Improvement trend for individual health guidance intervention according to Japan clinical guidelines by public health nurses for type 2 diabetes mellitus who visited for medical checkups regularly: a case-control preliminary report.

We conducted a retrospective case-control study to assess the efficacy of personalized health guidance interventions on individuals with type 2 diabetes mellitus and obesity. A selection was made of individuals in regular visits to the Takagi Hospital for medical checkups between January 2017, and October 2021. Totally, 108 subjects (cases) with health guidance were divided into 2 groups: one group without pharmacotherapy for diabetes mellitus in medical institutions (n = 92) and another group with pharmacotherapy (n = 116). Cases were provided with personalized health guidance interventions by public health nurses for 30 min, in accordance with the Japanese clinical guidelines for the prevention of lifestyle-related diseases. Sex- and age-matched controls were chosen from individuals with diabetes mellitus without health guidance. The intervention without pharmacotherapy resulted in improvements in health indicators, including body weight, waist circumference, diastolic blood pressure, triglyceride levels, and γ-glutamyl trans-peptidase. These positive effects were not observed in the control group without health guidance. The therapeutic effects of health guidance were observed in cases where pharmacotherapy was administered. In conclusion, the implementation of individual health guidance interventions may prove to be effective for individuals with type 2 diabetes mellitus and obesity who regularly attend medical checkups.

Impact of Tweeting Summaries by the Japanese Circulation Society Official Account on Article Viewership　- Pilot Trial.

BACKGROUND: The impact of promotional tweets from the official journal account (forCirculation JournalandCirculation Reports) on article viewership has not been thoroughly evaluated.Methods and Results:We retrospectively collected journal viewership data forCirculation JournalandCirculation Reportsfrom March 2021 to August 2021. We compared viewership between articles with (n=15) and without (n=250) tweets. After 1 : 4 propensity score matching (15 tweeted articles and 60 non-tweeted matched controls), journal viewership metrics within 7 days of the tweeting date (and the hypothetical tweeting date), was larger in tweeted articles than non-tweeted articles (median [interquartile range] Abstract page views 89 [60-104] vs. 18 [8-41]). CONCLUSIONS: This pilot study suggests a positive relationship between journal-posted promotional tweets and article viewership.

Transient receptor potential vanilloid 1-expressing cardiac afferent nerves may contribute to cardiac hypertrophy in accompany with an increased expression of brain-derived neurotrophic factor within nucleus tractus solitarius in a pressure overload model.

INTRODUCTION: Increased sympathetic output contributes to cardiac hypertrophy. Sympathoexcitation is induced by activating the cardiac sympathetic afferent nerves through transient receptor potential vanilloid 1 (TRPV1) in cardiac afferent endings. Brainstem nucleus tractus solitarius (NTS) receives the sensory cardiac afferent inputs. Brain-derived neurotrophic factor (BDNF) is released within NTS from sensory neurons in an activity-dependent manner. Additionally, BDNF in NTS tonically regulates sympathetic activity. Therefore, we hypothesized that TRPV1-expressing cardiac afferent nerves contribute to cardiac hypertrophy in accompany with an increased BDNF expression in NTS. METHODS AND RESULTS: Abdominal aortic banding (AB) or sham operation was conducted in wild-type C57BL/6 J (WT-AB) and TRPV1 knockout mice (TRPV1 KO-AB). At 8 weeks post-operation, echocardiographic left ventricular wall thickness and heart weight/body weight ratio were significantly greater in WT-AB than WT-Sham mice, and these hypertrophic indexes were attenuated in TRPV1 KO-AB mice. Among the groups, left ventricular fractional shortening was not different. The protein levels of TRPV1 in heart and BDNF in NTS were significantly increased in WT-AB compared to WT-Sham mice, whereas BDNF expression in NTS was not increased by AB in TRPV1-KO mice. Chemical ablation of TRPV1-expressing cardiac afferents attenuated the AB-induced cardiac hypertrophy and increase in BDNF in NTS. Sympathetic activity analyzed using heart rate variability, and sympathoexcitatory responses to the stimulation of cardiac afferents were increased in WT-AB compared to WT-Sham mice. CONCLUSION: TRPV1-expressing cardiac afferent nerves may contribute to pressure overload-induced cardiac hypertrophy in accompany with the increased BDNF within NTS.

