Delta Heart Rate Research Articles

Cardiac Acceleration at the Onset of Exercise: A Potential Parameter for Monitoring Progress During Physical Training in Sports and Rehabilitation

There is a need for easy-to-use methods to assess training progress in sports and rehabilitation research. The present review investigated whether cardiac acceleration at the onset of physical exercise (HRonset) can be used as a monitoring variable. The digital databases of Scopus and PubMed were searched to retrieve studies investigating HRonset. In total 652 studies were retrieved. These articles were then classified as having emphasis on HRonset in a sports or rehabilitation setting, which resulted in 8 of 112 studies with a sports application and 6 of 68 studies with a rehabilitation application that met inclusion criteria. Two co-existing mechanisms underlie HRonset: feedforward (central command) and feedback (mechanoreflex, metaboreflex, baroreflex) control. A number of studies investigated HRonset during the first few seconds of exercise (HRonsetshort), in which central command and the mechanoreflex determine vagal withdrawal, the major mechanism by which heart rate (HR) increases. In subsequent sports and rehabilitation studies, interest focused on HRonset during dynamic exercise over a longer period of time (HRonsetlong). Central command, mechanoreflexes, baroreflexes, and possibly metaboreflexes contribute to HRonset during the first seconds and minutes of exercise, which in turn leads to further vagal withdrawal and an increase in sympathetic activity. HRonset has been described as the increase in HR compared with resting state (delta HR) or by exponential modeling, with measurement intervals ranging from 0-4s up to 2min. Delta HR was used to evaluate HRonsetshort over the first 4s of exercise, as well as for analyzing HRonsetlong. In exponential modeling, the HR response to dynamic exercise is biphasic, consisting of fast (parasympathetic, 0-10s) and slow (sympathetic, 1-4min) components. Although available studies differed largely in measurement protocols, cross-sectional and longitudinal training studies showed that studies analyzing HRonset in relation to physical training primarily incorporated HRonsetlong. HRonsetlong slowed in athletes as well as in patients with a coronary disease, who have a relatively fast HRonsetlong. It is advised to include both HRonsetlong and HRonsetshort in further studies. The findings of this review suggest that HRonset is a potential tool for monitoring and titrating training in sports as well as in rehabilitation settings, particularly in patients with ventricular fibrillation. Monitoring HRonset in the early phase of training can help optimize the effectiveness of training and therapy. More research is needed to gain a better understanding of the mechanisms underlying HRonset in relation to their application in sports and rehabilitation settings.

Role of exercise testing in assessment of the cardiovascular system function in Zarda users

Background: Zarda is a widely used form of smokeless tobacco in India. Cigarette smoking has extensive effects on cardiovascular functions. Zarda is prepared by the user by mixing tobacco with lime in the palm and gives the user the choice to change the combination. This study aims to determine the effect of Zarda on the cardiovascular system adaptability to exercise. There are conflicting opinions about the degree of adaptability of the cardiovascular system in delivering the physiological needs in case of severe exercise. Role of the normal cardiovascular system in delivering oxygen to meet the demands of various degrees of exercise has been a topic of considerable debate. The effect of Zarda usage on this phenomenon is studied here. Materials and Methods: Cardiovascular functions were assessed after maximal exercise testing by recording parameters such as maximum heart rate (HR), delta HR, recovery HR and maximum oxygen pulse in two groups' viz., Zarda users and non-user controls. Results: On studying the differences in cardiovascular functions in users and controls, there was a significant difference in maximum HR. The other parameters such as delta HR and maximum oxygen pulse were on the higher side in controls while the recovery HR was significantly lower in the control group, which was consistently maintained after exercise testing. Based on these findings it is suggested that there is a higher adaptability of the cardiovascular system to the exercise stimulus in the form of better VO 2 max, faster recovery of the exercise HR and a lesser risk for cardiovascular mortality as suggested by the higher delta HR in non-Zarda users.

