Quality of life and the life itself depend on heart function. Examination on a regular basis helps to conduct early detection of disorders and prevent dangerous complications. Besides, the heart is a main body muscle. It is the first line of response to increasing the physical activity, so it is necessary to check the cardiac muscle (myocardium) state before any training.
Electrocardiography is considered as a classical method of assessment of the cardiovascular system state. It allows to detect abnormalities fast, determine contraindications to the certain types of physical activity or health improvement procedures. Electrocardiograph registers electrical signals produced by the heart. Measurement results are recorded as a graph of electrical signals, electrocardiogram (ECG).
There are a lot of portable electrocardiograph types. Some of them are designed only for the electrocardiography, while others combine different technologies. For example, HSC Bioscanner Wellness makes it possible to calculate the heart rate variability (HRV) when recording one-channel ECG (with the use of one chest electrode). Usually HRV is performed during pulseoxymetry procedure with the use of the finger sensor, but sometimes data cannot be received (for instance, because of opaque nail polish or when there is no a limb). Therefore Bioscanner allows to receive information for the HRV calculation both from finger sensor and from arm and leg electrodes while recording ECG.
Operating principle of any electrocardiograph is similar, but some technical features can impact the quality and accuracy of ECG recording. Digital and analogue filters distinguish the electrocardiograph of Bioscanner and make it possible to record a high-quality ECG.
How the method works
The heart is a kind of generator of electrical impulses. They can be “skimmed” from the body surface with the use of electrodes (sensors). They are placed on the certain skin areas in such a way as to register changes difference of potentials, produced by the heart, between two points, i. e. between two electrodes. That potential difference is called a lead. There are standard leads (electrodes are placed on legs and arms) and chest leads (electrodes are placed on chest).
Electrocardiogram makes it possible to assess cardiac muscle state, impulse conductance (cardiac conduction disturbances affect the normal heart function) as well as a cardiac rhythm and a heart beat. Bioscanner Wellness provides ECG recording in 3 or 12 leads: 3-channel or 12-channel electrocardiogram, respectively. In the second case, nine additional electrodes are placed on the chest. They can provide more information, including myocardium enlargement (it often points to cardiac failure) and abnormal focuses in remote heart regions (for instance, in posterior wall of the heart).
What it is used for
Any cardiac muscle damage (for example, when necrotic region appears (myocardial infarction) or heart inflammation (myocarditis)), large vessel disorders or mineral deficiency, affecting the heart function (potassium, magnesium, calcium) are reflected in ECG immediately. Many life-threatening conditions at their early stages have no symptoms. Even myocardial infarction may not be manifested by sharp pain and other typical signs. It is important to be examined by means of electrocardiography on a regular basis, because cardiac disorders, undetected in time, are often causes of sudden death. This is particularly important for pregnant women and athletes due to sharp increasing stress on the heart.
Electrocardiography is used actively as a screening diagnostics. It is well known that probability of cardiac and vessel disorders increases with age, especially a person has overweight problems, high blood cholesterol or other risk factors, including smoking. These days the telehealth is being actively developed. It allows long distance patient/clinician contact via telecommunication technologies such as Internet. Electrocardiogram recording by means of Bioscanner makes it possible to send ECG to the clinician by Skype, email etc. It facilitates regular preventive examination significantly.
Electrocardiography enables to assess the preparedness for the certain training level (both for the evaluation of professional athletes and unexercised people) or to check health state of drivers, high-rise building construction workers, crane operators, train drivers, pilots and other professionals, whose work relates to high-risk activity.
Besides, ECG is necessary to control the treatment course, especially a person has chronic cardiovascular disease (arterial hypertension, coronary heart disease, etc.). If a person feels worse, at occurrence or increased pain in the heart region, appearance of shortness of breath, abnormal or irregular heartbeat, it is necessary to record the electrocardiogram immediately and seek medical assistance.
One-channel ECG with use of three leads is usually a method of screening diagnostics, when there are no complaints related to the heart function, but it is necessary to evaluate possible latent disorders fast. To determine the cause of the cardiac rhythm disorder or a particular location of the cardiac muscle damage you should record ECG with use of 12 leads. Use of additional three unipolar limb leads (on the chest) enables to detect even low-grade changes.
