Heart Rate Increment Research Articles

Efeitos da reposição hidroeletrolítica sobre parâmetros cardiorrespiratórios em exercício e recuperação

INTRODUÇÃO: a necessidade de reposição ao máximo das perdas hídricas tornou-se estabelecida e difundida nos consensos internacionais. Entretanto, permanece pouco compreendida a influência da reposição quando administrada, igualmente, durante e após o exercício sobre parâmetros cardiorrespiratórios. OBJETIVO: analisar os efeitos da reposição hidroeletrolítica na frequência cardíaca (FC), pressão arterial sistólica (PAS), pressão arterial diastólica (PAD), saturação parcial de oxigênio (SpO2) e frequência respiratória (f) de jovens durante e após um exercício de longa duração. MÉTODOS: 31 jovens (21,55 ± 1,89 anos) realizaram três visitas ao laboratório (intervalo de 48 horas entre elas), sendo na primeira aplicado um teste incremental, para determinação da carga utilizada nas visitas seguintes, e nas duas últimas, denominadas protocolo controle (PC) e protocolo experimental (PE), os sujeitos foram submetidos a 10 min de repouso supino, 90 min de exercício em esteira ergométrica (60% do VO2pico) e 60 min de repouso supino. No PC não houve hidratação e no PE houve ingestão de solução isotônica. Os parâmetros FC, PAS, PAD, SpO2 e f foram mensurados no final do repouso; nos minutos 30, 60 e 90 do exercício, com exceção da f; e nos minutos 1, 3, 5, 7, 10, 20, 30, 40, 50 e 60 pós-exercício. Foi aplicado o teste t de Student ou teste de Mann-Whitney e ANOVA para medidas repetidas ou teste de Friedman seguidos de testes post hoc, com p < 0,05. RESULTADOS: a solução hidroeletrolítica proporcionou manutenção da PAS e da PAD, e menor incremento da FC durante o exercício; e promoveu retorno mais rápido da FC e conservou PAD, SpO2, PAS (a partir do 5º min) e f (a partir do 30º min) no período de recuperação. CONCLUSÃO: o protocolo de hidratação influenciou parâmetros cardiorrespiratórios de jovens durante e após a realização de atividade física submáxima de intensidade constante e longa duração.

Long-term follow-up of patients with postural tachycardia syndrome

Postural tachycardia syndrome (POTS) refers to the presence of orthostatic intolerance symptoms with a heart rate increment ≥ 30 bpm, usually up to ≥ 120 bpm. Pathophysiology and POTS's clinical presentation are heterogeneous and its prognosis is uncertain. We reviewed the major clinical characteristics of POTS patients and assessed their long-term follow-up. Our series results, one with the longest follow-up, illustrate POTS as a clinical entity with variable, but usually benign outcome, in which most patients can reassume their daily activities without great limitations, after proper diagnosis and treatment are made.

Heart rate increment in the diagnosis of obstructive sleep apnoea in an older population

To evaluate the ability of the heart rate power spectral density of the very low frequency component expressed as a percentage of the total power spectral band (%VLFI) to diagnose obstructive sleep apnoea (OSA) in the elderly. Eight hundred and thirty-two subjects aged 68.5±0.8 years were selected from the participants of a 7-year cross-sectional study on the association between OSA and vascular morbidity-mortality. All subjects underwent electrocardiogram Holter monitoring and an at-home polysomnogram to measure the apnoea/hypopnoea index (AHI). OSA was assessed as an AHI>15. The very low, the low frequency powers, and the %VLFI increased in subjects with OSA and were correlated with the autonomic arousal index and AHI (p<0.0001). A %VLFI of 2.4% and 4% demonstrated a sensitivity of 62% and 69% and a specificity of 45% and 44% to predict OSA in the population. The %VLFI did not provide a high level of diagnostic sensitivity and specificity at different degrees of OSA severity in an elderly healthy population. The ability for prediction was lower in mild cases and in women. These findings suggest that the ageing-related changes in the autonomic nervous system reduce the applicability of HRV to diagnose OSA in older populations.

Postural Tachycardia in Children and Adolescents: What is Abnormal?