Assessment of cardiovascular system adaptability in Khaini users

Background: Khaini is a widely used form of smokeless tobacco in India. Cigarette smoking has extensive effects on cardiovascular functions. Khaini is tobacco with slaked lime. Aims: This study aimed to determine the effect of Khaini on cardiovascular system adaptability to exercise. Materials and Methods: Cardiovascular functions were assessed after maximal exercise testing by recording parameters like maximum heart rate, delta heart rate, recovery heart rate and maximum oxygen pulse in two groups' viz., Khaini users and non-users. Results: On studying the differences in cardiovascular functions in users and controls, there was significant difference in maximum heart rate. The other parameters like delta heart rate and maximum oxygen pulse were on the higher side in controls while the recovery heart rate was significantly lower in the control group which was consistently maintained after exercise testing. Conclusion: Based on these findings there is a higher adaptability of the cardiovascular system to the exercise stimulus in the form of better VO 2 max, faster recovery of the exercise heart rate, and a higher delta heart rate in non-Khaini users.

Role of exercise testing in assessment of cardiovascular system function in Zarda users

Background: Zarda is a widely used form of smokeless tobacco in India. Cigarette smoking has extensive effects on cardiovascular functions. Zarda is prepared by a user by mixing tobacco with lime in palm and gives the user the choice to change the combination. This study aims to determine the effect of Zarda on cardiovascular system adaptability to exercise. There are conflicting opinions about the degree of adaptability of the cardiovascular system in delivering the physiological needs in case of severe exercise. A role of the normal cardiovascular system in delivering oxygen to meet the demands of various degrees of exercise has been a topic of considerable debate. The effect of Zarda usage on this phenomenon is studied here. Materials and Methods: Cardiovascular functions were assessed after maximal exercise testing by recording parameters like maximum heart rate, delta heart rate, recovery heart rate and maximum oxygen pulse in two groups, namely Zarda users and non-user controls. Results: On studying the differences in cardiovascular functions in users and controls, there was a significant difference found in maximum heart rate. The other parameters like delta heart rate and maximum oxygen pulse were on the higher side in controls while the recovery heart rate was significantly lower in the control group which was consistently maintained after exercise testing. Based on these findings it is suggested that there is a higher adaptability of the cardiovascular system to the exercise stimulus in the form of better VO 2 max, faster recovery of the exercise heart rate, and a lesser risk for cardiovascular mortality as suggested by the higher delta heart rate in non-Zarda users.

Effect of Fruit Rich Diet on Cardiopulmonary Efficiency in Short Term Smokers

Background: Use of tobacco in cigarettes leads to an oxidant antioxidant imbalance. As a consequence of its addictive qualities, the consumption of cigarettes often becomes a lifelong habit with cumulative and deleterious effects on health. Previous reports have described long-term harmful effects of nicotine on various body parameters, including oxidative injury and a lack of antioxidants in the body. Fruits are known to be a rich source of dietary antioxidants. This study was conducted to know the effect of consumption of fruits in a group of short term smokers on cardio-pulmonary efficiency parameters. Materials and Methods: Treadmill exercise testing and pulmonary function tests were done before and after maximal exercise testing to assess cardiopulmonary efficiency in two groups' viz., healthy sedentary controls and healthy cigarette smokers on a fruit rich diet. Results: On studying the differences in cardiopulmonary efficiency in the two groups the resting heart rate (HR) was found to be statistically significantly higher in the study group and the delta HR (δHR) was found to be statistically significantly lower among cigarette smokers. There was no significant difference seen in parameters like maximal oxygen consumption max, maximum oxygen pulse, maximum voluntary ventilation, maximum minute ventilation as an acute effect of cigarette smoking. Conclusion: In this study, it appears that cigarette smokers are physically fit like controls, but after immediate smoking a lesser δHR suggests a higher risk for cardiovascular mortality. There seems to be no effect of including fruits in the diet of smokers. The predominant effect of smoking over dietary measures is obvious. Stopping smoking at this juncture can be helpful in reverting back the risk and parameters like resting HR, recovery HR and δHR can be used as prognostic assessment tools for any intervention therapy to stop cigarette smoking in asymptomatic individuals.

