Dissociation of local and global skeletal muscle oxygen transport metrics in type 2 diabetes

AIMS

Exercise capacity is impaired in type 2 diabetes, and this impairment predicts excess morbidity and mortality. This defect appears to involve excess skeletal muscle deoxygenation, but the underlying mechanisms remain unclear. We hypothesized that reduced blood flow, reduced local recruitment of blood volume/hematocrit, or both contribute to excess skeletal muscle deoxygenation in type 2 diabetes.

METHODS

In patients with (n=23) and without (n=18) type 2 diabetes, we recorded maximal reactive hyperemic leg blood flow, peak oxygen utilization during cycling ergometer exercise (VO_2peak), and near-infrared spectroscopy-derived measures of exercise-induced changes in skeletal muscle oxygenation and blood volume/hematocrit.

RESULTS

We observed a significant increase (p<0.05) in skeletal muscle deoxygenation in type 2 diabetes despite similar blood flow and recruitment of local blood volume/hematocrit. Within the control group skeletal muscle deoxygenation, local recruitment of microvascular blood volume/hematocrit, blood flow, and VO_2peak are all mutually correlated. None of these correlations were preserved in type 2 diabetes.

CONCLUSIONS

These results suggest that in type 2 diabetes 1) skeletal muscle oxygenation is impaired, 2) this impairment may occur independently of bulk blood flow or local recruitment of blood volume/hematocrit, and 3) local and global metrics of oxygen transport are dissociated.

Leptin is associated with cardiopulmonary fitness independent of body-mass index and insulin sensitivity in adolescents with type 1 diabetes: a brief report from the EMERALD study

Cardiopulmonary fitness is decreased in type 1 diabetes for reasons that are incompletely understood. In this study, leptin was associated with exercise capacity independent of insulin sensitivity (IS) and body mass index (BMI), suggesting that leptin may relate to cardiopulmonary fitness by mechanisms beyond IS and/or obesity.

2016 AHA/ACC Guideline on the Management of Patients With Lower Extremity Peripheral Artery Disease: Executive Summary: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines

Since 1980, the American College of Cardiology (ACC) and American Heart Association (AHA) have translated scientific evidence into clinical practice guidelines with recommendations to improve cardiovascular health. These guidelines, based on systematic methods to evaluate and classify evidence, provide a cornerstone of quality cardiovascular care.

In response to reports from the Institute of Medicine1 ,2 and a mandate to evaluate new knowledge and maintain relevance at the point of care, the ACC/AHA Task Force on Clinical Practice Guidelines (Task Force) modified its methodology.3 –5 The relationships among guidelines, data standards, appropriate use criteria, and performance measures are addressed elsewhere.5

2016 AHA/ACC Guideline on the Management of Patients With Lower Extremity Peripheral Artery Disease: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines

Since 1980, the American College of Cardiology (ACC) and American Heart Association (AHA) have translated scientific evidence into clinical practice guidelines with recommendations to improve cardiovascular health. These guidelines, based on systematic methods to evaluate and classify evidence, provide a cornerstone of quality cardiovascular care.

In response to reports from the Institute of Medicine1 ,2 and a mandate to evaluate new knowledge and maintain relevance at the point of care, the ACC/AHA Task Force on Clinical Practice Guidelines (Task Force) modified its methodology.3 –5 The relationships among guidelines, data standards, appropriate use criteria, and performance measures are addressed elsewhere.5

Exenatide improves diastolic function and attenuates arterial stiffness but does not alter exercise capacity in individuals with type 2 diabetes

BACKGROUND

Exercise is recommended as a cornerstone of treatment for type 2 diabetes mellitus (T2DM), however, it is often poorly adopted by patients. Even in the absence of apparent cardiovascular disease, persons with T2DM have an impaired ability to carry out maximal and submaximal exercise and these impairments are correlated with cardiac and endothelial dysfunction. Glucagon-like pepetide-1 (GLP-1) augments endothelial and cardiac function in T2DM. We hypothesized that administration of a GLP-1 agonist (exenatide) would improve exercise capacity in T2DM.