To evaluate whether the use of adult heart rate (HR) criteria is appropriate for diagnosing orthostatic intolerance (OI) and postural tachycardia syndrome (POTS) in children and adolescents, and to establish normative data and diagnostic criteria for pediatric OI and POTS. A total of 106 normal controls aged 8-19 years (mean age, 14.5±3.3 years) underwent standardized autonomic testing, including 5 minutes of 70-degree head-up tilt. The orthostatic HR increment and absolute orthostatic HR were assessed and retrospectively compared with values in 654 pediatric patients of similar age (mean age, 15.5±2.3 years) who were referred to our Clinical Autonomic Laboratory with symptoms of OI. The HR increment was mildly higher in patients referred for OI/POTS, but there was considerable overlap between the patient and control groups. Some 42% of the normal controls had an HR increment of ≥30 beats per minute. The 95th percentile for the orthostatic HR increment in the normal controls was 42.9 beats per minute. There was a greater and more consistent difference in absolute orthostatic HR between the 2 groups, although there was still considerable overlap. The diagnostic criteria for OI and POTS in adults are unsuitable for children and adolescents. Based on our normative data, we propose new criteria for the diagnosis of OI and POTS in children and adolescents.

Functional Disability in Adolescents With Orthostatic Intolerance and Chronic Pain

A retrospective review identified 99 adolescents (79% female) referred to a tertiary care center to evaluate the relationship between symptoms of orthostatic intolerance and chronic pain. Regression analysis indicated that functional disability was strongly associated with pain intensity (P < .001) and depression (P = .024). The association between functional disability and number of symptoms of orthostatic intolerance trended toward significance (P = .057). Meeting a threshold heart rate increment of 30 beats per minute on head-up tilt was not associated with functional disability (P = .188). Separate regression analysis of female patients showed similar results to the full sample but with a stronger relationship between depression and functional disability and a weaker relationship between heart increment and functional disability. In this sample of adolescents with symptoms of orthostatic intolerance and chronic pain, pain intensity and depression were associated with functional status, but postural tachycardia was not. Further research is needed to clarify potential gender differences.

Driving electromechanically assisted Gait Trainer for people with stroke

Electromechanically assisted gait training is a promising task-oriented approach for gait restoration, especially for people with subacute stroke. However, few guidelines are available for selecting the parameter values of the electromechanical Gait Trainer (GT) (Reha-Stim; Berlin, Germany) and none is tailored to a patient's motor capacity. We assessed 342 GT sessions performed by 20 people with stroke who were stratified by Functional Ambulatory Category. In the first GT session of all patients, the body-weight support (BWS) required was higher than that reported in the literature. In further sessions, we noted a slow reduction of BWS and a fast increment of walking speed for the most-affected patients. Inverse trends were observed for the less-affected patients. In all the patients, the heart rate increment was about 20 beats per minute, even for sessions in which the number of strides performed was up to 500. In addition, the effective BWS measured during GT sessions was different from that initially selected by the physiotherapist. This difference depended mainly on the position of the GT platforms during selection. Finally, harness acceleration in the anteroposterior direction proved to be higher in patients with stroke than in nondisabled subjects. Our findings are an initial step toward scientifically selecting parameters in electromechanically assisted gait training.

Commentary on Supramaximal Verification of Peak Oxygen Uptake in Adolescents With Cystic Fibrosis

“How can I apply this information in adolescents with cystic fibrosis in my clinical practice?” Aerobic capacity and exercise testing are important tools within pediatric physical therapy practice, but often not a content area of comfort for the practicing pediatric physical therapist. Whereas cystic fibrosis (CF), a common pediatric disorder, requires a multidisciplinary approach, exercise testing and training, which has a critical role in the management of adolescents with CF, has received little attention. Studies have shown that higher peak VO2 and the time-dependent decline in peak VO2 assist in predicting survival in CF.1,2 Additionally, exercise training has been shown to improve aerobic fitness and is an important adjunct for mucociliary clearance.3-5 Physical therapists must continue to develop their expertise in the area of exercise testing and training, and this article describes a relatively simple means of determining exercise capacity in adolescents with CF. The accurate determination of O2 peak is critical in exercise testing and exercise prescription, yet the inconsistency between heart rate and VO2 raises some concerns that are addressed by this study. This study clarifies that O2 peak measured by traditional exercise testing does appear to reflect the true O2 peak. “What should I be mindful about in applying this information?” Pediatric therapists must continue to develop competence and expertise in the area of aerobic capacity and exercise testing. Clearly the authors are experienced with the technical aspects of exercise testing and metabolic analysis. This study specifically focused on stable adolescents with mild to moderate involvement. The clinician must be cautious to not generalize the findings to patients in other age groups or with different disease severities, including those with exercise induced hypoxemia, dysrhythmias, or patients being treated for a CF exacerbation. Whereas it is tempting to use the Steep Ramp test (SRT) as a measure of exercise capacity, additional validation of the SRT must be completed as noted by the authors. Until then, standard cardiopulmonary exercise testing (CPET) based on heart rate and work load increments should remain the standard of care.