A study of the short-term cardiopulmonary effect of mawa chewing in rural India

Background: Tobacco is consumed in smoking and smokeless forms all over the world. Smokeless tobacco has been advocated as a substitute for cigarette smoking. On the contrary, the use of smokeless tobacco is fraught with health risk and needs to be discouraged. Previous reports have described long-term harmful effects of nicotine on various body parameters, little is known about the acute effect of smokeless tobacco, such as mawa, consumed very rampantly in rural India, on cardiopulmonary parameters. Use of smokeless tobacco indeed represents a health concern of growing magnitude among these groups. As a consequence of its addictive qualities, the consumption of smokeless tobacco often becomes a lifelong habit with cumulative and deleterious effects on health. Very few studies have been undertaken on the acute effect of use of mawa, a common form of tobacco used in India, on cardiopulmonary parameters of youngsters. Materials and Methods: Treadmill Exercise Testing and Pulmonary Function Tests were done before and after maximal exercise testing to assess cardiopulmonary efficiency in two groups, namely, healthy sedentary controls and healthy mawa chewers. Results: On studying the differences in cardiopulmonary efficiency in the two groups, the resting heart rate was found to be statistically significantly higher in the study group and the delta heart rate was found to be statistically significantly lower among mawa chewers. There was no significant difference seen in parameters such as VO 2max , maximum oxygen pulse, MVV, VE max as an acute effect of mawa. Conclusion: In this study, it appears that mawa chewers are physically fit similar to the controls, but immediately after smoking a lesser delta HR suggests a higher risk for cardiovascular mortality. Stopping mawa at this juncture can be helpful in reverting back the risk, and parameters such as resting HR, recovery HR, and delta HR can be used as prognostic assessment tools for any intervention therapy to stop mawa chewing in asymptomatic individuals.

Arm exercise as an alternative to pharmacologic stress testing: Arm exercise stress testing and outcome

Treadmill exercise variables are powerful predictors of all-cause mortality but are unobtainable in at least 50% of patients because of disabilities precluding lower extremity exercise. Arm exercise stress testing is a potentially cost-effective alternative, but no long-term outcome data are available. We performed arm ergometer stress tests on 446 veterans aged 64.0 (11.1) years (mean [SD]) between 1997 and 2002 and investigated whether arm exercise capacity in resting metabolic equivalents, heart rate recovery (in beats per minute), delta (peak resting) heart rate (in beats per minute), and other exercise variables predict long-term all-cause mortality, myocardial infarction (MI), or coronary revascularization. During follow-up of 12.0 (1.3) years, 255 patients died (57.2%), 70 had MI (15.7%), and 118 underwent coronary revascularization (26.4%). After adjustment for significant demographic and clinical variables, death was predicted by arm metabolic equivalents (hazard ratio/SD 0.59, 95% CI 0.46-0.75, P < .001), heart rate recovery (hazard ratio/SD 0.64, 95% CI 0.49-0.83, P < .001), and delta heart rate (hazard ratio/SD 0.75, 95% CI 0.63-0.91, P < .001). No exercise variables prognosticated MI, but coronary revascularization was predicted by stress-induced ST-segment deviations (hazard ratio 2.64, 95% CI 1.16-4.33, P < .001), limiting angina (hazard ratio 4.70, 95% CI 1.81-12.22, P < .001), and an abnormal perfusion imaging result (hazard ratio 2.0, 95% CI 1.14-3.51, P < .02). Arm exercise capacity, heart rate recovery, and delta heart rate predict 12-year all-cause mortality and arm exercise-induced ST changes, limiting angina, and an abnormal nuclear imaging result portend coronary revascularization in lower extremity disabled veterans.

Abstract 15: Loss of Tumor Suppressor Protein p53 is linked to High Blood Pressure

