Exercise Testing

A Human Model of the Effects of an Instant Sheer Weight Loss on Cardiopulmonary Parameters during a Treadmill Run

Exercise tolerance is limited in obesity and improves after weight reduction; therefore, we mutually compared the relative changes in exercise capacity variables during cardiopulmonary exercise tests (CPET) in a 12 kg sheer weight reduction model. Twenty healthy male runners underwent two CPETs: CPET1 with the actual body weight, which determined the anaerobic threshold (AT) and respiratory compensation point (RCP); and CPET2 during which the participants wore a +12 kg vest and ran at the AT speed set during the CPET1. Running after body weight reduction shifted the CPET parameters from the high-mixed aerobic-anaerobic (RCP) to the aerobic zone (AT), but these relative changes were not mutually similar. The most beneficial changes were found for breathing mechanics parameters (range 12-28%), followed by cardiovascular function (6-7%), gas exchange (5-6%), and the smallest for the respiratory exchange ratio (5%) representing the energy metabolism during exercise. There was no correlation between the extent of the relative body weight change (median value ~15%) and the changes in CPET parameters. Weight reduction improves exercise capacity and tolerance. However, the observed relative changes are not related to the magnitude of the body change nor comparable between various parameters characterizing the pulmonary and cardiovascular systems and energy metabolism.

Usefulness of the Duke Activity Status Index to Select an Optimal Cardiovascular Exercise Stress Test Protocol

Exercise testing represents the preferred stress modality for individuals undergoing evaluation of suspected myocardial ischemia. Patients with limited functional status may be unable to achieve an adequate exercise stress, thus influencing the diagnostic sensitivity of the results. The Duke Activity Status Index (DASI) is a clinically applicable tool to estimate exercise capacity. The purpose of the current study was to assess the utility of the DASI to identify patients unable to achieve an adequate exercise stress result. Patients referred for exercise stress testing were administered the DASI pre-exercise. Baseline characteristics and exercise variables were evaluated including DASI-metabolic equivalents (DASI-METs), peak METs, exercise time (ET), and %-predicted maximal heart rate (%PMHR). Criteria for determining adequate exercise stress was defined as ≥85%PMHR or ≥ 5-METs at peak exercise. In 608 cardiovascular stress tests performed during the study period; 314 were exercise stress. The median DASI-METs (8.4 [interquartile range; 6.7 to 9.9]) was associated with estimated peak exercise METs (R=0.50, p <0.001), ET (R=0.29, p <0.001), and %PMHR (R=0.19, p = 0.003). DASI-METs were different between those with < or ≥85%PMHR (7.9 [6.6-9.0] vs. 8.9 [7.1-9.9], P=0.025) and those with < or ≥5-METs (5.8 [4.6 to 6.6] versus 8.9 [7.3-9.9], p <0.001). Receiver operating characteristic curve analysis identified a DASI-MET threshold of ≤/>7.4 to optimally predict adequate exercise stress (sensitivity=93%, specificity=71%). In conclusion, the DASI correlates with peak METs, ET, and %PMHR among patients referred for exercise testing and can be used to identify patients with an increased likelihood of an inadequate stress test result.

The effect of test modality on dynamic exercise biomarkers in children, adolescents, and young adults

Cardiopulmonary exercise testing (CPET) modalities, treadmill (TM), and cycle ergometer (CE), influence maximal gas exchange and heart rate (HR) responses. Little is known regarding CPET modality effect on submaximal biomarkers during childhood and adolescence. Ninety‐four healthy participants (7–34 y.o., 53% female) performed TM and CE CPET to address two major gaps: (1) the effect of modality on submaximal CPET biomarkers, and (2) estimation of work rate in TM CPET. Breath‐by‐breath gas exchange enabled calculation of linear regression slopes such as V˙O₂/ΔHR and ΔV˙E/ΔV˙CO₂. Lean body mass (LBM) was measured with dual X‐ray absorptiometry. We tested a novel TM CPET estimate of work rate based on TM velocity², incline, and body mass (VIM). Like the linear relationship between V˙O₂ and work rate in CE CPET, V˙O₂ increased linearly with TM VIM. TM ΔV˙O₂/ΔHR was highly correlated with CE (r = 0.92), and each increased substantially with LBM (P < 0.0001 for TM and CE). ΔV˙O₂/ΔHR was to a small (~8.7%) but significant extent larger in TM (1.6 mL/min/beat, P = 0.04). In contrast, TM and CE ΔV˙E/ΔV˙CO₂ decreased significantly with LBM, supporting earlier observations from CE CPET. For both CE and TM, males had significantly higher ΔV˙O₂/ΔHR but lower ΔV˙E/ΔV˙CO₂ than females. Novel TM CPET biomarkers such as ΔVIM/ΔHR and ∆V˙O₂/ΔVIM paralleled effects of LBM observed in CE CPET. TM and CE CPET submaximal biomarkers are not interchangeable, but similarly reflect maturation during critical periods. CPET analysis that utilizes data actually measured (rather than estimated) may improve the clinical value of TM and CE CPET.

