What will the ECG show with coronary artery disease? This is a common question. Let's look into it in more detail.
ECG is one of the most informative and accessible methods for diagnosing cardiac pathologies, which is based on the registration of impulses passing through the heart and their graphic recordings in the form of teeth on paper film.
Detailed description of the diagnostic method
Based on such data, one can draw conclusions not only about the electrical activity of this organ, but also about the structure of the heart muscle. This means that it is possible to diagnose various heart diseases with the help of an ECG.
Functioning and contractile activity of the heart are possible due to the fact that spontaneous impulses constantly arise in it. Within the normal range, their source is localized in the sinus node, which is located next to the right atrium. The purpose of such impulses is to pass through the conductive nerve fibers through all parts of the heart muscle, causing their contraction. When the momentumpasses through the atria, and then through the ventricles, they alternately contract, which is called systole. During the period when impulses do not arise, the heart begins to relax and diastole occurs.
Based on what?
ECG diagnostics is based on the registration of electrical impulses that occur in the heart. For this, an electrocardiograph is used, the principle of which is to register the difference in bioelectric potentials that occur in different parts of the organ at the time of contractions and relaxation. Such processes are recorded on heat-sensitive paper in the form of a graph, which consists of hemispherical or pointed teeth and horizontal lines in the form of gaps. ECG for coronary artery disease and angina pectoris is prescribed very often.
In order to register the electrical activity of the organ, it is necessary to fix the electrodes of the electrocardiograph on the legs and arms, as well as on the anterolateral surface of the sternum on the left. This allows you to register all directions of electrical impulses.
Each of the leads indicates that they register the passage of an impulse through a specific part of the heart, thanks to which doctors receive the following information:
- about the location of the heart in the chest;
- about the structure, thickness and nature of the blood circulation of the atria and ventricles;
- about the regularity of impulses in the sinus node;
- about obstacles in the path of impulses.
What is myocardial ischemia?
Find out what is coronary artery disease (ICD-10 I20-I25), or ischemic diseasehearts.
The heart is the most powerful muscle in the human body. It can pump up to 7,000 liters of blood per day at a speed of 1.5 km / h, which can be compared with the operation of a pump. Along with this, the heart is highly sensitive to oxygen starvation, which often leads to damage to the cardiac tissue. The main method in the study of heart disease, including any form of coronary artery disease, is an ECG, which is a recording of electrical impulses carried out in all leads, which helps to detect even chronic symptoms of myocardial ischemia. Patients who have previously experienced a lack of oxygen should be especially careful and undergo regular medical examinations to prevent the recurrence of spasms of the coronary arteries.
IHD (ICD-10 I20-I25) is a condition that occurs as a result of disturbances in the flow of arterial blood to the heart muscle against the background of blockage of the coronary vessels or their spasm, and occurs in a chronic or acute form. When the heart does not receive the volume of oxygen it needs, sections of connective tissue are formed in the gaps of the muscle fibers that have lost the ability to fully function. The process of damage to the heart muscle always occurs with the development of minor ischemia, which, without appropriate therapy, eventually provokes the occurrence of a true heart attack.
What can be seen on an ECG with coronary artery disease is interesting to many.
Pathogenesis of the disease on the ECG
The pathogenesis of IHD is as follows:
- Stable angina, which is characterized by pressing paroxysmal pain in the retrosternal region, which occurs under the influence of physical exertion and gradually disappears when stressful conditions are eliminated. Most often there is coronary artery disease with rhythm disturbance.
- Unstable angina, which is an intermediate period between stable ischemia of the heart muscle and the development of all kinds of complications. Its main clinical symptom is chest pain, which develops even at rest and can provoke damage to heart tissue cells.
- Small-focal myocardial infarction, which is a rather insidious variant of coronary artery disease and is characterized by the absence of a pathological Q wave on the ECG, as well as microscopic foci of tissue death. Often these violations go unnoticed, because they are masked as an attack of angina pectoris in an acute form.
- Q-myocardial infarction. The most dangerous complication of myocardial ischemia is considered to be macrofocal infarction, which is characterized by a transmural lesion of the heart muscle with S-T segment elevation and the formation of an additional Q wave, which persists even after the absolute replacement of necrotic areas with connective tissue.
This is how informative an ECG can be for coronary artery disease.
Additional examinations
Since the signs of ischemic processes in some subspecies of this disease are the same, a number of additional examinations have been established to determine a heart attack. Creatine phosphokinase and myoglobin are early markers of cardiac muscle necrosis. For the most accuratediagnosis after 7-9 hours, it is advisable to examine the level of troponins, aspartate aminotransferase and lactate dehydrogenase. Elevation of the S-T segment is sometimes observed not only with the development of a heart attack, it often occurs with unstable angina, as a result of which it is necessary to take into account all visual changes in the teeth on the electrocardiogram.
Manifestations of ischemia on the electrocardiogram
It is quite difficult to answer unequivocally how the ECG results for coronary artery disease on film will look. When hypoxia of the heart muscle occurs, the movement of electrical potentials slows down slightly, potassium ions exit the cells, which negatively affects the resting potentials. At the same time, compensatory processes are launched, the heart begins to overstrain, pressing pain behind the sternum develops, the patient is disturbed by an unpleasant feeling of lack of air.
Characteristic ECG signs in chronic ischemic heart disease and oxygen starvation of heart tissues are:
- Sloping or horizontal depression of the S-T segment.
