Towards Noninvasive Early Detection of Peripheral Arterial Disease and Assessing the Severity of Arterial Stenosis

Introduction: Recent guidelines suggest to measure the Ankle-Brachial index (ABI), even in asymptomatic patients in mitigating cardiovascular risk, despite its known limitations. We hypothesized that quantifying the perfusion dynamics would provide more sensitive indices for development of arterial-stenosis.

Methods: The perfusion dynamics was estimated noninvasively by novel miniature sensors and impedance electrodes and analyzed in the time and time-frequency domains. A Helsinki permit was obtained; arterial-compression (stenosis) was induced in heathy volunteers by inflating a blood-pressure cuff around the thigh to 45 and 90 mmHg.

Results: Cuff compression of 45 and 90 mmHg on the thigh had no significant effect on the ABI that remained above 0.9 (p>0.54,n=8), O₂ saturation that remained above 96.9% (p>0.59,n=8); and the pulse transit time (PTT), that is defined as the delay between the R-wave and the perfusion-wave onset. The PTT was 167 ± 12ms at baseline and 155 ± 41ms upon 90 mmHg compressions (p>0.42, n=8). However, compression yielded new pathognomonic indices, e.g. the peak perfusion delay (PPD) which was measured between the R-wave and the peak of the perfusion-wave. PPD increased from 355±12 at baseline to 399±16 (p<0.001) and 425±11ms (p<0.001) upon compression of: 45 and 90 mmHg, respectively. Arterial stiffening (arteriosclerosis) expedites the pressure pulse wave velocity and shortens the PTT. Arteriosclerosis also increases the ABI. In contrast, stenosis yields significant changes in the perfusion dynamics, as prolongation of the PPD, in the absence of measureable changes in the ABI. Part of the hydrostatic energy transforms into kinetic energy in the stenotic segment and returns back to hydrostatic energy after the narrowed region, without affecting the ABI.

Conclusion: The perfusion dynamic indices, as the PPD, are more sensitive than the ABI and the pressure-wave velocity indices in early detection of arterial stenosis. The utility in PAD evaluation requires further clinical studies.