How can artifacts be distinguished from arrhythmias? How can you discover artifacts or arrhythmias?

We repeatedly get emails and phone calls in the office, asking why the error rate of certain measurements is so high. Are these artifacts or cardiac arrhythmias? Therefore, we from Autonom Health want to explain the difference in this blog post.

The first steps

The measurement has been uploaded successfully to the Autonom Health Analysis Portal and is ready to be analyzed. But even at the first appearance, we can see that the error rate of the measurement is too high.

What now? What does the error rate declare? The error rate indicates that part of the measurement that is unusable. The reason may be artifacts, loss of signal or cardiac arrhythmia.

How do I find out what it is? What else needs to be considered?

First hint: The sample account contains several example measurements on this topic!

Second hint: In the e-learning area of the portal there are corresponding videos.

Artifacts

How to discover them:

Illustration: artifacts in the HRV-spectrogram

What are artifacts?  

Artifacts are false measurement data, which do not come from the heart, but are caused by interference in the signal recording and/or signal transmission.

How are artifacts identifiable?

LifeFire picture / spectrogram: unphysiologically too much intensity, density and height; very heterogeneous picture; repeatedly detections over 0.4 Hz (picture above)

Filter strip: many filtered areas (picture above)

Puls curve: very rough course with “peaks” and a nonphysiologically large area, which can show a 5-minute range of 40-190 bpm and more (picture above)

Scatterplot: in addition to the torpedo or comet form, a line-shaped area starting from the left lower edge, which would correspond to unphysiologically fast heart rates in the range of over 200 bpm (picture below left)

Histogram: often beginning at the intersection of the x-y axis and continuing from there to get wide (picture below middle)

Tachogram: unphysiological heart rates – especially too fast – up to 230 bpm and more unphysiological changes e.g. from 80 bpm to more than 200 bpm (picture below right)

Abb.: Illustration: arrhythmias in histogram, scatterplot and tachogram

How to avoid artifacts? 

Reasons for disturbances are mostly due to the signal transmission::

• The gel in the middle of the electrodes has dried out because the electrodes are too old or stored improperly.
• The electrodes were sloppily applied, are loose or stick in a bad way.
• The electrodes stick poorly due to excessive body hair (Caution: Breast hair especially from men! Shave the skin area or stick electrodes a few centimeters aside).
• Because of body lotion, the signal transmission is limited (attention especially for women!)
• Shriveled, sweaty or slipped electrodes prevent a clean signal transmission – change electrodes more often!
• Mechanical influences by pulling on the cable or on the electrodes cause artifacts.
• Recorders and cables are not properly connected or even attached upside down.
• The electrodes were glued too far apart so that the cable is too tense.
• The device is defect. Trick: a self-measurement brings clarification!

Basically: The more you take care during the measurement, the lower the artifact probability! If the electrodes are changed more often – especially for overweight people or people, who sweat very intensely – the occurrence of artifacts are avoided.

Arrhythmia

and how to discover that

Abb.: Illustration: arrhythmia in the HRV-spectrogram

What are arrhythmias?

Arrhythmias are disorders of arousal formation (e.g. supraventricular or ventricular extrasystoles) or excitation conduction (e.g. artrioventricular block) of the heart. Clinically dangerous are very rapid disorders, as they can lead to ventricular flutter and ventricular fibrillation, and very slow ones, which can lead to reduced blood flow to the brain – an indication for cardiac pacemakers.

A special form is the so-called atrial fibrillation, in which the impulse formation does not start from the sinus node, but from other areas in the atrium.

How are arrhythmias identifiable?

LifeFire picture / Spectrogram: too intense, too dense and too high LifeFire. Homogeneous and “prettier” than artifacts (picture above)

Filter strip: corresponding filtering of the affected areas (picture above)

Puls curve: age and activity-related too wide areas, no extreme “peaks” as in artifacts (picture above)

Scatterplot: too much dispersion or “archipelago” as a sign of regular deviations (picture below left)

Histogram: too large distribution on the x-axis (picture below middle)

Tachogramm: “Aesthetic picture”; regularly recurring deviations within physiological limits, e.g. starting from a middle HR of bpm 48 is interrupted by an extra impact with bpm 75 and followed by bpm 36 in the sense of a so-called “compensatory pause” (picture below right)

Illustration: arrhythmias in histogram, scatterplot and tachogram

What should be done if there are arrhythmias?

A clarification with the internist / cardiologist is necessary, if

• arrhythmias occur frequently,
• they are associated with “heart stumbling” or other symptoms,
• performance loss of unexplained cause is reported,
• dizziness or fainting occur,
• when particularly fast, salvos-like disorders appear
• or particularly slow disorders in the range of 30 bpm appear.

The picture of a transient or permanent atrial fibrillation (see example account) should be clear. If the patient is not aware of those facts, quickly send him to a doctor for stroke prevention.

If you have further questions about artifacts and arrhythmias, our professionals and partners are willing to help in a coaching or directly in the community.