- T wave reduction or movement below the horizontal line.
- T wave widening due to slow ventricular repolarization.
- The occurrence of a pathological Q wave with the development of macrofocal necrosis.
- The dynamics of changes on the electrocardiogram, which is a sign of the "freshness" of the pathological process.
ECG signs of IHD should not be ignored. Additionally, the picture may show signs of arrhythmias and blockades that occur inas a complication of ischemic processes. In most cases, with the development of ischemia of the heart muscle on the ECG, the QRS complex retains its normal shape, since oxygen deficiency mainly affects the recovery (repolarization) of the ventricles, which ends the cardiac cycle within the normal range.
Clinical recommendations for IHD will be given below.
Localization of the ischemic site on the ECG
The endocardium (inner layer) is most susceptible to a lack of oxygen, since blood enters it much worse than in the epicardium, as a result of which it receives much more blood pressure, which fills the ventricles.
ECG results can vary significantly depending on the volume and location of damaged cardiomyocytes. Oxygen starvation of the myocardium is often indicated by changes in the ST segment, for example, this may be a depression more than 0.5 mm deep in two or three adjacent leads. Such a depression can be horizontal and downward.
ECG changes in coronary artery disease can be directly related to the area of ischemia. This is observed:
- damage to the anterior wall of the left ventricle in the area of the endocardium, which is characterized by a high T wave and its sharp end, which is distinguished by visible symmetry;
- hypoxia of the anterior part of the left ventricle with damage to the transmural form of myocardial tissue, which is one of the most dangerous variants of oxygen starvation, in which there is a flattened drooping T wave;
- subendocardial ischemia, which is localizednext to the endocardium of the posterior left ventricle, the T wave will be nearly flat and low on this ECG variant;
- subepicardial ischemic disorders on the ECG at the anterior wall of the left ventricle are indicated by a negative T wave with a sharp apex;
- Lession of the posterior left ventricle of the transmural type is characterized by a high positive T wave with a sharp apex placed symmetrically.
Severe tachycardia
When an obliquely ascending S-T segment is observed on the image, this can be characterized by the presence of severe tachycardia in the patient. In such a case, after the elimination of the stress factor and tachycardia, the results of the electrocardiogram, as a rule, show the norm. If the patient was able to undergo an electrocardiographic examination during a heart attack in the acute stage, then the image can visualize the depression of the S-T segment of the oblique ascending type, turning into "coronary teeth" T, which are characterized by a significant amplitude.
ECG interpretation for IHD should be carried out by a qualified specialist.
Signs of ischemia on the ECG depending on the type of disease
The severity of oxygen starvation of the myocardium on the ECG depends largely on the severity and type of coronary heart disease. In cases of mild hypoxia of the heart muscle, this phenomenon can be detected only during physical activity, when clinical symptoms are not significantly expressed.
Examples of ECG depending on the complexity of the pathological process:
- If the patient has mild ischemia that only occurs during exercise, the test result will be normal at rest. With the onset of an attack during training, there will be S-T segment depression in lead D, indicating true ischemia. At the same time, the amplitude of the T wave may increase in leads A and I, which indicates the normal course of the repolarization process. At about 10 minutes of rest in lead D, S-T depression persists and T-wave deepening is noted, which is a direct sign of myocardial hypoxia.
- With stable angina, attacks of pain can occur after a 15-minute walk. At rest, the ECG of such patients in most situations is normal. After light exercise, there will be down-sloping S-T depression in certain precordial leads (V4-V6), and the T wave will be inverted in the three standard leads. The heart of such a patient quickly reacts to the load, and violations become noticeable almost immediately. What other forms of coronary artery disease are there?
- Unstable angina provokes a high risk of a heart attack and, as a rule, is clearly visible on the cardiogram. The presence of hypoxic disorders during ischemia in the anterolateral part of the left ventricle develops the following changes: oblique depression of the ST segment and negative T wave in aVL, I, V2-V6. Often single extrasystoles are noted on the ECG.
- Small focal heart attack resembles angina pectoris and often goes unnoticed, and to diagnosea non-Q infarction is helped by a specific troponin test and close examination of the ECG results. Necrotic lesions of the heart muscle are indicated by S-T depression in leads V4-V5 and in V2-V6 - a negative T wave with amplitude in the fourth lead.
It is clear that ECG results in coronary artery disease vary depending on the type of pathology.
Conclusions
In case of myocardial infarction, patients often turn to medical specialists for help, however, when it comes to the occurrence of angina pectoris, not all patients are able to adequately assess their condition. In order to prevent the transition of this pathological condition to an acute stage, with a history of coronary disease, it is necessary to periodically conduct electrocardiography.
Clinical guidelines for IHD
The basis of conservative treatment of stable coronary artery disease is the modification of avoidable risk factors and complex drug therapy.
It is recommended to inform patients about the disease, risk factors and treatment strategy.
If overweight, it is strongly recommended to reduce it with the help of dosed physical activity and a low-calorie diet. If necessary - diet correction and / or selection of drug treatment of obesity by a nutritionist.
All patients are advised to follow a special diet and regular monitoring of body weight.
Main goals of drug treatment:
- Elimination of symptomsdiseases.
- Prevention of cardiovascular complications.
Optimal drug therapy is at least one drug to treat angina/myocardial ischemia in combination with drugs to prevent CVD.
Effectiveness of treatment is assessed shortly after starting therapy.
