A Dynamic Objective Evaluation of Peripheral Arterial Disease by Near-Infrared Spectroscopy

Abstract

Near-Infrared Spectroscopy (NIRS), suitable for dynamic measurements, is not routinely used for peripheral arterial disease (PAD). We propose a dynamic NIRS-based measurement to quantify variations in muscle metabolism in PAD. Sixty-seven consecutive PAD patients (males=56, age 71.6+/-8.7 years) and 28 healthy subjects (males=12, age 30.4+/-11.9 years) were studied. An echo-colour Doppler (ECD) was performed and the ankle-brachial index (ABI) was calculated. Participants performed an incremental treadmill test with NIRS probes on the gastrocnemius. Variations in oxygenated (HbO(2)), deoxygenated (HHb), total (tHb=HbO(2)+HHb), and differential (dHb=HbO(2)-HHb) haemoglobin were recorded and quantified as area-under-curve (AUC) within the range 1.7-3.0 km h(-1). Heart rate was recorded, and the number of beats in the same interval was calculated (dHr). O(2)Hb(AUC), HHb(AUC) and dHb(AUC) differed between diseased and non-diseased legs (P<0.0001) and exhibited different patterns related to PAD severity according to the ABI value. A compensatory heart rate increase was observed in PAD patients. Compared with the ECD positivity for occlusions/stenoses or multiple plaques, only the receiver-operating characteristic (ROC) analysis of dHb(AUC) (area=0.932, P<0.0001) showed a sensitivity/specificity of 87.6/93.4 for values <or=-197 (LR+LR-: 13.36/0.13). The dynamic NIRS-based test, quantifying muscle metabolic response according to presence and degree of PAD, allows the evaluation of patients with walking disabilities.