Use of high-frequency peak in spectral analysis of heart rate increment to improve screening of obstructive sleep apnoea

Several studies have correlated the ratio of the very low frequency power spectral density of heart rate increment (%VLFI) with obstructive sleep apnoea syndrome (OSAS). However, patients with impaired heart rate variability may exhibit large variations of heart rate increment (HRI) spectral pattern and alter the screening accuracy of the method. To overcome this limitation, the present study uses the high-frequency increment (HFI) peak in the HRI spectrum, which corresponds to the respiratory influence on RR variations over the frequency range 0.2 to 0.4 Hz. We evaluated 288 consecutive patients referred for snoring, observed nocturnal breathing cessation and/or daytime sleepiness. Patients were classified as OSAS if their apnoea plus hypopnoea index (AHI) during polysomnography exceeded 15 events per hour. Synchronized electrocardiogram Holter monitoring allowed HRI analysis. Using a %VLFI threshold >2.4% for identifying the presence of OSAS, sensitivity for OSAS was 74.9%, specificity 51%, positive predictive value 54.9% and negative predictive value 71.7% (33 false negative subjects). Using threshold for %VLFI >2.4% and HFI peak position >0.4 Hz, negative predictive value increased to 78.2% while maintaining specificity at 50.6%. Among 11 subjects with %VLFI <2.4% and HFI peak >0.4 Hz, nine demonstrated moderate to severe OSAS (AHI >30). HFI represents a minimal physiological criterion for applying %VLFI by ensuring that heart rate variations are band frequency limited.

Developmental changes in the geometry, function and responsiveness of the mouse heart to β‐adrenergic stimulation as determined by high‐resolution echocardiography

1. The mouse is the preferred species for gene targeting as a tool for research into the heart and heart development. The developmental features of the geometry and function of the heart in young mice are not well defined and cardiac functional responses following stimulation of beta-adrenoceptors have not been investigated. 2. Using the VisualSonic (Toronto, ON, Canada) high-resolution ultrasound system, we investigated male C57BL/6 mice at 0.5-18 weeks of age. Echocardiography was performed at baseline and repeated after administration of the beta-adrenoceptor agonist isoproterenol (4 microg/kg). 3. The geometry of the left ventricle became mature 2 weeks after birth. A significant decline in left ventricular contractile function occurred at 2-3 weeks of age. 4. Inotropic and chronotropic responses to isoproterenol were significantly weaker in mice at a weaning age < 2 weeks compared with adult mice (heart rate increment 3 +/- 3% vs 32 +/- 4%, respectively; fractional shortening increment 19 +/- 5% vs 78 +/- 8%, respectively; P < 0.001). 5. In conclusion, significant changes occur in mice from birth until weaning with respect to the topography, function and beta-adrenoceptor responsiveness of the heart. The results of the present study provide a reference point for future studies in genotyping cardiac function during the postnatal phase in genetically engineered mice.