METHODS AND RESULTS

Twenty-three participants (64±4years; mean±SE) with uncomplicated T2DM were randomized in a double-blinded manner to receive either 10μg BID of exenatide or matching placebo after baseline measurements. Treatment with exenatide did not improve VO_2peak (P=0.1464) or VO₂ kinetics (P=0.2775). Diastolic function, assessed via resting lateral E:E', was improved with administration of exenatide compared with placebo (Placebo Pre: 7.6±1.0 vs. Post: 8.4±1.2 vs. Exenatide Pre: 8.1±0.7 vs. Post: 6.7±0.6; P=0.0127). Additionally, arterial stiffness measured by pulse wave velocity, was reduced with exenatide treatment compared with placebo (Placebo Pre: 10.5±0.8 vs. Post: 11.5±1.1s vs. Exenatide Pre: 11.4±1.8 vs. Post: 10.2±1.4s; P=0.0373). Exenatide treatment did not improve endothelial function (P=0.1793).

CONCLUSIONS

Administration of exenatide improved cardiac function and reduced arterial stiffness, however, these changes were not accompanied by improved functional exercise capacity. In order to realize the benefits of this drug on exercise capacity, combining exenatide with aerobic exercise training in participants with T2DM may be warranted.

Team Mentoring for Interdisciplinary Team Science: Lessons From K12 Scholars and Directors

PURPOSE

Mentoring is critical for academic success. As science transitions to a team science model, team mentoring may have advantages. The goal of this study was to understand the process, benefits, and challenges of team mentoring relating to career development and research.

METHOD

A national survey was conducted of Building Interdisciplinary Research Careers in Women's Health (BIRCWH) program directors-current and former scholars from 27 active National Institutes of Health (NIH)-funded BIRCWH NIH K12 programs-to characterize and understand the value and challenges of the team approach to mentoring. Quantitative data were analyzed descriptively, and qualitative data were analyzed thematically.

RESULTS

Responses were received from 25/27 (93%) program directors, 78/108 (72%) current scholars, and 91/162 (56%) former scholars. Scholars reported that team mentoring was beneficial to their career development (152/169; 90%) and research (148/169; 88%). Reported advantages included a diversity of opinions, expanded networking, development of stronger study designs, and modeling of different career paths. Challenges included scheduling and managing conflicting opinions. Advice by directors offered to junior faculty entering team mentoring included the following: not to be intimidated by senior mentors, be willing to navigate conflicting advice, be proactive about scheduling and guiding discussions, have an open mind to different approaches, be explicit about expectations and mentors' roles (including importance of having a primary mentor to help navigate discussions), and meet in person as a team.

CONCLUSIONS

These findings suggest that interdisciplinary/interprofessional team mentoring has many important advantages, but that skills are required to optimally utilize multiple perspectives.

Functional outcomes and quality of life in peripheral arterial disease: current status

This review examines current evidence for baseline functional impairment and changes with therapy in patients with peripheral arterial disease (PAD) - ranging from patients without claudication or critical limb ischemia (CLI) but other exertional leg symptoms (erroneously referred to as asymptomatic in the Fontaine classifi cation system), to patients with claudication and those with CLI. The review points out that the status of functional outcomes research is markedly different in focus and development in the different levels of disease severity - paradoxically less studied in the more severe CLI population than in patients with claudication, for example.

Functional Benefits of Peripheral Vascular Bypass Surgery for Patients with Intermittent Claudication

