Symptom-limited Maximal Exercise Test Research Articles

Variable prognostic value of blood pressure response to exercise

AimThe aim of this study was to evaluate the impact of patient background including exercise capacity on the relationship between the blood pressure (BP) response to exercise and prognosis in patients visiting a cardiovascular hospital. MethodsA total of 2134 patients who were referred to our hospital underwent symptom-limited maximal cardiopulmonary exercise testing, and were followed through medical records and mail. The BP response to exercise was defined as the difference between peak and rest systolic BP. The end point was set as cardiovascular events including cardiovascular death, acute coronary syndrome, hospitalization for heart failure, and cerebral infarction. ResultsDuring a median follow-up period of 3 years, 179 (8%) patients reached the end point (2.5%/year). Multivariate analysis showed that BP response was independently and negatively associated with the occurrence of the end point. This prognostic significance of BP response was consistent regardless of left ventricular ejection fraction, renal function, presence of heart failure symptoms, the presence of organic heart disease, and hypertension. However, peak VO2 showed a significant interaction with the effects of BP response on the end point, suggesting that the prognostic value of BP response was limited in patients with preserved exercise capacity. ConclusionsThe role of BP response to exercise as the predictor depends on exercise capacity of each patient.

Assessment of heart rate response to exercise and recovery during treadmill testing in arsenic-exposed workers.

Arsenic exposure is associated with various cardiovascular diseases. The aim of the present study was to assess cardiac autonomic function via heart rate response to exercise and recovery period of treadmill testing in arsenic-exposed workers. Sixty-five (65) occupationally arsenic-exposed workers and 35 healthy controls were enrolled. Blood and urinary arsenic levels were analyzed and symptom limited maximal treadmill exercise test were performed. Chronotropic response to exercise including age-predicted maximal heart rate (APMHR), heart rate reserve (HRreserve ), age-predicted HRreserve (APHRreserve ) and adjusted HRreserve and 1st-, 2nd-and 3rd-min heart rate recovery (HRR) indices were calculated. Baseline clinical and echocardiographic parameters, exercise test duration, resting and maximal heart rate, peak exercise capacity, HRreserve , APMHR, APHRreserve , and adjusted HRreserve were found to be similar between groups. HRR1 (22.0±4.3 vs. 24.3±3.1bpm, p=.003) and HRR2 (43.2±6.2 vs. 46.7±6.4bpm, p=.012) were significantly lower in arsenic-exposed workers compared to controls. Blood and urinary arsenic levels negatively correlated with HRR1 (r=-.477, p<.001 and r=-.438, p<.001, respectively) and HRR2 (r=-.507, p<.001 and r=-.412, p<.001 respectively). Arsenic-exposed workers had lower HRR indices than normal subjects but chronotropic response were similar. Cardiac autonomic dysregulation may be one of the cardiovascular consequences of arsenic exposure.

Reevaluating Modality of Cardiopulmonary Exercise Testing in Patients with Heart Failure and Resynchronization Therapy: Relevance of Heart Rate-Adaptive Pacing

BackgroundChronotropic incompetence (CI) in heart failure (HF) patients with cardiac resynchronization therapy (CRT) and activity sensors may vary according to exercise modality. We hypothesized that chronotropic response and exercise capacity differ when HF patients with CRT and heart rate (HR) adaptive pacing are exercised on cycloergometer versus treadmill. Methods and ResultsThis is a crossover study in which stable HF patients with CRT and HR-adaptive pacing triggered by activity sensors underwent maximal symptom-limited cardiopulmonary exercise testing on both a cycloergometer and treadmill. Adjusted percent of HR reserve (%HRR) was calculated as HRR/age-predicted HRR. CI was defined as ≤62% of age-predicted HRR. Among 16 patients (59 ± 10 years, ejection fraction 27 ± 12%, 87% on beta-blockers), prevalence of CI was high irrespective of exercise modality (87.5% on cycloergometer vs 62.5% on treadmill; P = .12). Chronotropic responses were better on the treadmill; %HRR was higher on a treadmill vs cycloergometer (61 ± 26% vs 22 ± 31%; P = .003). Peak oxygen consumption was increased by 24% on a treadmill vs cycloergometer (15.8 vs 12.7 mL/kg/min; P < .0001). ConclusionsIn HF patients with CRT and HR-adaptive pacing, treadmill cardiopulmonary exercise testing enhances chronotropic response, HRR, and peak oxygen consumption compared with a cycloergometer. These findings may have implications in exercise prescription and thresholds for advanced therapies such as heart transplantation and ventricular assist devices.

