Graded Treadmill Stress Testing: Patterns of Physician Use and Abuse

Treadmill stress testing is used in assessing the condition of patients with known or suspected heart disease. We did a prospective study to clarify physician ordering and integration of the test. Ordering criteria were always complied with, although most tests were ordered for evaluation of atypical chest pain and only a few for high risk patients with known cardiac dysfunction, indicating a misplaced emphasis on the diagnostic capabilities of the test. Tests in patients with atypical chest pain and stress-induced ischemic changes were always integrated, but in 30 percent of patients with atypical pain and no stress-induced electrocardiographic changes, the tests were not used in patient management. This was often due to the misconception that negative findings on a stress test excluded coronary disease. Physicians should be alerted to this misplaced emphasis and misconception.     

Prospect of Stress Testing

A new method for analyzing the data of stress electrocardiography, based on physiologically justified approximations of trends in the heart rate (HR) and ST, is discussed. The method makes it possible to determine how the HR and ST of an individual vary with time during graded exercise and how these parameters and the times of their regulation depend on the workload; to reveal general patterns of their behavior; and to derive new physiological characteristics. Analysis of the general patterns of only the load time dependences of HR and ST and of the workload dependence of HR in patients with ischemic heart disease allows us to detect brief episodes of myocardial ischemia; to assess the anaerobic thresholds of locally injured areas of the myocardium and of the whole body; and to propose unified parameters for assessing the coronary reserve, the physical working capacity, and the severity of ischemic injury to the myocardium. The proposed method of analysis of stress electrocardiographic data and the combined use of stress electrocardiography, positron emission tomography, myocardial scintigraphy, and stress echocardiography offer new opportunities for a better understanding of myocardial ischemia.     

Graded Maximal Exercise Testing to Assess Mouse Cardio-Metabolic Phenotypes

Functional assessments of cardiovascular fitness (CVF) are needed to establish animal models of dysfunction, test the effects of novel therapeutics, and establish the cardio-metabolic phenotype of mice. In humans, the graded maximal exercise test (GXT) is a standardized diagnostic for assessing CVF and mortality risk. These tests, which consist of concurrent staged increases in running speed and inclination, provide diagnostic cardio-metabolic parameters, such as, VO_2max, anaerobic threshold, and metabolic crossover. Unlike the human-GXT, published mouse treadmill tests have set, not staged, increases in inclination as speed progress until exhaustion (PXT). Additionally, they often lack multiple cardio-metabolic parameters. Here, we developed a mouse-GXT with the intent of improving mouse-exercise testing sensitivity and developing translatable parameters to assess CVF in healthy and dysfunctional mice. The mouse-GXT, like the human-GXT, incorporated staged increases in inclination, speed, and intensity; and, was designed by considering imitations of the PXT and differences between human and mouse physiology. The mouse-GXT and PXTs were both tested in healthy mice (C57BL/6J, FVBN/J) to determine their ability to identify cardio-metabolic parameters (anaerobic threshold, VO_2max, metabolic crossover) observed in human-GXTs. Next, theses assays were tested on established diet-induced (obese-C57BL/6J) and genetic (cardiac isoform Casq2^-/-) models of cardiovascular dysfunction. Results showed that both tests reported VO_2max and provided reproducible data about performance. Only the mouse-GXT reproducibly identified anaerobic threshold, metabolic crossover, and detected impaired CVF in dysfunctional models. Our findings demonstrated that the mouse-GXT is a sensitive, non-invasive, and cost-effective method for assessing CVF in mice. This new test can be used as a functional assessment to determine the cardio-metabolic phenotype of various animal models or the effects of novel therapeutics.     

踏车运动试验对高血压病合并冠心病的诊断意义

本文回顾了４７例无心肌缺血症状和平静心电图无ＳＴ段改变的原发笥高血压病患者的车运动试验结果。阴性率３２％,阳性患者中７４．５％为下斜型ＳＴ段降低,持续时间２－１２ｍｉｎ。提示踏车运动试验对原发性高血压病患者筛选有否合并冠心病,具有较高的辅助诊断价值。     

Diurnal Variation in Heart Rate Variability before and after Maximal Exercise Testing