Many patients with peripheral arterial disease (PAD) undergo peripheral bypass surgery to relieve the symptom of intermittent claudication. However, measurement of graft patency alone, assessed by change in ankle blood pres sure, may not adequately reflect the improvement in functional status following the operation. Fourteen patients with moderately severe intermittent claudica tion were evaluated before and after bypass surgery to assess changes in hemo dynamics (by resting ankle-brachial indices-ABIs), exercise performance (by a graded treadmill protocol), and community-based walking ability (by a ques tionnaire that characterizes self-reported walking speed and distance). Six weeks after surgery, resting ABIs improved in surgical patients (from 0.56 ± 0.09 to 0.93 ± 0.16, P < 0.05). Peak treadmill walking time improved from 6.2 ± 5.9 to 11.8 ± 7.1 min (90%), peak oxygen consumption from 15.5 ± 6.5 to 19.1 ± 8.5 mL/kg/min (23%), and pain-free walking time from 1.5 ± 0.4 to 6.0 5.5 min (290%). Questionnaire scores for walking distance improved by 203% and for walking speed by 130% (all P < 0.05). After twelve weeks, improve ments other than pain-free walking time were maintained. Changes in peak treadmill performance or questionnaire scores were not correlated with the ini tial ABI, changes in ABI six or twelve weeks after surgery, or the type or extent of bypass surgery. The results demonstrate that surgical treatment of PAD, indi cated for the relief of intermittent claudication, improves exercise performance and self-reported community-based walking ability. The change in functional status of the patient is an important outcome of surgery that cannot be pre dicted from routine noninvasive testing alone and should be measured directly.

Youth with type 1 diabetes have worse strain and less pronounced sex differences in early echocardiographic markers of diabetic cardiomyopathy compared to their normoglycemic peers: A RESistance to InSulin in Type 1 ANd Type 2 diabetes (RESISTANT) Study

OBJECTIVE

Diabetic cardiomyopathy is a major cause of morbidity, but limited data are available on early cardiac abnormalities in type 1 diabetes (T1D). We investigated differences in myocardial strain in adolescents with and without T1D. We hypothesized that adolescents with T1D would have worse strain than their normoglycemic peers, which boys would have worse strain than girls, and that strain would correlate with glycemic control and adipokines.

METHODS

We performed fasting laboratory measures and echocardiograms with speckle tracking to evaluate traditional echocardiographic measures in addition to longitudinal (LS) and circumferential (CS) strain, and in adolescents (15±2years) with (19 boys; 22 girls) and without (16 boys; 32 girls) type 1 diabetes.

RESULTS

Compared to controls, adolescents with type 1 diabetes had significantly lower CS (-20.9 vs. -22.7%, p=0.02), but not LS (p=0.83). Boys with T1D had significantly lower LS than girls with T1D (-17.5 vs. -19.7%, p=0.047), adjusted for Tanner stage. The significant sex differences observed in indexed left ventricular mass, left end-diastolic volume, diastolic septal and posterior wall thickness in our controls were lacking in adolescents with T1D.

CONCLUSIONS

Our observations suggest that youth with T1D have worse myocardial strain than normoglycemic peers. In addition, the relatively favorable cardiac profile observed in girls vs. boys in the control group, was attenuated in T1D. These early cardiovascular changes in youth with T1D are concerning and warrant longitudinal and mechanistic studies.

Cardiopulmonary Dysfunction and Adiponectin in Adolescents With Type 2 Diabetes

Background

Myocardial mechanics are altered in adults with obesity and type 2 diabetes (T2D); insulin resistance and adipokines have been implicated as important risk factors for cardiovascular disease, but these relationships are poorly described in adolescents. We hypothesized that obese adolescents and adolescents with T2D would have abnormal cardiac function compared to lean adolescents. In addition, we hypothesized that insulin sensitivity (IS), adiposity, and adipokines would be associated with altered cardiac strain and cardiopulmonary fitness in adolescents with T2D.

Methods and Results

Adolescents (15±2 years) with T2D (n=37), obesity without diabetes (n=41), and lean controls (n=31) of similar age and pubertal stage underwent echocardiography with speckle tracking, assessment of IS by hyperinsulinemic–euglycemic clamp, body composition by dual‐energy x‐ray absorptiometry, peak oxygen consumption (VO₂peak) by cycle ergometry, adiponectin, and leptin. Compared to lean and to obese controls, adolescents with T2D had significantly lower cardiac circumferential strain (CS) (−18.9±4.6 [T2D] versus −21.5±3.5 [obese] versus −22.0±4.2% [lean], P=0.04) and VO₂peak (37.6±7.5 [T2D] versus 43.4±8.2 [obese] versus 47.6±8.6 mL/lean kg/min [lean], P<0.0001). In T2D youth, VO₂peak was associated with CS, and the association remained significant after adjusting for age, sex, and IS (β±SE: −0.73±0.26, P=0.02). Among adolescents with T2D, CS was also associated with adiponectin, longitudinal strain with leptin, and VO₂peak with adiponectin and IS.

