Co-variation between walking ability and circulatory alterations in patients with intermittent claudication

Toe-brachial index and toe systolic blood pressure for the diagnosis of peripheral arterial disease

BACKGROUND

Peripheral arterial disease (PAD) of the lower limbs is caused by atherosclerotic occlusive disease in which narrowing of arteries reduces blood flow to the lower limbs. PAD is common; it is estimated to affect 236 million individuals worldwide. Advanced age, smoking, hypertension, diabetes and concomitant cardiovascular disease are common factors associated with increased risk of PAD. Complications of PAD can include claudication pain, rest pain, wounds, gangrene, amputation and increased cardiovascular morbidity and mortality. It is therefore clinically important to use diagnostic tests that accurately identify PAD. Accurate and timely detection of PAD allows clinicians to implement appropriate risk management strategies to prevent complications, slow progression or intervene when indicated. Toe-brachial index (TBI) and toe systolic blood pressure (TSBP) are amongst a suite of non-invasive bedside tests used to detect PAD. Both TBI and TSBP are commonly utilised by a variety of clinicians in different settings, therefore a systematic review and meta-analysis of their diagnostic accuracy is warranted and highly relevant to inform clinical practice.

OBJECTIVES

To (1) estimate the accuracy of TSBP and TBI for the diagnosis of PAD in the lower extremities at different cut-off values for test positivity in populations at risk of PAD, and (2) compare the accuracy of TBI and TSBP for the diagnosis of PAD in the lower extremities. Secondary objectives were to investigate several possible sources of heterogeneity in test accuracy, including the following: patient group tested (people with type 1 or type 2 diabetes, people with renal disease and general population), type of equipment used, positivity threshold and type of reference standard.

SEARCH METHODS

The Cochrane Vascular Information Specialist searched the MEDLINE, Embase, CINAHL, Web of Science, LILACS, Zetoc and DARE databases and the World Health Organization International Clinical Trials Registry Platform and ClinicalTrials.gov trials registers to 27 February 2024.

SELECTION CRITERIA

We included diagnostic case-control, cross-sectional, prospective and retrospective studies in which all participants had either a TSBP or TBI measurement plus a validated method of vascular diagnostic imaging for PAD. We needed to be able to cross-tabulate (2 x 2 table) results of the index test and the reference standard to include a study. To be included, study populations had to be adults aged 18 years and over. We included studies of symptomatic and asymptomatic participants. Studies had to use TSBP and TBI (also called toe-brachial pressure index (TBPI)), either individually, or in addition to other non-invasive tests as index tests to diagnose PAD in individuals with suspected disease. We included data collected by photoplethysmography, laser Doppler, continuous wave Doppler, sphygmomanometers (both manual and aneroid) and manual or automated digital equipment.

DATA COLLECTION AND ANALYSIS

Two review authors independently completed data extraction using a standardised form. We extracted data to populate 2 x 2 contingency tables when available (true positives, true negatives, false positives, false negatives). Where data were not available to enable statistical analysis, we contacted study authors directly. Two review authors working independently undertook quality assessment using QUADAS-2, with disagreements resolved by a third review author. We incorporated two additional questions into the quality appraisal to aid our understanding of the conduct of studies and make appropriate judgements about risk of bias and applicability.

MAIN RESULTS

Eighteen studies met the inclusion criteria; 13 evaluated TBI only, one evaluated TSBP only and four evaluated both TBI and TSBP. Thirteen of the studies used colour duplex ultrasound (CDU) as a reference standard, two used computed tomography angiography (CTA), one used multi-detector row tomography (MDCT), one used angiography and one used a combination of CDU, CTA and angiography. TBI was investigated in 1927 participants and 2550 limbs. TSBP was investigated in 701 participants, of which 701 limbs had TSBP measured. Studies were generally of low methodological quality, with poor reporting of participant recruitment in regard to consecutive or random sampling, and poor reporting of blinding between index test and reference standard, as well as timing between index test and reference standard. The certainty of evidence according to GRADE for most studies was very low.