As heart-rate variability (HRV) is under evaluation in clinical applications, the authors sought to better define the interdependent impact of age, maximal exercise, and diurnal variation under physiologic conditions. The authors evaluated the diurnal changes in HRV 24-h pre- and post-maximal aerobic exercise testing to exhaustion in young (19–25 yrs, n?=?12) and middle-aged (40–55 yrs, n?=?12) adults. Subjects wore a portable 5-lead electrocardiogram holter for 48?h (24?h prior to and following a maximal aerobic capacity test). Time-, frequency-, time-frequency-, and scale-invariant-domain measures of HRV were computed from RR-interval data analyzed using a 5-min window size and a 2.5-min step size, resulting in a different set of outputs every 2.5?min. Results were averaged (mean?±?SE) over four prespecified time periods during the morning, afternoon, evening, and night on Day 1 and Day 2. Diurnal changes in HRV in young and middle-aged adults were compared using a two-way, repeated-measures analysis of variance (ANOVA). Young adults demonstrated higher HRV compared to middle-aged adults during periods of wakefulness and sleep prior to maximal exercise stress testing (i.e., high-frequency power during Day 1: young adults: morning 1862?±?496?ms², afternoon 1797?±?384?ms², evening 1908?±?431?ms², and night 3202?±?728?ms²; middle-aged adults: morning 341?±?53?ms², afternoon 405?±?68?ms², evening 469?±?80?ms², and night 836?±?136?ms²) (p < .05). Exercise resulted in reductions in HRV such that multiple measures of HRV were not significantly different between age groups during the afternoon and evening periods. All measures of HRV demonstrated between-group differences overnight on Day 2 (p < .05). Young adults are associated with higher baseline HRV during the daytime. Sleep increases variability equally and proportionally to daytime variability. Given the higher baseline awake HRV and equal rise in HRV during sleep, the change in HRV from sleep to morning with exercise is greater in younger subjects. These physiologic results have clinical significance in understanding the pathophysiology of altered variability in ill patients. (Author correspondence: aseely@ohri.ca)     

The Application of Hunter's Inequality in Simultaneous Testing

Using the inequality given by HUNTER (1976) critical limits are derived on the basis of bivariate distributions of the respective statistics for various situations of simultaneous hypothesis testing. The gain in power as compared to the widely used Bonferroni-inequality can be considerable if at least some of the simultaneously investigated test-statistics are highly correlated. In such situations, the loss in power as compared to the use of the exact critical limits might be negligible for practical purposes, the exact limits often being hardly accessible.     

跑台运动在动物实验研究中的应用

跑台在实验动物研究中的应用越来越多,主要集中在建立运动模型以及探究运动对生理和病理的作用,以促进运动训练的科学化、竞技体育成绩的提高、运动疗法在疾病康复中合理有效的应用等,同时也是研究运动与代谢,运动与心脑血管病等的研究工具。本文对动物跑台的基本构造、使用方法和研究进展进行了分析和总结,为利用跑台进行研究提供一定的参考。     

Rapid Microbiological Testing: Monitoring the Development of Bacterial Stress

The ability to respond to adverse environments effectively along with the ability to reproduce are sine qua non conditions for all sustainable cellular forms of life. Given the availability of an appropriate sensing modality, the ubiquity and immediacy of the stress response could form the basis for a new approach for rapid biological testing. We have found that measuring the dielectric permittivity of a cellular suspension, an easily measurable electronic property, is an effective way to monitor the response of bacterial cells to adverse conditions continuously. The dielectric permittivity of susceptible and resistant strains of Escherichia coli and Staphylococcus aureus, treated with gentamicin and vancomycin, were measured directly using differential impedance sensing methods and expressed as the Normalized Impedance Response (NIR). These same strains were also heat-shocked and chemically stressed with Triton X-100 or H₂O₂. The NIR profiles obtained for antibiotic-treated susceptible organisms showed a strong and continuous decrease in value. In addition, the intensity of the NIR value decrease for susceptible cells varied in proportion to the amount of antibiotic added. Qualitatively similar profiles were found for the chemically treated and heat-shocked bacteria. In contrast, antibiotic-resistant cells showed no change in the NIR values in the presence of the drug to which it is resistant. The data presented here show that changes in the dielectric permittivity of a cell suspension are directly correlated with the development of a stress response as well as bacterial recovery from stressful conditions. The availability of a practical sensing modality capable of monitoring changes in the dielectric properties of stressed cells could have wide applications in areas ranging from the detection of bacterial infections in clinical specimens to antibiotic susceptibility testing and drug discovery.     

