Effect of temperature on digital systolic pressures in lower limb in arterial disease

Reliability of bedside tests for diagnosing peripheral arterial disease in patients prone to medial arterial calcification: A systematic review

BACKGROUND

Medial arterial calcification (MAC), frequently associated with diabetes mellitus (DM) and chronic kidney disease (CKD), is a systemic vascular disorder leading to stiffness and incompressible arteries. These changes impede the accuracy of bedside tests to diagnose peripheral arterial disease (PAD). This review aimed to evaluate the reliability of bedside tests for the detection of PAD in patients prone to MAC.

METHODS

A systematic search (Pubmed, Embase, Web of Science, Cochrane, and Emcare) was performed according to the PRISMA guidelines to identify relevant studies providing data on the performance of bedside tests for the detection of PAD in patients prone to MAC. Studies were included when bedside test were compared to a reference standard. Primary endpoints were the positive and negative likelihood ratios (PLR, NLR). Methodological quality and risk of bias were evaluated using the QUADAS-2 tool.

FINDINGS

In total, 23 studies were included in this review. The most commonly evaluated test was the ankle-brachial index (ABI), followed by toe-brachial index (TBI), toe pressure (TP) measurements, and continuous wave Doppler (CWD). The majority of patients were older, male, and had DM. We found that ABI <0·9 was helpful to diagnose PAD, but failed to rule out PAD (NLR >0·2). The same applied for TP (NLR >0·3) and TBI (5 out of 6 studies revealed an NLR >0·2). CWD (loss of triphasic pattern) is reliable to exclude PAD (NLR 0-0·09), but was only validated in two studies. Overall, methodological quality was poor which led to risk of bias in 20 studies.

INTERPRETATION

The diagnosis of PAD in patients prone to MAC remains challenging. The ABI performed reasonably in the diagnosis of PAD, while the CWD (loss of triphasic signal) can be used to rule out PAD. This systematic review showed that test performances were generally poor with serious concerns in methodological quality of the included studies. We therefore counsel against the use of a single bedside test.

FUNDING

None to declare.

Doppler Ultrasonography Derived Maximal Systolic Acceleration: Value Determination With Artificially Induced Stenosis

In diagnosing peripheral arterial disease (PAD), medial arterial calcification (MAC) hampers arterial compression and could lead to unreliable ankle brachial index (ABI), toe brachial index (TBI) and toe pressure (TP). Doppler ultrasonography (DUS) derived maximal systolic acceleration (ACCmax) might be more accurate to diagnose PAD. In an in vitro study, a strong correlation between ACCmax and the severity of stenotic disease was determined. The aim of this study was to investigate the ACCmax in correlation with conventional non-invasive diagnostics in an in vivo setting. Methods: In twelve healthy individuals, an arterial stenosis was mimicked by compression on the common femoral artery by an ultrasounds probe, creating a local stenosis of 50%, 70% and 90%. The ABI, TBI, TP and several DUS parameters (including ACCmax) were assessed at the ankle during these different degrees of stenosis. All DUS parameters were measured separately by two observers to determine the interobserver variability. Results: Overall the ABI, TBI, TP, ACCmax, ACCsys and PSV decreased significantly when the degree of stenosis increased. The ACCmax showed the highest correlation with the degree of stenosis (r −.884), compared to ABI (r −.726), TBI (r −.716) and TP (r −.758). Furthermore, the interobserver variability of ACCmax was excellent, with an intraclass correlation coefficient (ICC) of .97. Conclusion: ACCmax is an accurate non-invasive DUS parameter to diagnose and assess the severity of a mimicked arterial stenosis in healthy individuals. Further prospective assessment of the clinical value of ACCmax and its potential benefits in patients with PAD is needed.

Correlating Toe-Brachial Indices and Angiographically Confirmed Peripheral Artery Disease: A Retrospective Review

In advanced peripheral arterial disease (PAD), medial arterial calcification is known to inflate the ankle-brachial index. An alternative method of evaluating symptomatic patients is toe-brachial indexes (TBI), where a ratio less than .7 indicates PAD and less than .4 indicates a severe form. The objective of this retrospective analysis was to investigate the association between TBIs less than .7 and angiographically verified PAD. Patients were required to have either a leg angiogram 13 months prior to or 12 months after a 6-minute walk test. Of the 174 included patients, the mean overall TBI was .450. The mean TBI by location was highest at iliac and infra-geniculate with .544 and lowest at supra-geniculate with .372. Infra-geniculate lesions were also the most frequent (n = 46). A TBI less than .4 was found in 47.7% of patients. TBIs greater than .7 were present in 36 patients; however, only 16 had significant angiographic stenosis. In conclusion, the majority of patients with angiographic PAD had a TBI less than .7, especially less than .4. Contrary to suspicion, infra-geniculate lesions were the most common and had the highest TBI.

Association of Ankle-Brachial and Toe-Brachial Indexes With Mortality in Patients With CKD

Rationale & Objective

A low ankle-brachial index (ABI) is used to diagnose peripheral artery disease (PAD) but may be normal or elevated in patients with medial arterial calcification and stiff vessels, as is common in chronic kidney disease (CKD). The toe-brachial index (TBI) has been recommended because it is not influenced by medial arterial calcification, but alone the TBI does not capture risk associated with medial arterial calcification. We hypothesized that the difference between ABI and TBI (ABI − TBI) would capture both PAD and medial arterial calcification and thus better identify mortality risk from PAD, particularly in those with CKD.

Study Design

Prospective cohort study.

Setting & Participants

471 patients with clinical suspicion for PAD referred for vascular testing.

Exposures

ABI, TBI, and ABI − TBI.

Outcome

All-cause mortality.

