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The response of a filter matched to a delayed, Doppler-shifted version of a narrow-band transmitted signal in white noise is considered. Conditions under which the response is the one expected are arrived at by (1) setting up the response to a more accurate representation of the echo waveform, (2) applying Taylor's theorem, with the response considered a function of v/c (range rate over the speed of propagation), and (3) requiring that the remainder be small relative to the leading term (expected response). The resulting validity criteria differ from that put forward by several authors, namely, 2(|v|/c)B T < 1 (one also sees <), where B is a signal bandwidth, and T is the signal duration. It is shown that, to good approximation, the old criterion implies the new, and that modulations exist such that one of the new criteria is satisfied but the old is not. [ABSTRACT FROM AUTHOR]

Objective: The Vascular Quality of Life Questionnaire-6 (VascuQoL-6) is a short, disease specific instrument used to determine health related quality of life (HRQoL) in patients with peripheral arterial disease. This study aimed to assess the minimally important difference (MID) and substantial clinical benefit (SCB) of the VascuQoL-6 in Dutch patients with intermittent claudication (IC) receiving supervised exercise therapy (SET)., Methods: Consecutive patients with IC who were recruited from a single centre between January 2016 and December 2016 completed the VascuQoL-6 before initiation and after three months of SET. They subsequently answered an anchor question rating their current health status as much improved, improved, unchanged, deteriorated, or much deteriorated, compared with baseline. The MID for improvement and deterioration and SCB were calculated using anchor based and distribution based methods., Results: A total of 124 patients with IC (58% male, mean age 68 years) completed the study protocol. Baseline VascuQoL-6 scores increased from 16.3 ± 4.4 to 18.7 ± 3.8 after three months of SET (p < .001). MID values ranged from +2.0 to +3.8 points regarding HRQoL improvement and from +0.2 to -2.2 points regarding HRQoL deterioration. The SCB ranged from +3.7 to +5.0 points. Depending on the MID approach, 32% - 41% of patients achieved a clinically meaningful improvement in HRQoL., Conclusion: Approximately one in three patients with IC reported a clinically meaningful improvement in HRQoL after three months of SET. The range of MID and SCB values provides caregivers with an idea of how much change in VascuQoL-6 scores is considered relevant or substantial by their patients. Applying cutoff points for MID and SCB may optimise the interpretation of trial results and may help to set a benchmark for success of SET., Competing Interests: Conflict of interest statement and funding None., (Copyright © 2021 European Society for Vascular Surgery. Published by Elsevier B.V. All rights reserved.)

Objective: Peripheral artery disease (PAD) is underdiagnosed in primary care settings, partly because of limited accuracy of the Doppler ankle-brachial index (ABI). This study aimed to assess the diagnostic accuracy of an automated oscillometric ABI device compared with reference standard vascular laboratory Doppler ABI equipment and to examine the influence of oscillometric errors on performance., Methods: Consecutive patients who were referred to a large general hospital for an ABI measurement were invited to participate. In each patient, the oscillometric analysis was followed by the Doppler analysis. Legs with incompressible ankle arteries were excluded from analysis. ABI values were compared using the Bland-Altman method. Oscillometric errors were defined as the incapacity of the oscillometer to report a value of ABI. A receiver operating characteristic curve was constructed, and the area under the curve was computed., Results: A total of 201 patients participated. The Bland-Altman plot showed a mean difference of 0.05 ± 0.12 (limits of agreement, -0.20 to 0.29), representing a small ABI overestimation after oscillometry. Oscillometric errors occurred more commonly in limbs with PAD than in limbs without PAD (28% and 7%, respectively; P < .001). Considering a 0.9 threshold and after oscillometric error exclusion, the oscillometric ABI showed a 74% sensitivity and a 97% specificity for a diagnosis of PAD. When oscillometric errors were considered as abnormal ABIs, sensitivity increased to 86% and specificity was maintained at 95%. The receiver operating characteristic curve showed an area under the curve of 0.96. The best oscillometric ABI cutoff point was 1.00. Using this threshold and when considering oscillometric errors as abnormal ABIs, sensitivity improved to 94% while maintaining specificity at 92%., Conclusions: Oscillometric ABI showed good diagnostic accuracy compared with the reference standard. However, the high incidence of oscillometric errors and the challenges to correctly interpret readings may limit the use of the oscillometric method in PAD diagnosis., (Copyright © 2020 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.)