Molecular Choreography of Acute Exercise

Acute physical activity leads to several changes in metabolic, cardiovascular, and immune pathways. Although studies have examined selected changes in these pathways, the system-wide molecular response to an acute bout of exercise has not been fully characterized. We performed longitudinal multi-omic profiling of plasma and peripheral blood mononuclear cells including metabolome, lipidome, immunome, proteome, and transcriptome from 36 well-characterized volunteers, before and after a controlled bout of symptom-limited exercise. Time-series analysis revealed thousands of molecular changes and an orchestrated choreography of biological processes involving energy metabolism, oxidative stress, inflammation, tissue repair, and growth factor response, as well as regulatory pathways. Most of these processes were dampened and some were reversed in insulin-resistant participants. Finally, we discovered biological pathways involved in cardiopulmonary exercise response and developed prediction models revealing potential resting blood-based biomarkers of peak oxygen consumption.

A method for predicting peak work rate for cycle ergometer and treadmill ramp tests

BACKGROUND

Prediction of peak work rate (WRpeak) for incremental exercise testing (IET) is important to bring subjects to their maximal performance within the recommended 8-12 min. This study developed a novel method for prediction of WRpeak for IET on cycles and treadmills.

METHODS

Peak metabolic equivalent of task (METpred) was predicted based on an existing non-exercise prediction formula, and then, predicted peak work rate (WRpred) was derived from separate formulae for the cycle and the treadmill. Eighteen healthy subjects were included.

RESULTS

In males, there was no difference between WRpred versus WRpeak for both the cycle ergometer (277·7 versus 275·6 W, P = 0·70) and the treadmill (264·1 versus 260·5, P = 0·58). In females, there was no difference between WRpred versus WRpeak for the cycle ergometer (187·1 versus 188·3 W, P = 0·90), but a significant difference was found between WRpred versus WRpeak on the treadmill (178·6 versus 151·9 W, P<0·05). For males, the mean absolute percentage errors for WRpred versus WRpeak were 4·6% and 5·7% for the cycle and treadmill, respectively. For females, the errors were 12·2% and 20·8%. The algorithm was successful in achieving the required duration of 8-12 min in 33 of 36 cases.

CONCLUSIONS

The peak work rate prediction protocol was accurate in male subjects for both the cycle and the treadmill. In female subjects, the method was accurate for the cycle, but systematically overpredicted the peak work rate on the treadmill. The protocol requires further adaptation for females on the treadmill.

Upper extremity bioimpedance before and after treadmill testing in women post breast cancer treatment

Research on the effect of cardiorespiratory (CR) exercise on upper extremity (UE) limb volume is limited in women with breast cancer-related lymphedema (BCRL). The aim of this study was to compare changes in UE volume immediately following a symptom-limited CR treadmill test in women with and without BCRL. As part of a cross-sectional study, 133 women post unilateral BC treatment completed symptom-limited treadmill testing. Bioimpedance spectroscopy (BIS) was used to measure UE resistance before and immediately following treadmill testing. Resistance ratios >1 (unaffected side/affected side) indicate greater volume in the affected limb. T-tests and repeated measures ANOVA were performed to evaluate differences between and within groups. Mean age was 56.2 years (SD 9.4); BMI was 26.13 kg m(-2) (SD 5.04). For women with previously diagnosed BCRL (n = 63), the resistance ratio was 1.116 (SD 0.160) pre-treadmill and 1.108 (SD 0.155) post-treadmill. For women without BCRL (n = 70), the resistance ratio was 0.990 (SD 0.041) pre-treadmill and 1.001 (SD 0.044) post-treadmill. Resistance ratios for women with BCRL were higher than those for women without BCRL at both time points (main effect of group: p < 0.001). No main effects were found for time (p = 0.695). A statistically significant effect was found for the time-by-group interaction (p = 0.002). 78% of the women with BCRL wore a compression garment during testing. Following testing, the women with BCRL demonstrated a non-statistically significant decrease in the resistance ratio, suggesting an immediate decrease in interlimb volume difference. The women without BCRL demonstrated an increase in the resistance ratio.

Evaluation of association between airway hyperresponsiveness, asthma control test, and asthma therapy assessment questionnaire in asthmatic children

Background

Achieving asthma control is a major challenge in children, otherwise symptoms perception remain poor especially at this age. The aim of this study is to evaluate the relationship between Asthma Control Test (ACT^TM), Asthma Therapy Assessment Questionnaire (ATAQ^TM) and exercise-induced bronchospasm (EIB).