Analytical Approach

Cox proportional hazards models evaluating the association of ABI − TBI with mortality over 7 years.

Results

Mean age was 68 years, 89% were men, 35% had diabetes, 64% had CKD, and mean estimated glomerular filtration rate was 55 mL/min/1.73 m². Median ABI was 0.96 (interquartile range [IQR], 0.73-1.08), median TBI was 0.62 (IQR, 0.46-0.81), and median ABI − TBI was 0.23 (IQR, 0.14-0.39). Higher ABI − TBI values were associated with increased risk in mortality only among participants with ABI values ≥ 0.9 (P = 0.03). Among participants with CKD and ABI values ≥ 0.9, participants with ABI − TBI values higher than the median had greater (HR, 1.79; 95% CI, 1.18-2.72) risk for mortality (P = 0.005). This was attenuated after age adjustment (HR, 1.41; 95% CI, 0.91-2.20) but did not change after further adjustment for confounders.

Limitations

Mainly male cohort derived from a vascular laboratory; lack of limb outcomes and data for albuminuria.

Conclusions

A high ABI − TBI value may be associated with higher risk for mortality in persons with CKD and a normal ABI. Age affects this association, and further studies evaluating ABI − TBI in larger populations are required.

Bedside Toe Pressures Measurements in a Department of Vascular Surgery: A Study of Diagnostic Accuracy

OBJECTIVE

In patients with peripheral arterial disease (PAD), measurements of distal blood pressure form the basis of assessing the severity of the disease along with symptoms and objective findings. The reliability and accuracy of a fully automated bedside device (SysToe) vs. strain gauge plethysmography (SGP) in patients with low toe pressures in a bedside setting in an outpatient clinic of vascular surgery were investigated.

METHODS

This was a prospective, single blinded study carried out in compliance with the Standards of Reporting of Diagnostic Accuracy Studies. A total of 94 outpatients with symptomatic PAD in an outpatient vascular surgery clinic were included and had index measurements performed with the automated bedside device in a bedside setting by observers with no training in routine distal pressure measurements. SGP reference measurements were performed in a vascular laboratory.

RESULTS

There was agreement between modalities regarding the diagnostic classification of chronic limb threatening ischaemia (CLTI) in 79/94 (84%) patients. For detection of CLTI, Cohen's kappa was 0.57 with a sensitivity of 94%, specificity of 82%, positive predictive value (PPV) 52%, and negative predictive value (NPV) 98%. On average, the automated bedside device underestimated the pressures, compared with the SGP. The mean difference between SGP and SysToe was 9 ± 16 mmHg for right limbs and 10 ± 16 mmHg for left limbs (p < .001).

CONCLUSION

The automated bedside device showed a high sensitivity and a high NPV for excluding CLTI. However, the low PPV may result in overdiagnosis. The automated bedside device may function as a screening tool identifying patients in need of further diagnostics with more accurate equipment, for example SGP.

How does a short period of exercise effect toe pressures and toe-brachial indices? A cross-sectional exploratory study

BACKGROUND

Whilst post exercise ankle-brachial indices (ABI) are commonly used to help identify peripheral arterial disease (PAD), the role of post exercise toe pressures (TP) or toe-brachial indices (TBI) is unclear. The aim of this study was to determine, in a population without clinical signs of PAD, the effect that 30 s of weight-bearing heel raises has on TP and TBI values. Additionally, the ability of resting TP and TBI values to predict change in post-exercise values using the heel raise method was investigated.

METHODS

Participants over the age of 18 with a resting TBI of ≥0.60 and ABI between 0.90 and 1.40, without diabetes, history of cardiovascular disease and not currently smoking were included. Following ten minutes of supine rest, right TP and bilateral brachial pressures were performed in a randomized order using automated devices. Participants then performed 30 s of weight-bearing heel raises, immediately after which supine vascular measures were repeated. Data were assessed for normality using the Shapiro-Wilk test. For change in TP and TBI values the Wilcoxon Signed-Rank Test was performed. For correlations between resting and change in post exercise values, the Spearman Rank Order Correlations were performed, and where significant correlation identified, a linear regression undertaken.

RESULTS

Forty-eight participants were included. A statistically significant decrease was seen in the median TP from resting 103.00 mmHg (IQR: 89.00 to 124.75) to post exercise 98.50 mmHg (IQR: 82.00 to 119.50), z = - 2.03, p = 0.04. This difference of 4.50 mmHg represents a 4.37% change and is considered a small effect size (r = 0.21). The median TBI also demonstrated a statistically significant decrease from resting 0.79 (IQR: 0.68 to 0.94) to post exercise 0.72 (IQR: 0.60 to 0.87), z = - 2.86, p = < 0.01. This difference of 0.07 represents an 8.86% change and is considered a small effect size (r = 0.29). Linear regression demonstrated that resting TBI predicted 22.4% of the variance in post exercise TBI, p = < 0.01, coefficients beta - 0.49.

CONCLUSIONS

Thirty seconds of weight-bearing heel raises resulted in a similar decrease in TBI values seen in longer periods of exercise. TP values also showed a decrease post exercise; however this was contrary to previous studies.

How sensitive and specific is continuous-wave Doppler for detecting peripheral arterial disease in people with and without diabetes? A cross-sectional study

BACKGROUND

Continuous-wave Doppler is frequently used for detecting peripheral arterial disease in patients with diabetes; however, there is limited evidence investigating diagnostic accuracy. This study aimed to determine sensitivity and specificity of continuous-wave Doppler for detecting peripheral arterial disease in populations with, and without, diabetes and to investigate the influence of disease severity on sensitivity of continuous-wave Doppler for detecting peripheral arterial disease.

