Saturday, July 10, 2021

ECG Arrythmia/Artifact visualization - some tips

Now that we have an easy to implement way to capture HRV artifacts as ECG snippets with Fatmaxxer, I wanted to share a few tips and tricks for going through the visualization sequence quickly and with minimal cost.  If you have Kubios premium, just opening the .ecg file and viewing it is all we need:

But, for those who don't have Kubios premium, we need to rely on Excel.  The issue here is it can be time consuming to go through each segment one at a time to see what's there.  However, with the help of an Excel plugin which allows zoom and plot axis shifting, you can quickly scan through the ECG file and locate the areas in question for further analysis. 

Basic steps:

  • Download and install the plugin.
  • Follow the directions in the prior post on Fatmaxxer ECG strips to obtain the .ecg file
  • Open the file in Excel.
  • Add a new column as "A" - then create an auto number sequence starting at 1 
  • Select the A column as X and the yV column as Y - make a XY scatter plot

  • Change the points to lines but leave the axis alone
  • Make sure the ecg chart is actively selected
  • Open the EnginExcel tab - select Zoom chart
  • Change the X axis scale zoom - use the "Only X" choice for zooming the time, the Y should not need much zoom.

  • Start at the beginning of the file - by first zooming in, then moving to the Left (beginning) and then progressively move to the Right frame by frame.
  • When you find a wide QRS complex, stop and zoom further
  • Locate the segment for analysis
  • Look at the X axis and find the segment that corresponds to the number in column A
  • Match up the time stamp to the heart rate/part of the exercise session for informational purpose.  In this example, I would see what I was doing at 8:29.  Stress, high effort, dehydration, high temps etc should be noted.

  • To get a better look you can isolate the segment
  • Plot out just the segment (using the sampleNr and yV columns) and make sure the axis scale is correct
  • Figure out the beat type - generally a ventricular premature complex will be wide, have a different T wave morphology and not reset the atrial pacemaker.  Therefore the beat sequence will be preserved.  
  • The trace below is from the entire file - The first 2 beats (blue circle) represent the joining of segments, so the timing will be different - do not mistake that for an APC.

  • Below is an early beat, an atrial premature complex (APC) - it has normal morphology, a slightly abnormal appearing P wave and a short PR interval (red circle).  It generally should reset the pacemaker and the pause after would not be compensatory - but it occasionally is.  Although this example is atypical, the narrow complex is fairly diagnostic for an APC.

  • Continue scanning until the end:

Comments on ECG reading from a single lead:

Recently I noted some wide complex beats in my own ECG strips and could not decide whether they were atrial or ventricular in origin.  Although atrial beats are usually of normal narrow appearance, occasionally they will show as wide complexes due to conduction system blockade (usually right bundle branch block).  The reason behind this is that the conduction fibers themselves have a non uniform refractory period, so the ventricle is not excited in the usual pattern.  There are a set of clues in making the decision on abnormal beat origin, of which some rely on the presence of beat timing (VPC does not reset the pacer but APC does).  But, some APCs do not reset the pacer, so we usually look at other leads to help decide.  Without those other leads, it can be problematic.

I asked for several opinions on this from both cardiology and ER docs (they did not agree).

The cardiologist felt this was an APC with conduction delay, followed by a VPC.  However, the first APC did not reset the pacer.

And this was felt to be a VPC.

The reason is based purely on the timing issue:

Bottom line - interpretation of wide complex beats using a single lead depends on timing, P wave visualization and can be difficult.  If you see many of these - get it checked out by an expert.


  • An easy to use Excel plugin makes scanning the .ecg file quick and easy.
  • For most people, some APC activity is to be expected.
  • Having many VPC/wide complexes during rest or exertion may indicate a problem.
  • Reading a single lead tracing can be a challenge and occasionally it is impossible to separate a VPC from an APC with a conduction block.
  • If you are concerned, bringing this data to your physicians attention is a reasonable idea.

Heart rate variability during dynamic exercise

No comments:

Post a Comment