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. Author manuscript; available in PMC: 2012 Apr 1.
Published in final edited form as: IEEE Trans Biomed Eng. 2010 Oct 28;58(4):894–904. doi: 10.1109/TBME.2010.2089984

Fig. 1.

Fig. 1

Optical signal recordings and APD alternans results derived from the control channel during statically-timed and control-perturbed pacing (preparation #1). (a) Pre-processed optical recording during static pacing (top – left axis; BCL = 350 ms); superimposed X’s denote APD values (right axis). Bottom-axis shows the preceding pacing cycle length (CL) for the corresponding action potential. APD threshold values and stimuli are shown as the dashed black line and the red trace, respectively. (b) Pre-processed optical recording during the application of control (BCL = 350 ms); immediately followed that shown in (a). Superimposed red (gray) X’s denote APD values for control-on (control-off). Note change in cycle lengths as a function of preceding APD values. (c) Subsequent control-off optical recording resulted in the re-emergence of robust alternans at the control site (post-processed six-AP AM = 55 +/− 1.8 ms). (d)–(e) Action potential waveforms of post-processed six-AP sequences during control-off (d; six-AP AM = 56 +/− 2.4 ms) and control-on (e; six-AP AM = 5 +/− 1.7 ms) conditions; sequence selected according to the methods described in Section II.E. (f) Control-off and control-on six-AP AM values calculated at the control channel derived from all experiment trials performed on preparation #1 (BCL = 500, 450, 400, 375, and 350 ms).