RESULTS

Data from 396 participants were included. Using colour Duplex ultrasound as reference standard (N=66), printed continuous-wave Doppler waveform analysis sensitivity was 81.75% (95% confidence interval: 76.75 to 85.88) and specificity 89.34% (95% confidence interval: 82.62 to 93.67). Printed continuous-wave Doppler waveform analysis sensitivity for peripheral arterial disease was comparable to sensitivity calculated using angiography as the reference standard (81.67%; 95% confidence interval: 69.56 to 90.48). Sensitivity and specificity were unaffected by diabetes diagnosis (n = 176), sensitivity 82.76% (95% confidence interval: 74.86 to 88.55), and specificity 88.33% (95% confidence interval: 77.82 to 94.23).

CONCLUSION

Continuous-wave Doppler is a fair assessment tool for peripheral arterial disease in a community-based sample with suspected peripheral arterial disease. Diagnostic accuracy of continuous-wave Doppler for peripheral arterial disease is unaffected by the presence of diabetes.

Relationship of femoral artery ultrasound measures of atherosclerosis with chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is strongly associated with peripheral artery disease (PAD). Detection of subclinical PAD may allow early interventions for or prevention of PAD in persons with CKD. Whether the presence of atherosclerotic plaque and femoral intima-media thickness (IMT) are associated with kidney function is unknown.

METHODS

We performed a cross-sectional observational study of 1029 community-living adults. We measured superficial and common femoral artery IMT and atherosclerotic plaque presence by ultrasound. Estimated glomerular filtration rate (eGFR; continuous) and eGFR <60 mL/min/1.73 m2 (binary) were evaluated as outcomes.

RESULTS

Mean age was 70 ± 10 years, mean eGFR was 78 ± 17 mL/min/1.73 m2, and 156 (15%) individuals had eGFR <60 mL/min/1.73 m2; 260 (25%) had femoral artery plaque. In models adjusted for demographics and cardiovascular risk factors, individuals with femoral artery plaque had mean eGFR approximately 3.0 (95% confidence interval, -5.3 to -0.8) mL/min/1.73 m2 lower than those without plaque (P < .01). The presence of plaque was also associated with a 1.7-fold higher odds of eGFR <60 mL/min/1.73 m2 (95% confidence interval, 1.1-2.8; P < .02). Associations were similar in persons with normal ankle-brachial index. The directions of associations were similar for femoral IMT measures with eGFR and CKD but were rendered no longer statistically significant with adjustment for demographic variables and cardiovascular disease risk factors.

CONCLUSIONS

Femoral artery plaque is significantly associated with CKD prevalence in community-living individuals, even among those with normal ankle-brachial index. Femoral artery ultrasound may allow evaluation of relationships and risk factors linking PAD and kidney disease earlier in its course.

Peripheral vascular disease assessment in the lower limb: a review of current and emerging non-invasive diagnostic methods

BACKGROUND

Worldwide, at least 200 million people are affected by peripheral vascular diseases (PVDs), including peripheral arterial disease (PAD), chronic venous insufficiency (CVI) and deep vein thrombosis (DVT). The high prevalence and serious consequences of PVDs have led to the development of several diagnostic tools and clinical guidelines to assist timely diagnosis and patient management. Given the increasing number of diagnostic methods available, a comprehensive review of available technologies is timely in order to understand their limitations and direct future development effort.

MAIN BODY

This paper reviews the available diagnostic methods for PAD, CVI, and DVT with a focus on non-invasive modalities. Each method is critically evaluated in terms of sensitivity, specificity, accuracy, ease of use, procedure time duration, and training requirements where applicable.

CONCLUSION

This review emphasizes the limitations of existing methods, highlighting a latent need for the development of new non-invasive, efficient diagnostic methods. Some newly emerging technologies are identified, in particular wearable sensors, which demonstrate considerable potential to address the need for simple, cost-effective, accurate and timely diagnosis of PVDs.

Diagnostic accuracy of the postexercise ankle–brachial index for detecting peripheral artery disease in suspected claudicants with and without diabetes

The postexercise ankle–brachial index (ABI) is recommended in patients with normal resting ABI when peripheral artery disease (PAD) is suspected. The aims of this study were to determine the comparative diagnostic accuracy of the resting and postexercise ABI for detecting PAD, and, the effect of the presence of diabetes on these. Three methods of interpretation currently in use were also investigated: a reduction in postexercise ABI by >20% compared to resting ABI, an ABI value of ≤0.90 postexercise, or a reduction in systolic ankle pressure of >30 mmHg postexercise. This retrospective study used colour duplex ultrasound (CDU) as the reference standard. In 278 limbs (whole group), the resting ABI had an overall area under the curve (AUC) of 0.71, with the postexercise ABI yielding a similar diagnostic accuracy of AUC 0.72. In the non-diabetes group ( n=171), the resting ABI had an overall AUC of 0.74 and the postexercise ABI had a similar AUC of 0.76. In the diabetes group ( n=107), overall accuracy was reduced compared to the non-diabetes group, with the resting ABI having an overall AUC of 0.65 and the postexercise ABI yielding a similar accuracy with an AUC of 0.64. The overall diagnostic accuracy of the postexercise ABI for diagnosing PAD was not greatly improved compared to resting ABI. Given the lower overall diagnostic accuracy in the diabetes group, both the resting and the postexercise ABI results in diabetes populations should be interpreted with caution. There is a risk of undiagnosed disease if relying on these results alone to determine lower limb vascular status.

Diagnostic accuracy of resting systolic toe pressure for diagnosis of peripheral arterial disease in people with and without diabetes: a cross-sectional retrospective case-control study

BACKGROUND

The resting systolic toe pressure (TP) is a measure of small arterial function in the periphery. TP is used in addition to the ankle-brachial index when screening for peripheral arterial disease (PAD) of the lower limb in those with diabetes, particularly in the presence of lower limb medial arterial calcification. It may be used as an adjunct assessment of lower limb vascular function and as a predictor of wound healing. The aim of this study was to determine the diagnostic accuracy of TP for detecting PAD in people with and without diabetes.

