Infrared Thermography as a Diagnostic Tool for the Assessment of Patients with Symptomatic Peripheral Arterial Disease Undergoing Infrafemoral Endovascular Revascularisations

Aim: The aim of this study was to evaluate the utility and reliability of temperature foot changes measured by infrared thermography (IRT) for the evaluation of patients with atherosclerotic peripheral arterial disease (PAD) before and after endovascular revascularisation. Methods: This is an observational prospective study carried out on symptomatic PAD patients. Evaluations consisted of a clinical examination, duplex scan with ankle–brachial index calculation (ABI) and IRT measurements with infrared camera FLIR-ONE connected to a smartphone with android technology. Locations on the foot sampled with IRT were the anterior tibial, pedal, posterior and arcuate arteries. Results obtained with IRT on the symptomatic foot were compared to the contralateral foot and with the ABI values obtained bilaterally before and 24 h after revascularisation. Results: Within one year, 40 patients were enrolled, among whom 87,5% suffered from critical limb ischaemia. In three patients, it was impossible to obtain ABI measurements because of ulcerations on the limb. Skin temperature changes obtained by IRT between the symptomatic limb and the contralateral limb had a mean difference of 1.7 °C (range: 1.1–2.2 °C), p < 0.001. There was a positive correlation between ABI and temperature values of the limb needed for treatment before revascularisation (p = 0.025; r = 0.36) and after revascularisation (p = 0.024, r = 0.31). The technical success rate was 100% in all cases, achieving a significant increase in temperature at all points of the foot analysed, with a median change of 2 °C (p < 0.001). Conclusion: IRT is a safe, reliable and simple application. It could be a valuable tool for the assessment of the clinical presentation and severity of foot blood perfusion in symptomatic PAD patients and the evaluation of the technical success of endovascular revascularisation. IRT might have a role in follow-up of revascularisation procedures.

A Toe Flexion NIRS assisted Test for Rapid Assessment of Foot Perfusion in Peripheral Arterial Disease: Feasibility, Validity, and Diagnostic Accuracy

OBJECTIVES

Feasibility, validity, and diagnostic accuracy of a non-invasive dynamic ambulatory test were assessed with near infrared spectroscopy (NIRS) evaluating foot perfusion in peripheral arterial disease (PAD).

METHODS

This was a prospective observational study. Eighty PAD patients (63 males, 71 ± 9 years), including 41 patients with coexisting diabetes, participated. Thirteen healthy subjects (8 males, 26 ± 8 years) were also studied by echo colour Doppler providing 160 diseased and 26 non-diseased limbs. Under identical clinostatic conditions, participants performed a 10-repetition toe flexion tests with NIRS probes on the dorsum of each foot; the area under the curve of the oxygenated haemoglobin trace ("toflex area") was calculated and the ankle-brachial index (ABI) was measured. Time of execution, rate of wrong tests, and adverse reactions were recorded. Within session reliability was assessed by administering the test twice, with a 5 minute interval between tests. The validity was assessed determining whether the toflex area was (a) dependent on the oxygen delivery from the lower limb arteries simulating PAD conditions by a progressive blood flow restriction (40-120% of systolic pressure) in healthy subjects; (b) consistent with the degree of PAD ranked by ABI and correlated with ABI and ankle pressure values in PAD patients. The diagnostic accuracy in detecting PAD was compared with examination using echo colour Doppler ultrasound.

RESULTS

All tests were rapidly, satisfactorily (<1% mistakes), and safely performed. Toflex area values, superimposable in the two sessions (intra-class correlation coefficient 0.92), were comparable to PAD values following blood flow restriction, consistent with PAD severity, correlated with dorsal pedis artery pressure (r = .21; p = .007) and ABI (r = .65; p < .001) in PAD, but not in the presence of diabetes. Toflex area was similar to echo colour Doppler for detecting PAD following receiver operating characteristic curve analysis (area = 0.987, p < .001; toflex area values ≤ -28 arbitrary units, sensitivity/specificity 95.6/100).

CONCLUSION

The toe flexion test enables ambulatory assessment of foot perfusion and PAD detection, even in the presence of non-measurable ABI or diseases affecting the microcirculation.

Atypical leg symptoms: does routine measurement of the ankle brachial pressure index (ABPI) in primary care benefit patients?