Changes in cardiorespiratory fitness predict incident hypertension: A population-based long-term study.

We investigated whether long-term changes in cardiorespiratory fitness (CRF) predict the risk of incident hypertension, independent of risk factors, in initially normotensive men. This prospective study from the Kuopio Ischemic Heart Disease Study included 431 male participants without hypertension who underwent symptom-limited maximal cardiopulmonary exercise testing at baseline and during a second examination, 11-years later, who were re-evaluated for hypertension at 20-year follow-up. Changes in CRF (%) were calculated as the difference in directly measured maximal oxygen uptake (VO2max ) between the baseline and second examination, and classified into decreasing tertiles as percentages. Hypertension was defined as systolic and/or diastolic blood pressure ≥140/90 mmHg or hypertension that required antihypertensive medication as diagnosed by a physician. During a 10-year follow-up after the second examination, 165 men (38%) developed hypertension. Men who demonstrated the largest decline in CRF between evaluations (-62.1% to -20.2%) had a 4.33-fold (95% CI 2.32-8.07, P < .001) risk of incident hypertension compared to men with the smallest decrease or improvement in CRF (-8.8% to 82.0%), after adjusting for age, follow-up duration, alcohol consumption, cigarette smoking, serum low and high density lipoprotein cholesterol, body mass index, daily energy expenditure (kcal) via physical activity, glomerular filtration rate, and baseline systolic blood pressure and VO2max . The present findings indicate that more marked decreases in measured CRF over time are independently associated with the risk of incident hypertension in men, suggesting that CRF should be considered a causal risk factor to predict future hypertension.

Correlation between VE/VCO2slope and echocardiographic derived systolic pulmonary artery pressure in patients with chronic heart failure

To explore the relationship between ventilator efficiency of cardiopulmonary exercising test (the slope of the relation between ventilation and carbon dioxide production, VE/VCO(2)slope) and systolic pulmonary artery pressure (sPAP) measured by echocardiography in patients with chronic heart failure (HF). Data from 86 HF patients who were treated in Fuwai Hospital between December 2012 and July 2014 and performed the symptom limited maximal cardiopulmonary exercise test (CPET) and echocardiography were retrospectively analyzed.H F patients were divided into 3 groups (mild, moderate and severe) according to the maximum oxygenconsumption (peakVO(2)). There is a significant linear correlation between VE/VCO(2)slope and sPAP (r=0.260, P=0.016). Using VE/VCO(2)slope>34.2 as a cutoff value to predict patients with sPAP>50 mmHg (1 mmHg=0.133 kPa) yielded a sensitivity of 70.0% and a specificity of 64.3%. The degree of the linear correlation between VE/VCO(2)slope and sPAP is stronger in mild HF patients (peakVO(2)>14 ml·kg(-1)·min(-1), r=0.686, P<0.001). Using VE/VCO(2) slope>34.2 as a cutoff value to predict sPAP>50 mmHg in mild HF patients, the sensitivity is 71.4% and the specificity is 93.8%. There is a significant linear correlation between VE/VCO(2)slope and sPAP in HF patients. VE/VCO(2)slope>34.2 is linked with a high possibility of sPAP>50 mmHg in HF patients, especially for patients with mild HF. Invasive hemodynamic examination and impact of special therapy are warranted in future studies to veryfy present results.

Prescribing and Regulating Exercise with RPE after Heart Transplant: A Pilot Study.