Objective: The "gold standard" treatment of intermittent claudication (IC) is supervised exercise therapy (SET). Intermittent vacuum therapy (IVT) has recently been promoted as an additional treatment of IC. During IVT, negative pressure and atmospheric pressure are alternatingly applied to the lower extremities, possibly resulting in improved circulation. The aim of this study was to determine a potential additional effect of IVT in IC patients undergoing a standardized SET program., Methods: IC patients were recruited from three Dutch general hospitals between December 2015 and July 2017. They received a standardized SET program but were also randomly assigned to an intervention group receiving an IVT treatment (-50 mBar negative pressure) or a control group receiving a sham treatment (-5 mBar negative pressure). IVT was provided in a dedicated clinic during 12 sessions of 30 minutes during a 6-week period. The primary outcome measure was a change in maximal treadmill walking distance. Secondary outcome measures were a change in functional treadmill walking distance, 6-minute walk test, ambulatory ability, and quality of life., Results: A total of 78 patients were randomized, of whom 70 were available for intention-to-treat analysis (control, n = 34; intervention, n = 36). At 6 and 12 weeks, increases in walking distance were of equal magnitude. Median (interquartile range) change in maximal treadmill walking distance during 12 weeks was +335 (205-756) meters in control patients and +250 (77-466) meters in intervention patients (P = .109), whereas functional treadmill walking distance increased +230 (135-480) meters and +188 (83-389) meters (P = .233), respectively. Mean ± standard deviation change in the 6-minute walk test was +36 ± 48 meters and +55 ± 63 meters (P = .823), respectively. Ambulatory ability and quality of life improved equally in both groups., Conclusions: IVT does not confer any additional beneficial effects in IC patients undergoing a standardized SET program., (Copyright © 2019 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.)

Background: It is unclear whether supervised exercise therapy (SET), home based exercise therapy (HBET), and endovascular revascularisation (ER) for intermittent claudication (IC) have a meaningful impact on physical activity, despite extensive research on their effect on walking performance., Methods: Multiple databases were searched systematically up to May 2018 for randomised controlled trials with objective measurements of physical activity in patients with IC. A Bayesian network meta-analysis was performed comparing the change in physical activity between baseline and follow up between treatments (SET, HBET, ER) and control (usual care). The standardised mean difference (SMD) with 95% credible interval (CI) was calculated as a summary statistic and converted into steps per day to aid interpretation., Results: Eight trials involving 656 patients with IC investigating the short-term effect of treatment on daily physical activity were included. Both SET (SMD 0.41, 95% CI 0.10-0.72: this corresponds to a difference of + 803 steps/day on a pedometer) and HBET (SMD 0.50, 95% CI 0.18-0.88: + 980 steps/day) displayed a benefit over control, based on evidence of moderate and low quality, respectively. The benefit of ER compared with control was SMD 0.36 (95% CI -0.22 to 0.99: + 705 steps/day), but only one trial supplied direct evidence, resulting in a low rating of the quality of evidence. Comparisons between treatments yielded no statistically significant differences. The results were robust to several sensitivity analyses., Conclusion: SET improves daily physical activity levels in patients with IC over control. HBET may have a similar benefit, while invasive treatment failed to lead to a statistically significant improvement of physical activity compared with control. However, the underlying quality of evidence for comparisons with ER and HBET is low, impeding definite conclusions., (Copyright © 2019 European Society for Vascular Surgery. Published by Elsevier B.V. All rights reserved.)