Conclusions

Adolescents with T2D had abnormal CS and reduced VO₂peak compared to obese and lean controls, which may represent the earliest evidence of cardiac functional impairment in T2D. Low adiponectin, rather than conventional risk factors and IS, correlated with CS, while both adiponectin and IS related to cardiopulmonary fitness.

Sex differences in the effects of type 2 diabetes on exercise performance

PURPOSE

People with uncomplicated type 2 diabetes (T2D) have impaired peak exercise performance compared with that of their nondiabetic counterparts. This impairment may represent the earliest indication of cardiovascular (CV) abnormalities in T2D. Women with T2D are known to have worse CV outcomes than those in men with T2D. We hypothesized that women with diabetes have a greater exercise impairment than that in men with diabetes compared with that in their nondiabetic counterparts.

METHODS

We studied 15 women (premenopausal) and 14 men with T2D as well as their nondiabetic counterparts (22 women and 13 men). Exercise testing was performed. Additional outcomes included measurements of insulin sensitivity, endothelial function, blood flow, and resting cardiac function.

RESULTS

Men and women with T2D but not controls had impaired insulin sensitivity. Women with T2D had a lower peak oxygen consumption (V˙O2peak) compared with that of nondiabetic women (24%, P < 0.05) than men with diabetes compared with that in nondiabetic men (16%, P < 0.05) (P value between groups < 0.05). The time constants (phase 2) of the V˙O2 kinetic response tended to be slower in men and women with T2D than those in nondiabetic controls (P = 0.08). There were no differences in resting ventricular function by Doppler echocardiography techniques between groups. Women with T2D had significantly lower flow-mediated dilation and blood flow responses to hyperemia than those in nondiabetic women (both P < 0.05), whereas men with T2D had lower flow-mediated dilation but not lower blood flow than those in nondiabetic men.

CONCLUSIONS

Although both men and women with uncomplicated T2D had a lower V˙O2peak, the abnormality in women with T2D compared with that in nondiabetic women was greater than that seen in men. Because V˙O2peak has a strong inverse correlation with mortality, sex disparities observed in exercise capacity among people with T2D suggest a possible rationale for the increased CV morbidity and mortality observed in women compared with those observed in men with uncomplicated T2D.

Method for controlled mitochondrial perturbation during phosphorus MRS in children

Insulin resistance is increasingly prevalent in children and may be related to muscle mitochondrial dysfunction, necessitating development of mitochondrial assessment techniques. Recent studies used phosphorus magnetic resonance spectroscopy (P-MRS), a noninvasive technique appealing for clinical research. P-MRS requires exercise at a precise percentage of maximum volitional contraction (MVC). MVC measurement in children, particularly in those with a disease, is problematic because of variability in perception of effort and motivation. We therefore developed a method to predict MVC using maximal calf muscle cross-sectional area (MCSA) to assure controlled and reproducible muscle metabolic perturbations.

METHODS

Data were collected from 66 sedentary 12- to 20-yr-old participants. Plantarflexion MVC was assessed using an MRI-compatible exercise treadle device. MCSA of the calf muscles were measured from magnetic resonance images. Data from the first 26 participants were used to model the relation between MVC and MCSA (predicted MVC = 24.763 + 0.0047 MCSA). This model was then applied to the subsequent 40 participants.

RESULTS

MVC versus model-predicted mean MVC was 43.9 ± 0.8 kg versus 44.2 ± 1.81 (P = 0.90). P-MRS results when predicted and MVC were similar showed expected changes during MVC-based exercise. In contrast, MVC was markedly lower than predicted in four participants and produced minimal metabolic perturbation. Upon repeat testing, these individuals could perform their predicted MVC with coaching, which produced expected metabolic perturbations.