AUTHORS' CONCLUSIONS

Whilst a small number of diagnostic test accuracy studies have been completed for TBI and TSBP to identify PAD, the overall methodological quality was low, with most studies providing a very low certainty of evidence. The evidence base to support the use of TBI and TSBP to identify PAD is therefore limited. Whilst both TBI and TSBP are used extensively clinically, the overall diagnostic performance of these tests remains uncertain. Future research using robust methods and clear reporting is warranted to comprehensively determine the diagnostic test accuracy of the TBI and TSBP for identification of PAD with greater certainty. However, conducting such research where some of the reference tests are invasive and only clinically indicated in populations with known PAD is challenging.

Limb hemodynamics are not predictive of functional capacity in patients with PAD

To the practicing clinician, it seems obvious that limb hemodynamics would be the primary determinant of walking distance. However, other determinants, such as skeletal muscle metabolism, may play a role. Accordingly, in the current study, we examined the relationship between measures of limb hemodynamics and walking capacity in patients with peripheral arterial disease (PAD). We measured toe and ankle pressures for calculation of toe-(TBI) and ankle (ABI)-brachial indices; basal and hyperemic calf blood flow (CBF; by plethysmography); and initial (ICT) and absolute (ACT) claudication time using the Skinner-Gardner protocol. As expected, PAD patients had impaired limb hemodynamics with reduced TBI, ABI and a reduction in ABI post-exercise. However, there was no relationship between any of the hemodynamic variables (including ABI, ABI reduction post-exercise, TBI, baseline or maximal CBF) and walking distance as assessed by ICT or ACT. A subset of PAD patients with an ACT >750 s (n =16; ‘long claudicators’) were compared with a subset of PAD patients with an ACT <260 s (n = 16; ‘short claudicators’). The average ACT in the long claudicants was over fivefold greater than the short claudicators. Surprisingly, there were no differences between the two groups in any of the hemo-dynamic variables. There was also no relationship between the initial ABI, TBI, toe pressure, baseline or hyperemic CBF, and the improvement in ACT over the 3-month course of the study. This study found little relationship between hemodynamic variables and functional capacity in PAD. Accordingly, to assess the response to therapeutic interventions, exercise performance and functional status need to be directly measured, and cannot be predicted from hemodynamic measurements.

Bicycle testing as an alternative diagnostic tool in patients suspected of intermittent claudication

BACKGROUND

The ankle-brachial index (ABI) obtained after a treadmill challenge is often used to confirm the diagnosis of intermittent claudication (IC). However, some patients fail treadmill testing due to (temporary) orthopedic or neurologic comorbidity or fear of falling. The aim of this study was to evaluate the role of bicycle testing as an alternative for treadmill testing. It was hypothesized that ABIs obtained after bicycle tests were not different compared with values after standard treadmill testing.

METHODS

In this validation study, newly diagnosed IC patients (Rutherford 1-3) underwent a standard treadmill test (TT, "gold standard") and two bicycle protocols, one with a continuous resistance submaximal character (submaximal bicycle test, SBT) and a second with an incremental ramp form having a maximal character (maximal bicycle test, MBT). ABIs of both legs were obtained before and twice after each of these three different exercise tests. Healthy individuals matched for age and gender served as controls.

RESULTS

The study population consisted of 32 patients (68 ± 11 years, 21 men). ABIs of each leg (n = 64) obtained after TT correlated significantly with values obtained after either bicycle test (TT vs. SBT: r = 0.90, P < 0.001; TT vs. MBT: r = 0.88, P < 0.001). Drops in ABI after both types of exercise were significantly correlated (TT vs. SBT: r = 0.66, P < 0.001; TT vs. MBT: r = 0.32, P < 0.01). A 98% sensitivity and 86% specificity for diagnosis of IC was observed after the SBT. After the MBT, these values were 98% and 43%, respectively. Healthy controls (n = 13) demonstrated ABI values >0.9 after cycling in all tests.