Objective/background: The Dutch College of General Practitioners' guideline on peripheral arterial disease (PAD) provides clear recommendations on the management of PAD. An ankle brachial index (ABI) measurement, prescription of antiplatelet drugs and statins, and supervised exercise therapy (SET) for intermittent claudication (IC) are advised. The aims of this study were to determine the adherence of general practitioners (GPs) to their own guideline on PAD and to evaluate the reliability of primary care ABI measurements., Methods: This was a cross-sectional study. All patients suspected of having symptomatic PAD who were referred by GPs to a large hospital in 2015 were evaluated regarding three of the guideline criteria: (i) ABI measurement; (ii) prescription of secondary prevention; (iii) initiation of SET. ABI values obtained in primary care and the hospital's vascular laboratory were compared using correlation coefficients and regression analysis. An abnormal ABI was defined as a value <.9 (normal ABI ≥.9)., Results: Of 308 potential patients with new onset PAD, 58% (n = 178) had undergone ABI measurement prior to referral. A modest correlation between ABI values obtained in primary care and the vascular laboratory was found (r = .63, p < .001). Furthermore, a moderate reliability was calculated (intraclass correlation coefficient 0.60, 95% confidence interval 0.49-0.69, p < .001). Of the new patients with an abnormal ABI, 59% used antiplatelet drugs and 55% used statins. A referral for SET was initiated by a GP in 10% of new PAD patients with IC symptoms., Conclusions: Adherence by Dutch GPs to their own society's PAD guideline has room for improvement. The reliability of ABI measurements is suboptimal, whereas rates of prescription of secondary prevention and initiation of SET as primary treatment for IC need upgrading., (Copyright © 2018 European Society for Vascular Surgery. Published by Elsevier B.V. All rights reserved.)

Background: Although supervised exercise therapy (SET) provides significant symptomatic benefit for patients with intermittent claudication (IC), it remains an underutilized tool. Widespread implementation of SET is restricted by lack of facilities and funding. Structured home-based exercise therapy (HBET) with an observation component (e.g., exercise logbooks, pedometers) and just walking advice (WA) are alternatives to SET. This is the second update of a review first published in 2006., Objectives: The primary objective was to provide an accurate overview of studies evaluating effects of SET programs, HBET programs, and WA on maximal treadmill walking distance or time (MWD/T) for patients with IC. Secondary objectives were to evaluate effects of SET, HBET, and WA on pain-free treadmill walking distance or time (PFWD/T), quality of life, and self-reported functional impairment., Search Methods: The Cochrane Vascular Information Specialist searched the Cochrane Vascular Specialised Register (December 16, 2016) and the Cochrane Central Register of Controlled Trials (2016, Issue 11). We searched the reference lists of relevant studies identified through searches for other potential trials. We applied no restriction on language of publication., Selection Criteria: We included parallel-group randomized controlled trials comparing SET programs with HBET programs and WA in participants with IC. We excluded studies in which control groups did not receive exercise or walking advice (maintained normal physical activity). We also excluded studies comparing exercise with percutaneous transluminal angioplasty, bypass surgery, or drug therapy., Data Collection and Analysis: Three review authors (DH, HF, and LG) independently selected trials, extracted data, and assessed trials for risk of bias. Two other review authors (MvdH and JT) confirmed the suitability and methodological quality of trials. For all continuous outcomes, we extracted the number of participants, mean outcome, and standard deviation for each treatment group through the follow-up period, if available. We extracted Medical Outcomes Study Short Form 36 outcomes to assess quality of life, and Walking Impairment Questionnaire outcomes to assess self-reported functional impairment. As investigators used different scales to present results of walking distance and time, we standardized reported data to effect sizes to enable calculation of an overall standardized mean difference (SMD). We obtained summary estimates for all outcome measures using a random-effects model. We assessed the quality of evidence using the GRADE approach., Main Results: For this update, we included seven additional studies, making a total of 21 included studies, which involved a total of 1400 participants: 635 received SET, 320 received HBET, and 445 received WA. In general, SET and HBET programs consisted of three exercise sessions per week. Follow-up ranged from six weeks to two years. Most trials used a treadmill walking test to investigate effects of exercise therapy on walking capacity. However, two trials assessed only quality of life, functional impairment, and/or walking behavior (i.e., daily steps measured by pedometer). The overall methodological quality of included trials was moderate to good. However, some trials were small with respect to numbers of participants, ranging from 20 to 304.SET groups showed clear improvement in MWD/T compared with HBET and WA groups, with overall SMDs at three months of 0.37 (95% confidence interval [CI] 0.12 to 0.62; P = 0.004; moderate-quality evidence) and 0.80 (95% CI 0.53 to 1.07; P < 0.00001; high-quality evidence), respectively. This translates to differences in increased MWD of approximately 120 and 210 meters in favor of SET groups. Data show improvements for up to six and 12 months, respectively. The HBET group did not show improvement in MWD/T compared with the WA group (SMD 0.30, 95% CI -0.45 to 1.05; P = 0.43; moderate-quality evidence).Compared with HBET, SET was more beneficial for PFWD/T but had no effect on quality of life parameters nor on self-reported functional impairment. Compared with WA, SET was more beneficial for PFWD/T and self-reported functional impairment, as well as for some quality of life parameters (e.g., physical functioning, pain, and physical component summary after 12 months), and HBET had no effect.Data show no obvious effects on mortality rates. Thirteen of the 1400 participants died, but no deaths were related to exercise therapy. Overall, adherence to SET was approximately 80%, which was similar to that reported with HBET. Only limited adherence data were available for WA groups., Authors' Conclusions: Evidence of moderate and high quality shows that SET provides an important benefit for treadmill-measured walking distance (MWD and PFWD) compared with HBET and WA, respectively. Although its clinical relevance has not been definitively demonstrated, this benefit translates to increased MWD of 120 and 210 meters after three months in SET groups. These increased walking distances are likely to have a positive impact on the lives of patients with IC. Data provide no clear evidence of a difference between HBET and WA. Trials show no clear differences in quality of life parameters nor in self-reported functional impairment between SET and HBET. However, evidence is of low and very low quality, respectively. Investigators detected some improvements in quality of life favoring SET over WA, but analyses were limited by small numbers of studies and participants. Future studies should focus on disease-specific quality of life and other functional outcomes, such as walking behavior and physical activity, as well as on long-term follow-up.