Low Body Mass Index without Malnutrition Is an Independent Risk Factor for Major Cardiovascular Events in Patients with Hemodialysis.

We retrospectively analyzed major cardiovascular events (MACE), a composite of cardiac death, nonfatal myocardial infarction, unplanned revascularization, heart failure leading to hospitalization, and stroke during a 3-year follow-up of patients with hemodialysis at the dialysis center of our general hospital that can treat comprehensive diseases. Moreover, we conducted an exploratory study that focuses on the risk factor for MACE in patients with hemodialysis.A total of 132 patients with hemodialysis at our dialysis center as of June 2017 were included in the study. Data on event incidence, including death and various clinical indicators, were collected in the electronic medical record for three years until June 2020. Between June 2017 and June 2020, of the 132 patients with hemodialysis, 31 patients experienced MACE (10 cardiovascular deaths, 3 nonfatal myocardial infarction, 11 unplanned revascularizations, 5 heart failure leading to hospitalization, and 2 stroke). The patients with MACE had a lower body mass index (BMI), longer duration of dialysis with more preexisting gastrointestinal (GI) bleeding, and took more aspirin compared to the MACE-free patients. Malnutrition markers (serum total protein, serum albumin, and serum total cholesterol) were similar in both groups. In a univariate analysis for MACE, the odds ratio was significantly higher for BMI < 18.5, duration of hemodialysis, and history of GI bleeding. Multivariable-adjusted odds ratios for MACE were significantly higher for BMI < 18.5.In conclusion, BMI < 18.5 without malnutrition may be an independent risk factor for MACE in patients with hemodialysis.

Association Between Statin Use Prior to Admission and Lower Coronavirus Disease 2019 (COVID-19) Severity in Patients With Cardiovascular Disease or Risk Factors.

BACKGROUND: Cardiovascular diseases and/or risk factors (CVDRF) have been reported as risk factors for severe coronavirus disease 2019 (COVID-19).Methods and Results:In total, we selected 693 patients with CVDRF from the CLAVIS-COVID database of 1,518 cases in Japan. The mean age was 68 years (35% females). Statin use was reported by 31% patients at admission. Statin users exhibited lower incidence of extracorporeal membrane oxygenation (ECMO) insertion (1.4% vs. 4.6%, odds ratio [OR]: 0.295, P=0.037) and septic shock (1.4% vs. 6.5%, OR: 0.205, P=0.004) despite having more comorbidities such as diabetes mellitus. CONCLUSIONS: This study suggests the potential benefits of statins use against COVID-19.

Clinical and Biomarker Profiles and Prognosis of Elderly Patients With Coronavirus Disease 2019 (COVID-19) With Cardiovascular Diseases and/or Risk Factors.

BACKGROUND: This study investigated the effects of age on the outcomes of coronavirus disease 2019 (COVID-19) and on cardiac biomarker profiles, especially in patients with cardiovascular diseases and/or risk factors (CVDRF).Methods and Results:A nationwide multicenter retrospective study included 1,518 patients with COVID-19. Of these patients, 693 with underlying CVDRF were analyzed; patients were divided into age groups (<55, 55-64, 65-79, and ≥80 years) and in-hospital mortality and age-specific clinical and cardiac biomarker profiles on admission evaluated. Overall, the mean age of patients was 68 years, 449 (64.8%) were male, and 693 (45.7%) had underlying CVDRF. Elderly (≥80 years) patients had a significantly higher risk of in-hospital mortality regardless of concomitant CVDRF than younger patients (P<0.001). Typical characteristics related to COVID-19, including symptoms and abnormal findings on baseline chest X-ray and computed tomography scans, were significantly less prevalent in the elderly group than in the younger groups. However, a significantly (P<0.001) higher proportion of elderly patients were positive for cardiac troponin (cTn), and B-type natriuretic peptide (BNP) and N-terminal pro BNP (NT-proBNP) levels on admission were significantly higher among elderly than younger patients (P<0.001 and P=0.001, respectively). CONCLUSIONS: Elderly patients with COVID-19 had a higher risk of mortality during the hospital course, regardless of their history of CVDRF, were more likely to be cTn positive, and had significantly higher BNP/NT-proBNP levels than younger patients.