Emerging evidence suggests that chronic inflammation plays a critical role in the development of hypertension. The tumor suppressor protein p53 is a key regulator of inflammation pathways. We therefore hypothesized that loss of p53 activity increases blood pressure (BP) by unleashing inflammatory responses. To test this hypothesis 8-week old p53-null (p53 -/- ) and wild-type mice (N=6, each group) were implanted with telemetry transmitters into the carotid arteries. After a 2 week recovery period post-surgery, BP was recorded continuously for 72 hours. Autonomic functions were assessed using IP administration of Methylatropine (dose 1mg/kg), propranolol (6mg/kg), and ganglionic blocker chlorisondamine (5mg/kg). Daytime BP (MAP: 109.4±2.3 vs. 95.5±1.1mmHg) is significantly higher in p53 -/- mice compared to wild-type mice (P&lt; 0.05). Heart rate (HR) response to propranolol was significantly greater in p53 -/- mice (delta HR: 89.9±13.2bpm) compared to wild-type mice (delta HR: 45.9±7.8bpm, P&lt;0.05) indicating that p53 -/- mice have greater cardiac sympathetic tone. Furthermore, the BP response to chlorisondamine is greater in p53 -/- mice (delta BP: 43.3±2.6mmHg) compared to wild-type mice (delta BP: 20.7±2.0mmHg, P&lt;0.01), suggesting that p53 -/- mice harbor higher vasomotor sympathetic tone. To gain insight into the involvement of neural components in elevating BP in the null mice, transcriptome analysis was done on hypothalamic genes. Gene Ontological Biological Process (GO_BP) classification of differentially regulated genes revealed genes involved in immune response and inflammation. These includes chemokine ligand 17 (1.8 fold increase, P&lt;0.05), tumor necrosis factor receptor 1B (2.2 fold increase, P&lt;0.05), and nerve growth factor receptor (TNFR superfamily, member 16, Ngfr) (1.5 fold increase, P&lt;0.05). In summary, p53 deletion increases BP, HR, and cardiac and vasomotor sympathetic activity and is associated with increases in genes involved in immune response and inflammatory pathways in the hypothalamus of the brain. These data provide a hitherto unrecognized link between tumor suppression, inflammation and blood pressure.

Abstract 399: Whole-Body Deletion of PPAR? in Mice Increases Sympathetic Nerve Activity

PPARγ and sympathetic nerve activity (SNA) antagonistically regulate energy metabolism and cardiovascular function with the former promoting anabolism and vasorelaxation and the later favoring catabolism and vasoconstriction. However, the precise relationship between these two factors is not known. The present study examined the influence of PPARγ deletion on SNA. Systemic inactivation of PPARγ was generated constitutively by using Mox2-Cre mice (MoxCre/flox) or inducibly by using the tamoxifen system (EsrCre/flox/TM). Radiotelemetry demonstrates consistent increases in resting daytime heart rate (HR) in both strains of null mice; this was associated a more than 10-fold increase in urinary epinephrine and norepinephrine levels. Subsequently, more detailed analysis of SNA was performed in Esr/flox/TM mice. In response to a bolus ip injection of the gangalion blocker pentolinium at 7.5 mg/kg, the decreases in HR and MAP were greater in the null mice than in the flox controls (delta HR:-254.2 vs. 92.3 beat/min; delta MAP: -67.8 vs. 33.4 mmHg). The HR decrease in response to the beta-blocker metaprolol (12 mg/kg, ip) was greater in the null mice than in the flox controls so was the MAP decease in response to the alpha1-blocker prazosin (1 mg/kg, ip). Baroreflex sensitivity (BRS) was assessed by the measurement of the HR responses to bolus injections of sodium nitroprusside (NP-BRS) or phenylephrine (PE-BRS). EsrCre/flox/TM mice displayed normal PE-BRS but blunted NP-BRS. Echocardiography under anesthesia demonstrated that the ejection fraction (EF) was 11% lower after administration of metaprolol contrasting to a drop of only 1.5% for the flox controls, in parallel with a greater reduction of HR in the KO mice. In contrast, the increase in HR following administration of the beta1 agonist dobutamine (0.8 mg/kg, ip) was less in the KO mice than in the flox controls. Together, we conclude: 1) PPARγ deletion causes the activation of SNA, 2) the parasympathetic nervous system may be unaffected, 3) the blunted response to dobutamine suggest suppressed beta1 receptor activity possibly as a result of compensatory response to sympathoactivation.

Effect of heart rate reduction by ivabradine on collateral function in patients with chronic stable coronary artery disease

Background: In the absence of beta-blockers, a low heart rate is known to be related to improved coronary collateral function. So far, the effect of heart rate reduction by ivabradine in patients with chronic stable coronary artery disease (CAD) on coronary collateral function has not been investigated. Methods and results: This was a prospective study in 43 patients with chronic stable CAD who were randomly allocated to placebo or ivabradine given for the duration of 6 months. The primary study endpoint was collateral flow index (CFI) as obtained during a 1-minute coronary artery balloon occlusion at study inclusion (baseline) and at the 6-month follow-up examination. CFI was calculated as the ratio between simultaneously recorded mean coronary occlusive pressure divided by mean aortic pressure both subtracted by mean central venous pressure. During follow-up, heart rate changed by +0.2±7.8 beats/min in the placebo group and by -7.7±11.7 beats/min in the ivabradine group (p=0.0143; left panel). In the placebo group, CFI decreased from 0.140±0.095 at baseline to 0.109±0.068 at follow-up (p=0.12); it increased from 0.118±0.089 at baseline to 0.152±0.092 at follow-up in the ivabradine group (p=0.08). The difference in CFI between the 6-month follow-up and baseline examination amounted to -0.031±0.090 in the placebo group and to +0.038±0.095 in the ivabradine group (p=0.0179; right panel). Delta heart rate and delta CFI Conclusions: Heart rate reduction by ivabradine appears to have a positive effect on coronary collateral function in patients with chronic stable CAD.