Background: Although supervised exercise therapy (SET) is generally accepted as an effective noninvasive treatment for intermittent claudication (IC), Dutch vascular surgeons were initially somewhat hesitant as reported by a 2011 questionnaire study. Later on, a nationwide multidisciplinary network for SET was introduced in the Netherlands. The aim of this questionnaire study was to determine possible trends in conceptions among Dutch vascular surgeons regarding the prescription of SET., Methods: In the year of 2015, Dutch vascular surgeons, fellows, and senior residents were asked to complete a 26-item questionnaire including issues that were considered relevant for prescribing SET such as patient selection criteria and comorbidity. Outcome was compared to the 2011 survey., Results: Data of 124 respondents (82% males; mean age 46 years; 64% response rate) were analyzed. SET referral rate of new IC patients was not different over time (2015: 81% vs. 2011: 75%; P = 0.295). However, respondents were more willing to prescribe SET in IC patients with chronic obstructive pulmonary disease (2015: 86% vs. 2011: 69%; P = 0.002). Nevertheless, a smaller portion of respondents found that SET was also indicated for aortoiliac disease (2015: 63% vs. 2011: 76%; P = 0.049). Insufficient health insurance coverage and/or personal financial resources were the most important presumed barriers preventing patients from initiating SET (80% of respondents). Moreover, 94% of respondents judged that SET should be fully reimbursed by all Dutch basic health insurances., Conclusions: The concept of SET for IC is nowadays generally embraced by the vast majority of Dutch vascular surgeons. SET may have gained in popularity in IC patients with cardiopulmonary comorbidity. However, SET remains underutilized for aortoiliac disease. Reimbursement is considered crucial for a successful SET implementation., (Copyright © 2017 Elsevier Inc. All rights reserved.)