METHODS

This was a retrospective case-control study. Two researchers extracted information from consecutive patient records, including TP measurements, colour Duplex ultrasound results, demographic information, and medical history. Measures of diagnostic accuracy were determined by receiver operating curve (ROC) analysis, and calculation of sensitivity, specificity, and positive and negative likelihood ratios.

RESULTS

Three hundred and nintey-four participants with suspected PAD were included. In the diabetes group (n = 176), ROC analysis of TP for detecting PAD was 0.78 (95%CI: 0.69 to 0.84). In the control group (n = 218), the ROC of TP was 0.73 (95%CI: 0.70 to 0.80). TP had highest sensitivity when anatomical distribution of disease was both proximal and distal (diabetes group: 79.49%, the control group: 82.61%). TP yielded highest sensitivity in mild disease (50-75% stenosis) in diabetes group, (81.82%) and moderate disease (>75% stenosis) in control group (80.77%).

CONCLUSIONS

Our findings indicate that TPs are useful to assist in diagnosing PAD in clinical practice, however, results should be interpreted with caution due to the small probability of PAD being present with a negative test.

The Influence of Heating on Toe pressure in Patients with Peripheral Arterial Disease

BACKGROUND AND AIM

The toe skin temperature in vascular patients can be low, making reliable toe pressure measurements difficult to obtain. The aim of this study was to evaluate the effect of heating on the toe pressure measurements.

MATERIALS AND METHODS

A total of 86 legs were examined. Brachial pressure and toe pressure were measured at rest in a supine position using a laser Doppler device that also measured skin temperature. After heating the toes for 5 min with a heating pad, we re-measured the toe pressure. Furthermore, after heating the skin to 40° with the probe, toe pressures were measured a third time.

RESULTS

The mean toe skin temperature at the baseline measurement was 24.0 °C (standard deviation: 2.8). After heating the toes for 5 min with a warm heating pad, the skin temperature rose to a mean 27.8 °C (standard deviation: 2.8; p = 0.000). The mean toe pressure rose from 58.5 (standard deviation: 32) to 62 (standard deviation: 32) mmHg (p = 0.029). Furthermore, after the skin was heated up to 40 °C with the probe, the mean toe pressure in the third measurement was 71 (standard deviation: 34) mmHg (p = 0.000). The response to the heating varied greatly between the patients after the first heating-from -34 mmHg (toe pressure decreased from 74 to 40 mmHg) to +91 mmHg. When the toes were heated to 40 °C, the change in to toe pressure from the baseline varied between -28 and +103 mmHg.

CONCLUSION

Our data indicate that there is a different response to the heating in different clinical situations and in patients with a different comorbidity.

A systematic review of the sensitivity and specificity of the toe–brachial index for detecting peripheral artery disease

The toe–brachial index (TBI) is used as an adjunct to the ankle–brachial index (ABI) for non-invasive lower limb vascular screening. With increasing evidence suggesting limitations of the ABI for diagnosis of vascular complications, particularly in specific populations including diabetes cohorts, the TBI is being used more widely. The aim of this review was to determine the sensitivity and specificity of the TBI for detecting peripheral artery disease (PAD) in populations at risk of this disease. A database search was conducted to identify current work relating to the sensitivity and specificity of toe–brachial indices up to July 2015. Only studies using valid diagnostic imaging as a reference standard were included. The QUADAS-2 tool was used to critically appraise included articles. Seven studies met the inclusion criteria. Sensitivity of the TBI for PAD was reported in all seven studies and ranged from 45% to 100%; specificity was reported by five studies only and ranged from 16% to 100%. In conclusion, this review suggests that the TBI has variable diagnostic accuracy for the presence of PAD in specific populations at risk of developing the disease. There was a notable lack of large-scale diagnostic accuracy studies determining the diagnostic accuracy of the TBI in detecting PAD in different at-risk cohorts. However, standardised normal values need to be established for the TBI to conclusively determine the diagnostic accuracy of this test.

Non-invasive vascular assessment in the foot with diabetes: sensitivity and specificity of the ankle brachial index, toe brachial index and continuous wave Doppler for detecting peripheral arterial disease

BACKGROUND & AIMS

Non-invasive lower limb vascular assessment in people at risk of peripheral arterial disease (PAD) including those with diabetes is crucial. There is evidence that standard assessment techniques such as the ankle-brachial index (ABI) may be less effective in people with diabetes. However there is limited evidence for other frequently used tests including continuous wave Doppler (CWD), and the toe-brachial index (TBI). The aim of this study was to determine the sensitivity and specificity of, ABI, CWD and TBI in a population with, and without diabetes.

METHODS

Participants with and without diabetes who met current guidelines for vascular screening were recruited, and CWD waveforms, an ABI and a TBI were obtained from the right lower limb. Diagnostic accuracy was determined using colour duplex ultrasound (CFDU). Receiver operating characteristic curves were calculated.

RESULTS

117 participants were recruited, seventy-two with diabetes and forty-five without diabetes. CWD had the highest sensitivity in people with diabetes (74%) and without (84%). CWD also had the highest specificity in people with diabetes (74%) and without (84%) compared to both TBI and ABI. In participants with diabetes, the ABI was a poor test, area under the curve: 0.58 (p=0.27).

CONCLUSIONS

CWD waveform is more likely to detect significant PAD compared to ABI and TBI in people with and without diabetes.