Abstract 36: Arm Exercise Stress Test Predictors of Outcome Over 12 Years

For patients with lower extremity disabilities precluding treadmill exercise, pharmacologic nuclear imaging stress tests necessitate administration of ionizing radiation, require much greater equipment and personnel resources, and are several times more expensive and time-consuming than exercise electrocardiography (ECG). In addition, they do not provide powerful prognostic and clinically relevant information on exercise capacity or on symptomatic, hemodynamic and ECG responses to exercise. In lower extremity disabled individuals, we have reported that arm exercise (AXT) capacity in METs and delta (peak exercise - rest) heart rate ([[Unable to Display Character: &amp;#8710;]]HR) prognosticate survival and an abnormal exercise ECG predicts all-cause mortality. However, these data included follow-up of only 5.3 years and did not provide information on heart rate recovery (HRR), an important prognosticator of survival for leg exercise. Furthermore, the predictive role of HRR has not been well-characterized in high-risk populations or for arm exercise. Thus, the purpose of the current investigation was to determine whether arm exercise HRR, AXT METs, [[Unable to Display Character: &amp;#8710;]]HR and an abnormal ECG response independently prognosticate all-cause mortality, subsequent myocardial infarction (MI) or coronary revascularization (CVASC) over a longer follow-up period in patients who cannot perform leg exercise. A total of 446 veterans, aged 64 +/- 11 yrs. underwent AXT between 1997 and 2002 and were followed to an endpoint of death or at least 10 years. Average annual mortality, MI, CVASC and combined event rates were 7.0%, 1.9%, 2.8% and 12.1%, respectively. Over an average follow-up of 12.0 +/- 1.3 years for survivors, HRR at both 1 and 2 minutes post-exercise was highly and inversely related to mortality (p &lt; 0.0001) by univariate analysis and remained highly significant after adjustment for demographic and clinical clinical variables (p&lt; 0.0001 for HRR 1 minute post-exercise; hazard ratio (HR)/bpm = 0.95 for death; confidence interval (CI ) = 0.94-0.97). AXT METs was independently related to survival by univariate and multivariate analyses (both p &lt; 0.0001; HR/MET = 0.55 for death; CI=0.46-0.66). Delta HR also predicted survival by both univariate and multivariate analyses (p &lt; 0.0001; HR/bpm = 0.98 for death; CI = 0.98-0.99). An abnormal AXT ECG was predictive of mortality by univariate (p = 0.03) but not multivariate analysis. None of these variables predicted MI but an exercise endpoint of typical chest pain and an abnormal AXT ECG prognosticated subsequent CVASC (multivariate p &lt; 0.0001; HR = 4.70; CI = 1.81-12.22 and p = 0.0002; HR = 2.64; CI = 1.61-4.33, respectively). We conclude that in high risk patients who cannot perform lower extremity exercise, HRR, AXT METs, and [[Unable to Display Character: &amp;#8710;]]HR are independently associated with survival, an abnormal AXT ECG predicts univariate mortality, and an AXT endpoint of typical chest pain and abnormal AXT ECG portend subsequent CVASC.

