Hallucal thenar index: A new index to detect peripheral arterial disease using laser speckle flowgraphy

Abstract

<jats:sec><jats:title>Objectives</jats:title><jats:p> Laser speckle flowgraphy is a technology using reflected scattered light for visualization of blood distribution, which can be used to measure relative velocity of blood flow easily without contact with the skin within a short time. It was hypothesized that laser speckle flowgraphy may be able to identify foot ischemia. This study was performed to determine whether laser speckle flowgraphy could distinguish between subjects with and without peripheral arterial disease. </jats:p></jats:sec><jats:sec><jats:title>Materials and methods</jats:title><jats:p> All subjects were classified based on clinical observations using the Rutherford classification: non-peripheral arterial disease, class 0; peripheral arterial disease group, class 2–5. Rutherford class 6 was one of the exclusion criteria. Laser speckle flowgraphy measured the beat strength of skin perfusion as an indicator of average dynamic cutaneous blood flow change synchronized with the heartbeat. The beat strength of skin perfusion indicates the strength of the heartbeat on the skin, and the heartbeat strength calculator in laser speckle flowgraphy uses the blood flow data to perform a Fourier transform to convert the temporal changes in blood flow to a power spectrum. A total of 33 subjects with peripheral arterial disease and 40 subjects without peripheral arterial disease at a single center were prospectively examined. Laser speckle flowgraphy was used to measure hallucal and thenar cutaneous blood flow, and the measurements were repeated three times. The hallucal and thenar index was defined as the ratio of beat strength of skin perfusion value on hallux/beat strength of skin perfusion value on ipsilateral thenar eminence. The Mann–Whitney U-test was used to compare the median values of hallucal and thenar index and ankle brachial index between the two groups. A receiver operating characteristic curve for hallucal and thenar index of beat strength of skin perfusion was plotted, and a cutoff point was set. The correlation between hallucal and thenar index of beat strength of skin perfusion and ankle brachial index was explored in all subjects, the hemodialysis group, and the non-hemodialysis (non-hemodialysis) group. </jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p> The median value of the hallucal and thenar index of beat strength of skin perfusion was significantly different between subjects with and without peripheral arterial disease (0.27 vs. 0.87, respectively; P &lt; 0.001). The median value of ankle brachial index was significantly different between subjects with and without peripheral arterial disease (0.8 vs. 1.1, respectively; P &lt; 0.001). Based on the receiver operating characteristic of hallucal and thenar index, the cutoff was 0.4416 and the sensitivity, specificity, positive predictive value, and negative predictive value were 68.7%, 95%, 91.7%, and 77.6%, respectively. The correlation coefficients of all subjects, the hemodialysis group, and the non-hemodialysis group were 0.486, 0.102, and 0.743, respectively. </jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p> Laser speckle flowgraphy is a noninvasive, rapid, and widely applicable method. Laser speckle flowgraphy using hallucal and thenar index would be helpful to determine the differences between subjects with and without peripheral arterial disease. The correlation between hallucal and thenar index of beat strength of skin perfusion and ankle brachial index indicated that this index was especially useful in the non-hemodialysis group. </jats:p></jats:sec>

Which plantar region can predict peripheral arterial disease by using laser speckleflowgraphy?

“…The study results do not support LSFG as an immediate replacement for ABI. However, ABI and HTI using LSFG show a positive correlation [5], LSFG may be used to estimate the blood flow status in the plantar skin. In particular, the ROI setting on toe 1 may be considered the most sensitive screening in the plantar region.…”

“…The AUC tended to have higher accuracy in the load part and lower accuracy in the nonload part. LSFG can capture the movement of erythrocytes 1-2 mm under the skin [1][2][3][4][5], which is the depth of the subpapillary vascular nets. The unique structure of the plantar soft tissue dissipates stress by loading [8] and maintains normal plantar pressures [9].…”

“…There are a few reports describing the use of LSFG in evaluating lower-limb ischemia [1,5]; thus, there is no consensus on how to use the measurement results. We previously reported that the hallucal thenar index (HTI) using LSFG could be used to assess peripheral arterial disease (PAD) [5].…”

“…There are a few reports describing the use of LSFG in evaluating lower-limb ischemia [1,5]; thus, there is no consensus on how to use the measurement results. We previously reported that the hallucal thenar index (HTI) using LSFG could be used to assess peripheral arterial disease (PAD) [5]. The HTI in patients with PAD was significantly lower than that of those without PAD, and it demonstrated a strong correlation with ankle-brachial index (ABI) in nonhemodialysis patients (r = 0.743).…”

“…The HTI in patients with PAD was significantly lower than that of those without PAD, and it demonstrated a strong correlation with ankle-brachial index (ABI) in nonhemodialysis patients (r = 0.743). The HTI selected one point in the foot and did not fully utilize the performance of the LSFG, which can measure a range of 20 × 15 cm at a time and set a maximum of six regions of interest (ROI) on the monitor [1][2][3][4][5].…”