The objective of this study is to analyze the use of the 6-20 RPE scale for prescribing and self-regulating heated water-based exercise (HEx) and land-based exercise (LEx) in heart transplant recipients. Fifteen (five females) clinically stable heart transplant recipients (time since surgery = 4.0 ± 2.5 yr) age 46.7 ± 11.8 yr underwent a symptom-limited maximal graded exercise test on a treadmill to determine their HR at anaerobic threshold (HRAT), respiratory compensation point (HRRCP), and maximal effort (HRmax). After a week, patients were randomized to perform 30 min of both HEx (walking inside the pool) and LEx (treadmill walking) sessions at a pace between 11 and 13 on the 6-20 RPE scale and had their HR measured every 4 min. The interval between sessions was 48-72 h. No significant differences between sessions were found in the average HR during HEx and LEx. Patients showed a delay in HR increase during both interventions, with the stabilization beginning after 8 min of exercise. Exercise HR was maintained between the HRAT and HRRCP (in the aerobic exercise training zone) for the most part of both HEx (72% of HR measurements) and LEx (66% of HR measurements). Only a few HR measurements stayed below HRAT (HEx = 9%, LEx = 13%) or above HRRCP (HEx = 19%, LEx = 21%) during both exercise sessions. Exercise HR was maintained in the aerobic exercise training zone (between HRAT and HRRCP) for the most part of both sessions, suggesting that the 6-20 RPE scale may be an efficient tool for prescribing and self-regulating HEx and LEx in heart transplant recipients.

Cardiorespiratory Fitness And Brain Structures - The Finger Study

Executive processes and frontal cortical regions supporting them show notable changes with age. Structural magnetic resonance imaging studies have revealed a positive relationship between cardiorespiratory fitness (CRF) and brain volume in several cortical regions and in the medial temporal lobe. However, previous studies have been mainly focused on cognitively intact subjects. Furthermore, no sex differences have been reported. PURPOSE: To investigate whether CRF is associated with total gray matter (GM) and white matter volumes as well as medial temporal lobe and striatum volumes in a population-based sample of subjects with increased risk of Alzheimer’s disease. We also examined the role of sex in the association of CRF with brain volumes. METHODS: We used baseline data from the FINGER study. Participants had elevated CAIDE Dementia Risk Score. Inclusion criteria was set to select persons with cognitive performance at the mean level or slightly lower than expected for age according to Finnish population norms. Our substudy included 68 randomly selected individuals (39 men and 29 women) with 61-75 years of age. Cardiorespiratory fitness was assessed as peak oxygen consumption (VO2peak, ml/kg/min) measured directly in a symptom-limited maximal exercise test on cycle ergometer. Structural imaging was performed using a 1.5-Tesla scanner. Volumetric segmentation was performed with the Freesurfer automated image analysis suite. All brain volumes were expressed as ratios after normalizing by the total intracranial volume. RESULTS: In whole group, VO2peak was associated with left caudate volume (β=0.32, p=0.03), cortical GM volume (β=0.37, p=0.01) and total GM volume (β=0.40, p=0.007). In men, VO2peak was associated with cortical GM volume (β=0.61, p=0.001) and total GM volume (β=0.59, p=0.001). In women, VO2peak was associated with the left caudate volume (β=0.49, p=0.04). Peak oxygen consumption accounted for 23 and 1 percent of total variance of cortical GM volume in men and women, respectively. Likewise, VO2peak accounted for 25 and 4 percent of total variance of total GM volume in men and women, respectively. CONCLUSION: Cardiorespiratory fitness is associated with cortical and total gray matter volumes in elderly men with increased risk for Alzheimer’s disease.

Is It Dextrocardia or Not - FBS College Football Player

HISTORY: A 19 year old African American male underwent a physical examination for football participation at a FBS school. He is 190.5 cm tall, weighs 143.2 kilograms. He has a history of left foot 5th metatarsal shaft fracture. Routine laboratory blood analysis confirmed negative sickle cell trait. No observable symptomology was noted. PHYSICAL EXAM: Physical examination revealed a resting blood pressure of 130/80 and a standing pre-exercise pressure of 118/76. A 12-lead ECG was obtained from the subject. Examination of the ECG yielded a heart rate of 79, no discernable rhythm disturbances, Right Axis Deviation (approximately 150 degrees), a PR-interval of .16 seconds, a QRS interval of .08 seconds, a QT interval of .36 seconds, no signs of left or right atrial enlargement, non-specific ST&T wave changes, and poor R wave progression. This, in conjunction with Right Axis Deviation, cast suspicion on the presence of Dextrocardia. DIFFERENTIAL DIAGNOSIS: 1. Abnormal ECG 2. Dextrocardia TESTS AND RESULTS: The patient underwent symptom limited maximal graded exercise testing; achieving a peak heart rate of 200, a peak blood pressure of 202/68 and a maximum oxygen consumption of 33.3 ml/kg body weight/minute. No ECG abnormalities were noted during testing. The patient subsequently was referred to the student health services radiology department for a two view chest x-ray. A cardiologist performed a resting ECG in addition to an echocardiogram. The team physician also performed a cardiac MRI. The chest x-ray, echocardiogram, and cardiac MRI all confirmed Dextrocardia in the patient. FINAL /WORKING DIAGNOSIS: Abnormal ECG, Dextrocardia TREATMENT AND OUTCOMES: The patient, given that all testing confirmed normal cardiovascular function, was cleared for all athletic activities without restrictions. No additional treatments were ordered.