Methods

We studied 80 asthmatic children. Airways hyperresponsiveness (AHR) was assessed by exercise-induced bronchospasm (Balke Protocol). Asthma control was evaluated using two questionnaires in all subjects: ACT (composed by Childhood-ACT and ACT) and ATAQ. In addition the use of short acting beta 2 agonist agents (SABAs) was assessed for each patient. Non-parametric variables were compared by Chi Square Test. Binomial logistic regression was performed to estimate the two questionnaires Odds Ratio (OR) in finding AHR.

Results

We have found that ATAQ has a sensitivity and a specificity of 0.72 and 0.45 respectively; instead, ACT has a sensitivity and a specificity of 0.5 and 0.39 respectively in evaluating AHR. Patients with uncontrolled asthma according to ATAQ revealed a significant higher percentage of AHR compared with ACT (72% vs 50%, p < 0.01).

Confirming this finding, patients declaring uncontrolled asthma to ATAQ have a significantly higher percentage (34%) of frequent SABAs use than the group with uncontrolled asthma to ACT (21%) (p <0.01).

Binomial logistic regression shows how a test revealing uncontrolled asthma is associated with the increasing odds of having AHR according to ATAQ (OR = 3.8, p = 0.05), not to ACT (OR = 0.2, p = 0.1).

Conclusions

Our results show that ATAQ reflects AHR and asthma control better than ACT. Children with uncontrolled asthma according to ATAQ have higher odds of having AHR and use of rescue medications (SABAs) compared to patients declaring uncontrolled asthma according to ACT. However both questionnaires are not sufficient alone to fully evaluate asthma control in children and it is always necessary to perform functional tests and investigate patients lifestyle, drug use and other important data that a simple questionnaire is not able to point out

Aerobic exercise prescription in patients with chronic heart failure: a review in the beta-blocker era

Aerobic exercise training is a well-established nonpharmacological tool in patients with clinically stable chronic heart failure. In recent years, β-blocker therapy has become a primary pharmacologic intervention in patients with chronic heart failure. Despite the undeniable improvements in patients, the β-blocker era has aroused uncertainties about aerobic exercise intensity prescription. It is well known that aerobic exercise prescription is performed by a percentage of the patient's heart rate reserve and the use of β-blockers could interfere in this method. For this reason, the aim of this review is to provide an update about aerobic exercise prescription in patients with chronic heart failure who are using β-blockers.

Heart rate recovery: a practical clinical indicator of abnormal cardiac autonomic function

The autonomic nervous system (ANS) and cardiovascular function are intricately and closely related. One of the most frequently used diagnostic and prognostic tools for evaluating cardiovascular function is the exercise stress test. Exercise is associated with increased sympathetic and decreased parasympathetic activity and the period of recovery after maximum exercise is characterized by a combination of sympathetic withdrawal and parasympathetic reactivation, which are the two main arms of the ANS. Heart rate recovery after graded exercise is one of the commonly used techniques that reflects autonomic activity and predicts cardiovascular events and mortality, not only in cardiovascular system disorders, but also in various systemic disorders. In this article, the definition, applications and protocols of heart rate recovery and its value in various diseases, in addition to exercise physiology, the ANS and their relationship, will be discussed.

Short-term effects of right ventricular pacing on cardiorespiratory function in patients with a biventricular pacemaker

The intention of this study was to evaluate the short-term effect of right ventricular (RV) pacing on cardiorespiratory function in patients with a biventricular pacemaker. A group of 26 patients with a biventricular pacemaker was enrolled in this cross-over, single-blind study. All patients underwent spiroergometry and electrocardiography in RV and biventricular pacing mode. Peak work capacity (102+/-32 W and 107+/-34 W for RV and biventricular pacing mode, respectively; P<.01) and peak oxygen consumption (21.4+/-6.7 mL/min/kg and 22.6+/-7.0 mL/min/kg for RV and biventricular pacing mode, respectively; P<.01) were significantly lower in the RV pacing mode. Heart rate at rest was significantly higher with active RV pacing. Short-term RV pacing in patients with a biventricular pacemaker resulted in a higher heart rate at rest, a lower peak work capacity, and a lower peak oxygen consumption compared with that in the biventricular pacing mode.

Long-term mortality with multiple treadmill exercise test abnormalities: comparison between patients with and without cardiovascular disease

BACKGROUND

Poor exercise capacity, abnormal heart rate responses, and electrocardiographic abnormalities during treadmill exercise testing independently predict mortality. The combined relationship of these 3 variables to determine the incremental increase in mortality was compared in groups with and without known cardiovascular disease (CVD).

METHODS

Patients referred for treadmill exercise testing during 1986 to 1991 were included. Exercise capacity <74% (of age- and gender-predicted value), heart rate reserve of <68 beat/min, and horizontal or down-sloping ST depression of > or =1 mm were considered abnormal. Cox proportional hazards regression was used to determine all-cause mortality (average follow-up of 16 years) based on the number of exercise test abnormalities (0, 1, 2, or all 3).