Recommendations for Maintaining the Cardiovascular Care System Under the Conditions of the COVID-19 Pandemic　- 1st Edition, April 2020.

BACKGROUND: The Japanese Circulation Society proposes recommendations for all healthcare professionals involved in cardiovascular medicine to protect them from infection and ensure that seriously ill patients requiring urgent care receive proper treatment.Methods and Results:Patients are divided into "Positive or suspected coronavirus disease 2019 (COVID-19)" and "All others". Furthermore, tests and treatments are divided into emergency or standby. For each category, we propose recommendations. CONCLUSIONS: To maintain the cardiovascular care system, The Japanese Circulation Society recommends completely preventing nosocomial COVID-19 infections, ensuring adequate PPE necessary for healthcare personnel, and learning and implementing standard precautions.

Coronavirus Disease 2019 (COVID-19) Information for Cardiologists　- Systematic Literature Review and Additional Analysis.

BACKGROUND: Despite the rapidly increasing attention being given to Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection, more commonly known as coronavirus disease 2019 (COVID-19), the relationship between cardiovascular disease and COVID-19 has not been fully described.Methods and Results:A systematic review was undertaken to summarize the important aspects of COVID-19 for cardiologists. Protection both for patients and healthcare providers, indication for treatments, collaboration with other departments and hospitals, and regular update of information are essentials to front COVID-19 patients. CONCLUSIONS: Because the chief manifestations of COVID-19 infection are respiratory and acute respiratory distress syndrome, cardiologists do not see infected patients directly. Cardiologists need to be better prepared regarding standard disinfection procedures, and be aware of the indications for extracorporeal membrane oxygenation and its use in the critical care setting.

Selexipag for Chronic Thromboembolic Pulmonary Hypertension in Japanese Patients　- A Double-Blind, Randomized, Placebo-Controlled, Multicenter Phase II Study.

BACKGROUND: Selexipag is an oral prostacyclin receptor (IP receptor) agonist with a non-prostanoid structure. This study examined its efficacy and safety in Japanese patients with non-operated or persistent/recurrent chronic thromboembolic pulmonary hypertension (CTEPH).Methods and Results:This Phase II study was a randomized, double-blind, placebo-controlled parallel-group comparison. The primary endpoint was a change in pulmonary vascular resistance (PVR) from baseline to week 17. The main analysis involved a per-protocol set group of 28 subjects. The change in PVR (mean±SD) after 17 weeks of treatment in the selexipag group was -104±191 dyn·s/cm5, whereas that in the placebo group was 26±180 dyn·s/cm5. Thus, the treatment effect after 17 weeks of selexipag treatment was calculated as -130±189 dyn·s/cm5(P=0.1553). Although the primary endpoint was not met, for the group not concomitantly using a pulmonary vasodilator the PVR in the selexipag group was significantly decreased compared with placebo group (P=0.0364). The selexipag group also showed improvement in total pulmonary resistance and cardiac index. CONCLUSIONS: Selexipag treatment improved pulmonary hemodynamics in Japanese patients with CTEPH, but PVR did not show a significant difference between the selexipag and placebo groups. (Trial registration: JAPIC Clinical Trials Information [JapicCTI-111667]).

Estimation of the baroreflex total loop gain by the power spectral analysis of continuous arterial pressure recordings.