Effect of duration of data averaging interval on reported peak VO2 in patients with heart failure

AimTo describe the effect of the duration of the data averaging interval on the calculated peak oxygen uptake (VO2) reported from a symptom-limited maximal exercise test in patients with heart failure. MethodsMaximal exercise test results from 275 patients diagnosed with stable heart failure due to left ventricular systolic dysfunction (ejection fraction<45%; age: 45–75years; peak VO2: 8.0–20.0mL/kg/min), were examined. Sampling rates of 10, 20, 30 and 60s were used to calculate peak VO2, which was identified as the highest interval value that occurred during the final minute of exercise or the first interval in immediate recovery. ResultsMean peak VO2 (mL/kg/min) across the four sampling periods was as follows: 14.0±3.0 (10s), 13.7±3.0 (20s), 13.5±3.0 (30s) and 13.2±2.9 (60s) and there was a significant reduction with increasing averaging duration (p<0.0001). Peak VO2 was significantly different between the 10s and 60s sampling times (p<0.0001). Peak respiratory exchange ratio (RER) was also significantly different between 10 and 60s sampling rates (p<0.0001). Sub-analyses showed peak VO2 values in those people achieving RER>1.05 to be +0.8±0.7mL/kg/min higher than those who had not achieved RER values>1.05; similar findings, +0.8±0.7mL/kg/min, were seen in those patients achieving RER>1.10 versus those who did not. ConclusionsSampling rate method has a significant effect on calculated peak VO2 and RER. We suggest that laboratories standardize their sampling rate method to ensure consistency.

Guiding the failing heart to exercise.

Guiding the failing heart to exercise.

Selected Abstracts From Recent Publications in Cardiopulmonary Disease Prevention and Rehabilitation

Selected Abstracts From Recent Publications in Cardiopulmonary Disease Prevention and Rehabilitation

Supervised Phase II Cardiac Exercise Therapy Shortens the Recovery of Exercise Capacity in Patients with Acute Myocardial Infarction.

[Purpose] To investigate the effects of Phase II cardiac exercise therapy (CET) on exercise capacity and changes in coronary risk factors (CRFs) of patients with acute myocardial infarction (AMI). [Subjects] Thirty male subjects with AMI were divided into an experimental group (EG) and a control group (CG). Another 30 age-matched subjects with patent coronary arteries served as a normal-control group (NCG). [Methods] Subjects in EG (n=20) trained using a stationary bicycle for 30 min at their target heart rate twice a week for 8 weeks. Exercise capacity was defined as the maximal metabolic equivalents (METs) that subjects reached during the symptom-limited maximal exercise test. HR, BP and RPP were recorded. Subjects in EG and CG received exercise tests and screening for CRFs at the beginning of, end of, and 3 months after Phase II CET, while subjects in NCG participated only in the 1st test. [Results] METs of CG did not improve until the 3rd test, while RPP at the 2nd test showed a significant increase. However, EG showed increased METs at the 2nd test without increase of RPP, and increased their high density lipoprotein cholesterol (HDL-C) during the follow-up period between the 2nd and 3rd tests. [Conclusion] Phase II CET shortens the recovery time of exercise capacity, helps to maintain the gained exercise capacity and increases HDL-C in phase III.

Associations of cardiorespiratory fitness, physical activity, and obesity with metabolic syndrome in Hong Kong Chinese midlife women.