RESULTS

Among 10,897 patients, 20.9% (n = 2,277) had CVD. Poor exercise capacity and limited heart rate reserve were associated with increased risk of mortality (P < .0001) in both groups; however, abnormal exercise electrocardiogram was associated with an increased risk of mortality in the no-CVD group only (P < .0001). A graded increase in mortality was observed with increase in number of abnormal exercise test results in both groups. Patients without CVD having 2 or 3 abnormal exercise test results had a similar age-adjusted risk of long-term mortality as those with CVD but normal exercise test results, with a hazard ratio comparing these groups = 1.01 (95% CI 0.79-1.28).

CONCLUSIONS

The combinatorial approach validates the prognostic significance of multiple exercise test variables. The presence of > or =2 exercise test abnormalities may constitute a "CVD risk equivalent" in patients without CVD.

Randomised controlled trial of a supervised exercise rehabilitation program for colorectal cancer survivors immediately after chemotherapy: study protocol

BACKGROUND

Colorectal cancer (CRC) diagnosis and the ensuing treatments can have a substantial impact on the physical and psychological health of survivors. As the number of CRC survivors increases, so too does the need to develop viable rehabilitation programs to help these survivors return to good health as quickly as possible. Exercise has the potential to address many of the adverse effects of CRC treatment; however, to date, the role of exercise in the rehabilitation of cancer patients immediately after the completion of treatment has received limited research attention. This paper presents the design of a randomised controlled trial which will evaluate the feasibility and efficacy of a 12-week supervised aerobic exercise program (ImPACT Program) on the physiological and psychological markers of rehabilitation, in addition to biomarkers of standard haematological outcomes and the IGF axis.

METHODS/DESIGN

Forty CRC patients will be recruited through oncology clinics and randomised to an exercise group or a usual care control group. Baseline assessment will take place within 4 weeks of the patient completing adjuvant chemotherapy treatment. The exercise program for patients in the intervention group will commence a week after the baseline assessment. The program consists of three supervised moderate-intensity aerobic exercise sessions per week for 12 weeks. All participants will have assessments at baseline (0 wks), mid-intervention (6 wks), post-intervention (12 wks) and at a 6-week follow-up (18 wks). Outcome measures include cardio-respiratory fitness, biomarkers associated with health and survival, and indices of fatigue and quality of life. Process measures are participants' acceptability of, adherence to, and compliance with the exercise program, in addition to the safety of the program.

DISCUSSION

The results of this study will provide valuable insight into the role of supervised exercise in improving life after CRC. Additionally, process analyses will inform the feasibility of implementing the program in a population of CRC patients immediately after completing chemotherapy.

TRIAL REGISTRATION

ACTRN012606000395538.

A negative finding in an exercise test is reliable among elderly people: a follow-up study

BACKGROUND

Coronary heart disease (CHD) is very common among elderly people.

OBJECTIVE

To specify the diagnostic value of bicycle exercise tests conducted for elderly patients by trained general practitioners in primary health care.

METHODS

We performed a 2-year follow-up study at the Kangasala Health Centre, Finland. The study population comprised all patients at least 60 years old (n = 311) suspected of having CHD without prior diagnosis who were examined by an exercise test carried out by trained general practitioners during a period of 3 years. Specificity and sensitivity as well as positive and negative predictive values of the tests were calculated based on whether or not the participants had a diagnosis of CHD by the end of the follow-up period. The numbers of patients referred for coronary angiography and bypass operation were registered. For analysis, the patients were divided into two age categories: 60-69 years and >or=70 years.

RESULTS

A negative finding in the test proved very reliable: CHD manifested in only 3% of these cases in both age groups. The specificity of the test was 72% in the group 60-69 years and 66% in the group >or=70 years; the sensitivity values were 81 and 67%, respectively. The positive predictive values were 26 and 12%, the negative predictive value was 97% in both age groups. 1 in 4 patients yielding a positive finding eventually underwent coronary angiography and 1 in 6 patients coronary bypass surgery.

CONCLUSIONS

Exercise tests may predict the clinical outcome of CHD among elderly patients. A negative finding in an exercise test is very reliable.

Understanding the basics of cardiopulmonary exercise testing

Cardiopulmonary exercise testing adds important additional information to that provided by the standard exercise test. In particular, cardiopulmonary exercise testing provides precise determination of aerobic capacity, the causes of dyspnea with exertion, and prognosis in patients with systolic heart failure. This review provides basic, practical information about cardiopulmonary exercise testing for the clinician.

The treadmill exercise-tolerance test is useful for the prediction and prevention of ischemic coronary events in elderly diabetics

BACKGROUND

Approximately 80% of cases of ischemic heart disease (IHD) occur in patients with nonstenotic coronary arteries, and few studies have systematically assessed exercise testing (TMT) as a predictor of risk in the elderly.