Baroreflex dysfunction contributes to the pathogenesis of cardiovascular diseases. The baroreflex comprises a negative feedback loop to stabilize arterial pressure (AP); its pressure-stabilizing capacity is defined as the gain ( G) of the transfer function ( H) of the baroreflex total loop. However, no method exists to evaluate G in a clinical setting. A feedback system with H attenuates pressure disturbance (PD) to PD/(1 + H). We hypothesized that the baroreflex attenuates the power spectrum density (PSD) of AP in the baroreflex functioning frequency range. We created graded baroreflex dysfunction in rats using a modified sinoaortic denervation (SAD) method [SAD; control (no SAD): n = 9; partial SAD (SAD in the right carotid sinus): n = 6, and total SAD (SAD in the bilateral carotid sinuses): n = 6] and evaluated the PSD of 12-h telemetric AP recordings in the light phase. Using the ratio of PSD at 0.01-0.1 Hz (PSD slope), we normalized them with the PSD in rats with complete baroreflex failure and derived the baroreflex index (BRI), which directly reflects G. We compared BRI and G obtained from a baroreflex open-loop experiment (reference G). The PSD slope became steeper with progression of baroreflex dysfunction. BRI (control: 2.00 ± 0.31, partial SAD: 1.28 ± 0.30, and total SAD: 0.06 ± 0.10, P < 0.05) was linearly correlated with reference G ( R2 = 0.91, P < 0.01). BRI accurately estimated G of the baroreflex and may serve as a novel tool for estimating the pressure-stabilizing capacity of the baroreflex in clinical settings. NEW & NOTEWORTHY This study proposed a novel method to estimate the gain of the baroreflex total loop, the so-called "baroreflex index" (BRI). BRI focuses on action potential variability in the frequency domain, considering baroreflex low-pass filter characteristics within 0.01-0.1 Hz. We demonstrated that BRI was linearly correlated with the reference gain of baroreflex in rats. Thus, BRI may contribute greatly to the development of a clinical tool for estimating baroreflex pressure-stabilizing capacity.

Diabetes mellitus attenuates the pressure response against hypotensive stress by impairing the sympathetic regulation of the baroreflex afferent arc.

Patients with diabetes mellitus (DM) often show arterial pressure (AP) lability associated with cardiovascular autonomic neuropathy. Because the arterial baroreflex tightly regulates AP via sympathetic nerve activity (SNA), we investigated the systematic baroreflex function, considering the control theory in DM by open-loop analysis. We used Zucker diabetic fatty (ZDF) rats as a type 2 DM model. Under general anesthesia, we isolated the carotid sinuses from the systemic circulation, changed intracarotid sinus pressure (CSP), and recorded SNA and AP responses. We compared CSP-AP (total loop), CSP-SNA (afferent arc), and SNA-AP (efferent arc) relationships between ZDF lean ( n = 8) and ZDF fatty rats ( n = 6). Although the total loop gain of baroreflex (ΔAP/ΔCSP) at the operating point did not differ between the two groups, the average gain in the lower CSP range was markedly reduced in ZDF fatty rats (0.03 ± 0.01 vs. 0.87 ± 0.10 mmHg/mmHg, P < 0.001). The afferent arc showed the same trend as the total loop, with a response threshold of 139.8 ± 1.0 mmHg in ZDF fatty rats. There were no significant differences in the gain of efferent arc between the two groups. Simulation experiments indicated a markedly higher AP fall and lower total loop gain of baroreflex in ZDF fatty rats than in ZDF lean rats against hypotensive stress because the efferent arc intersected with the afferent arc in the SNA unresponsive range. Thus, we concluded that impaired baroreflex sympathetic regulation in the lower AP range attenuates the pressure response against hypotensive stress and may partially contribute to AP lability in DM. NEW & NOTEWORTHY In this study, we investigated the open-loop baroreflex function, considering the control theory in type 2 diabetes mellitus model rats to address the systematic mechanism of arterial pressure (AP) lability in diabetes mellitus. The unresponsiveness of baroreflex sympathetic regulation in the lower AP range was observed in type 2 diabetic rats. It may attenuate the baroreflex pressure-stabilizing function and induce greater AP fall against hypotensive stress.

Pupillary Light Reflex as a New Prognostic Marker in Patients With Heart Failure.