Maximal exercise testing as an evaluation tool in assessment of cardiovascular system adaptability in trained athletes

Background: There are conflicting opinions about the degree of adaptability of the cardiovascular system in delivering the physiological needs in case of severe exercise. Role of the normal cardiovascular system in delivering oxygen to meet the demands of various degrees of exercise has been a topic of considerable debate. One view holds that the cardiovascular system is not normally the most limiting factor in the delivery of oxygen, others hold the absence of structural adaptability to physical training cause of limitation of the cardiovascular system. Methods: Cardiovascular functions were assessed after maximal exercise testing by recording parameters like maximum heart rate, delta heart rate, recovery heart rate and maximum oxygen pulse in two groups' viz., athletes and non-athletes. Results: On studying the differences in cardiovascular functions in two groups of non-athletes and athletes, there was no significant difference in maximum heart rate. The other parameters like delta heart rate and maximum oxygen pulse were on the higher side in trained subjects while the recovery heart rate was significantly lower in the athlete group which was consistently maintained after exercise testing. Based on these findings it is suggested that there is a higher adaptability of the cardiovascular system to the training stimulus in the form of better VO2 max (maximum oxygen consumption), faster recovery of the exercise heart rate, and a lesser risk for cardiovascular mortality as suggested by the higher delta heart rate.

A study of the short term effect of cigarette smoking on cardiopulmonary efficiency

Background: All over the world, tobacco is taken in several forms. Use of tobacco in cigarettes indeed represents a health concern of growing magnitude among these groups. As a consequence of its addictive qualities, the consumption of cigarettes often becomes a lifelong habit with cumulative and deleterious effects on health. Smokeless tobacco has been advocated as a substitute for cigarette smoking. On the contrary, the use of smokeless tobacco is fraught with health risk and needs to be discouraged. Previous reports have described long-term harmful effects of nicotine on various body parameters, little is known about acute effect of cigarette smoking on cardiopulmonary parameters. Very few studies have been undertaken on the acute effect of use of cigarettes, a common form of tobacco use in India on cardiopulmonary parameters of youngsters. Materials and Methods: Treadmill exercise testing and pulmonary function tests were done before and after maximal exercise testing to assess cardiopulmonary efficiency in two groups' viz., healthy sedentary controls and healthy cigarette smokers. Results: On studying the differences in cardiopulmonary efficiency in the two groups the resting heart rate (HR) was found to be statistically significantly higher in the study group and the delta heart rate (δ HR) was found to be statistically significantly lower among cigarette smokers. There was no significant difference seen in parameters like VO 2 max, maximum oxygen pulse, maximal voluntary ventilation, VE max as an acute effect of cigarette smoking. Conclusion: In this study, it appears that cigarette smokers are physically fit like controls, but after immediate smoking a lesser δ HR suggests a higher risk for cardiovascular mortality. Stopping smoking at this juncture can be helpful in reverting back the risk and parameters such as resting HR, recovery HR, and δ HR can be used as prognostic assessment tools for any intervention therapy to stop cigarette smoking in asymptomatic individuals.

Acute Effect of Gutkha Chewing on Cardiopulmonary Efficiency in Short Term Users

Tobacco has been used orally alone or in combination with other ingredients. In India tobacco is taken in several forms. Use of smokeless tobacco indeed represents a health concern of growing magnitude among these groups. As a consequence of its addictive qualities, the consumption of smokeless tobacco often becomes a lifelong habit with cumulative and deleterious effects on health. Smokeless tobacco has been advocated as a substitute for cigarette smoking. On the contrary, the use of smokeless tobacco is fraught with health risk and needs to be discouraged. Previous reports have described long term harmful effects of nicotine on various body parameters, little is known about acute effect of smokeless tobacco on cardiopulmonary parameters. Very few studies have been undertaken on the acute effect of use of Gutkha, a common form of smokeless tobacco in India on cardiopulmonary parameters of youngsters. Methods: Treadmill Exercise Testing & Pulmonary Function Tests were done before and after maximal exercise testing to assess cardiopulmonary efficiency in two groups’ viz., healthy sedentary controls and healthy gutkha chewers. Results: On studying the differences in cardiopulmonary efficiency in the two groups the resting heart rate was found to be statistically significantly higher in the study group and the delta heart rate was found to be statistically significantly lower among gutkha chewers. There was no significant difference seen in parameters like VO2 max, maximum oxygen pulse, MVV, VE max as an acute effect of gutkha chewing. Conclusion: In this study it appears that tobacco chewers are physically fit like controls, but after immediate tobacco chewing a lesser delta HR suggests a higher risk for cardiovascular mortality. Stopping tobacco chewing at this juncture can be helpful in reverting back the risk and parameters like resting HR, recovery HR, and delta HR can be used as prognostic assessment tools for any intervention therapy to stop gutkha chewing in asymptomatic individuals.

