our findings offer the potential to reduce false-positive TWA results and to achieve more accurate detection of true repolarization alternans.