CONCLUSIONS

Both submaximal and a maximal bicycle tests may serve as alternative noninvasive tools for detecting intermittent claudication. Bicycle tests can potentially be used for patients unable to perform a treadmill test.

A new device for the measurement of disease severity in patients with intermittent claudication

OBJECTIVES

To assess a new method of determining functional impairment in patients with intermittent claudication, the Double Physiological Walking Test (DPWT) using the PADHOC (Peripheral Arterial Disease Holter Control) device, against a standard treadmill test.

DESIGN

Patients with intermittent claudication presenting to the department were considered for both the DPWT and a standard treadmill test.

METHODS

initial claudicating distance, maximal walking distance and speed of walking were determined for both parts of the DPWT. Initial claudicating distance and maximal walking distance were determined from the treadmill test. Comparisons were made between the treadmill test and the DPWT.

RESULTS

The treadmill test was unable to be performed in 22% of patients due to defined contraindications. There were strong correlations in both walking distances and disease severity when comparing the DPWT and the treadmill test. Patients in whom the treadmill test was contraindicated had significantly shorter walking distances on the DPWT than those who were able to complete a treadmill walking test.

CONCLUSIONS

The DPWT correlates strongly with walking distances obtained from a standard treadmill test. However, the PADHOC can be used in a number of differing locations and settings as well as in patients in whom a treadmill test is contraindicated. It therefore has a role to play in the initial assessment of patients presenting with intermittent claudication.

Intermittent claudication: magnitude of the problem, patient evaluation, and therapeutic strategies

Intermittent claudication (IC), the symptom of exercise-induced muscle ischemia of peripheral arterial disease (PAD), afflicts and limits the activities of a significant number of patients. Incidence and prevalence of IC depends on the population studied and the diagnostic instruments used. In large studies, prevalence has ranged from 3% to 10%, with a sharp increase in those aged > or =70 years. Over the next 20 years, the total number of patients affected is expected to increase significantly due to anticipated demographic changes. Analysis of the natural history of IC demonstrates that the risk of cardiovascular morbidity and mortality far exceeds that of severe limb ischemia or limb loss. In fact, only 2% to 4% of all patients with IC will require a major amputation in their lifetime. However, life expectancy is approximately 10 years less than that of an age-matched cohort. By now, PAD is well recognized as a marker of systemic atherosclerosis. The cornerstone of patient evaluation is a history and physical examination, including a detailed atherosclerotic risk-factor assessment. In the differential diagnosis of IC, clinicians should consider etiologies such as arthritis, spinal stenosis, radiculopathy, venous claudication, or inflammatory processes. In >80% of all patients, it is possible to locate the responsible arterial segment by combining the location and severity of pain with a pulse examination. Noninvasive diagnostic studies help determine the level of disease, may unmask a hemodynamically significant stenosis, and are useful in follow-up. Arteriography is reserved for patients in whom the decision for revascularization has been made. Knowing the anatomic detail of a lesion allows the clinician to determine whether and what type of intervention is feasible. Standard therapy for all patients should be directed at both peripheral and systemic atherosclerosis, beginning with risk-factor modification in the form of smoking cessation, optimal diabetes control, and lipid normalization. The benefits of supervised exercise rehabilitation include significantly increased walking distance and enhanced quality of life. Platelet inhibition has been shown to reduce the risk of ischemic stroke, myocardial infarction, and vascular death and should be prescribed for all but those in whom it is medically contraindicated. Symptom-specific pharmacotherapy with a broad range of medications has yielded disappointing results in the past. However, recent studies have demonstrated that patients receiving the novel agent cilostazol experienced increases in walking distance and improvements in quality of life.

