Part 2 -
ECG arrhythmia and artifact visualization tips
The latest version of Fatmaxxer has an incredibly useful feature for those of us interested in heart rate variability quality and interpretation - namely the ability to inspect the ECG details surrounding the alleged artifact. As previously reviewed here, there are many reasons for a "beat" not to occur where it was supposed to be. Having software tell us that there are artifacts does not "diagnose" the particular cause. Although one can infer some causation such as missed beats (HR becomes 1/2 normal), arrhythmia can't easily be diagnosed this way. Yes, some new algorithms have been developed to detect atrial fibrillation from HRV, but they are not "gold standard" as of yet. As one engages in higher exercise intensity, artifacts rise and the importance of understanding the cause increases. Are they serious or not? In this first post on the matter, we will go through a brief guide on how to setup, record and graph the ECG extraction from Fatmaxxer. Although Kubios premium can easily display this ECG, we will not be using that so users with simple spreadsheet software can take advantage of this feature.
Requirements - Fatmaxxer with developer settings on, "preferred device" set for the Polar H10 currently in use, Excel or similar
Use case - you have recorded a session with Fatmaxxer, there were artifacts present. Each time Fatmaxxer detects an artifact, that series of electrical data will be written to a file with a suffix of .ecg. In addition, the app will take a baseline recording at about 10s elapsed time
Note - the following was not a true artifact, but serves as an example. It was created by having the artifact correction threshold at the aggressive 5% during resting, where HRV is high and "false" artifacts are detected.
Step one - find and export the ECG log either through the menu system or straight out of the Android/data/online Fatmaxxer/files/logs folder
Next step - open the file with Excel:
The 4 columns represent the
- A - timestamp of the artifact (Unix time),
- B - segment (the "number" designation of the artifact - if you have 10 artifacts, you will see 0 to 9 for segment number).
If artifacts continue frequently enough, the segment may contain multiple instances and be longer than 10s. About 5 s of no artifact beats are needed to "end" a particular segment.
- C - sampleNr (the granular time of the ECG signal - since the same rate is 130Hz, each unit is 1/130 of a second) and
- D - yV (the ECG signal strength - in other words the mV of the signal at that particular time)
Next step is to simply graph a given segment numbers worth of data:
As an example, I chose the sampleNr and yV of segment "0" as x and y to plot, but did not include past the green line where segment 1 begins
The familiar Excel default "scatter" graph of the third (sampleNr) and forth (yV) column yields the following:
The next step is to change point size, color, add line connections, adjust axis and add some fixed time markers (arrows) to get an idea of regularity.
- This is the entire, approximate 10s strip from Fatmaxxer.
Here is the same type of data in Kubios premium:
Zoomed Fatmaxxer ECG in Excel to explore waveform morphology:
- Good looking narrow QRS waveform, defined P and T waves are present.
- To do this, just change the x axis scale.
A further example of a "segment" containing an artifact. The artifact (atrial premature complex) is not that apparent until the x axis (time) is zoomed to a smaller scale. Then we see the early RR interval of the APC, then the delay in the next normal beat, then resumption of normal timing:
The APC occurs at about the 450 timing mark which is more obvious now that we know where it is (red circle):
Here is an interesting example of a recent issue with high artifacts seen with the H10. After looking at the strip from Fatmaxxer, there were only a few APCs.What I noticed was a very low voltage/signal strength of some of the beats (<500mV). This could lead to the module not detecting the beat at all. Optimization of signal strength by changing the belt position is another modality to improving HRV and HR precision.
- ECG strips of artifact related segments are now possible with Fatmaxxer.
- This is an incredibly helpful feature for HRV, sports researchers and consumer users alike.
- Potential capture of atrial, ventricular arrhythmia's, fibrillation and differentiation of artifact type is possible.
- Although a great tool, avoidance of Kubios premium makes this affordable for all.
- For the recording of accurate, finely granular time varying DFA a1 as well as pertinent ECG tracings, Fatmaxxer is a fantastic tool to have. Many thanks and compliments to the developer for this new feature.
See also - Pitfalls in DFA a1 - Polar belt position
Heart rate variability during dynamic exercise
- Firstbeat VO2 estimation - valid or voodoo?
- Heart rate variability during exercise - threshold testing
- Exercise in the heat and VO2 max estimation
- DFA alpha1, HRV complexity and polarized training
- HRV artifact avoidance vs correction, getting it right the first time
- VT1 correlation to HRV indexes - revisited
- DFA a1 and Zone 1 limits - the effect of Kubios artifact correction
- HRV artifact effects on DFA a1 using alternate software
- A just published article on DFA a1 and Zone 1 demarcation
- DFA a1 vs intensity metrics via ramp vs constant power intervals
- DFA a1 decline with intensity, effect of elevated skin temperature
- Fractal Correlation Properties of Heart Rate Variability (DFA a1): A New Biomarker for Intensity Distribution in Endurance Exercise
- Movesense Medical ECG V2.0 Firmware brief review
- Movesense Medical ECG - improving the waveform and HRV accuracy
- DFA a1 and the aerobic threshold, video conference presentation
- DFA a1 - running ramp and sample rate observations with the Movesense ECG
- DFA a1 calculation - Kubios vs Python mini validation
- Frontiers in Physiology - Validation of DFA a1 as a marker of VT1
- Real time Aerobic thresholds and polarized training with HRV Logger
- Active Recovery with HRV Logger
- DFA a1 and exercise intensity FAQ
- DFA a1 agreement using Polar H10, ECG, HRV logger
- DFA a1 post HIT, and as marker of fatigue
- DFA a1 stability over longer exercise times
- DFA a1, Sample rates and Device quirks
- DFA a1 and the HRVT2 - VT2/LT2
- Low DFA a1 while running - a possible fix?
- Runalyze vs Kubios DFA a1 agreement
- DFA a1 - Runalyze vs Kubios vs Logger results in a cyclist
- Best practices for Runalyze and DFA a1 thresholds
- ACSM - HRVT validation in a cardiac disease population
- FatMaxxer - a new app for real time a1
- Another look at indoor exercise without a fan
- ECG artifact strips from Fatmaxxer - a guide
- Pitfalls in DFA a1 - Polar belt position
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