BackgroundSeveral studies have simultaneously examined physical activity (PA) and cardiorespiratory fitness (CRF) with metabolic syndrome (MS). However, the independent roles of both PA and CRF with MS are less firmly established. The combined contributions of PA and CRF with MS are less studied, particularly among Chinese women. There is uncertainty over the extent to which metabolically healthy but overweight/obese individuals have a higher CRF level.MethodsThe sample included 184 Chinese women aged 55 to 69 years with available metabolic data and lifestyle factors. PA was assessed by self-reported questionnaire; CRF was assessed by maximal oxygen consumption (VO2max) during a symptom-limited maximal exercise test on a cycle ergometer. Metabolically healthy/abnormal was defined on the basis of absence or presence of MS. Overweight was defined as a body mass index (BMI) of ≥ 23 kg/m2 and obese was defined as a BMI of ≥ 25 kg/m2.ResultsThe prevalence of MS was 21.7%. PA was inversely associated with the prevalence of MS after adjustment for age, BMI, and dietary total calories intake, but the association was eliminated after further adjustment for CRF. CRF was inversely associated with the prevalence of MS independent of age, BMI, and dietary total calories intake, and the association remained significant after further adjustment for PA. In the PA and CRF combined analysis, compared with those in the lowest tertile of PA (inactive) and lowest tertile of CRF (unfit), the OR (95%CI) of having MS was 0.31 (0.09–1.06) for subjects in the higher tertiles (2nd–3rd) of PA (active) but were unfit, 0.23 (0.06–0.88) for subjects who were inactive but in the higher tertiles (2nd–3rd) of CRF (fit), and 0.14 (0.04–0.45) for subjects who were active and fit. Metabolically healthy but overweight/obese subjects had a higher CRF level than their metabolically abnormal and overweight/obese peers. However, the difference did not reach statistically significance.ConclusionsCRF has greater association with the prevalence of MS compared with PA in Chinese midlife women. The interrelationships between CRF, obesity, and MS needs further study.

Circulating microRNA-126 increases after different forms of endurance exercise in healthy adults

MicroRNAs (miRNAs) are small non-coding molecules regulating gene expression. Recently circulating miRNAs could be detected in the plasma, serving as novel biomarkers. Different forms of exercise mobilize progenitor cells from the bone marrow, helping in tissue repair. Data of different forms of exercise on endothelial cell damage are lacking. The aim of the study was to evaluate the impact of different exercise modalities on the plasma concentration of miRNA-126, as a marker for endothelial damage. The plasma concentration of miRNA-126 and miRNA-133 (marker for muscle damage) was assessed by qRT-PCR analysis in plasma samples from healthy individuals performing one of the following exercise tests: (1) maximal symptom-limited exercise test, (2) bicycling for 4 h, (3) running a marathon, and (4) resistance exercise. A maximal symptom-limited exercise test resulted in a significant increase of circulating miRNA-126 at maximum power (2.1-fold versus begin), whereas the concentration of miRNA-133 remained unchanged. In line, four hours of cycling increased plasma concentration of miRNA-126 with a maximum 30 minutes after begin (4.6-fold versus begin) without an impact on miRNA-133 concentration. Finishing a marathon race resulted in an increase of miRNA-126 and miRNA-133. In contrast, eccentric resistance training led to an isolated increase of miRNA-133 level (2.1-fold versus begin) with unchanged miRNA-126. Different endurance exercise protocols lead to damage of the endothelial cell layer as evident by an increase in miRNA-126. On the other hand, resistance exercise has no impact on the endothelial cells, but leads to a destruction of muscular cells.

Development and Safety of an Exercise Testing Protocol for Patients with an Implanted Cardioverter Defibrillator for Primary or Secondary Indication

Performing exercise tests in patients with an implantable cardioverter defibrillator (ICD) presents specific challenges because of susceptibility to ventricular arrhythmias during maximal levels of exertion. The purpose of this paper is to outline the exercise testing protocol from the Anti-Arrhythmic Effects of Exercise after an ICD trial and to report baseline test results and safety outcomes using the protocol. Maximal cardiopulmonary exercise testing was performed to assess levels of physical fitness as part of a randomized trial of walking exercise in patients with ICDs. Subjects were randomized after baseline testing to aerobic exercise plus usual care or usual care alone. A modified Balke treadmill exercise test was used and specific ICD programming procedures were implemented to avoid unnecessary shocks, which included programming off ventricular tachycardia (VT) therapies during testing. To date, 161 baseline tests have been performed. One ventricular fibrillation (VF) cardiac arrest occurred following completion of an exercise test and three tests were stopped by the investigators due to nonsustained ventricular tachycardia. Eleven subjects were not able to achieve maximum exercise, defined as reaching an anaerobic threshold (AT) at baseline testing. There have been no deaths as a result of exercise testing. Symptom-limited maximal exercise testing can be performed safely and effectively in patients with ICDs for both primary and secondary prevention indications. Specific strategies for ICD programming and preparation for treating ventricular arrhythmias needs to be in place before exercise testing is performed.

