Noninvasive assessment of endothelial activity in patients with peripheral arterial disease and cardiovascular risk factors

Microvascular endothelial activity (EA) after stimulation with iontophoretically administered acetylcholine was evaluated using laser Doppler fluxmetery (LDF) and calibrated photoplethysmography (c-PPG) in normal patients and patients with peripheral artery disease (PAD). The patients included 79 non-PAD subjects and 51 patients with PAD. Upper and lower extremity EA was examined using LDF and c-PPG after acetylcholine iontophoresis for 10 min. Sensitivity and specificity were assessed using integrated area under response curve. In non-PAD patients, the EA by LDF in the upper extremity was significantly lower in the older patients compared to the younger patients. Conversely, EA by LDF detected no significant difference between these groups in the lower extremity. With c-PPG, the EA was slightly reduced in the upper but not in the lower extremity in older patients. Comparing PAD patients to the older patients, there was a significantly lower EA response in the upper and lower extremities by LDF. Likewise, c-PPG detected a highly significantly reduced EA in the upper and lower extremities for PAD patients. These results indicated that using a noninvasive technique to determine EA, there were significant differences in the EA response to acetylcholine between those with PAD and normal patients over the age of 50. Importantly, the EA response was reduced in the upper and lower extremities, indicating systemic disease of the endothelium in PAD patients.