METHODS

TMT was carried out using a protocol for the independent and active elderly (n=176). After 4.1+/-0.5 years follow-up, logistic regression analysis was performed for each coronary risk factor such as diabetes mellitus (DM) and hypercholesterolemia (HC). According to the results, patients were divided into Gp HC, hypercholesterolemic patients; Gp DM, diabetics; Gp HC+DM, hypercholesterolemic diabetics; and Gp C, nonhyperlipidemic and nondiabetics. Sensitivity and specificity of TMT for IHD (significant stenosis or acute coronary syndrome) were analyzed.

RESULTS

Odds ratios for each risk factors are as follows: DM, 4.167; HC, 4.485; and DM+HC, 8.652. Notably, TMT was 17.59. Age was a significant risk, but hypertension was not. Positive ischemic signs in TMT were observed in 52.7%, 28.6%, 33.3%, and 16.3% in the Gp HC+DM, HC, DM, and C groups, respectively. Only three participants complained of chest pain during the TMT. Significant stenosis was observed in 75.0%, 71.4%, 69.2%, and 60.0% of coronary angiography (CAG)-receiving patients of Gp HC, DM, HC+DM, and C. During the observation term, acute coronary syndromes occurred in 4.7%, 3.3%, 5.5%, and 0% of patients in the Gp HC, DM, HC+DM, and C groups, respectively. The sensitivity of TMT for IHD was higher than 66.7% and specificity was higher than 94.1% in each group.

CONCLUSION

An exercise tolerance test in the elderly, especially for diabetics and hypercholesterolemic patients, is useful for the diagnosis of IHD.

Exercise treadmill test may predict clinical outcome among working-aged patients suspected of coronary heart disease in general practice

OBJECTIVE

To specify the diagnostic value of treadmill tests conducted in primary health care by trained GPs for working-aged patients.

DESIGN

A two-year follow-up study.

SETTING

Kangasala Health Centre, Finland.

SUBJECTS

All patients under the age of 60 (n = 348) examined by exercise treadmill test carried out by trained GPs during a period of three years.

MAIN OUTCOME MEASURES

The number of patients having a diagnosis of coronary heart disease at the end of two years' follow-up. Predictive values of the exercise test.

RESULTS

During the two years' follow-up period CHD was diagnosed in six of the patients who did not yield a positive finding in the test. A negative finding in the test was very reliable; coronary heart disease manifested in only 2% of these cases. Almost half of the patients yielding a positive finding ended up having coronary angiography and 1 in 10 underwent coronary bypass surgery.

CONCLUSION

Among working-aged patients suspected of coronary heart disease an exercise treadmill test may predict clinical outcome in general practice.

[Long-term results of percutaneous transmyocardial laser revascularization therapy at the University of Vienna Medical Center]

INTRODUCTION

Percutaneous transmyocardial laser revascularization (PTMR) was used for treating patients with therapy refractory angina pectoris who are not amenable for angioplasty or bypass surgery ("no-option patients"). The aim of this study was to evaluate the short- and long-term results of PTMR-interventions performed at the University of Vienna between February 1999 and May 2000.

PATIENTS AND METHODS

Twenty-four "no-option" patients underwent PTMR. The chronically ischemic myocardial areas were determined by perfusion scintigraphy; after coronary angiography and contrast ventriculography 10 patients were treated with the Biosense laser using 3D-NOGA-mapping guidance and 14 patients with the Eclipse laser using biplane fluoroscopic guidance. After an average follow-up period (FUP) of 7.7 +/- 4.2 months, all patients underwent perfusion scintigraphy, coronary angiography and contrast ventriculography. Global and regional left ventricular (LV) function were calculated by the area-length method.

RESULTS

The ischemic myocardial areas of the patients were treated with an average of 16 laser points. In one patient, an intramural hematoma caused by the Biosense laser catheter was observed, in another patient the ventricular wall was perforated by the Eclipse laser (both events were resolved conservatively); during the in-hospital stay 2 patients suffered from severe angina pectoris and in one patient a pacemaker was implanted. During the 7-month-FUP one patient had a myocardial infarction; in one patient a stent implantation, in another one coronary bypass surgery had to be performed (in not-lasered areas), 2 patients died. Thus, the composite MACE rate was 33.3%. Angina class improved significantly during the FUP, but a trend to deterioration of global ejection fraction was observed. The rest and late rest myocardial perfusion remained unchanged.

CONCLUSION

While the angina class of the patients improved significantly, no significant change of myocardial perfusion but a trend to deterioration of LV function after the FUP were observed.

Using baseline respiratory function data to optimize cycle exercise test duration

BACKGROUND

It is often difficult to select an appropriate workload increment for progressive cycle exercise tests in order to achieve optimal test duration (8-12 min). We hypothesize that baseline respiratory function can be systematically used to select appropriate workload increment to optimize test duration in patients referred to the clinical laboratory.