Sensitivity and Specificity of the Toe-Brachial Index for Detecting Peripheral Arterial Disease: Initial Findings

OBJECTIVES

The toe-brachial index (TBI) is an alternative to the ankle-brachial index (ABI) in screening for peripheral arterial disease (PAD); however, there is limited evidence comparing their diagnostic accuracy. This study compared the diagnostic accuracy of the ABI and TBI in a population at risk of PAD.

METHODS

The sensitivity and specificity of the ABI and TBI were determined by color duplex sonography. Receiver operating characteristic (ROC) analysis was performed.

RESULTS

A total of 119 participants were recruited (75 male and 44 female). The sensitivity for PAD was highest for the TBI (71%; ABI, 45%), and the specificity was highest for the ABI (93%; TBI, 78%). Receiver operating characteristic analysis indicated that the TBI (ROC area, 0.77; P = .0001) had greater clinical efficacy for diagnosis of PAD than the ABI (ROC area, 0.65; P = .005).

CONCLUSIONS

In specific populations, the TBI may have greater clinical efficacy than the ABI for diagnosis of PAD.

A systematic review of the effect of pre-test rest duration on toe and ankle systolic blood pressure measurements

Background

Measurement of toe and ankle blood pressure is commonly used to evaluate peripheral vascular status, yet the pre-test rest period is inconsistent in published studies and among practitioners, and could affect results. The aim of this systematic review is to evaluate all research that has investigated the effect of different periods of pre-test rest on toe and ankle systolic blood pressure.

Methods

The following databases were searched up to April 2012: Medline (from 1946), EMBASE (from 1947), CINAHL (from 1937), and Cochrane Central Register of Controlled Trials (CENTRAL) (from 1800). No language or publication restrictions were applied. Eighty-eight content experts and researchers in the field were contacted by email to assist in the identification of published, unpublished, and ongoing studies. Studies evaluating the effect of two or more pre-test rest durations on toe or ankle systolic blood pressure were eligible for inclusion. No restrictions were placed on participant characteristics or the method of blood pressure measurement. Outcomes included toe or ankle systolic blood pressure and adverse effects. Abstracts identified from the search terms were independently assessed by two reviewers for potential inclusion.

Results

1658 abstracts were identified by electronic searching. Of the 88 content experts and researchers in the field contacted by email a total of 33 replied and identified five potentially relevant studies. No studies were eligible for inclusion.

Conclusions

There is no evidence of the effect of different periods of pre-test rest duration on toe and ankle systolic blood pressure measurements. Rigorous trials evaluating the effect of different durations of pre-test rest are required to direct clinical practice and research.

Ankle-brachial index, toe-brachial index, and cardiovascular mortality in persons with and without diabetes mellitus

BACKGROUND

The prognostic utility of the ankle-brachial index (ABI) may be hampered in persons with diabetes due to peripheral arterial stiffening in the ankles. Stiffening of toe arteries occurs infrequently in diabetes. We aimed to determine the nature of the relationship of the toe-brachial index (TBI) and ABI with cardiovascular disease (CVD) mortality and to determine whether the associations are modified in individuals with diabetes.

METHODS

Individuals with clinically suspected atherosclerotic peripheral arterial disease who underwent ABI and TBI measurements in a vascular laboratory were monitored longitudinally for CVD mortality.

RESULTS

Among 469 participants (89% men), the mean age was 68 ± 9 years, and 36% had diabetes. The mean ABI was 0.83 ± 0.28 and the mean TBI was 0.60 ± 0.24. During median 7.0 years of follow-up, there were 158 CVD deaths. The association of the ABI categories with CVD deaths differed in diabetic vs nondiabetic participants (P = .002 for interaction). In contrast, the association of the TBI categories with CVD deaths was similar, irrespective of diabetes status (P = .17 for interaction). Among diabetic patients, a U-shaped relationship was observed between ABI categories and CVD death: those with low (<0.90) and high (>1.30) ABIs were both at higher risk than those with normal ABIs (range, 0.90-1.30). In nondiabetic patients, association of ABI categories with CVD death was linear, such that those with an ABI >1.30 were at the lowest risk, whereas those with an ABI <0.90 were at higher risk. In contrast, the association of TBI categories with CVD death was linear irrespective of diabetes status. High TBI categories consistently predicted low risk, whereas risk was higher with progressively lower TBI categories.

CONCLUSIONS

Among diabetic individuals with clinically suspected peripheral arterial disease, those with low and high ABIs are both at higher risk of CVD death. In contrast, a linear relationship was observed between TBI categories and CVD death irrespective of diabetes status. These findings suggest that stiffened ankle arteries may limit the predictive value of the ABI in individuals with diabetes, a limitation that may be overcome by measurement of the TBI.

Prevalence and risk factors of PAD among patients with elevated ABI

OBJECTIVES

To assess the prevalence and clinical significance of elevated ankle-brachial index (ABI) in patients referred to vascular consultation.

DESIGN

Retrospective clinical study.

MATERIAL AND METHODS

In 1,762 patients referred with a suspicion of peripheral arterial disease (PAD), ABI and toe brachial index (TBI) were measured by photoplethysmography. ABI>/=1.3 was considered falsely elevated and TBI<0.60 was the diagnostic criterion for PAD.

RESULTS

The prevalence of elevated ABI was 8.4% and that of PAD among these patients 62.2%. PAD was significantly more prevalent among subjects with severe symptoms (rest pain, ulcers or gangrene) than in those with intermittent claudication (83.8% and 45.3%, respectively, p<0.001). The risk of PAD diagnosis was ten-fold (OR 10.31, 95% CI 2.07-51.30) among those with chronic renal failure, five-fold among patients with a history of smoking (OR 5.63, 95% CI 1.22-26.00) and over three-fold (OR 3.44, 95% CI 1.46-8.12) among those with coronary heart disease. The specificities of elevated ABI threshold levels (1.3, 1.4 and 1.5) in identifying PAD were 86%, 94% and 96%, respectively, the sensitivities being 44%, 38% and 36%, respectively.

