Objectives: The evaluation of technical success of peripheral endovascular interventions relies largely on angiography, which bears inherent limitations and does not inform about the adequacy of tissue perfusion. Thus, there is a need for adjunctive peripheral blood flow monitoring during revascularization procedures. A non-invasive peripheral blood flow monitoring system using laser speckle optical imaging was developed to detect and display real-time digit blood flow waveforms during endovascular procedures. However, evaluation of the waveforms remains subjective. The purpose of this study is to objectively quantify the waveforms using digital acceleration time (DAT) and compare it to gold-standard clinical tests.
Methods: This single-center, prospective study obtained toe blood flow waveforms from healthy volunteers and patients being evaluated for peripheral artery disease (PAD) using the FlowMet-R intraprocedural monitoring system (Medtronic, Minneapolis, MN). DAT was calculated algorithmically as the time required to accelerate from the trough to the peak of the flow waveform, such that a shorter DAT corresponds with a more brisk upstroke. DAT was compared to ankle-brachial index (ABI), toe-brachial index (TBI), and Rutherford Clinical Category (RCC). Receiver operating characteristic (ROC) curves were used to evaluate the ability of DAT to classify symptomatic PAD and severe disease.
Results: A total of 133 limbs were evaluated in 71 arterial patients and 10 healthy volunteers between October 2019 and January 2020. Participants were grouped by symptom severity and a comparison of ABI, TBI, and DAT between groups was performed. In RCC 0, RCC 1-3, and RCC 4-6 participants, the mean ABIs were 0.97±0.24, 0.80±0.27, and 0.57±0.31, respectively; the mean TBIs were 0.60±0.18, 0.35±0.20, and 0.18±0.17; and the mean DAT values were 105±26, 175±77, and 303±96. The relationship between DAT and RCC is shown in Figure 1. The correlation between RCC and DAT was ρ=0.79. For classifying asymptomatic limbs (RCC 0, n=61) from symptomatic limbs (RCC 1-6, n=72), the ROC area under the curve (AUC) was 0.74 for ABI, 0.84 for TBI, and 0.87 for DAT. For classifying limbs with severe ischemia (RCC 4-6, n=31) from limbs without severe ischemia (RCC < 4, n=102), the ROC AUC was 0.76 for ABI, 0.79 for TBI, and 0.92 for DAT (Figure 2).
Conclusions: DAT can be used by physicians to characterize dampening of the digit blood flow waveform and provide information on the presence of PAD and its severity. Additional study is required to define intraprocedural DAT parameters that predict clinical outcomes.