The Diagnostic Value of Treadmill Exercise Test Parameters for Coronary Artery Disease

The aim of this study was to determine the diagnostic value of treadmill exercise test (TET) in patients with coronary heart disease (CHD) by comparing the diagnostic conclusions with coronary angiography (CAG). Patients (445) with CHD and suspected CHD underwent TET and CAG, and the corresponding diagnostic conclusions were compared. (1) Out of the 200 cases that had the positive result with TET, 150 cases had been diagnosed CHD by means of CAG; Out of the 245 cases that had the negative result during TET, only 39 cases had been diagnosed CHD by means of CAG. The sensitivity, specificity, positive predictive value, negative predictive value, the false positive incidence, the false negative incidence, and agreement rate in diagnosis of CHD by TET were 79.36, 80.40, 75.00, 84.08, 25.00, 15.92, and 80.00 %, respectively. The patients with multi-vessel disease had a higher positive rate of TET as compared with those with single-vessel disease (P < 0.05). (2) The parameters for 189 cases positive CAG (patients diagnosed CHD by CAG) and 256 cases negative CAG (the control group), including the general exercise time, peak heart rate, and the beginning time of ST depression, were lower than that of control group (P < 0.05). However, the extent of ST depression and duration of ST depression were higher in these patients than in the control group (P < 0.05). (3) 189 cases positive CAG, include 87 cases of single coronary artery and 102 cases of binary or more coronary arteries (the control group). The parameters, including the general exercise time, peak heart rate, and the beginning time of ST depression, were lower than the control group (P < 0.05). However, the extent of ST depression and duration of ST depression were higher in these patients than the control group (P < 0.05). The TET is valuable for noninvasive diagnosis of CHD, especially for patients with multi-vessel disease.     

平板运动试验对心律失常的诊断价值

目的:探讨平板运动试验对心律失常的诊断意义,及对临床诊断积极的补充作用。方法:选择2002年-2006年间187例(男性86例,女性101例)病人,这些病人有心悸症状,既做过24hDCG又进行过平板运动试验;对这些资料进行分析。结果:187例患者中44例(23.5%)在24hDCG监测中未发现或偶然发现心律失常,而在进行平板运动试验中,却表现为频发心律失常。其中10例检出潜在恶性心律失常。结论:对有心律失常病史的病人进行平板运动试验可增加心律失常的诊断率和敏感性。这对临床诊断起到积极的补充作用。     

Modular Control of Treadmill vs Overground Running

Motorized treadmills have been widely used in locomotion studies, although a debate remains concerning the extrapolation of results obtained from treadmill experiments to overground locomotion. Slight differences between treadmill (TRD) and overground running (OVG) kinematics and muscle activity have previously been reported. However, little is known about differences in the modular control of muscle activation in these two conditions. Therefore, we aimed at investigating differences between motor modules extracted from TRD and OVG by factorization of multi-muscle electromyographic (EMG) signals. Twelve healthy men ran on a treadmill and overground at their preferred speed while we recorded tibial acceleration and surface EMG from 11 ipsilateral lower limb muscles. We extracted motor modules representing relative weightings of synergistic muscle activations by non-negative matrix factorization from 20 consecutive gait cycles. Four motor modules were sufficient to accurately reconstruct the EMG signals in both TRD and OVG (average reconstruction quality = 92±3%). Furthermore, a good reconstruction quality (80±7%) was obtained also when muscle weightings of one condition (either OVG or TRD) were used to reconstruct the EMG data from the other condition. The peak amplitudes of activation signals showed a similar timing (pattern) across conditions. The magnitude of peak activation for the module related to initial contact was significantly greater for OVG, whereas peak activation for modules related to leg swing and preparation to landing were greater for TRD. We conclude that TRD and OVG share similar muscle weightings throughout motion. In addition, modular control for TRD and OVG is achieved with minimal temporal adjustments, which were dependent on the phase of the running cycle.     

负二项分布概率的最大值点

本文给出了负二项分布概率取的最大值的点,并给出了证明及例子.     

Factors in the Testing and Application of Algicides

A review is presented of some of the factors affecting the laboratory testing and practical applications of chemicals toxic to algae. The basic factor demonstrated is that the amount of chemical required to inhibit the growth of algae is dependent on the amount of algae present and not on the volume of water in which the algae are dispersed. It is shown how a chemical can be tested for algistatic or algicidal properties, thus enabling one to decide how best to apply a particular chemical. The selectivity of chemicals and the development of resistance in algae towards certain chemicals is demonstrated. Also, it is shown how certain algae can appear to be resistant to chemical treatments because of their growth habit or their production of extracellular products which affect the toxicity of added chemicals. With a better understanding of how various factors can influence the effectiveness of toxic chemicals, it is hoped that the selection of a chemical and method of application to a particular problem will be more successful.     

