Heart is a fibro-muscular organ that provides the movement of blood through the blood vessels. Human heart, a hollow muscular sac, has form of a cone with a size of a fist of the person (approximately). Heart is located in of the chest behind the breastbone and surrounded by the pericardium, in other words, a double envelope filled with small, a few ml of water pericardium, which is a matter of fact the blood plasma, which significantly reduces the friction of the heart. Heart provides blood flow through the blood vessels. The work of the heart is similar to the mechanical (suction and ejection) phenomenon. The form of the heart depends on the age, sex, stature, health, and other factors. The weight of a heart is about 300 g.
The heart performs motor functions in the circulatory system and continuously pumps blood into the arteries. Ordinary calculations show that within 70 years the heart of ordinary people performs more than 2.5 billion beats and pumps 250 ml of blood (AHA, n.d.).
The most popular ways to diagnose cardiovascular diseases are: electrocardiography, Holter monitoring, echocardiography, and magnetic resonance imaging. Each year, these studies are applied to thousands of patients who are sent to specialists for diagnosis of diseases of the cardiovascular system.
Electrocardiography (ECG) in the Diagnosis of Heart Disease
The essence of the ECG lies in the registration graphic recording pulse, or electrical potentials that occur in the period of the cardiac contractions. With the help of special electrodes ECG "reads" the activity of the heart. Cardiogram writing process takes just a few minutes, and then a specialist or a special program interprets it.
ECG provides an opportunity to identify the source of heart rhythm, frequency, and regularity of the heartbeat. This allows one to see the changes in the ischemic myocardium, assess the rate of pulses, and see an increase in various parts of the heart. Such data is necessary for the diagnosis of arrhythmias.
Indications for ECG are: the deterioration of the cardiac patient, suspected coronary artery disease, the presence of risk (professional) for the cardiovascular system, or suspected occurrence of complications on the heart (patients with diseases of the nervous and endocrine systems, kidney disease, etc.), the upcoming operation (in order to eliminate the risk of complications).
Electrocardiography refers to the informative and the most common method of examination of patients with heart diseases. ECG also provides an opportunity to diagnose diseases and syndromes that require emergency of a cardiac care, especially myocardial infarction, paroxysmal tachycardia, and conduction disturbances (different types of blockades).
According to Ganz (2011), "An ECG is usually the first test done to determine whether a person has heart disease." Doctors around the world appreciate the simplicity of the method for performing an ECG (a low cost, versatility).
The Principle of ECG
Heart is the most unusual organ in the human body. The activity of the heart is controlled by the nervous system (vasomotor centre , sympathetic and vagal nerves ) and through the influence of various substances (hormones , ions). However, in this regard, the heart does not differ from the other organs.
The most amazing thing is that the heart has its own autonomous "nervous system". In nineteenth century, scientists have noted the fact that the isolated (without outside influence ) heart is able to function properly for a while. This is possible due to the existence of areas of activation in the sino-atrial node (called "pacemaker") and the specific neural pathways (AHA, n.d.). Impulse, being born in the pacemaker in a matter of seconds is held up by the muscle cells of the heart conduction paths. As a result, there is a contraction of the muscle wall due to increased blood pressure in the artery is directed chambers.
ECG and Heart
In order to record any heart diseases, ECG measures the electrical wave produced with every heartbeat. It is a banal electrical current that can be caught anywhere in the body, since the body can easily conduct electricity. Approximately, 12 electrodes are stuck to the various parts of patient's body. One can use a simple oscilloscope complete with sensors and wires, and the doctor can determine whether the electrical activity of the heart is regular or not. This is the basic principle of the ECG.
With the advent of ECG, doctors have obtained considerable potential in vivo diagnosis of heart disease. Moreover, there are no risks, as neither x-rays pass through one's body, nor injections are given because the electrodes do not penetrate the skin. It is an extremely simple method (the recording of ECGs can be carried by any health care worker), universal (the doctor from any country may interpret the results of the ECG), non-invasive (does not affect the integrity of the organism, is practically harmless), and inexpensive one (Heart and Stroke Foundation, 2012).
The Main Groups of Diseases Recorded on an ECG
- Rhythm disturbances (arrhythmias) paroxysmal tachycardia, extrasystoles, atrial fibrillation, atrial flutter (innate characteristics, metabolic disorder, intoxication, myocardial infarction, etc.)