CONCLUSIONS

The prevalence of elevated ABI in patients referred to vascular consultation is 8.4% and that of PAD among these 62.2%. PAD is significantly more probable among those with chronic renal failure, a history of smoking and coronary heart disease. Furthermore, the specificity of elevated ABI (>/=1.3) in recognizing PAD is good, whereas the sensitivity is only satisfactory.

Are ankle and toe brachial indices (ABI-TBI) obtained by a pocket Doppler interchangeable with those obtained by standard laboratory equipment?

PURPOSE

The aim of this study was to determine if the ankle and toe brachial indices obtained by an experienced registered nurse (RN) using a pocket Doppler were within acceptable levels of agreement with those obtained by a registered vascular technologist (RVT) using standard laboratory equipment.

DESIGN

A within-subjects comparative design was used.

SETTING AND SUBJECTS

Thirty subjects who were referred to a vascular laboratory for arterial studies were recruited. All tests were performed in the outpatient vascular laboratory of a large, urban medical center.

METHODOLOGY

Ankle and toe brachial indices were measured on each subject by the RN and the RVT during each visit. Data were analyzed using the Bland-Altman method to assess the level of agreement between the RN's pocket Doppler and the RVT's standard laboratory equipment.

RESULTS

Differences between each instrument's ankle brachial indices were within the a priori 15% limit of agreement. Differences between each instrument's toe brachial indices exceeded the a priori 15% limit of agreement.

CONCLUSION

The ankle brachial index obtained by using a pocket Doppler by an experienced RN is interchangeable with vascular laboratory testing for detection of lower extremity arterial disease (LEAD). The pocket Doppler-derived toe brachial index was not interchangeable with vascular laboratory testing for detection of LEAD.

‘Pole Test’ Measurements in Critical Leg Ischaemia

BACKGROUND

For the quantification of critical limb ischaemia (CLI) most vascular surgery units use sphygmo-manometric and transcutaneous oxygen pressure (TcPO2) measurements. However, measurements obtained by cuff-manometry can be overestimated especially in diabetic patients because of medial calcification that makes leg arteries less compressible. TcPO2 measurements present a considerable overlap in the values obtained for patients with different degrees of ischaemia and its reproducibility has been questioned. Arterial wall stiffness has less influence on the pole test, based on hydrostatic pressure derived by leg elevation, and this test seems to provide a reliable index of CLI.

OBJECTIVE

The objective of this study was to evaluate the pole pressure test for detection of critical lower limb ischaemia, correlating results with cuff-manometry and transcutaneous oxygen pressure.

DESIGN

University hospital-prospective study.

MATERIALS AND METHODS

Seventy-four patients (83 legs) with rest pain or gangrene were evaluated by four methods: pole test, cuff-manometry, TcPO2 and arteriography. CLI was present if the following criteria were met: (a) important arteriographic lesions+rest pain with an ankle systolic pressure (ASP) < or = 40 mmHg and/or a TcPO2 < or = 30 mmHg, or (b) important arteriographic lesions+tissue loss with an ASP < or = 60 mmHg and/or a TcPO2 < or = 40 mmHg. Fifty-seven lower limbs met the criteria for CLI.

RESULTS

Measurements obtained by cuff-manometry were significantly higher to those obtained by pole test (mean pressure difference: 40 mmHg, p<0.001). The difference between the two methods remained statistically significant for both diabetics (50.73, p<0.001) and non-diabetics (31.46, p<0.001). Mean TcPO2 value was 15.51 mmHg and there was no important difference between patients with and without diabetes. Overall, there was a correlation between sphygmomanometry and pole test (r = 0.481). The correlation persisted for patients without diabetes (r = 0.581), but was not evident in patients with diabetes. Correlation between pole test and TcPO2 was observed only for patients with diabetes (r = 0.444). There was no correlation between cuff-manometry and TcPO2. The pole test offered an accuracy of 88% for the detection of CLI. The sensitivity of this test was 95% and the specificity 73%.

Get the LEAD Out

Lower extremity arterial disease affects approximately one third of individuals 66 years of age and older and has a high risk for nonhealing wounds, infection, and limb loss. Much wound care is given by or under the direction of nurses. Therefore, the assessment and management of these patients presents many opportunities and challenges. Assessment is the cornerstone of effective care, but traditional methods of lower extremity arterial assessment, such as pulse palpation and pain history, are insufficient to determine the presence and extent of ischemia. Recently published national guidelines for assessment and management of patients with lower extremity wounds have recommended using noninvasive tests such as the ankle brachial index and toe brachial index to rule out lower extremity arterial disease, which complicates wound healing. However, the ankle brachial index can be falsely elevated in patients with diabetes and renal failure because of calcification of the arteries, which causes them to be incompressible. In these situations, it has been advised to obtain a toe pressure or toe brachial index because digital arteries are usually less affected by calcification. There is a paucity of data about the knowledge of principles and performance of the ankle brachial index/toe brachial index by nurses, particularly in the United States, using pocket-sized portable Doppler equipment. Therefore, the purpose of this article is to provide an overview and synthesis of relevant studies and published expert opinion regarding noninvasive arterial assessment using ankle brachial and toe brachial indexes as a basis for developing protocols for performing the tests and identifying gaps in research where further investigation is needed.