The Obesity Paradox, Cardiorespiratory Fitness, and Coronary Heart Disease

ObjectiveTo investigate associations of cardiorespiratory fitness (CRF) and different measures of adiposity with cardiovascular disease (CVD) and all-cause mortality in men with known or suspected coronary heart disease (CHD). Patients and MethodsWe analyzed data from 9563 men (mean age, 47.4 years) with documented or suspected CHD in the Aerobics Center Longitudinal Study (August 13, 1977, to December 30, 2002) using baseline body mass index (BMI) and CRF (quantified as the duration of a symptom-limited maximal treadmill exercise test). Waist circumference (WC) and percent body fat (BF) were measured using standard procedures. ResultsThere were 733 deaths (348 of CVD) during a mean follow-up of 13.4 years. After adjustment for age, examination year, and multiple baseline risk factors, men with low fitness had a higher risk of all-cause mortality in the BMI categories of normal weight (hazard ratio [HR], 1.60; 95% confidence interval [CI], 1.24-2.05), obese class I (HR, 1.38; 95% CI, 1.04-1.82), and obese class II/III (HR, 2.43; 95% CI, 1.55-3.80) but not overweight (HR, 1.09; 95% CI, 0.88-1.36) compared with the normal-weight and high-fitness reference group. We observed a similar pattern for WC and percent BF tertiles and for CVD mortality. Among men with high fitness, there were no significant differences in CVD and all-cause mortality risk across BMI, WC, and percent BF categories. ConclusionIn men with documented or suspected CHD, CRF greatly modifies the relation of adiposity to mortality. Using adiposity to assess mortality risk in patients with CHD may be misleading unless fitness is considered.

Oxygen Uptake Efficiency Slope, Aerobic Fitness, and V˙ E –V˙CO2 Slope in Heart Failure

The oxygen uptake efficiency slope (OUES) is a promising submaximal index of exercise capacity, but its relationships to other indices characterizing physical fitness and ventilatory efficiency have not been widely investigated in heart failure. Sixty-three male patients with stable chronic heart failure performed a symptom-limited maximal exercise test on a cycle ergometer. Nineteen of them performed two exercise tests, 6 months apart. The peak oxygen uptake (VO2peak), ventilatory anaerobic threshold (VAT), OUES using all data (OUES(100)) or only the data up to the point where the RER was 1 (OUE(SRER1)), and V(E)-VCO2 slope were determined. OUES(100), OUE(SRER1), and VAT were significantly correlated with measured VO2peak (r = 0.883, r = 0.814, and r = 0.877, respectively). The Bland-Altman limits of agreement between measured VO2peak and the values predicted by calculation from OUES(100), OUE(SRER1), and VAT were ±0.46, ±0.57, and ±0.48 L·min(-1), respectively. The variation in OUE(SRER1) between the first and second tests in the 19 patients was significantly related to the variation in VO2peak but not to the variation in the V(E)-VCO2 slope. To predict VO2peak in patients with chronic heart failure, the index OUE(SRER1) is not better than the VAT. This, however, does not question the theoretical interest of its calculation because it may provide additional information on the oxygen uptake limitation steps.

Insulin resistance and exercise tolerance in heart failure patients: linkage to coronary flow reserve and peripheral vascular function