Delayed vasoconstrictor response to venous pooling in the calf is associated with high orthostatic tolerance to LBNP

Central blood volume loss to venous pooling in the lower extremities and vasoconstrictor response are commonly viewed as key factors to distinguish between individuals with high and low tolerance to orthostatic stress. In this study, we analyzed calf vasoconstriction as a function of venous pooling during simulated orthostatic stress. We hypothesized that high orthostatic tolerance (OT) would be associated with greater vasoconstrictor responses to venous pooling compared with low OT. Nineteen participants underwent continuous stepped lower body negative pressure at -10, -20, -30, -40, -50, and -60 mmHg each for 5 min or until exhibiting signs of presyncope. Ten participants completed the lower body negative pressure procedure without presyncope and were categorized with high OT; the remaining nine were categorized as having low OT. Near-infrared spectroscopy measurements of vasoconstriction (Hachiya T, Blaber A, Saito M. Acta Physiologica 193: 117-127, 2008) in calf muscles, along with heart rate (HR) responses for each participant, were evaluated in relation to calf blood volume, estimated by plethysmography. The slopes of this relationship between vasoconstriction and blood volume were not different between the high- and low-tolerance groups. However, the onset of vasoconstriction in the high-tolerance group was delayed. Greater HR increments in the low-tolerance group were also observed as a function of lower limb blood pooling. The delayed vasoconstriction and slower HR increments in the high-tolerance group to similar venous pooling in the low group may suggest a greater vascular reserve and possible delayed reduction in venous return.

Electrocardiographic changes after dipyridamole infusion in patients undergoing myocardial perfusion imaging

Although the diagnostic and prognostic importance of perfusion defects has been clearly established, the meaning of the development and characteristics of electrocardiographic (ECG) changes during dipyridamole infusion is less well defined. This study tries to evaluate the prevalence and significance of ECG changes after dipyridamole infusion and their relation to ischemia in myocardial perfusion single-photon emission computed tomography (SPECT). Two hundred patients underwent 2-day dipyridamole stress/rest Tc-99m-sestamibi myocardial perfusion SPECT. Basal and post dipyridamole ECGs were analyzed. Myocardial perfusion images were interpreted visually and semiquantitatively. New ECG changes were noted in 20.2% of cases and consisted of 1.1% T-wave flattening, 1.1% T-wave inversion and 14.8% ST depression and 4.2% psuedonormalization. Abnormal ECG changes were noted after dipyridamole infusion in approximately 27.7% of patients with and 14.3% of patients without reversible defect in myocardial perfusion SPECT. A new ST depression was noted in lateral leads in 72.2% of new ST changes. The mean post-dipyridamole heart rate increment in patients with reversible or partially reversible defects was significantly lesser than in patients with normal myocardial perfusion SPECT. In addition, the corrected QT interval (QTc) increment in patients with reversible defects was significantly more than in patients with fixed defects; however, there was no difference when compared with patients with no defects. Using linear regression model, the severity of ST depression and QTc increment were significant predictors of summed difference score. Sensitivity, specificity, and negative and positive predictive values of ST-segment depression for the diagnosis of ischemia were 20.2, 89.5, 60.7, and 58.4%, respectively. The most common ECG change seen after dipyridamole infusion is ST-segment depression. The new ST-segment depression after dipyridamole infusion is highly specific for ischemia. Reversible defects are associated with a lesser increment in heart rate, whereas QTc increment and severity of ST segment depression were significant predictors of summed difference score.

Global Disturbances in Autonomic Function Yield Cardiovascular Instability and Hypertension in the Chromogranin A Null Mouse

We reported previously that chromogranin A (Chga) knockout (KO) mice are hypertensive and hyperadrenergic. Here we sought to determine the basis of such alterations by probing physiological, biochemical, and pharmacological responses to perturbations of the autonomic nervous system. In the conscious state, KO mice had substantially elevated basal high blood pressure (BP) and heart rate (HR); immobilization stress caused increments in systolic BP and HR in both wild-type (WT) and KO mice, with higher maxima but blunted increments in the KO state. Catestatin (CST; CHGA(352-372)) selectively diminished stress-induced increments in BP and HR in KO mice, implicating CST as an antihypertensive peptide, even in stressful conditions. Heightened plasma catecholamines in KO mice returned to WT level after CST. Stress caused further increments in catecholamines in WT mice but no change in KO mice. KO mice displayed diminished baroreflex sensitivity in response to either phenylephrine or sodium nitroprusside, accounting for exaggerated pressor and depressor responses to these compounds; baroreceptor function was normalized by CST. To probe the relative roles of endogenous/basal sympathetic vs. parasympathetic tone in control of BP and HR, we used the muscarinic-cholinergic antagonist atropine or the beta-adrenergic antagonist propranolol; HR and BP responses to each antagonist were exaggerated in KO animals. We conclude that ablation of Chga expression results in global disturbances in autonomic function, both sympathetic and parasympathetic, that can be abrogated (or rescued), at least in part, by replacement of CST. The results point to mechanisms whereby CHGA and its CST fragment act to control cardiovascular homeostasis.