CONCLUSIONS

Compared with using MVC testing alone, using magnetic resonance imaging to predict muscle strength allows for a more accurate and standardized P-MRS protocol during exercise in children. This method overcomes a major obstacle in assessing mitochondrial function in youths. These studies have importance as we seek to determine the role of mitochondrial function in youths with insulin resistance and diabetes and response to interventions.

Supervised exercise, stent revascularization, or medical therapy for claudication due to aortoiliac peripheral artery disease: the CLEVER study

BACKGROUND

Treatment for claudication that is due to aortoiliac peripheral artery disease (PAD) often relies on stent revascularization (ST). However, supervised exercise (SE) is known to provide comparable short-term (6-month) improvements in functional status and quality of life. Longer-term outcomes are not known.

OBJECTIVES

The goal of this study was to report the longer-term (18-month) efficacy of SE compared with ST and optimal medical care (OMC).

METHODS

Of 111 patients with aortoiliac PAD randomly assigned to receive OMC, OMC plus SE, or OMC plus ST, 79 completed the 18-month clinical and treadmill follow-up assessment. SE consisted of 6 months of SE and an additional year of telephone-based exercise counseling. Primary clinical outcomes included objective treadmill-based walking performance and subjective quality of life.

RESULTS

Peak walking time improved from baseline to 18 months for both SE (5.0 ± 5.4 min) and ST (3.2 ± 4.7 min) significantly more than for OMC (0.2 ± 2.1 min; p < 0.001 and p = 0.04, respectively). The difference between SE and ST was not significant (p = 0.16). Improvement in claudication onset time was greater for SE compared with OMC, but not for ST compared with OMC. Many disease-specific quality-of-life scales demonstrated durable improvements that were greater for ST compared with SE or OMC.

CONCLUSIONS

Both SE and ST had better 18-month outcomes than OMC. SE and ST provided comparable durable improvement in functional status and in quality of life up to 18 months. The durability of claudication exercise interventions merits its consideration as a primary PAD claudication treatment.

Community-based walking exercise for peripheral artery disease: An exploratory pilot study

Supervised walking exercise is an effective treatment to improve walking ability of patients with peripheral artery disease (PAD), but few exercise programs in community settings have been effective. The aim of this study was to determine the efficacy of a community-based walking exercise program with training, monitoring and coaching (TMC) components to improve exercise performance and patient-reported outcomes in PAD patients. This was a randomized, controlled trial including PAD patients (n=25) who previously received peripheral endovascular therapy or presented with stable claudication. Patients randomized to the intervention group received a comprehensive community-based walking exercise program with elements of TMC over 14 weeks. Patients in the control group did not receive treatment beyond standard advice to walk. The primary outcome in the intent-to-treat (ITT) analyses was peak walking time (PWT) on a graded treadmill. Secondary outcomes included claudication onset time (COT) and patient-reported outcomes assessed via the Walking Impairment Questionnaire (WIQ). Intervention group patients (n=10) did not significantly improve PWT when compared with the control group patients (n=10) (mean ± standard error: +2.1 ± 0.7 versus 0.0 ± 0.7 min, p=0.052). Changes in COT and WIQ scores were greater for intervention patients compared with control patients (COT: +1.6 ± 0.8 versus -0.6 ± 0.7 min, p=0.045; WIQ: +18.3 ± 4.2 versus -4.6 ± 4.2%, p=0.001). This pilot using a walking program with TMC and an ITT analysis did not improve the primary outcome in PAD patients. Other walking performance and patient self-reported outcomes were improved following exercise in community settings. Further study is needed to determine whether this intervention improves outcomes in a trial employing a larger sample size.