Background : Managing patients with atypical leg symptoms in primary care can be problematic. Determining the ankle brachial pressure index (ABPI) may be readily performed to help diagnose peripheral arterial disease, but is often omitted where signs and symptoms are unclear. Question: Does routine measurement of ABPI in patients with atypical leg symptoms aid management increase satisfaction and safely reduce hospital referral? Methodology: Patients with atypical leg symptoms but no skin changes or neurological symptoms underwent clinical review and Doppler ABPI measurement (suspicious finding ≤ 1.0). Testing was performed by the same doctor (study period: 30 months). Patient outcomes were determined from practice records, hospital letters and a telephone survey. Results : The study comprised 35 consecutive patients (males: N = 15), mean age 64 years (range: 39-88). Presentation included pain, cold feet, cramps, irritation and concerns regarding circulation. Prior to ABPI measurement, referral was considered necessary in 10, not required in 22 and unclear in 3. ABPI changed the referral decision in 10 (29%) and confirmed the decision in 25 (71%). During the study, 10 (29%) patients were referred (9 vascular, 1 neurology). Amongst the vascular referrals, significant peripheral arterial disease has been confirmed in six patients. A further two patients are under review and one did not attend. To date, lack of referral in patients with atypical leg symptoms but a normal ABPI has not increased morbidity. Current status was assessed by telephone review in 16/35 (46% contact rate; mean 18 months, range 2-28). Fifteen patients (94%) appreciated that their symptoms had been quickly and conveniently assessed, 8/11 (73%) with a normal ABPI were reassured by their result and in 8/11 symptoms have resolved. Discussion/Conclusion: APBI conveniently aids management of atypical leg symptoms by detecting unexpected peripheral arterial disease, avoids /confirms the need for referral, reassures patients and guides reassessment. This study suggests ABPI should be used more widely.

Relative value of the Ankle-Brachial Index of intermittent claudication

INTRODUCTION

The Ankle-Brachial Index (ABI) makes it possible to identify patients with peripheral artery disease (PAD). Intermittent claudication (IC) is the first major symptom of PAD, although many patients with an ABI ≤ 0.9 do not exhibit IC, and the range of ABI among those who do have IC is very variable. This study evaluates the correlation between ABI and the perception (symptomatology) of claudicant patients.

MATERIAL AND METHODS

An observational, cross-sectional and multicentre, study of 920 patients with IC. Clinical history, ABI, Walking Impairment Questionnaire (WIQ) and European Quality of Life Questionnaire (EQ-5D) were recorded. Associations were analysed using Spearman's correlation coefficient.

RESULTS

The mean ABI of the series was 0.63 (SD = 0.19). The mean WIQ-distance was 34.07 (SD = 26.77), values being smaller for lower ABI values (r = 0.343, p < 0.001). The mean EQ-5D score of the series was 0.58 (SD = 0.21), also showing lower values as the ABI decreased (r = 0.278, p < 0.001). The correlations of WIQ and EQ-5D with ABI were statistically significant in both cases, but always less than 0.400 (between 0.278 and 0.343).

CONCLUSIONS

The correlations of ABI with the questionnaires of walking capacity and quality of life are weak. For this reason, although in clinical practice the ABI of CI patients is commonly measured, decisions should not be taken during the development of IC exclusively on the basis of the ABI.

Collateral Vessel Formation Causes Clinical Recovery From Limb Ischemia in a Mouse Model

Experimental models of recovery from limb ischemia are required for evaluating novel means of treating ischemia. We describe a mouse model to assess gait after inducing limb ischemia. Gait analysis was performed using a Plexiglass tube, the floor of which contained load cells. Gait was measured in 20 mice; 10 underwent ligation of the right hind limb artery and the other 10 underwent a sham operation. The gait of the animals was measured at 1, 2, and 4 weeks following the procedure. In sham-operated animals, the gait showed no measurable change. In the ligated animals, the ratio of the right fore-to-hind limb changed from 1.07 at baseline to 1.4 at day 0 (P = .001), 1.16 (P = .012 compared with control), and 1.04 (P = .37 compared with control) at weeks 2 and 4, respectively. Gait returned to normal within 4 weeks of induction of ischemia. This model may be helpful in testing potential novel therapies.