- Feeding disorders of the heart muscle (ischemia), acute myocardial infarction, PIS (unstable angina) , a non-critical ischemia of the heart (angina ), etc.
- Changing the size of the heart: thickening of the wall of the heart (hypertrophy) with hypertension, the increase in cameras (dilatation) with valvular bulging of the wall (aneurysm)
- Violations of the pulse (block): atrial block, atrioventricular block I, II, III degrees, bundle- branch block.
- Heart failures are usually diagnosed by an abnormal ECG as normal ECG findings are not diagnostic (Merck, 2013).
The Value of the ECG in the Patient Survey Program
At present, the ECG is a list of the required (screening) studies that are needed to be done before visiting a doctor, as in a clinic or in a hospital. Patients with heart disease may meet with the ECG after the first visit to the physician (cardiologist), when one calls an ambulance to the hospital for examination.
ECG does not require special preparation of a patient, has no contraindications, and is completely safe (the device only receives the pulses coming from the electric grid of the heart) (E-Medicine). ECG is immensely universal method of heart disorders diagnosis. Almost in all cases, the ECG can successfully be registered except for increased muscle tone and seizures.
Patients with heart disease are recommended to periodically have the ECG test to assess the success of treatment or the progression of the disease. The results should be stored in a special folder so that the doctor could at any moment assess the dynamics of the disease.
Holter Monitoring as a Method for Diagnosis of Cardiovascular Diseases
According to Merck (2012), "Holter monitoring is continuous monitoring and recording of the ECG, BP, or both for 24 or 48 h." All the time the patient spends in the usual way, journaling his actions. Patient notes activities, physical loads, and features of state of health, time of taking drugs, and related complaints. Continuous recording using the Holter method helps to assess heart function accurately.
Holter monitoring can identify short-term cardiac conduction and rhythm, which on a normal ECG record fails to reveal episodes of ischemia. This method allows diagnosing cardiovascular disease and prescribing effective treatment more accurately.
Diagnosis of Heart Disease Using Echocardiography (Echocardiogram)
Echocardiography allows to explore the changes in the structure and operation of cardiac tissue exposure of signal recording and ultrasonic waves reflected from structures (moving ) of the heart .
This examination is conducted using a special ultrasonic probe at positions which provide the best overview of the various parts of the heart. The apparatus fixes an each static and the moving picture of the investigated plane.
This method of diagnosis is indicated for the diagnosis of myocardial infarction, angina pectoris, with suspected tumours of the heart to identify complications after an illness with an aim to evaluate the effectiveness of surgical interventions.
This method is usually used when a patient has a disease of valves, myocardium and pericardium pathology, noises in the heart, inflammatory processes, cardiomyopathy, and congenital and acquired heart defects. This method is also used to assess the effectiveness of therapy in cardiovascular diseases to clarify the nature of cardiac arrhythmias for the diagnosis of a soldier's heart. According to Merck (2013), "it helps assess heart wall thickness and motion and provides information about ischemia and infarction."
Magnetic Resonance Imaging as a Method for Diagnosis of Cardiovascular Diseases
This is a highly accurate imaging diagnostic method that provides a detailed picture of all the sites in the heart and blood vessels in different planes, using a three-dimensional reconstruction.
Image obtained by MRI makes it possible to obtain clear information about the work of the myocardium, heart valves, and blood vessels and consider the structural condition of all the tissues of the heart. MRI helps to evaluate the pumping function of the heart, measured blood velocity in the heart and great vessels. This allows identifying changes during contraction in the cavities of the heart. Such a method of research helps to evaluate the state of the coronary vessels and the blood supply to the myocardium and reveal anatomical malformations.
The control over the work of the heart in the present conditions of constant time pressure, multiple stresses, and physical inactivity is a universal guarantor of health and, therefore, a positive attitude and success in implementing many promising life plans. Thus, it is of paramount importance to apply the method, which could be universal, accurate, cheap and simple in use at the same time.
ECG is the most widely used key test in heart diseases diagnosis and thus, the most important one. All of the above methods allow diagnosing cardiovascular disease and prescribing the correct treatment accurately. However, only ECG is applicable for almost all main types of cardiovascular disorders. It is successfully applied for predicting a heart attack and monitoring the heart rhythm.