Delayed skeletal muscle mitochondrial ADP recovery in youth with type 1 diabetes relates to muscle insulin resistance

Insulin resistance (IR) increases cardiovascular morbidity and is associated with mitochondrial dysfunction. IR is now recognized to be present in type 1 diabetes; however, its relationship with mitochondrial function is unknown. We determined the relationship between IR and muscle mitochondrial function in type 1 diabetes using the hyperinsulinemic-euglycemic clamp and (31)P-MRS before, during, and after near-maximal isometric calf exercise. Volunteers included 21 nonobese adolescents with type 1 diabetes and 17 nondiabetic control subjects with similar age, sex, BMI, Tanner stage, and activity levels. We found that youths with type 1 diabetes were more insulin resistant (median glucose infusion rate 10.1 vs. 18.9 mg/kglean/min; P < 0.0001) and had a longer time constant of the curve of ADP conversion to ATP (23.4 ± 5.3 vs. 18.8 ± 3.9 s, P < 0.001) and a lower rate of oxidative phosphorylation (median 0.09 vs. 0.21 mmol/L/s, P < 0.001). The ADP time constant (β = -0.36, P = 0.026) and oxidative phosphorylation (β = 0.02, P < 0.038) were related to IR but not HbA1c. Normal-weight youths with type 1 diabetes demonstrated slowed postexercise ATP resynthesis and were more insulin resistant than control subjects. The correlation between skeletal muscle mitochondrial dysfunction in type 1 diabetes and IR suggests a relationship between mitochondrial dysfunction and IR in type 1 diabetes.

Type 2 diabetes exaggerates exercise effort and impairs exercise performance in older women

OBJECTIVE

Type 2 diabetes mellitus (T2DM) is associated with high levels of disability and mortality. Regular exercise prevents premature disability and mortality, but people with T2DM are generally sedentary for reasons that are not fully established. We previously observed that premenopausal women with T2DM report greater effort during exercise than their counterparts without diabetes, as measured by the Rating of Perceived Exertion (RPE) scale. We hypothesized that RPE is greater in older women with T2DM versus no T2DM.

RESEARCH DESIGN AND METHODS

We enrolled overweight, sedentary women aged 50-75 years with (n=26) or without T2DM (n=28). Participants performed submaximal cycle ergometer exercise at 30 W and 35% of individually-measured peak oxygen consumption (35% VO2peak). We assessed exercise effort by RPE (self-report) and plasma lactate concentration.

RESULTS

VO2peak was lower in T2DM versus controls (p=0.003). RPE was not significantly greater in T2DM versus controls (30 W: Control, 10.4±3.2, T2DM, 11.7±2.3, p=0.08; 35% VO2peak: Control, 11.1±0.5, T2DM, 12.1±0.5, p=0.21). However, lactate was greater in T2DM versus controls (p=0.004 at 30 W; p<0.05 at 35% VO2peak). Greater RPE was associated with higher lactate, higher heart rate, and a hypertension diagnosis (p<0.05 at 30 W and 35% VO2peak).

CONCLUSIONS

Taken together, physiological measures of exercise effort were greater in older women with T2DM than controls. Exercise effort is a modifiable and thereby targetable end point. In order to facilitate regular exercise, methods to reduce exercise effort in T2DM should be sought.

TRIAL NUMBER

NCT00785005.

Renal function is associated with peak exercise capacity in adolescents with type 1 diabetes

OBJECTIVE

Diabetic nephropathy and cardiovascular disease are strongly related in adults with type 1 diabetes, yet little is known about this relationship in adolescents prior to the onset of detectable clinical disease. We hypothesized that cardiopulmonary fitness would be directly associated with albumin-to-creatinine ratio (ACR) and inversely related to estimated glomerular filtration rate (eGFR) in adolescents with type 1 diabetes.

RESEARCH DESIGN AND METHODS

Sixty-nine adolescents with type 1 diabetes and 13 nondiabetic control subjects of similar pubertal stage and BMI had insulin sensitivity (glucose infusion rate [GIR]), measured by hyperinsulinemic-euglycemic clamp, and lean body mass, measured by DEXA. Cardiopulmonary fitness was measured by cycle ergometry to obtain peak volume of oxygen (VO2peak), and renal function was measured by eGFR using the Bouvet equation (measuring creatinine and cystatin C levels) and ACR.

