Time-variant spectral analysis for the studying of transient ischemia during dipyridamole stress test

The effects of dipyridamole and dipyridamole induced ischemia on the traditional spectral parameters of heart rate variability (HRV) were investigated in normal and coronary artery disease (CAD) patients, who underwent a dipyridamole echocardiography test (DET). The relevant spectral parameters (LF and NF powers, LF/HF ratio) were monitored on a beat-to-beat basis and their variations were linked to the different test epochs and the different pathological events as detected by echocardiographic and electrocardiographic changes. A recursive least square (RLS) identification algorithm was used to this purpose, which is able to track the dynamical changes in nonstationary signals. Spectral parameters were obtained by means of a pole-tracking algorithm which fulfils an efficient extraction of these parameters on a beat-to-beat basis. The estimated parameters allow one, to achieve more information on the autonomic nervous system (ANS) status during drug infusion and the correspondence with the induced ischemia