Principle of method
The heart is a hollow muscular organ, consisting of two ventricles and two atria. When left ventricle contracts, it pushes the blood into aorta. From the aorta oxygen-rich blood moves to all organs and then returns to the right atrium. From the right atrium the blood goes to the right ventricle. When it contracts, the blood moves to the pulmonary artery (to become oxygenated in lungs), then the blood returns to the left atrium to go to the left ventricle. This sequence of myocardium contraction and relaxation, regulated by nervous impulse produced by the heart, is called cardiac cycle and reflects on the electrocardiogram.
So called ECG reading can be challenging, so the nuances should be left to the professionals of functional diagnostics. However, the basics of electrocardiography, if desired, almost everyone can learn.
There are 12 standard leads that are registered during ECG recording:
- three standard (bipolar) leads (I, II, III),
- six chest leads ((V1-V6),
- three unipolar extremity leads (аVR, аVL, аVF).
So the first standard lead is a potential difference between electrodes on the right and left arms. The second standard lead is a potential difference between a left leg and a right arm. The third standard lead is a potential difference between a left leg and a left arm. The electrode on the right leg is necessary to ground.
ECG contour analysis
The hardware-software complex Bioscanner Wellness make it possible to carry out the ECG contour analysis. This module is intended for finding diagnostically significant points on ECG graph as well as calculation of the cardiogram parameters. The obtained data help to detect different heart diseases.
ECG graph of a normal person depends on their body type, level of training and other factors. However, normal sequence and position of certain waves and segments are always similar. To evaluate ECG it is necessary to compare the values of wave height, duration and deviation of segments to normal values.
To work successfully with the module of contour analysis you should understand the basic principles of the cardiosignal structure. Standard ECG graph includes a lot of repetitive, similar segments, called cardiointervals. Each cardiointerval in turn consists of set of peaks and lows (waves) specific to the different time intervals of cardiac activity.
More detailed about the contour analysis and ECG parameters you can read in our article. Please note that the contour analysis takes into account the base ECG characteristics only and cannot be considered as a ground for the establishment of clinical diagnosis. In case you suspect a disorder, a cardiologist must read the ECG.
How the procedure is performed
Bioscanner Wellness is connected to a laptop or a computer via a USB port. Examination can be conducted anywhere, because this portable device is independent from external power supplies. Accumulator or batteries are also not required. An electric shock hazard is excluded.
There is no discomfort during the procedure of electrocardiography. To provide the best contact between skin and electrodes it is necessary to wipe the skin on these areas with alcohol solution. After that wipes should be put on the left leg and on the both forearms. The wipes must be moisten with saline solution 9 % (to prepare it, you should dissolve a whole teaspoon of salt in 100 ml of cooled boiled water).
Placement of the chest electrodes (video)
Red electrode — on the right arm,
Yellow electrode — on the left arm,
Green electrode — on the left leg,
Black electrode — on the right leg.
V1 — active electrode is placed at IV intercostal space to the right of the sternum,
V2 — active electrode is placed at IV intercostal space to the left of the sternum,
V3 — active electrode is placed between IV and V intercostal spaces along the left parasternal line (it passes in a vertical direction along the left border of the sternum),
V4 — active electrode is placed at V intercostal space along the left medioclavicular line (it passes in a vertical direction through the middle of the collar bone),
V5 — active electrode is placed at V intercostal space along the anterior axilar line (it passes in a vertical direction along the anterior border of the underarm),
V6 — active electrode is placed at V intercostal space along the middle axilar line (it passes in a vertical direction through the middle of the underarm).
Electrocardiogram displays with the clear reference grid (1 mm2 grid-like squares). There is a possibility of automatic wave and segment size measurement. There is a possibility to print the electrocardiogram as well.
Electrocardiography does not affect the body, because ECG is a registration of the electric signals produced by the heart itself. There are no contraindications. Electrocardiography can be performed at any age, during pregnancy, in any diseases. Skin damage in the areas of electrode placement can be considered as a relative contraindication.
One hour before the ECG recording the examined person should not smoke, eat, drink tea or coffee. Before electrode placement it is necessary to lie down for the several minutes to exclude the impact of physical activity.