System Features Questions

Q: What should I do if the ECG on our stimulator disappears when we pace?

A: If ECG disappears during pacing and then returns after a few seconds then you are probably sensing internally in the stimulator from the paced electrodes - ie Catheter Tip and the disappearance is due to charge build up on the paced bipole.

To correct this, change to external ECG sensing by pressing 'Alt-1' on the EPS320 to sense from its EXT_ECG1 input and connect your EP Recorder's ECG output (usually a BNC connector labelled 'Analogue Out' or similar) to the EPS320 "ECG-1 INPUT" on the rear of the Stimulus Generator Unit (MP3008), suitable cable BNC to Phone Cable - MP3109. Don't forget to press 'Alt-S' to save setting.

If the ECG signal disappears when you change pacing channel on the stimulator, your sensing is probably from Auto-Ext whereby sensing is from External ECG-1 INPUT when pacing Chan1 and automatically changes to ECG-2 INPUT when pacing Chan 2. To correct this, press 'Alt-1' to set sensing permanently from ECG-1 INPUT. Don't forget to press 'Alt-S' to save setting.

To learn more - on the EPS320 press 'H' for help and select "b.ECG Sensing Diagram".

Q: What should I do if I want to set the Trigger-S1 delay to be adaptive to sensed RR?

A: The Trigger-S1 delay in the EPS320 is called QRS_Sync_Delay and may be set to the S1 value, an absolute ms value or to a percentage of the sensed RR interval. It is controlled by the Config Var 33 "QRS Sync Dly:0,1-99,>100". Here is its help text:

Var_33. QRS Sync Delay:

  1. Stimulator waits this long AFTER detection of QRS before starting to pace; i.e. pacing will not commence until either -

    a. QRS is detected followed by a delay set by variable 'QRS_Sync_delay' in Config. Different values of this variable are interpreted differently as shown here below:

    0: Delay equals the setting of S1 in ms units.
    1-99%: % of RR. Delay derived from a percentage of average RR (adaptively exponentially filtered).
    >=100ms: Absolute delay in ms.
    (-1 to -99: 'Back door' way to set delay to 1ms to 99ms, in case this is ever required - see below on how to enter -ve values)
    Default value is 0.


    b. If no QRS is detected, timeout set by QRS_Sync_Timeout in Config (default=1000ms).

    E.g. if ECG RR interval is 800ms, and QRS_Sync_Delay value is 70, then pacing will commence 800 x 70%= 560ms after detection of QRS.

  2. This time period adds to QRS_Sync_Timeout period if no QRS is detected.

Q: What should I do if I want to disable PAUSE in the Nodal ERP protocol so S2 is followed by next S1?

A: You can 'turn off' PAUSE by setting its value to 'Pause=S1'. Do this by focusing PAUSE, pressing INS and choosing this value from the menu.

Q: What should I do if I want to deliver successive trains of 15 S1's starting at 250ms, reducing by 10ms each time?

A: Your task can be archived with Load-ATP:

  1. Press 'L'.
  2. Highlight Percent (Green) and press DEL (to turn off adaptive S1 calculation)
  3. Set S1 to required starting S1 value
  4. Set Train to 15
  5. Set Decr to 10
  6. Set PAUSE to required pause and ensure it is set to Repeat
  7. Start pacing

Q: Can I sense from one channel and pace into another?

A: Yes - this means triggered pacing mode - e.g. sense Atrium, delay and pace Ventricle - this can be set up easily using Procedure Menu - Triggered pacing.

Q: Can the EPS320 be used for Oesophageal Pacing?

A: Yes, The EP320 Cardiac Stimulator is intended to be used for diagnostic electrical stimulation of the heart for the purpose of initiation and termination of tachyarrhythmias, refractory measurements and measurements of electrical conduction. Stimulation may be endocardial, epicardial or trans-esophageal.

Oesophageal stimulation typically requires longer pulse widths of 10-20ms for lowest pacing thresholds of 5 to 15mA. The EPS320 features a maximum pulse width of 10ms and maximum stimulation current of 25mA. Micropace has anecdotal evidence of successful use of the EPS320 for oesophageal stimulation. Please contact Micropace for further information.

Q: Can the EPS320 Cardiac Stimulator be used for high frequency stimulation of intra-cardiac Vagal Ganglia?

A: The EPS320 Cardiac Stimulator's intended use and indications for use do not include stimulation of nerve or autonomic ganglii and there are no safety or efficacy data for this application, however there are no known contra-indications or hazards to the stimulation of any part of the heart using its full range of stimulation parameters.

High Freq Vagal Ganglion stimulation has been performed in a number of centres with the EPS320 Cardiac Stimulator.

Studies using various types of cardiac or nerve stimulators, including the EPS320 Cardiac Stimulator used typically S1=50ms (20 Hz), Pulse Duration 5-10ms, Current 3-15mA (which = 3-15V assuming typical impedance 1 kOhm).

Q: How do I instantly increase stimulation current to be able to do para-hissian pacing?

A: In para-hissian pacing, some protocols require changing stimulation current from small to large value and back again from stimulus to stimulus.

Use following steps:

  1. Focus the 'Current' parameter by touching it or pressing 'C'
  2. Set the low value of current and start pacing
  3. Press Ctrl-INS to increase stimulus current to 20mA instantly
  4. Press Ctrl-DEL to revert the stimulus Current to previous (low) value

Note that S1 and extra-stimulus current values are also independently programmable from the Joined-Chan Menu ('J').

Q: How can I make the SNRT protocol stop automatically at the end of the period, can it then restart automatically with next S1 value?

A: Setting SNRT auto-stop:

(i) Open Configure page (hotkey 'K' and password: 'henry',
(ii) move down to Variable: 13_SNRT_Auto_Stop and set it to '1' (press 'h' for help if you want more information). SNRT will now stop at end of pacing period programmed by the Variable 14 below it.

SNRT cannot be made to restart pacing - this is intentional, as automated restarting of stimulation at say, 270ms after a 60 sec pause would not be considered safe - many thing can happen in 60 sec in the EP lab which could make such pacing inappropriate.