Currently, dsTool is plotting b vs. x. You can tell this by the labels for the horizontal and vertical axes. To make an ECG you simply have to tell dsTool that your horizontal axis is time and your vertical axis is b. To make the scaling correct, chang e the range of time from 10000 to 20-50.
Everytime you change the range or axes you must tell DsTool to "Refresh" the phase portrait. To do this, go to "Refresh" under the "Options" menu which is located in the phase portrait window.