Introduction: Patients with asymptomatic peripheral arterial disease (PAD) are at high risk of morbidity. Recent guidelines stress the importance of detecting PAD in mitigating the risks of cardiovascular diseases. The guidelines suggest to measure the Ankle-Brachial index (ABI) despite its known limitations. We hypothesized that quantifying the perfusion dynamics would provide sensitive indices for the development of arterial stenosis.
Methods: A noninvasive technology that continuously monitors extremity perfusion by miniature sensors and impedance electrodes was developed. The perfusion dynamics is analyzed in the time and frequency domains and by wavelet correlations between the legs and various hemodynamic signals. A Helsinki permit was obtained; arterial stenosis was induced in heathy volunteers by inflating a blood-pressure cuff around the thigh to 45 and 90 mmHg. The perfusion indices were measured and compared to ABI and saturation.
Results: Cuff compression of 45 and 90 mmHg on the thigh had no significant effect on the ABI (p>0.54, n=8) or O2 saturation (pulse oximetry). However, it yielded new pathognomonic indices, e.g. phase delays between hemodynamic signals (p<0.001, n=8), that were proportional to the degree of the occlusion. The method may differentiate between arterial and venous problems. No significant pressure drop was detected since part of the hydrostatic energy turns into kinetic energy in the narrowed region that retransforms into hydrostatic pressure after the obstruction.
Conclusion: Monitoring perfusion dynamics outperformed the ABI thus supporting our hypothesis. The utility in early detection of PAD and restenosis, and assessing the severity of atherosclerotic disease require further clinical studies.