Daily Life Stress and the Cortisol Awakening Response: Testing the Anticipation Hypothesis

The cortisol awakening response (CAR) is a distinct facet of the circadian cortisol rhythm associated with various health conditions and risk factors. It has repeatedly been suggested that the CAR could be a result of the anticipated demands of the upcoming day (stress anticipation) and could support coping with daily life stress. In a sample of 23 healthy participants CARs were assessed on two consecutive days by measures of salivary cortisol upon awakening (S1) and 30 and 45 minutes later, which were aggregated to the area under the curve increase (AUCI). Stress anticipation was assessed immediately after awakening. On the same days, daily life stress and distress were assessed six times per day based on a quasi-randomized design using handheld computers. Associations were tested by day using regression analysis and standard multilevel/mixed effects models for longitudinal data. The CAR AUCI moderated the effect of daily life stress on distress; higher CAR increases were associated with attenuated distress responses to daily life stress on both days (day 1: p = .039; day 2: p = .004) adjusted for age, gender, sleep quality, time of awakening and oral contraceptive use. Lagged-effects and redundancy models showed that this effect was not due to prior-day CAR increases but specific for same day CARs. On day 2, associations between daily life stress and distress were stronger when individuals showed a higher S1 cortisol level, but this effect was similar for S1 on day 1, and the day 2 effect of S1 became non-significant when S1 on day 1 was controlled. No associations were found between stress anticipation and CARs. Findings indicate that the CAR increase is associated with successful coping with same-day daily life stress.     

Testing the Relationship between Human Occupancy in the Landscape and Tadpole Developmental Stress

Amphibian population declines are widespread; the main causal factors are human related and include habitat fragmentation due to agriculture, mining, fires, and urban development. Brazil is the richest country in species of amphibians, and the Brazilian regions with the greatest amphibian diversity are experiencing relatively high rates of habitat destruction, but there are presently relatively few reports of amphibian declines. It is thus important to develop research methods that will detect deterioration in population health before severe declines occur. We tested the use of measurements of fluctuating asymmetry (FA) taken on amphibian larvae to detect anthropogenic stress. We hypothesized that greater human occupancy in the landscape might result in more stressful conditions for amphibians. We conducted this study at the Espinhaço mountain range in southeastern Brazil, using as a model an endemic species (Bokermannohyla saxicola, Hylidae). We chose two tadpole denticle rows and eye-nostril distance as traits for FA measurement. We measured percent cover of human-altered habitats in the landscape around tadpole sampling points and measured FA levels in sampled tadpoles. We found FA levels to differ among localities but found no relationship between human modification of the landscape and tadpole FA levels. Levels of FA in the traits we examined may not be strongly affected by environmental conditions, or may be affected by local variables that were not captured by our landscape-scale measures. Alternatively, populations may be genetically differentiated, affecting how FA levels respond to stress and obscuring the effects of anthropogenic disturbance.     

应激与颞下颌关节紊乱病研究新进展

颞下颌关节紊乱病是慢性面部疼痛最常见的诱因,常常与躯体和心理主诉症状密切联系,包括疲劳,睡眠失调,焦虑和抑郁等。即使未发现任何能够合理解释疼痛原因的时候,健康专业人士也常常忽略疼痛感受的主观性。从严格的生物医学角度来讲,对疼痛的这种理解是不科学的。本文的主要目的是通过查阅近年来大量的研究文献资料,发现应激引起疼痛感觉的生物学途径以及导致颞下颌关节紊乱的原因。研究发现下丘脑-垂体-肾上腺轴、5-羟色胺和阿片样物质通路都与颌面部疼痛的发病密切相关,同时也提出了未来可能使用的治疗方法。同时,也希望本文能把与疼痛学科差别较大的口腔医学融入到需要多学科合作的颞下颌关节紊乱的诊断和治疗中,从科学角度提高对该病的临床诊疗效率。     

物理方法在提高植物抗逆性中的应用

介绍了物理因素处理,主要包括磁场、电场、热激、冷激与低温以及激光处理等提高植物抗逆性的研究进展.