BACKGROUND: Autonomic function can be evaluated based on the pupillary light reflex (PLR). However, the relationship between PLR and prognosis in patients with heart failure (HF) remains unclear. This study was performed to examine whether PLR could be used as a prognostic indicator in patients with HF. METHODS AND RESULTS: A retrospective review was performed in 535 consecutive Japanese patients hospitalized for acute HF (mean age 66.1 ± 13.7 y). PLR was recorded at least 7 days after hospitalization for HF with the use of a pupilometer. Fifty-three patients died over a median follow-up period of 1.3 years (interquartile range 0.6-2.3 y). After adjustment for several preexisting prognostic factors, including Seattle Heart Failure Score (SHFS), PLR as assessed by recovery time (time to 63% redilation) was independently associated with all-cause mortality (hazard ratio 0.50, 95% confidence interval 0.35-0.73; P < .001). The addition of recovery time to SHFS resulted in a significant increase in the area under the curve on receiver-operating characteristic curve analysis (0.69 vs 0.77; P < .001). CONCLUSIONS: PLR assessed by recovery time was an independent predictor of mortality and added prognostic information to the SHFS in patients with HF. Our results suggest that PLR may be useful as a new prognostic marker in HF patients.

Suppressed baroreflex peripheral arc overwhelms augmented neural arc and incapacitates baroreflex function in rats with pulmonary arterial hypertension.

NEW FINDINGS: What is the central question of this study? The impact of pulmonary arterial hypertension on open-loop baroreflex function, which determines how powerfully and rapidly the baroreflex operates to regulate arterial pressure, remains poorly understood. What is the main finding and its importance? The gain of the baroreflex total arc, indicating the baroreflex pressure-stabilizing function, is markedly attenuated in rats with monocrotaline-induced pulmonary arterial hypertension. This is caused by a rightward shift of the baroreflex neural arc and a downward shift of the peripheral arc. These findings contribute greatly to our understanding of arterial pressure regulation by the sympathetic nervous system in pulmonary arterial hypertension. ABSTRACT: Sympathoexcitation has been documented in patients with established pulmonary arterial hypertension (PAH). Although the arterial baroreflex is the main negative feedback regulator of sympathetic nerve activity (SNA), the way in which PAH impacts baroreflex function remains poorly understood. In this study, we conducted baroreflex open-loop analysis in a rat model of PAH. Sprague-Dawley rats were injected with monocrotaline (MCT) s.c. to induce PAH (60 mg kg-1 ; n = 11) or saline as a control group (CTL; n = 8). At 3.5 weeks after MCT injection, bilateral carotid sinuses were isolated, and intrasinus pressure (CSP) was controlled while SNA at the coeliac ganglia and arterial pressure (AP) were recorded. To examine the static baroreflex function, CSP was increased stepwise while steady-state AP (total arc) and SNA (neural arc) responses to CSP and the AP response to SNA (peripheral arc) were measured. Monocrotaline significantly decreased the static gain of the baroreflex total arc at the operating AP compared with CTL (-0.80 ± 0.31 versus -0.22 ± 0.22, P < 0.05). Given that MCT markedly increased plasma noradrenaline, an index of SNA, by approximately 3.6-fold compared with CTL, calibrating SNA by plasma noradrenaline revealed that MCT shifted the neural arc to a higher SNA level and shifted the peripheral arc downwards. Monocrotaline also decreased the dynamic gain of the baroreflex total arc (-0.79 ± 0.16 versus -0.35 ± 0.17, P < 0.05), while the corner frequencies that reflect the speed of the baroreflex remained unchanged (0.06 ± 0.02 versus 0.08 ± 0.02 Hz, n.s.). In rats with MCT-induced PAH, the suppressed baroreflex peripheral arc overwhelms the augmented neural arc and, in turn, attenuates the gain of the total arc, which determines the pressure-stabilizing capacity of the baroreflex.

Disruption of Central Antioxidant Property of Nuclear Factor Erythroid 2-Related Factor 2 Worsens Circulatory Homeostasis with Baroreflex Dysfunction in Heart Failure.