METHODOLOGY

One hundred and eighty consecutive exercise tests (with increments of 15 W/min) were retrospectively assessed. Using regression analysis, an equation was generated that predicts the work rate increment that would provide exercise duration of 8-12 min. The validity of this equation was tested prospectively in 231 consecutive tests performed with the calculated workload increment rounded to the nearest 5 watts (W).

RESULTS

The best regression equation was: workload increment (W/min)=1.94 x FEV1 (L) + 0.63 x TLCO (mmol/min per kPa) - 0.07 x age + 1.94 x gender (male=1, female=0) + 4.12 (r=0.85, P < 0.0001). Using this equation allowed selection of the most appropriate workload increment in 79% of tests and reduced the number of tests of non-optimal duration from 72% (for a fixed increment of 15 W/min) to 38%.

CONCLUSIONS

Utilization of this regression equation allows standardization in the selection of workload increment, and reduces the number of cycle exercise tests of inadequate duration.

Reference values for the physical work capacity on a bicycle ergometer for women between 20 and 80 years of age

A sample of women (n=87) uniformly distributed in age (20-80 years) was randomly selected from the municipal population register and conventional clinical exercise tests were performed on a bicycle. The load started at 30 W and increased (5 W/30 s) until exhaustion. Care was taken to perform a maximum exercise test. The women were required to be cardiovascularly healthy and not on regular medication to be included in the study. The maximum work load was found to be dependent on age and height. The following equation described the maximum load. Max load (W)=(137.7 * Height (m) - 23.1)/(1 + exp (0.064 * (Age (years) - 75.9))). The upper and lower limits of the reference interval were 120 and 80% of the predicted load, respectively. The upper and lower limits for maximum heart rate were 110 and 90% of the maximum heart rate given by 190.2/(1 + exp (0.0453 * (Age - 107.5))). The reference value for maximum systolic blood pressure was taken as the interval between the two lines 153.3 + 0.281 * Age and 172.0 + 1.13 * Age. The reference values presented for work capacity are higher than those normally used in Sweden.

Development of a servo-controller of heart rate using a treadmill

Although treadmill exercise involves a more familiar range of motions and is thus more physiological in terms of daily activity than cycle ergometer exercise, difficulties in controlling the exercise intensity have limited its utility. As heart rate (HR) has been used as a measure of exercise intensity, controlling HR should allow for the proper control of exercise intensity during treadmill exercise. Thus, a servo-controller framework was applied to regulate HR during treadmill exercise. After estimating an averaged transfer function from speed command to HR, feedback parameters were optimized via a computer simulation in order to achieve a quick and stable HR response. The performance of the servo-controller of HR was then examined in 10 healthy subjects. Standard deviations of the steady-state difference between the target and measured HRs were 2.7+/-0.9 and 5.0+/-1.4 beats/min in the stepwise and ramp target HR protocols, respectively. The rise time to reach 90% of the target HR was 93+/-20 s in the stepwise protocol. It was concluded that a treadmill implemented with a negative feedback mechanism made it possible to precisely regulate HR and thus exercise intensity.

Is nurse-supervised exercise stress testing safe practice?

OBJECTIVE

Nurses have been performing exercise stress tests (EST) without medical supervision since 1978 in our hospital-based cardiac rehabilitation unit. This study was conducted to examine the incidence of cardiovascular complications and to describe the competency-based training program for the nurses performing the EST.

DESIGN

Descriptive, retrospective audit of prospective data.

SETTING

Single comprehensive cardiac rehabilitation center in a large tertiary referral hospital in western Sydney, Australia.

SUBJECTS

Seventeen thousand, four hundred and sixty-seven patients were included in this study over a 12-year period.

METHOD

Data were collected on all ESTs performed by the cardiac rehabilitation nurses from January 1986 to December 1997 in relation to serious cardiovascular complications and other EST parameters.

RESULTS

In this study, 17,467 ESTs were performed on 5054 patients who had 6273 separate presentations. The most common entry diagnosis was after an acute myocardial infarction (50%). The mean age was 58 +/- 10.5 years (range 15 to 87 years; 80% male). The left ventricular ejection fraction (n = 2822) was 49% +/- 14%. In a subgroup analysis of 14,454 patients, 14% had a positive EST (ST segment >1.9 mm depression). There were no deaths associated with the EST, and there were 13 major complications in 12 patients. This figure included no cardiac arrests, 11 episodes of conscious sustained ventricular tachycardia, 1 reinfarction, and 1 mitral valve rupture, representing a 0% mortality rate and a 0.075% major morbidity rate.

CONCLUSION

This study shows that nurse-supervised EST of higher risk patients in the hospital-based cardiac rehabilitation setting has been a safe practice from a mortality and morbidity rate perspective. This finding may be accounted for by the high training standard and reaccreditation of the nurses on the advanced practice of performing EST.

Enhanced exercise-induced hyperkalemia in patients with syndrome X

OBJECTIVES

The purpose of this study was to determine whether patients with syndrome X have altered potassium metabolism.