Heart rate increment analysis is not effective for sleep-disordered breathing screening in patients with chronic heart failure

Frequency domain analysis of heart rate variation has been suggested as an effective screening tool for sleep-disordered breathing (SDB) in the general population. The aim of this study was to assess this method in patients with chronic congestive heart failure (CHF). We included prospectively 84 patients with stable CHF, left ventricular ejection fraction (LVEF) <45% and sinus rhythm. The patients underwent polygraphy to measure the apnoea/hypopnoea index (AHI) and simultaneous Holter electrocardiogram monitoring to measure the power spectral density of the very low frequency component of the heart rate increment, expressed as the percentage of total power spectral density [% very low frequency increment (%VLFI)]. %VLFI could be determined in 54 patients (mean age, 52.8 +/- 12.3 years; LVEF, 33.5 +/- 9.8%). SDB defined as AHI > or =15 h(-1) was diagnosed in 57.4% of patients. Percent VLFI was not correlated with AHI (r = 0.12). Receiver-operating characteristic curves constructed using various AHI cut-offs (5-30 h(-1)) failed to identify a %VLFI cut-off associated with SDB. The 2.4% VLFI cut-off recommended for the general population of patients with suspected SDB had low specificity (35%) and low positive and negative predictive values (35% and 54%, respectively). Heart rate increment analysis has several limitations in CHF patients and cannot be recommended as an SDB screening tool in the CHF population.

Mid-term results, and therapeutic management, for patients suffering hypertension after surgical repair of aortic coarctation

We designed our study to investigate the efficacy of a new therapeutic approach to late onset hypertension in patients after surgical repair of aortic coarctation. Several studies have shown a higher incidence of hypertension during daily activities, and during exercise, in patients after surgical correction of coarctation. To the best of our knowledge, however, no data exists concerning haemodynamics, the response of arterial pressures, and the effects of medications for lowering blood pressure during exercise or during daily activities.We studied 128 patients, aged 15.6 +/- 4.3 years, to determine the response of blood pressure as we administered treatment in the attempt to achieve a normotensive state. We excluded patient with associated cardiac abnormalities, apart from those with bicuspid aortic valves. We evaluated blood pressure at rest in both the right arm and leg to establish presence of any gradient, as well as the blood pressure in the arm during exercise testing, and by 24-hour ambulatory monitoring.Atenolol was prescribed for those with elevated values of blood pressure but with a normal increment of heart rate during exercise. We prescribed Candesartan for those with elevated levels of blood pressure but with reduced increments of heart rate, specifically maximal heart rates of less than 85% of their predicted value. Both drugs were used when one alone was not effective. We found that, in young patients, candesartan provided better control of blood pressure with no side-effects, especially as demonstrated using 24-hour ambulatory monitoring, while atenolol was less effective, with more side-effects. Our experience suggests that both drugs should be used in patients who are non-responsive to monotherapy.

Association of heart rate profile during exercise with the severity of coronary artery disease