Reference equations for the six-minute walk distance based on a Brazilian multicenter study

BackgroundIt is important to include large sample sizes and different factors that influence the six-minute walking distance (6MWD) in order to propose reference equations for the six-minute walking test (6MWT). ObjectiveTo evaluate the influence of anthropometric, demographic, and physiologic variables on the 6MWD of healthy subjects from different regions of Brazil to establish a reference equation for the Brazilian population. MethodIn a multicenter study, 617 healthy subjects performed two 6MWTs and had their weight, height, and body mass index (BMI) measured, as well as their physiologic responses to the test. Delta heart rate (∆HR), perceived effort, and peripheral oxygen saturation were calculated by the difference between the respective values at the end of the test minus the baseline value. ResultsWalking distance averaged 586±106m, 54m greater in male compared to female subjects (p<0.001). No differences were observed among the 6MWD from different regions. The quadratic regression analysis considering only anthropometric and demographic data explained 46% of the variability in the 6MWT (p<0.001) and derived the equation: 6MWDpred=890.46-(6.11×age)+(0.0345×age2)+(48.87×gender)-(4.87×BMI). A second model of stepwise multiple regression including ∆HR explained 62% of the variability (p<0.0001) and derived the equation: 6MWDpred=356.658-(2.303×age)+(36.648×gender)+(1.704×height)+(1.365×∆HR). ConclusionThe equations proposed in this study, especially the second one, seem adequate to accurately predict the 6MWD for Brazilians.

Heart Rate Response to a Timed Walk and Cardiovascular Outcomes in Older Adults: The Cardiovascular Health Study

Objectives: To determine the relationship between heart rate response during low-grade physical exertion (6-min walk) with mortality and adverse cardiovascular outcomes in the elderly. Methods: Participants in the Cardiovascular Health Study who completed a 6-min walk test were included. We used delta heart rate (difference between postwalk heart rate and resting heart rate) as a measure of chronotropic response and examined its association with (1) all-cause mortality and (2) incident coronary heart disease event, using multivariable Cox regression models. Results: We included 2,224 participants (mean age 77 ± 4 years; 60% women; 85% white). The average delta heart rate was 26 beats/min. Participants in the lowest tertile of delta heart rate (<20 beats/min) had higher risk-adjusted mortality [hazard ratio (HR) 1.18, 95% confidence interval (CI) 1.00–1.40] and incident coronary heart disease (HR 1.37, 95% CI 1.05–1.78) compared to subjects in the highest tertile (≥30 beats/min), with a significant linear trend across tertiles (p for trend <0.05 for both outcomes). This relationship was not significant after adjustment for distance walked. Conclusion: Impaired chronotropic response during a 6-min walk test was associated with an increased risk of mortality and incident coronary heart disease among the elderly. This association was attenuated after adjusting for distance walked.

(Pro)renin receptor deletion prevents the development of DOCA‐salt hypertension in neuron‐specific (pro)renin receptor knockout mice

We previously found the presence of (pro)renin receptor (PRR) in the brain. To elucidate the physiological importance of brain PRR, we developed a neuron‐specific PRR knockout mouse model (Nefh‐PRR). Using real time PCR and immunofluorescence, we observed PRR deletion throughout the brain. Blood pressure (BP) and heart rate (HR) were recorded continuously by telemetry in conscious Nefh‐PRR and control mice (n=5/group) before and during 21 days of deoxycorticosterone acetate‐salt (DOCA, 50mg, 0.9% NaCl drinking solution + tap water) treatment. At baseline, Nefh‐PRR mice exhibited normal BP (mmHg), sympathetic and parasympathetic tone. DOCA‐salt induced hypertension in control mice (137.0±10.5), while Nefh‐PRR mice remained normotensive (114.1±2.9; P&lt;0.05) at the end of experiments. DOCA‐salt significantly increased cardiac (delta HR: −219±6 vs. −66±10 bpm) and vasomotor sympathetic tone (delta BP: −63.7 ± 10.2 vs. −28.7 ± 1.2), and decreased parasympathetic tone (delta HR: 25±7 vs. 147±6 bpm) in control mice. Nefh‐PRR mice exhibited lower sympathetic tone (delta HR: −155±6 bpm; P=0.002, delta BP: − 32.4±5; P=0.05) and higher parasympathetic tone (delta HR: 101±27 bpm; P=0.03) compared to control mice following DOCA‐salt treatment. These data indicate neuron‐specific PRR knockout prevents DOCA‐salt induced hypertension via improvement of autonomic function. (NIH 1P30HL101285, AHA 11SDG7360050)