BACKGROUND

Patients with syndrome X have angina pectoris and exercise induced ST segment depression on the electrocardiogram despite normal coronary angiograms. Increasing evidence suggests that myocardial ischemia is uncommon in these patients. Altered potassium metabolism causing interstitial potassium accumulation in the myocardium may be an alternative mechanism for chest pain and ST segment depression in syndrome X.

METHODS

We compared the magnitude of exercise-induced hyperkalemia in 16 patients with syndrome X (12 female and four male, mean +/- SD age 53 +/- 6 years) and 15 matched healthy control subjects. The participants underwent a bicycle test at a fixed load of 75 W for 10 min, and blood samples were taken for analysis of potassium, catecholamines and lactate before, during and in the recovery period after exercise. In five patients with syndrome X, the test was repeated during alpha1 adrenoceptor blockade.

RESULTS

Baseline concentrations of serum potassium, plasma catecholamines and plasma lactate were similar in patients and control subjects. The rate of exercise-induced increment of serum potassium was increased in the patients (70 +/- 29 vs. 30 +/- 21 micromol/liter/min in control subjects, p < 0.001). Six patients, who stopped before 10 min of exercise, showed very rapid increments in serum potassium concentration. Compared to the control subjects, patients also demonstrated larger increments in rate-pressure product, plasma norepinephrine and lactate concentrations during exercise. The rate of serum potassium increment correlated with the rate of plasma norepinephrine increment in the patients (r = 0.63, p < 0.02), but not in the control subjects (r = 0.01, p = 0.97). Blockade of alpha1 adrenoceptors decreased systolic blood pressure at baseline, but did not influence the increment of serum potassium, plasma catecholamines and lactate.

CONCLUSIONS

Patients with syndrome X have enhanced exercise induced hyperkalemia in parallel with augmented increases of circulating norepinephrine and lactate. The prevailing mechanisms behind the abnormal potassium handling comprise sources distinct from alpha1-adrenoceptor activation.

Exaggerated reactivity to mental stress is associated with exercise-induced myocardial ischemia in an asymptomatic high-risk population

BACKGROUND

This study was done to determine whether cardiovascular reactivity to mental stress is associated with exercise-induced occult ischemia in an asymptomatic population at high risk for premature coronary heart disease (CHD).

METHODS AND RESULTS

One hundred fifty-two siblings of persons with premature CHD underwent mental stress testing. Exercise thallium tomography and 24-hour Holter monitoring were also performed. Hemodynamic changes were monitored during both stressors. Siblings positive for exercise-induced ischemia were offered cardiac catheterization. During mental stress, siblings with an abnormal exercise ECG and/or thallium scan (n=15) had greater maximal increases in systolic blood pressure (SBP, P=.0004) and diastolic blood pressure (DBP, P=.05) and had greater heart rate variability in the normalized low frequency domain of an analysis of Holter monitor recordings, compared with siblings without exercise-induced ischemia. Coronary arteriography confirmed coronary atherosclerosis in 85% of siblings with exercise-induced ischemia. Regression analyses showed that occult ischemia during exercise was a strong independent predictor of maximal change in SBP and DBP during mental stress. A multivariate logistic model demonstrated that siblings with exercise-induced occult ischemia were 21 times more likely to be "hot" responders (top quartile of change in SBP and DBP) during mental stress.

CONCLUSIONS

An exaggerated cardiovascular response to mental stress is associated with exercise-induced myocardial ischemia in persons with preclinical coronary heart disease.

Insulin resistance in cardiac syndrome X and variant angina: influence of physical capacity and circulating lipids

Insulin resistance has been demonstrated in patients with angina pectoris irrespective of detectable atherosclerosis at coronary angiograms. We compared insulin sensitivity, lipid profiles, and exercise capacity in 20 patients with syndrome X, 15 patients with variant angina, and 20 healthy controls to investigate whether the presentation of the insulin resistance syndrome differs between the two patient groups with disparate vascular abnormalities. All patients had angiographically normal coronary arteries. Maximal oxygen uptake (VO2 max) was determined at bicycle exercise testing. Insulin sensitivity (SI) was assessed by the minimal model analysis of the intravenous glucose tolerance test. Patients with variant angina had significantly lower VO2 max than controls (mean +/- SE, 25.6 +/- 1.5 vs 30.6 +/- 1.4 ml x kg-1 x min-1, p < 0.05), whereas VO2 max in patients with syndrome X was intermediate (27.1 +/- 1.3 ml x kg-1 x min-1). Compared with controls, patients with syndrome X and variant angina had reduced insulin sensitivity (controls, 1.47 +/- 0.16 10(-4) x min-1/per pmol/L vs syndrome X, 0.86 +/- 0.11 10(-4) x min-1 per pmol/L and variant angina, 0.96 +/- 0.15 x 10(-4) x min-1 per pmol/L; analysis of variance, p < 0.05). Only patients with syndrome X exhibited fasting hyperinsulinemia. Patients with syndrome X also had higher fasting concentrations of triglycerides and total cholesterol and lower concentrations of high-density lipoprotein cholesterol than controls. When adjusting SI for variances of VO2 max, differences in SI vanished between controls and patients with variant angina but not between controls and patients with syndrome X. Thus syndrome X and variant angina are both associated with insulin resistance, but lipid abnormalities are only prominent in patients with syndrome X. A variable expression in terms of concomitant disturbances of lipid profiles and disparate influences of physical capacity suggests different underlying mechanisms.