Heart failure is defined as a disruption of circulatory homeostasis. We have demonstrated that baroreflex dysfunction strikingly disrupts circulatory homeostasis. Moreover, previous many reports have suggested that central excess oxidative stress causes sympathoexcitation in heart failure. However, the central mechanisms of baroreflex dysfunction with oxidative stress has not been fully clarified. Our hypothesis was that the impairment of central antioxidant property would worsen circulatory homeostasis with baroreflex dysfunction in heart failure. As the major antioxidant property in the brain, we focused on nuclear factor erythroid 2-related factor 2 (Nrf2; cytoprotective transcription factor). Hemodynamic and baroreflex function in conscious state were assessed by the radio-telemetry system. In the heart failure treated with intracerebroventricular (ICV) infusion of angiotensin II type 1 receptor blocker (ARB), sympathetic activation and brain oxidative stress were significantly lower, and baroreflex sensitivity and volume tolerance were significantly higher than in heart failure treated with vehicle. ICV infusion of Nrf2 activator decreased sympathetic activation and brain oxidative stress, and increased baroreflex sensitivity and volume tolerance to a greater extent than ARB. In conclusion, the disruption of central antioxidant property of Nrf2 worsened circulatory homeostasis with baroreflex dysfunction in heart failure.

Prediction of hemodynamics under left ventricular assist device.

Left ventricular assist device (LVAD) saves lives in patients with severe left ventricular (LV) failure. However, predicting how much LVAD boosts total cardiac output (CO) remains difficult. This study aimed to develop a framework to quantitatively predict the impact of LVAD on hemodynamics. We adopted the circulatory equilibrium framework and incorporated LVAD into the integrated CO curve to derive the circulatory equilibrium. In anesthetized dogs, we ligated left coronary arteries to create LV failure and inserted a centrifugal pump as LVAD. Using CO and right (PRA) and left atrial pressure (PLA) measured before LVAD support, we predetermined the stressed volume (V) and logarithmic slope of right heart CO curve (SR). Next, we initiated LVAD at maximum level and then decreased LVAD flow stepwise while monitoring hemodynamic changes. We predicted LVAD-induced CO and PRA for given PLA from the predetermined SR and V and compared with those measured experimentally. The predicted CO [r2 = 0.907, SE of estimate (SEE) = 5.59 ml·min-1·kg-1, P < 0.001] and PRA (r2 = 0.967, SEE = 0.307 mmHg, P < 0.001) matched well with measured values indicating the validity of the proposed framework. We further conducted simulation using the validated framework to analyze the impact of LVAD on PRA under various right ventricular (RV) functions. It indicated that PRA is relatively insensitive to changes in RV end-systolic elastance or pulmonary arterial resistance, but sensitive to changes in V. In conclusion, the circulatory equilibrium framework predicts quantitatively the hemodynamic impact of LVAD. This knowledge would contribute to safe management of patients with LV failure undergoing LVAD implantation. NEW & NOTEWORTHY: Hemodynamic response to left ventricular assist device (LVAD) has not been quantitatively investigated. This is the first report of quantitative prediction of the hemodynamics on LVAD using circulatory equilibrium framework. The validated framework allows us to simulate the impact of LVAD on right atrial pressure under various right ventricular functions.

Baroreflex failure increases the risk of pulmonary edema in conscious rats with normal left ventricular function.

In heart failure with preserved ejection fraction (HFpEF), the complex pathogenesis hinders development of effective therapies. Since HFpEF and arteriosclerosis share common risk factors, it is conceivable that stiffened arterial wall in HFpEF impairs baroreflex function. Previous investigations have indicated that the baroreflex regulates intravascular stressed volume and arterial resistance in addition to cardiac contractility and heart rate. We hypothesized that baroreflex dysfunction impairs regulation of left atrial pressure (LAP) and increases the risk of pulmonary edema in freely moving rats. In 15-wk Sprague-Dawley male rats, we conducted sinoaortic denervation (SAD, n = 6) or sham surgery (Sham, n = 9), and telemetrically monitored ambulatory arterial pressure (AP) and LAP. We compared the mean and SD (lability) of AP and LAP between SAD and Sham under normal-salt diet (NS) or high-salt diet (HS). SAD did not increase mean AP but significantly increased AP lability under both NS (P = 0.001) and HS (P = 0.001). SAD did not change mean LAP but significantly increased LAP lability under both NS (SAD: 2.57 ± 0.43 vs. Sham: 1.73 ± 0.30 mmHg, P = 0.01) and HS (4.13 ± 1.18 vs. 2.45 ± 0.33 mmHg, P = 0.02). SAD markedly increased the frequency of high LAP, and SAD with HS prolonged the duration of LAP > 18 mmHg by nearly 20-fold compared with Sham (SAD + HS: 2,831 ± 2,366 vs. Sham + HS: 148 ± 248 s, P = 0.01). We conclude that baroreflex failure impairs volume tolerance and together with salt loading increases the risk of pulmonary edema even in the absence of left ventricular dysfunction. Baroreflex failure may contribute in part to the pathogenesis of HFpEF.