Toe pressure measurements compared to ankle artery pressure measurements

The Trans-Atlantic Inter-Society Consensus (TASC)-recommended absolute toe pressure is < 30-50 mm Hg for definition of chronic critical limb ischemia (CLI). Toe pressures can be measured by different techniques. The authors analyzed the clinical use of the Doppler technique and an automatic device with optical sensors and estimated their value in documentation of chronic critical limb ischemia compared to ankle artery pressures. Three different investigations were performed: (1) In 16 healthy subjects the digital artery pressures were measured by using 3 different optical sensors (transmission, reflection, and microcirculation sensor) and compared to the systolic brachial pressure. (2) In 50 patients with and without peripheral arterial occlusive disease the toe pressures at digits 1 and 2 of both feet were determined by Doppler technique (8 MHz) and by optical sensors (cuff width constant 1.5 cm) and were compared to the ankle artery pressure determined by Doppler technique. (3) In 175 patients the toe pressures were measured at 1 toe and the ankle artery pressures were determined. In this group they estimated the clinical use of the toe pressure in regard to the definition of CLI (toe pressure < 50 mm Hg) compared to the ankle pressure < 70 mm Hg. The digital artery pressures measured with the different optical sensors, and the systolic brachial pressures were not significantly different and the correlation coefficients were around 0.7. In 21 of 50 patients the toe pressure at D1 and D2 could not be measured by Doppler technique because with the applied cuff no Doppler signal could be detected at the tip of the toe, but in 24 of these 29 patients the optical measurement was possible. Mean toe pressures at D1 were 108 +/- 45 mm Hg and D2 102 +/- 45 mm Hg, which were statistically not different. The correlation coefficient for the highest ankle artery pressure and the highest toe pressure determined by the Doppler technique was 0.389; for the highest ankle artery pressure and the toe pressure measured by the optical sensors it was 0.369, and for the toe pressures measured by Doppler technique and the optical sensors it was 0.506. Defining systolic ankle artery pressure < or = 50 to 70 mm Hg as the golden standard for CLI, the sensitivity of optical toe pressure measurement for the detection of CLI was 8%, the specificity was 96%, the positive predictive value 12%, and the negative predictive value was 94%. Independent of technique the absolute systolic toe pressures did not correlate with the absolute systolic ankle pressures. The optical measurement was more suitable for toe pressure measurement because it could be used in 90% of all patients. All in all, toe pressure measurements are more useful to exclude CLI than to prove it.

Interobserver and intraobserver reproducibility of peripheral blood and oxygen pressure measurements in the assessment of lower extremity arterial disease

INTRODUCTION

Peripheral blood pressure measurements play a prominent role in the diagnosis and follow-up of patients with peripheral vascular diseases. Toe pressure of the hallux (TP1) and second toe (TP2) and transcutaneous oxygen pressure (TCPO2) measurements are becoming more important. The ankle/brachial pressure index (ABPI) is known to be a reliable parameter, but the toe pressure and TCPO2 are evaluated less thoroughly. Therefore, we evaluated the reproducibility of TP1, TP2, TCPO2, ABPI, ankle pressure (AP), and brachial pressure (BP).

PATIENTS AND METHODS

In 54 patients with various stages of peripheral vascular disease, the intraobserver and interobserver reproducibility of BP, AP, ABPI, TP1, TP2, and TCPO2 was investigated by calculating the repeatability coefficient (RC) and the intraclass correlation coefficient (ICC) and by using Bland-Altman plots.

RESULTS

The intraobserver and interobserver reproducibility at 1 day and after 1 week of BP, AP, ABPI, and TP1 was substantial and comparable (ICC range, 0.80-0.99), except for the BP after 1 week. The TP2 and TCPO2 were less reproducible (ICC range, 0.62-0.98). The interobserver RC of BP was 31 mm Hg; of AP, 44 mm Hg; of ABPI, 27%; of TP1, 41 mm Hg; of TP2, 67 mm Hg; and of TCPO2; 30 mm Hg. The difference plot showed that the observer variability was equally distributed across the range of pressure in all measurements.

CONCLUSION

The BP, AP, ABPI, and TP1 have a substantial intraobserver and interobserver reproducibility, whereas TP2 and TCPO2 show worse reproducibility. Especially when low values (or values around a cutoff value) are measured, the RC should be taken into account, and repetition of the measurement is advocated.

The value of toe pulse waves in determination of risks for limb amputation and death in patients with peripheral arterial disease and skin ulcers or gangrene

OBJECTIVES

The purpose of this study was to determine whether the presence of low amplitude of pulse waves recorded from the toes is related to the risk of subsequent amputation and death in patients with skin ulcers or gangrene and peripheral arterial disease, and how the risk of low wave amplitude relates to the risk associated with low peripheral pressures.

METHODS

A total of 309 patients with 346 limbs with skin lesions and arterial disease referred to the vascular laboratory were followed up for an average of 5 years (range, 1-8 years). Measurements were carried out to obtain ankle and toe pressures, pressure indices, and toe pulse wave amplitude. These variables were related to the risks of major amputation and total and cardiovascular death by means of the Cox proportional hazards model.

RESULTS

Low toe pulse wave amplitude (< or = 4 mm) was associated with increased risk of amputation (relative risks 4.20 in all limbs and 2.63 in those with toe pressure < or = 30 mm Hg; P <.01). Wave amplitude remained significantly associated with increased risk of amputation after controlling for each pressure variable (P <.01). Low pulse wave amplitude and toe/brachial index were associated with increased risks of both total and cardiovascular death in all patients (relative risks ranged from 1.43-1.73; P <.05) and in those with toe pressure of 30 mm Hg or less (relative risks 1.56-1.90; P <.05).

CONCLUSIONS

Low toe pulse wave amplitude is related significantly to increased risks of amputation and death in patients with skin lesions and arterial disease. The presence of low wave amplitude provides significant information in addition to peripheral pressures with respect to the risk of amputation.