RESULTS

Adolescents (15.5 ± 2.2 years of age) with type 1 diabetes (6.3 ± 3.8 years diabetes duration) had reduced VO2peak (31.5 ± 6.3 vs. 36.2 ± 7.9 mL/kg ⋅ min, P = 0.046) and VO2peak/lean kg (43.7 ± 7.0 vs. 51.0 ± 8.6 mL/lean kg ⋅ min, P = 0.007) compared with nondiabetic control subjects. eGFR was inversely associated with VO2peak and VO2peak/lean kg after adjusting for sex, Tanner stage, GIR, HbA1c level, systolic blood pressure, and LDL cholesterol level (β ± SE, VO2peak: -0.19 ± 0.07, P = 0.02; VO2peak/lean kg: -0.19 ± 0.09, P = 0.048). Moreover, participants in the highest tertile for eGFR had significantly lower sex- and Tanner-adjusted VO2peak and VO2peak/lean kg compared with participants in the lowest tertile.

CONCLUSIONS

Adolescents with type 1 diabetes had reduced exercise capacity, which was strongly associated with renal health, independent of insulin sensitivity. Future studies should examine the underlying interrelated pathophysiology in order to identify probable targets for treatment to reduce cardiovascular and renal complications.

Cardiovascular control during exercise in type 2 diabetes mellitus

Controlled studies of male and female subjects with type 2 diabetes mellitus (DM) of short duration (~3-5 years) show that DM reduces peak VO2 (L·min(-1) and mL·kg(-1)·min(-1)) by an average of 12-15% and induces a greater slowing of the dynamic response of pulmonary VO2 during submaximal exercise. These effects occur in individuals less than 60 years of age but are reduced or absent in older males and are consistently associated with significant increases in the exercise pressor response despite normal resting blood pressure. This exaggerated pressor response, evidence of exertional hypertension in DM, is manifest during moderate submaximal exercise and coincides with a more constrained vasodilation in contracting muscles. Maximum vasodilation during contractions involving single muscle groups is reduced by DM, and the dynamic response of vasodilation during submaximal contractions is slowed. Such vascular constraint most likely contributes to exertional hypertension, impairs dynamic and peak VO2 responses, and reduces exercise tolerance. There is a need to establish the effect of DM on dynamic aspects of vascular control in skeletal muscle during whole-body exercise and to clarify contributions of altered cardiovascular control and increased arterial stiffness to exertional hypertension.

Cost-effectiveness of supervised exercise, stenting, and optimal medical care for claudication: results from the Claudication: Exercise Versus Endoluminal Revascularization (CLEVER) trial

BACKGROUND

Both supervised exercise (SE) and stenting (ST) improve functional status, symptoms, and quality of life compared with optimal medical care (OMC) in patients with claudication. The relative cost-effectiveness of these strategies is not well defined.

METHODS AND RESULTS

The Claudication: Exercise Versus Endoluminal Revascularization (CLEVER) study randomized patients with claudication due to aortoiliac stenosis to a 6-month SE program, to ST, or to OMC. Participants who completed 6-month follow-up (n=98) were included in a health economic analysis through 18 months. Costs were assessed using resource-based methods and hospital billing data. Quality-adjusted life-years were estimated using the EQ-5D. Markov modeling based on the in-trial results was used to explore the impact of assumptions about the longer term durability of observed differences in quality of life. Through 18 months, mean healthcare costs were $5178, $9804, and $14 590 per patient for OMC, SE, and ST, respectively. Measured quality-adjusted life-years through 18 months were 1.04, 1.16, and 1.20. In our base case analysis, which assumed that observed differences in quality of life would dissipate after 5 years, the incremental cost-effectiveness ratios were $24 070 per quality-adjusted life-year gained for SE versus OMC, $41 376 for ST versus OMC, and $122 600 for ST versus SE. If the treatment effect of ST was assumed to be more durable than that of SE, the incremental cost-effectiveness ratio for ST versus SE became more favorable.

CONCLUSIONS

Both SE and ST are economically attractive by US standards relative to OMC for the treatment of claudication in patients with aortoiliac disease. ST is more expensive than SE, with uncertain incremental benefit.

CLINICAL TRIAL REGISTRATION URL

www.clinicaltrials.gov, Unique identifier: NCT00132743.