Physiological signals play an essential role in medical diagnosis, as they reflect the patient’s health status. When properly analyzed, they enable the detection and classification of various diseases. Among all physiological signals, those from electrocardiograms are crucial because they provide information on the cardiac, cardiovascular, and cardiorespiratory systems.
The quality of the signals in an ECG directly affects the accuracy of the diagnosis. Recognizing irregular patterns or the presence of noise in the signals can impact the interpretation of results. Therefore, it is vital to have an advanced electrocardiograph that ensures the cleanest and most accurate signals possible, as any distortion can lead to incorrect diagnoses. In this article, we focus on the importance of physiological signals in diagnosis.
By América Torres
The Bioelectric Activity in the Electrocardiograph
As you know, the heart’s electrical conduction system is made up of the sinoatrial (SA) node, which initiates the cardiac cycle, the internodal atrial pathways, the atrioventricular (AV) node, and the bundle of His, which ends in the Purkinje fibers. This system allows electrical impulses generated in the SA node to propagate from the right atrial wall to the deeper tissues of the ventricular muscles. The ultimate result of this bioelectrical action is the heartbeat.
The depolarization of the atria generates the P wave, followed by the QRS complex, which represents ventricular depolarization. The cardiac cycle ends with the cell repolarization phase, which manifests as the T wave, and in some cases, a second deflection, the U wave, may appear. The electrocardiogram records the combined activity of the phases of the electrical conduction system, i.e., the P-QRS-T complexes (ECG trace). The quality of this signal depends on factors such as the size, shape, and position of the heart within the chest cavity, as well as tissue conductivity, genetic traits, congenital disorders, and each patient’s heart disease.
Factors Affecting Signal Quality in an Electrocardiograph
Signal Quality Indices (SQIs) are essential to improve diagnostic accuracy and the reliability of ECG analysis systems. A noise-affected ECG signal can have severe consequences in a clinical environment. This highlights the need for a powerful electrocardiograph capable of eliminating noise that may interfere with different types of physiological signals.
Several factors generate interference noise. The most common artifacts in an electrocardiograph include:
- Power line artifact: This is one of the most common types of noise, caused by electromagnetic fields, faulty power lines, or poor grounding of the electrocardiograph or the patient. This type of interference distorts the P, Q, S, and T peaks, which are crucial for pathological decision-making. The impact of this interference varies depending on the frequency of the electrical network (which differs by country).
Characteristic appearance: Regular undulations at a frequency of 50 or 60 Hz. - Baseline noise: Also known as baseline wander, it is low-frequency noise (0.1-0.2 Hz) caused by patient-related factors such as body movement (motion artifact), poor electrode adhesion, or impedance between the electrode and skin (contact artifact) or breathing (respiration artifact). This appears as a prolonged sinusoidal signal, which, along with fluctuations in the ECG signal, affects threshold-based decision-making systems.
Characteristic appearance:
- Motion artifact: Abrupt variations in the trace.
- Poor contact artifact: Background noise or undulating lines.
- Broken or disconnected cable artifact: Flat line or severe noise in specific leads.
- Respiration artifact: Shifts in baseline corresponding to breathing.
- Muscle artifact (or tremor artifact): Caused by muscle movement, it can be divided into two types: controllable movements such as resting and exercising, and uncontrollable movements like shivering, chills, and chest compression.
Characteristic appearance: Irregular, spasmodic undulations in the trace. - Electrode movement: Poor adhesion or incorrect placement of electrodes on the body generates noise from electrode movement and distorts the P, Q, R, S, and T ECG traces.
Characteristic appearance:
- Broken or disconnected cable artifact: Flat line or severe noise in specific leads.
- Incorrect lead placement artifact: Unusual patterns, often opposite to expected.
- Sweat artifact: Sweating can also contribute to noise in the ECG, as body moisture may cause the electrode to detach and increase impedance between the skin and the electrode.
Characteristic appearance: Random electrical noise.
Additionally, it’s important to consider other uncontrollable noises, such as body movement, blinking, and device circuit noise. Therefore, it is crucial to quantify the signal quality relative to the added noise before integrating it into a clinical decision-making system.
Pathologies Confused with Artifacts
A noise-altered ECG signal can have serious consequences in medical care. For example, in a scenario where a patient’s heart activity is continuously monitored and an automated system issues alerts for abnormalities, the noise could trigger a false alarm. Therefore, it is essential to evaluate the signal quality before generating an alert. Here are some of the most common confusions:
- Power line artifact → Ventricular fibrillation.
- Muscle artifact → Irregular heart rhythm or ventricular tachycardia.
- Motion artifact → Episodes of tachycardia or ventricular fibrillation.
- Poor contact artifact → Irregular heart rhythm or electrical interference.
- Broken or disconnected cable artifact → Asystole.
- Incorrect lead placement artifact → Ischemic event or T wave inversion.
- Electromagnetic interference artifact → Tachycardia or ventricular fibrillation.
- Respiration artifact → ST segment shift, characteristic of an ischemic event.
- Sweat artifact → Conduction disorder or arrhythmia.
Fortunately, advanced electrocardiographs help reduce issues caused by artifacts during an ECG. It is crucial for doctors, clinics, and hospitals to use cutting-edge equipment that not only saves time during testing but also provides accurate and precise information.
Why the CARDIOVIT FT-1 Is Key to Getting Results Without Artifacts
The CARDIOVIT FT-1 is the star of our electrocardiograph line, and there are many reasons for this. It is a 12-lead portable electrocardiograph with advanced technology, preferred by top cardiologists due to its high signal quality, efficiently filtering out artifacts thanks to its 0.05-250 Hz bandwidth, making it ideal for ECGs of both adults and pediatric patients.
Some of the standout features that help reduce artifact errors and ensure reliable ECG results include:
- Anatomical model with zoom and rotation, guiding the user to place electrodes correctly, reducing the incorrect lead placement artifact.
- The device allows you to check the signal quality before performing the ECG to avoid poor contact or broken/disconnected cable artifacts.
- Includes a pacemaker function to avoid pacemaker interference.
- Myogram filter (LP 25, LP 40, or LP 150Hz) to reduce muscle tremor artifact and AC filter (50 or 60 Hz) to avoid power line artifact.
These are just some of the features that make the CARDIOVIT FT-1 an essential electrocardiograph for delivering top-quality medical care. Imagine all that it can do for you and your patients!
During February 2025, We Celebrate Heart Month with a Special Promotion on the CARDIOVIT FT-1. Throughout the month, you can request a free demo with your local SCHILLER distributor, discover all the advantages of this cutting-edge equipment, and find out about the exclusive offer your distributor has for you.
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Simply request the device of your choice and try it for 15 business days. If you love it, you can buy and keep it. If not, return it—no questions asked! The SCHILLER Trial Program is available only in the U.S.
REFERENCES:
Saifur Rahman et al. “Robustness of electrocardiogram signal quality indices”. Journal of the Royal Society Interface. Published 13th April 2022. https://doi.org/10.1098/rsif.2022.0012
Enfermería Evidente. ¿Qué artefactos pueden aparecer en un electrocardiograma?. 2023. https://enfermeriaevidente.com/que-artefactos-pueden-aparecer-en-un-electrocardiograma/