Haptoglobin polymorphism and peripheral arterial occlusive disease

Haptoglobin (Hp) 2-2 phenotype is a genetic risk factor in coronary atherosclerosis. In this study, haptoglobin phenotypes were determined in 141 patients with peripheral arterial occlusive disease (PAOD) and compared to a reference population (n = 1000). The relative Hp1 allele frequency was decreased among PAOD patients (0.294 vs. 0.403 for the reference population, P < 0.01) due to an overrepresentation of the Hp 2-2 phenotype (50%, odds ratio 1.82 (95% C.I. 1.28-2.60), P < 0.001). This finding was even more pronounced in non-diabetic and in non-smoking PAOD patients (Hp1 allele frequencies: 0.265 and 0.228, respectively). Serum lipids, inflammatory parameters, and blood pressure levels were comparable among the Hp phenotypes, but serum levels of the antioxidant vitamin C were lower in Hp 2-2 patients than in patients with another phenotype (P < 0.05). In PAOD patients with severe atherosclerotic lesions, maximal walking distance of patients carrying a Hp 2-2 phenotype (225-525 m) exceeded that of other Hp phenotypes (50-242 m) (interquartile ranges) (P < 0.05). The findings demonstrate that, despite an increased risk for developing PAOD, the Hp 2-2 phenotype is associated with a longer maximal walking distance which might be attributed to the earlier reported in vitro angiogenic properties of the Hp 2-2 molecule.

Oxygen uptake kinetics during exercise are slowed in patients with peripheral arterial disease

Patients with peripheral arterial disease (PAD) have arterial occlusions that limit peripheral blood flow. This study evaluated the dynamic response in O(2) consumption (VO(2)) at the onset of constant-load exercise (VO(2) kinetics) in patients with PAD. Eight patients with bilateral PAD, seven patients with unilateral PAD, nine age-matched nonsmoking controls, and seven smoking controls performed graded treadmill exercise to assess peak VO(2). Subjects also performed constant-load exercise tests at 2.0 miles/h at 0 and 4% grade to determine VO(2) kinetics. Peak VO(2) was reduced 50% in patients with PAD compared with both control groups (P < 0.05). At 4% grade, phase 2 VO(2) kinetics were significantly slowed for the PAD groups compared with controls (60.1 +/- 15.7 and 58.7 +/- 8.3 s, unilateral and bilateral PAD groups, respectively; compared with 28. 4 +/- 19.3 and 27.9 +/- 8.1 s, nonsmoking and smoking controls, respectively; P < 0.05). No relationship was found between VO(2) kinetics and disease severity. These data demonstrate that VO(2) kinetics are markedly slowed in patients with PAD. The impairment in VO(2) kinetics is not related to smoking status or arterial disease severity and therefore may reflect altered control of skeletal muscle metabolism.

Treatment of intermittent claudication: the impact on quality of life

OBJECTIVES

To measure changes in claudicant's quality of life after surgery, angioplasty or unsupervised exercise. To explore the relationship between clinical indicators of limb perfusion and patient's perception of health change.

DESIGN

Prospective study.

SETTING

University Hospital vascular outpatients.

MATERIALS AND METHODS

202 claudicants referred for Duplex of lower limb arterial disease over a 12 month period. The short form 36 questionnaire was used to determine quality of life. Ankle pressures and walking distances were determined.

MAIN RESULTS

The SF-36 was completed by 186 patients (92%) before and after treatment (34 operative patients, 74 angioplasty and 78 treated by exercise alone). Baseline quality of life was worse in surgical patients. Unsupervised exercise produced minimal changes in quality of life. Angioplasty and operation produced similar, significant improvements in physical functioning and pain. Changes in physical function or pain scores were unrelated to changes in ankle pressure.

CONCLUSIONS

Unsupervised exercise programs are unlikely to significantly improve patient's quality of life. The benefits of surgery and angioplasty support a relaxation in the indications for investigation and treatment of claudicants. Patients with impaired perceived health should not be denied treatment on the basis of preintervention ankle pressure or walking distance alone.