Effects of deep-brain bilateral stimulation of the subthalamic nucleus on heart rate and blood pressure in Parkinson's disease

We studied the effects of deep-brain stimulation (DBS) of the subthalamic nucleus (STN) on autonomic cardiovascular activities in subjects with Parkinson's disease. In 20 subjects with Parkinson's disease undergoing bilateral deep brain stimulation of the subthalamic nucleus, we measured heart rate, blood pressure, and heart rate variability (HRV), at rest and orthostatically, and compared these variables at baseline and three weeks after deep brain stimulation. No significant changes were seen in any variable during rest after surgery compared to baseline, nor in delta (baseline-orthostatic) heart rate or delta blood pressure.

Orthostatic haemodynamics may be impaired in frailty†

orthostatic hypotension (OH) is a physical sign that reflects a final common pathway of various forms of disordered physiology, which is the hallmark of geriatric frailty. Fried et al. recognise three increasing frailty phenotypes in older people, based on measurements of weight loss, exhaustion, grip strength, walking speed and physical activity. Orthostatic haemodynamics have not been considered as markers of frailty in older people. to classify a community sample of older people into three increasing frailty phenotypes and compare their orthostatic haemodynamics. cross-sectional study. geriatric research clinic. a total of 442 subjects (mean age 72, 72% females) without dementia or risk factors for autonomic neuropathy. the sample was classified according to modified Fried criteria. Orthostatic systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR) responses were monitored during an active stand with Finometer®. one hundred and ninety-eight subjects (44.8%) were classified as non-frail, 213 (48.2%) as pre-frail, and 31 (7.0%) as frail. Across groups, there was a significant increasing gradient in baseline HR (P = 0.008) and decreasing gradients in Delta HR (i.e. maximum HR within 30 s-baseline HR) (P < 0.001) and maximum HR by 30 s (P < 0.001). On average, by 30 s after stand, non-frail subjects had recovered 98% of their baseline SBP, while pre-frail and frail subjects had recovered 95 and 92%, respectively (P for trend = 0.064). the orthostatic HR response and, to a lesser extent, SBP recoverability, appear impaired in frailty. Orthostatic haemodynamics may be useful markers of frailty.

平常生活活動時の微量尿蛋白および酵素N-acetyl-β-D-glucosarninidase(NAG)尿中排泄の日内変動

The present investigation was performed to confirm the relationship between the circadian variation of microproteinuria and physical activity. Urine samples from 10 normal male volunteers, collected during six consecutive 4-h periods, were examined for albumin, alpha 1-, beta 2-microglobulin, NAG, electrolytes and hormones. The fluctuations in heart rate (HR) and blood pressure (BP) over 24-h were measured at 30-min and 1-h intervals, respectively. Energy expenditure (EE) was calculated using the equation of regression between HR and oxygen uptake measured on another day. The variations of HR (delta HR) and EE (delta EE) based on a 24-h average (bpm and kcal/kg/h) were used as indices of change in physical activity during an ordinary day. The correlation coefficients between delta HR and the variations of albumin (delta Alb) and beta 2-microglobulin (delta beta 2M) from the 24-h average (micrograms/h.cr 1 mg) were 0.619 and 0.670 (p less than 0.001), respectively. Increased excretions of both glomerular and tubular proteins were correlated with the increase in HR and/or EE during daytime activity. During rest time at night, the variations in alpha 1M, beta 2M and NAG excretion were different from the variations in albumin. A temporary inhibition of tubular protein excretion was observed only in the early morning (04:00-08:00), although albumin excretion was inhibited throughout the nighttime. These findings suggested that physical activity may influence the diurnal variations in protein excretions, that albuminuria may be more sensitive to daytime activity, and that fluctuation of tubular protein excretion may be preferably controlled by an endogenous mechanism. Timed overnight or first-morning urine may be recommendable as a sample for determination of microalbuminuria for screening of clinical diabetic nephropathy.