Time-variant heart-rate variability spectral parameters during dobutamine test

Time-variant spectral parameters are used to monitor the Autonomic Nervous System (ANS) status in normal and coronary artery disease (CAD) patients during pharmacological infusion of Dobutamine in Dobutamine Echocardiography Test (DET). During the test, the spectral parameters (LF and HF power, LF/HF ratio) are estimated on a beat-to-beat basis through the time-variant identification of an AutoRegressive (AR) model, using a Recursive Least Square (RLS) algorithm. Different LF responses have been found in the early stages of drug infusion (10-20 /spl gamma/) sequentially before the appearance of echo, ECG or clinical signs of ischemia. An early increase of LF/LF/sub basal/ value was found in 6 of 8 (75%) positive tests, and only in 2 of 9 (22%) negative ones, suggesting that the different neurovegetative response in the sub-maximal stages of drug infusion may be a marker of an actual or successive ischemia.