Coronary artery disease is the leading cause of morbidity and mortality around the world. Autonomic nervous system abnormalities are associated with coronary artery disease and its complications. Exercise stress tests are routinely used for the detection of the presence of coronary artery disease. In this study, we observed the association between heart rate profile during exercise and the severity of coronary artery disease. One hundred and sixty patients with abnormal exercise treadmill test (> or =1 mm horizontal or downsloping ST-segment depression; 119 men, 41 women; mean age = 57 +/- 9 years) were included in the study. Use of any drug affecting heart rate was not permitted. Resting heart rate before exercise, maximum heart rate during exercise, and resting heart rate after exercise (5 min later) were measured and two parameters were calculated: heart rate increment (maximum heart rate - resting heart rate before exercise) and heart rate decrement (maximum heart rate - resting heart rate after exercise). All patients underwent selective coronary angiography and subclassified into two groups according to stenotic lesion severity. Group 1 had at least 50% of stenotic lesion and group 2 had less than 50%. Patients in the first group had increased resting heart rate, decreased maximum heart rate, decreased heart rate increment, and decreased heart rate decrement compared with second group. All patients were classified into tertiles of resting heart rate, heart rate increment, and heart rate decrement level to evaluate whether these parameters were associated with severity of coronary artery stenosis in the study. The multiple-adjusted odds ratio of the risk of severe coronary atherosclerosis was 21.888 (95% confidence interval 6.983-68.606) for the highest tertile of resting heart rate level compared with the lowest tertile. In addition, the multiple-adjusted odds ratio of the risk of severe coronary atherosclerosis was 20.987 (95% confidence interval 6.635-66.387) for the lowest tertile of heart rate increment level compared with the highest tertile and 2.360 (95% confidence interval 1.004-5.544) for the lowest tertile of heart rate decrement level compared with the highest tertile. Altered autonomic nervous system regulation affects heart rate profile, increased resting heart rate, decreased heart rate increment, and decreased heart rate decrement, during exercise and this effect is strongly and independently associated with the severity of coronary artery disease.

H013 Heart rate variability analysis is not effective for sleep-apnoea-syndrome screening in patients with chronic heart failure

Frequency-domain analysis of heart rate variation has been suggested as an effective screening tool for sleep apnoea syndrome (SAS) in the general population. The aim of this study was to determine whether this method could be effective in patients with chronic congestive heart failure (CHF). 84 patients with stable CHF, left ventricular ejection fraction (LVEF) <45 %, and sinus rhythm were included prospectively. Patients underwent simultaneous polygraphy to measure apnoea/hypopnoea index (AHI) and ECG Holter monitoring to measure the power spectral density of the very low frequency component of the heart rate increment, expressed as the percentage of total power spectral density (% VLFI). VLFI could be determined in 54 patients (mean age 52.8+/-12.3 years and LVEF 33.5+/-9.8 %). SAS defined as AHI >=15•h-1 was diagnosed in 57.4 % of patients. % VLFI was not correlated with AHI (R = 0.12). Receiver operating characteristic curves constructed using various AHI cut-offs (5 to 30.h-1) failed to identify a % VLFI cut-off associated with SAS. The 2.4 % VLFI cut-off recommended for the general population of patients with suspected SAS had low values for specificity (35 %), positive and negative predictive value (35 % and 54 % respectively). Heart rate increment analysis demonstrated several limitations in CHF. At this time, HRV methodology could not be proposed as the first step of SAS screening in CHF population.

Postural Tachycardia Syndrome (POTS)

POTS is defined as the development of orthostatic symptoms associated with a heart rate (HR) increment >or=30, usually to >or=120 bpm without orthostatic hypotension. Symptoms of orthostatic intolerance are those due to brain hypoperfusion and those due to sympathetic overaction. We provide a review of POTS based primarily on work from the Mayo Clinic. Females predominate over males by 5:1. Mean age of onset in adults is about 30 years and most patients are between the ages of 20-40 years. Pathophysiologic mechanisms (not mutually exclusive) include peripheral denervation, hypovolemia, venous pooling, beta-receptor supersensitivity, psychologic mechanisms, and presumed impairment of brain stem regulation. Prolonged deconditioning may also interact with these mechanisms to exacerbate symptoms. The evaluation of POTS requires a focused history and examination, followed by tests that should include HUT, some estimation of volume status and preferably some evaluation of peripheral denervation and hyperadrenergic state. All patients with POTS require a high salt diet, copious fluids, and postural training. Many require beta-receptor antagonists in small doses and low-dose vasoconstrictors. Somatic hypervigilance and psychologic factors are involved in a significant proportion of patients. POTS is heterogeneous in presentation and mechanisms. Major mechanisms are denervation, hypovolemia, deconditioning, and hyperadrenergic state. Most patients can benefit from a pathophysiologically based regimen of management.