BackgroundInsulin resistance has been linked to exercise intolerance in heart failure patients. The aim of this study was to assess the potential role of coronary flow reserve (CFR), endothelial function and arterial stiffness in explaining this linkage.Methods39 patients with LVEF < 35% (median LV ejection fraction (LVEF) 31 (interquartile range (IQ) 26–34), 23/39 of ischemic origin) underwent echocardiography with measurement of CFR. Peak coronary flow velocity (CFV) was measured in the LAD and coronary flow reserve was calculated as the ratio between CFV at rest and during a 2 minutes adenosine infusion. All patients performed a maximal symptom limited exercise test with measurement of peak oxygen uptake (VO2peak), digital measurement of endothelial function and arterial stiffness (augmentation index), dual X-ray absorptiometry scan (DEXA) for body composition and insulin sensitivity by a 2 hr hyperinsulinemic (40 mU/min/m2) isoglycemic clamp.ResultsFat free mass adjusted insulin sensitivity was significantly correlated to VO2peak (r = 0.43, p = 0.007). Median CFR was 1.77 (IQ 1.26-2.42) and was correlated to insulin sensitivity (r 0.43, p = 0.008). CFR (r = 0.48, p = 0.002), and arterial stiffness (r = −0.35, p = 0.04) were correlated to VO2peak whereas endothelial function and LVEF were not (all p > 0.15). In multivariable linear regression adjusting for age, CFR remained independently associated with VO2peak (standardized coefficient (SC) 1.98, p = 0.05) whereas insulin sensitivity (SC 1.75, p = 0.09) and arterial stiffness (SC −1.17, p = 0.29) were no longer associated with VO2peak.ConclusionsThe study confirms that insulin resistance is associated with exercise intolerance in heart failure patients and suggests that this is partly through reduced CFR. This is the first study to our knowledge that shows an association between CFR and exercise capacity in heart failure patients and links the relationship between insulin resistance and exercise capacity to CFR.

Age-Related Decline in Cardiorespiratory Fitness among Career Firefighters: Modification by Physical Activity and Adiposity

Firefighting is a very hazardous occupation, and strenuous fire duties require high levels of physical fitness. In the general adult population, cardiorespiratory fitness (CRF) declines with aging. We sought to investigate the effect of increasing age on CRF in male career firefighters as well as the modifying effects of physical activity and adiposity. We cross-sectionally examined 804 male career firefighters from two Midwestern states. CRF was determined from symptom-limited maximal treadmill exercise testing in metabolic equivalents (METS) following the Bruce protocol. Physical activity self-reports were extracted from responses to a health and lifestyle questionnaire. We found as expected that CRF declines with advancing age; however, the decline is greatly attenuated among leaner firefighters who report more physical activity. Furthermore, in a linear regression model including age, BMI, and variables describing physical activity behaviors, we could predict CRF (R2 = 0.6286). The total weekly duration of aerobic exercise as well as the duration of weight lifting sessions both had significant impacts on age-related decline. We conclude that firefighters are more likely to maintain the high levels of CRF needed to safely perform their duties if they engage in frequent exercise and maintain healthy weights.

Peak Oxygen Uptake Correlates With Survival Without Clinical Deterioration in Ambulatory Children With Dilated Cardiomyopathy

Children stable at home with dilated cardiomyopathy remain at risk of death; there is evidence of survival benefit for transplantation out to 4 years postoperatively. The limited supply of donor organs makes risk stratification imperative, but although cardiopulmonary exercise test is well established as a powerful tool in adults with heart failure, no published studies have linked oxygen uptake to prognosis in children. Between 2001 and 2009, using cardiopulmonary exercise test and echocardiography, we studied 82 children (mean age, 13.5±2.3 years) with dilated cardiomyopathy. All were ambulatory, outpatients, and >120 cm in height. All children completed a symptom-limited maximal exercise test. Resting left ventricular shortening fraction was 20±9%; peak heart rate was 87±13% of predicted; peak oxygen uptake (VO(2)) was 67±22% of predicted; and ventilatory efficiency was 32±8. Follow-up was available for 100% of the children, and was a mean of 32.3±7.5 months. Eighteen patients reached the defined clinical end point of death or listing for urgent heart transplantation. On univariate analysis, left ventricular shortening fraction, peak heart rate, peak VO(2), peak systolic blood pressure, and ventilatory efficiency were all associated with adverse outcome. On multivariable Cox analysis, only peak VO(2) (P=0.003) was associated with the study end point. Patients with a peak VO(2) ≤62% of predicted had a higher 24-month event rate (50.6% versus 4.4%; hazard ratio, 10.78). We have demonstrated that a cardiopulmonary exercise test is feasible in ambulatory children with dilated cardiomyopathy who are >120 cm height and for the first time have linked peak VO(2) with outcome in children.