System Questions

Q: What should I do if there is no ECG trace visible on EPS320 Cardiac Stimulator screen although patient is connected?


  1. Select Alt-I, i.e. sense from catheter tip of paced electrode – this should always show an ECG if adequately placed in the heart.
  2. If EPS320 is using External ECG inputs, verify connection between EP recorder and EPS320 Cardiac Stimulator and verify that EP Recorder has a sensing channel selected (e,g, highlight trace and press ‘s’ or similar).
  3. Verify that ECG is indeed connected into the ECG inputs, and not the Sync Output on the rear of the SGU.
Q:What should I do if the ECG Sensing is not triggering stimulation correctly?


  1. If there is no visible ECG trace on the EPS320 Cardiac Stimulator, refer to ‘No ECG’ above.
  2. Sense site possibly from wrong channel / cardiac chamber – verify that sensing is from correct EP Recorder channel and cardiac chamber.
  3. Try catheter-tip sensing (hotkey Alt-I).
  4. Some EP Recorders, e.g. older DOS version Prucka CardioLab outputs ECG from a specified displayed channel – changing Recorder ‘Page’ may change the outputted ECG channel.
Q:What should I do if the stimulator does not pace?


  1. If High Impedance is showing, then it is always caused by a disconnection in the pacing circuit – see High impedance FAQ below.
  2. If no High Impedance, try increasing current but if no success, check measured impedance on EPS320 Cardiac Stimulator display – if < 100 Ohms, look for short in the system – also may be set to the same electrode on Stim Setup on EP Recorder; if impedance > 2000, look for faulty equipment in line with the stimulus circuit, eg. RF Ablation switch box.
  3. Connect Test LED (MP3058) to the Stimulus Connection Box and verify that EPS320 Cardiac Stimulator functions OK.
Q:What should I do if high impedance message is observed when pacing?

A:  This indicates disconnection in the pacing circuit external to the stimulator – it is not a EPS320 Cardiac Stimulator fault. Ninety-nine percent of time high impedance is caused by incorrect settings in the EP recorder, ie Stim channel not enabled or directed into channels with no catheter connected. Other times it is caused by disconnected or broken catheter.

  1. Check that Stim channel is enabled on EP Recorder and correct electrodes for stimulation are programmed.
  2. Verify that electrodes are connected into correct catheter input module.
  3. Check continuity of pacing catheters, replace catheters if open circuit found. NB: continuity may be checked by demonstrating presence of stimulus at a particular site with the Test LEDs supplied by Micropace.
  4. Connect Test LED (MP3058) to the Catheter Input Module Stimulus Bypass Outputs and verify that stim circuit is intact to the input of the EP Recorder – if OK, then circuit break must be in EP Recorder or its Catheter Input Module / catheters.
  5. Connect Test LED (MP3058) to the EPS320 Stimulus Connection Box (MP3014) or SM-Box and verify that EPS320 Cardiac Stimulator cabling is intact up to that point.
  6. High impedance. It means that the resistance in the pacing circuit is too high – and pacing current is not being delivered. It does NOT usually mean a fault in the stimulator.

90% of time high impedance is due to incorrect settings in the CardioLab – ie Stim channel not switched on, or directed into channels with no catheter connected. Rest of the time it is caused by disconnected catheter or broken catheter.

This is thus a very helpful feature in diagnosing cause of failure to capture pacing.

Q:What should I do if I am getting noise on the stimulated EP Recorder channel?

A: This (50Hz noise) may occur especially when EPS320 Cardiac Stimulator is installed remotely from patient (in the control room) with a long Stimulus Extension Cable in between or when other equipment is connected into the pacing circuit such as RF Ablators or 3D Mapping system.

We suggest you first connect pacing electrodes directly to the EP Recorder Catheter Input Module Stimulus Bypass outputs:

  1. If noise persists then it is probably being induced in the Stimulus Extension Cable and you should check all cable connections and ensure cable is away from interference such as computer monitors and it is laid in a non-conductive conduit away from noisy cables.
  2. If noise resolves, then it is being induced in the EP Recorder or attached equipment – remove these one by one.

If noise intractable, EPS320 Cardiac Stimulator system may be split, locating the Stimulus Generator Unit under the bed, joined to the Bona PC via an RS232 cable.

Q:What should I do if I am getting large stimulus spikes on paced IECG channel?

A: Large stimulus spikes may occur with high stimulation currents, unipolar pacing or high impedance is pacing circuit. Check your settings and adjusting the clip on the EP Recorder channel may resolve the problem.

If you are getting high impedance warning and not capturing myocardium as well, then you have a break in one only of the +ve or -ve legs of the stimulation circuit. The remaining one connected circuit leg conveys a maximal voltage (almost 30V) to the myocardium trying to deliver the programmed current, but there is no return pathway for the current so none flows but a large spike is produced on the EP recorder. Correct this by rectifying broken circuit.

To locate the circuit break, connect pacing electrodes to the EP Recorder Catheter Input Module Stimulus Bypass outputs – if this rectifies problem then break is in connection between the stimulator and the EP Recorder Stim inputs; rarely the stimulator itself is faulty.

There have been unconfirmed reports of intermittent stimulus circuit interruption in EP Recorders, suspected to be related to concurrent use of 3D mapping devices.

Q:What should I do if I am getting a secondary spike on the stimulus artefact in the HRA channel and it looks a little like a capture?

A: This may occur with earlier EPS320 Cardiac Stimulator systems when used with GE CardioLab System. An upgrade to the EPS320 Stimulus Generator Unit resolves this issue. Contact Micropace.

Q:What should I do if the EPS320 Touch Screen occasionally freezes?

A: This was due to a third party driver fault in software version 3.20.05, shipped from April 2005 to Dec 2005. Computer freeze occurs rarely and randomly on touching the touch screen anywhere. Stimulus Generator Unit enters Manual Backup mode, ready for emergency stimulation if required; product performance degradation causes no hazards. Rebooting computer recovers computer function.

More that 90% of affected software has been electively field-upgraded to 3.20.09 (SR3) between March 2005 and Nov 2005.

Workaround – use keyboard only and call Micropace for software upgrade which is performed on site via a USB Flash Drive.

Q:What should I do if I am getting noise on the EPS320 Cardiac Stimulator ECG trace?

A: Assuming noise is the commonest 50Hz – the circuit is picking up 50Hz – either being injected by some third party equipment or due to unbalancing of the stim outputs – unequal resistance in connections or selective grounding of the +ve or -ve wires in the Stim circuit.

You will need to determine more information and then contact your distributor or Micropace with it:

Questions / Suggestions:
  1. Is this new noise in an existing Micropace installation or a new installation?
  2. Describe installation – stim extension cable used ? – Micropace or custom made there? How long roughly (2m , 10m. 20m)?
  3. Have they added any new equipment recently to the circuit – RF ablator, mapping system?
  4. Check all connection – disconnect and reconnect all connectors? Fixed noise?
  5. Swap channels – use Chan 2 Ventric to pace – if noise remains – must be wiring, if it disappears, must be Stimulus Generator – Chan A.
  6. Use Bypass pacing outputs – if noise disappears could be in STAMP (unlikely)
  7. What is the pacing impedance shown on the Micropace EPS320 Cardiac Stimulator?
    Try bypassing the personality module of the RF Ablator.