Optimal Titration Is Important to Maximize the Beneficial Effects of Vagal Nerve Stimulation in Chronic Heart Failure.

BACKGROUND: Although vagal nerve stimulation (VNS) benefits patients with chronic heart failure (CHF), the optimal dose of VNS remains unknown. In clinical trials, adverse symptoms limited up-titration. In this study, we evaluated the impact of various voltages of VNS which were titrated below symptom threshold on cardiac function and CHF parameters in rat myocardial infarction (MI) models. METHODS AND RESULTS: We randomly allocated MI rats to vagal (VNS; n = 41) and sham (Sham; n = 16) stimulation groups. We stimulated the right vagal nerve with 20 Hz at 3 different voltages for 4 weeks. We defined Max as the highest voltage that did not evoke any symptom, Half as one-half of Max, and Quarter as one-fourth of Max. All 3 VNS groups significantly reduced biventricular weight compared with Sham (P < .05). In contrast, only Half decreased left ventricular (LV) end-diastolic pressure (Half: 17.5 ± 2.0 mm Hg; Sham: 24.2 ± 1.2 mm Hg; P < .05) and increased LV ejection fraction (Half: 37.9 ± 3.1%; Sham: 28.4 ± 2.3%,-P < .05) and LV maximum +dP/dt (Half: 5918.6 ± 2.0 mm/Hg/s; Sham: 5001.2 ± 563.2 mm Hg/s; P < .05). The number of large vagal nerve fibers was reduced with Max (Max: 163.1 ± 43.0 counts/bundle; Sham: 360.0 ±61.6 counts/bundle; P < .05), indicating significant neural damage by VNS. CONCLUSION: The optimal titration of VNS would maximize benefits for CHF and minimize adverse effects.

Heart Failure as a Disruption of Dynamic Circulatory Homeostasis Mediated by the Brain.

Circulatory homeostasis is associated with interactions between multiple organs, and the disruption of dynamic circulatory homeostasis could be considered as heart failure. The brain is the central unit integrating neural and neurohormonal information from peripheral organs and controlling peripheral organs using the autonomic nervous system. Heart failure is worsened by abnormal sympathoexcitation associated with baroreflex failure and/or chemoreflex activation, and by vagal withdrawal, and autonomic modulation therapies have benefits for heart failure. Recently, we showed that baroreflex failure induces striking volume intolerance independent of left ventricular dysfunction. Many studies have indicated that an overactive renin-angiotensin system, excess oxidative stress and excess inflammation, and/or decreased nitric oxide in the brain cause sympathoexcitation in heart failure. We have demonstrated that angiotensin II type 1 receptor (AT1R)-induced oxidative stress in the rostral ventrolateral medulla (RVLM), which is known as a vasomotor center, causes prominent sympathoexcitation in heart failure model rats. Interestingly, systemic infusion of angiotensin II directly affects brain AT1R with sympathoexcitation and left ventricular diastolic dysfunction. Moreover, we have demonstrated that targeted deletion of AT1R in astrocytes strikingly improved survival with prevention of left ventricular remodeling and sympathoinhibition in myocardial infarction-induced heart failure. From these results, we believe it is possible that AT1R in astrocytes, not in neurons, have a key role in the pathophysiology of heart failure. We would like to propose a novel concept that the brain works as a central processing unit integrating neural and hormonal input, and that the disruption of dynamic circulatory homeostasis mediated by the brain causes heart failure.