The appearance of gallop rhythm after exercise stress testing

BACKGROUND AND HYPOTHESIS

Although it is generally assumed that the appearance of an early diastolic gallop, or third heart sound, appearing immediately after exercise during treadmill stress testing, indicates the presence of serious myocardial disease, no systemically collected data are available to test this hypothesis.

METHODS

The author performed auscultation on 3,679 patients undergoing routine treadmill testing together with thallium-201 perfusion scans. Exercise-induced diastolic sounds were related to the available clinical information and electrocardiographic and nuclear test results. These findings were compared with those of 665 randomly selected patients undergoing stress testing in whom such sounds were absent.

RESULTS

A total of 165 patients had audible third heart sounds (Group 1). In comparison with those patients lacking such sounds (Group 2), there was a considerably greater prevalence of myocardial scarring (68.5 vs. 26.9%), abnormal lung uptake of thallium (40 vs. 12.8%), diabetes mellitus (20.6 vs. 6.2%), and left bundle-branch block on the resting electrocardiogram (ECG) (15.1 vs. 1.2%). In addition, 65 patients (39.3%) had dilatation of the left ventricle after exercise; 31 (18.8%) of these were also dilated at rest, but only 2 (1.2%) had a drop in blood pressure during stress. In those individuals also subjected to nuclear ventriculography, the average resting ejection fraction was 35%. Estimated exercise capacity was generally reduced in Group 1 (average peak of 6.6 METs), but 29 (17.6%) exceeded 9 METs. Sensitivity and specificity of electrocardiographic ST depression were relatively poor in the detection of perfusion defects within this group (36 and 62%, respectively). Of the 39 patients in Group 1 with a normal resting ECG, 19 (48.7%) had scar (usually posterior or lateral) on nuclear scans. In an additional 10 of this group, nuclear evidence of ischemia (often extensive) was found.

CONCLUSIONS

An early or mid-diastolic gallop sound developing after exercise virtually always signifies myocardial disease with reduced myocardial function. Common associated findings are prior infarction (with or without associated ischemia), diabetes, and left bundle-branch block. When found in the presence of a normal resting ECG, this sound commonly signals the presence an occult left ventricular scar and, less commonly, extensive myocardial ischemia. In those patients manifesting such sounds, electrocardiographic ST changes in response to exercise appear limited in the detection of coronary ischemia.

Exercise intolerance in patients with chronic heart failure

Patients with chronic heart failure (CHF) experience significant morbidity because of dyspnea and fatigue with activities of daily living. Although central hemodynamic abnormalities are the hallmark of this disorder, investigators have not shown a relationship between left ventricular ejection fraction or exercise pulmonary capillary wedge pressure and exercise intolerance in this disorder. Recent studies have focused on the contributions of pulmonary abnormalities and alterations in peripheral vasomotor control and skeletal muscle in exercise intolerance in this disorder. Early anaerobic metabolism occurs in patients with CHF and appears to be caused by a combination of reduced skeletal muscle blood flow and decreased aerobic enzyme content in skeletal muscle. Atrophy in skeletal muscle and alterations in skeletal muscle fiber typing are accompanied by alterations in contractile function in skeletal muscle. These results suggest that exercise intolerance in patients with CHF is multifactorial, and that research efforts must consider central hemodynamic abnormalities, pulmonary abnormalities, and alterations in peripheral blood flow and skeletal muscle biochemistry and histology. The present review will explore current research in this area and develop a model for understanding exercise intolerance in CHF.

Effect of spontaneous alcohol intake on heart rate and dietary intake of free-living women

Moderate alcohol consumers obtain excess calories from alcohol and these additional calories do not result in weight gain. This study examined the contribution of alcohol to the total caloric intakes and expenditures of light to moderate alcohol consumers and compared the data to soda drinkers. Physical activity levels were measured by employing continuous heart rate monitoring for a 6-day normal phase and a 6-day abstinence phase. The normal food intake of both groups was recorded in diet diaries. Subjects' overall intake of food energy during the alcohol week was significantly higher than during any of the other three phases (an excess of 241 kcal/day). This study suggests that excess alcohol calories are compensated by an increase in energy expenditure, as evidenced indirectly by increased heart rates occurring between the hours of 2300 and 0700 h, increased self-reported nightly restlessness, increased wake time, and exercise.