Time marks navigation
This module satisfies the necessity of browsing in the recordings at specific time moments defined by marks. For example, we used ECG detector/delineator to delineate T waves. We know that our recording has parts with no signal due to the bad electrodes contact with skin. So, we have in mind that T waves are not going to be consecutive and we want to check it. We will use time marks navigation over T wave peaks to browse in the signal but in the times of the T waves.
Other example, our database has external marks given by a electrophysiologist. The clinician marked qrs complexes as: normal (N), ventricular (V) and supraventricular (S). And our intention is to analyze the heart rate variability. Thus, we only want normal beats (N). If we want to know where are the other type of beats, we can use time navigation over qrs marks and then select the subtype V, for instance. In such a way we browse in the signal just in the time positions of the V beats.
As it happens in the other visualizing modules, it is needed at least one loaded annotation file containing annotations to enable the following menus:
- On/Off: enables or disables the time navigation mode.
- Select mark to navigate: only annotations or events are available for time navigation.
- Legends navigation: type of MIT annotations related with heartbeat classification are shown as well as rhythm change annotation labels, ST change and T change labels as well. These labels are the mostly used and are a kind of standardization.
- Advanced options: in this setup, user can change the relative position of the mark of navigation (Left, center, right, anywhere) and also the velocity of change when auto-browse mode is on (from “as fast as”, 1 s delay to 15 s).
When time mark navigation is mode on, Signal Window shows a blue square centered in the time mark as it is shown in the Fig. 24.