Optimisation of the non-invasive assessment of critical limb ischaemia requiring invasive treatment

OBJECTIVE

to assess the optimal cut-off values of toe blood pressure (TBP) and transcutaneous oxygen pressure (TcpO(2)) in the supine and sitting positions, in order to accurately detect the presence of severe leg ischaemia requiring invasive treatment.

METHODS

in 49 consecutive patients (65 legs) with severe ischaemia according to clinical symptoms of Fontaine III or IV and a lowered ankle blood pressure, TBP and TcpO(2)were measured in the supine and sitting positions. Treatment within 6 weeks after the diagnosis was classified as either conservative or invasive (revascularisation or amputation).

RESULTS

of the 65 legs, 38 (58%) required invasive treatment. The mean ankle pressure for this group was 70 mmHg. The optimal cut-off value for TBP was 38 mmHg and for TcpO(2)35 mmHg. A TBP of </=30 mmHg and a TcpO(2)</=25 mmHg while supine, showed likelihood ratios (LR) of 7.0 and 3.3, respectively, and when combined an LR of 12.4. Measurements in the sitting position did not enhance diagnostic power.

CONCLUSIONS

the need for invasive therapy in patients with severe leg ischaemia might be predicted by measuring TBP and TcpO(2), using the above-mentioned cut-off values.

Quantitative and qualitative progression of peripheral arterial disease by non-invasive testing

There is little information on the progression of peripheral arterial disease (PAD) over time. A series of 508 patients with a prior examination for PAD were contacted and brought in for follow-up to evaluate the natural history of PAD. A total of 85 patients were excluded because they had interventions in both limbs prior to their return visit. Progression was assessed in the remaining 423 patients for a total of 755 limbs, both quantitatively and qualitatively using six categories of PAD severity. There was a modest overall categorical progression of disease: 228 limbs (30.2%) displayed categorical progression, while 172 limbs (22.8%) improved over a 4.6-year average follow-up. Through analysis of quantitative change, it was determined that more quantitative progression occurred than was evident from categorical progression. Two of the three non-invasive tests employed, the ankle/brachial index (ABI) and posterior tibial peak forward flow velocity (peak PT), showed statistically significant progression during follow-up: mean ABI change = -0.019, 95% confidence interval (CI)= -0.031 to -0.007; mean peak PT change = -2.32 cm/s, 95% CI = -3.20 to -1.44. The toe/brachial index (TBI) also suggested progression: mean change= -0.013, but the 95% CI included no change. Standard scores (sum of the Z-scores for ABI, peak PT and TBI) were calculated. The standard score progressed approximately 0.34 units (standard deviations), p-value <0.001, over 4.6 years; or about 0.07 standard deviations per year. There were independent and statistically significant (p<0.05) associations between the rate of PAD progression (standard score change) and age, diabetes, classic ('Rose') intermittent claudication, moderate to severe PAD in the same limb, moderate to severe PAD in the contralateral limb and future therapeutic intervention. There were independent and suggestive associations (0.05<p-value<0.15) between PAD progression and pain at rest, mild PAD in the same limb, and mild PAD in the contralateral limb. PAD progression was not associated with gender, atypical claudication, or amputation status. Thus, in this cohort of PAD patients, PAD on average progressed significantly over 4.6 years. This progression was independently related to age, diabetes and several markers of disease severity.

The challenge and importance of defining critical limb ischemia

Patients with critical limb ischemia are at risk of limb loss and have very high cardiovascular and total mortality rates, which are greater than can be accounted for by the usual risk factors for atherosclerosis. A definition of critical ischemia is necessary to determine the natural history of the disease and to assess and compare the efficacy of various forms of therapy. The definition needs to be based on hemodynamic criteria because clinical manifestations and outcomes are not reliable. The reasons for the difficulties in arriving at a generally acceptable definition are explored. Building on the previous work of others, modified hemodynamic definitions for critical and subcritical ischemia, which include measurements of pressures and of indices of microcirculation, are proposed.

The value of non-invasive techniques for the assessment of critical limb ischaemia

OBJECTIVE

The European Consensus Document (ECD) defines critical ischaemia (CI) according to clinical (Fontaine) and blood pressure parameters. However, clinical symptoms may be non-specific and CI may exist without severely reduced blood pressures. This study prospectively investigated the additive value of transcutaneous oxygen tension (pO2) and toe blood pressure measurements to assess the presence of CI.

METHODS

Forty-nine patients with 65 legs clinically classified as Fontaine stages III (n = 23) and IV (n = 26) were studied. Ankle and toe systolic blood pressure and pO2 were measured to assess the presence of CI (cut-off values were 50, 30 and 30 mmHg, respectively). The surgeon was blinded for the toe pressure and pO2 results. The treatment received within 1 month after presentation was recorded as being either conservative or invasive (vascular surgery or PTA).

RESULTS

An ankle pressure of < or = 50 mmHg classified only 17% of the legs as having CI. By adding toe pressure and pO2, significantly more legs (63%; p < 0.0001) were classified as CI, of which 68% received invasive therapy. Forty-nine percent of the legs with an ankle pressure > 50 mmHg were treated invasively, whereas only 32% of the legs classified as not having CI by means of toe pressure and pO2 underwent invasive therapy. If the need for invasive treatment is used as the "gold standard" for the presence of CI, 54% of the legs would accurately be classified on the basis of the ankle blood pressure. The combination of toe pressure and pO2 would have yielded 71% and the ECD criteria 72% and accurately classified legs. The odds ratio for invasive therapy given a pO2 or toe pressure above the cut-off value was 14.

CONCLUSION

Ankle blood pressure measurements have limited diagnostic value. Adding toe and/or oxygen pressures enhances the detection of CI requiring invasive therapy.