Sympathetic Excitation during Exercise as a Cause of Attenuated Heart Rate Recovery in Patients with Myocardial Infarction

Heart rate recovery (HRR) after exercise is known as a predictor of cardiac death in patients with heart disease. The mechanism is not fully understood, although a parasympathetic mechanism has been reported. To elucidate the factors that influence HRR, we evaluated the relationship of HRR with exercise performance and plasma norepinephrine (NE), lactic acid and B-type natriuretic peptide (BNP) responses to exercise testing. The study population consisted of 52 male patients (age 58 +/- 9.6 years) who had experienced myocardial infarction without residual ischemia, uncompensated heart failure or atrial fibrillation. All subjects underwent a symptom-limited cardiopulmonary exercise test without a cool-down period and echocardiography. NE, lactic acid and BNP were measured at rest and at peak exercise. HRR did not correlate with the left ventricular ejection fraction, peak VO(2), lactic acid and BNP. HRR significantly correlated with the increment in heart rate (HR) from rest to peak exercise (DeltaHR) (r=0.30, p<0.05). When we divided DeltaHR into two phases at the anaerobic threshold (AT), HRR significantly correlated with DeltaHR (peak-AT) (r=0.409, p<0.01), but not with DeltaHR (AT-rest). There was a significant negative correlation between HRR and NE both at rest and at peak exercise (r=-0.286, p<0.05, r=-0.310, p<0.05). HRR was also correlated significantly with DeltaHR/logDeltaNE as an index of sensitivity to NE (r=0.421, p<0.01). Based on multiple regression analysis, DeltaHR and logDeltaNE predicted HRR (R(2)=0.467, p=0.0027). Present findings suggest that enhanced sympathetic excitation at maximum exercise suppresses parasympathetic reactivation and results in attenuation of HRR.

Assured Evacuation Guide with Mobile Terminal Communication and RFID System under Lack of Power Supply

In this paper, we propose a method which aims to let people inside a building evacuate when a disaster occurs. Especially, it is very difficult for them to evacuate safely under the situation of blackout which makes servers down. In the proposed method, passive RFID tags are put on walls of the building and each user has a mobile terminal that is battery-powered and equipped with an RFID reader. It identifies evacuation routes by passive RFID tags the user touched. The method identifies safe routes using the movement of people who have evacuated safely. Mobile terminal communication and RFID tags realize to share information of the safe routes with many evacuees.An experiment is conducted to let people evacuate in two routes in an actual building, giving about half of them mobile terminals. We have measured the increment of blood pressure and heart rate of the evacuees before and after the evacuation. In both routes, the increasing rates of the evacuees with the terminal have been smaller than those of evacuees without the terminals. It proves that the proposed method brings assurance to evacuees.

Long-term prognostic importance of resting heart rate in patients with left ventricular dysfunction in connection with either heart failure or myocardial infarction: The DIAMOND study

Background Elevated resting heart rate is associated with increased mortality in a variety of cardiac diseases, but comparisons between different clinical settings are lacking. We investigated the long-term prognostic importance of resting heart rate in patients hospitalized with left ventricular dysfunction in connection with either heart failure (HF) or myocardial infarction (MI). Methods In the Danish Investigations and Arrhythmia ON Dofetilide (DIAMOND) study; patients with left ventricular dysfunction were randomized to Dofetilide (class III antiarrhythmic drug) or placebo. One part of the study enrolled 1518 patients with HF and another 1510 patients with MI. Mortality analyses were performed using multivariable adjusted Cox proportional hazard models. Results During 10 years of follow-up, 1076 (72%) patients with MI and 1336 (89%) patients with HF died. In multivariable adjusted models, every increment in baseline heart rate of 10 bpm was associated with an increase in mortality in both MI-patients (hazard ratio, 1.14; 95%-confidence interval (CI): 1.09–1.19; P < .0001) and HF-patients (hazard ratio, 1.10; CI: 1.06–1.15; P < .0001). The importance of resting heart rate on short-term prognosis was stronger in the MI patients compared to the HF patients ( P < .0001 for interaction). There was no interaction between heart rate and β-blockade, and inclusion of β-blockade in the model did not change the results. Conclusions Resting heart rate was independently associated with increased risk of overall mortality. The prognostic importance of resting heart rate is stronger in patients with MI compared to patients with HF, especially in the short term.