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Right Axis Deviation
The electrical axis of the heart is the net direction in which the wave of depolarization travels. It is measured using an electrocardiogram (ECG). Normally, this begins at the sinoatrial node (SA node); from here the wave of depolarisation travels down to the apex of the heart. The hexaxial reference system can be used to visualise the directions in which the depolarisation wave may travel. On a hexaxial diagram (see figure 1): * If the electrical axis falls between the values of -30° and +90° this is considered normal. * If the electrical axis is between -30° and -90° this is considered left axis deviation. * If the electrical axis is between +90° and +180° this is considered right axis deviation (RAD). RAD is an ECG finding that arises either as an anatomically normal variant or an indicator of underlying pathology. Signs, symptoms and risk factors There are often no symptoms for RAD and it is usually found by chance during an ECG. Many of the symptoms exhibited by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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Depolarization
In biology, depolarization or hypopolarization is a change within a cell (biology), cell, during which the cell undergoes a shift in electric charge distribution, resulting in less negative charge inside the cell compared to the outside. Depolarization is essential to the function of many cells, communication between cells, and the overall physiology of an organism. Most cells in higher organisms maintain an internal environment that is negatively charged relative to the cell's exterior. This difference in charge is called the cell's membrane potential. In the process of depolarization, the negative internal charge of the cell temporarily becomes more positive (less negative). This shift from a negative to a more positive membrane potential occurs during several processes, including an action potential. During an action potential, the depolarization is so large that the potential difference across the cell membrane briefly reverses polarity, with the inside of the cell becoming p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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Pneumothorax
A pneumothorax is collection of air in the pleural space between the lung and the chest wall. Symptoms typically include sudden onset of sharp, one-sided chest pain and dyspnea, shortness of breath. In a minority of cases, a one-way valve is formed by an area of damaged Tissue (biology), tissue, and the amount of air in the space between chest wall and lungs increases; this is called a tension pneumothorax. This can cause a steadily worsening Hypoxia (medical), oxygen shortage and hypotension, low blood pressure. This leads to a type of shock called obstructive shock, which can be fatal unless reversed. Very rarely, both lungs may be affected by a pneumothorax. It is often called a "collapsed lung", although that term may also refer to atelectasis. A primary spontaneous pneumothorax is one that occurs without an apparent cause and in the absence of significant lung disease. A secondary spontaneous pneumothorax occurs in the presence of existing lung disease. Smoking increases ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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Left Axis Deviation
In electrocardiography, left axis deviation (LAD) is a condition wherein the mean electrical axis of ventricular contraction of the heart lies in a frontal plane direction between −30° and −90°. This is reflected by a QRS complex positive in lead I and negative in leads aVF and II. There are several potential causes of LAD. Some of the causes include normal variation, thickened left ventricle, conduction defects, inferior wall myocardial infarction, pre-excitation syndrome, ventricular ectopic rhythms, congenital heart disease, high potassium levels, emphysema, mechanical shift, and paced rhythm. Symptoms and treatment of left axis deviation depend on the underlying cause. Defining left axis deviation Cardiac axis in electrocardiography represents the sum of depolarization vectors generated by individual cardiac myocytes. To interpret the cardiac axis, one has to determine the relationship between the QRS axis and limb leads of the ECG. Usually, left ventricles ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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QRS Complex
The QRS complex is the combination of three of the graphical deflections seen on a typical electrocardiogram (ECG or EKG). It is usually the central and most visually obvious part of the tracing. It corresponds to the depolarization of the right and left ventricles of the heart and contraction of the large ventricular muscles. In adults, the QRS complex normally lasts ; in children it may be shorter. The Q, R, and S waves occur in rapid succession, do not all appear in all leads, and reflect a single event and thus are usually considered together. A Q wave is any downward deflection immediately following the P wave. An R wave follows as an upward deflection, and the S wave is any downward deflection after the R wave. The T wave follows the S wave, and in some cases, an additional U wave follows the T wave. To measure the QRS interval start at the end of the PR interval (or beginning of the Q wave) to the end of the S wave. Normally this interval is 0.08 to 0.10 seconds. W ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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Hexaxial Reference System
The hexaxial reference system, better known as the Cabrera system, is a convention to present the extremity leads of the 12 lead electrocardiogram, that provides an illustrative logical sequence that helps interpretation of the ECG, especially to determine the heart's electrical axis in the frontal plane. The most practical way of using this is by arranging extremity leads according to the Cabrera system, reversing polarity of lead aVR and presenting ECG complexes in the order (aVL, I, -aVR, II, aVF, III). Then determine the direction the maximal ECG vector is "pointing", i.e. in which lead there are most positive amplitude - this direction is the electrical axis - see diagram. Example: If lead I has the highest amplitude (higher than aVL or -aVR), the axis is approximately 0°. Conversely, if lead III has the most negative amplitude it means the vector is pointing away from this lead, i.e. towards -60°. An alternative use is to locate the most isoelectric (or equiphasic) lead (I, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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Dextrocardia
Dextrocardia () is a rare congenital condition in which the apex of the heart is located on the right side of the body, rather than the more typical placement towards the left. There are two main types of dextrocardia: dextrocardia of embryonic arrest (also known as isolated dextrocardia) and dextrocardia ''situs inversus''. Dextrocardia ''situs inversus'' is further divided. Classification Dextrocardia of embryonic arrest In this form of dextrocardia, the heart is simply placed further right in the thorax than is normal. It is commonly associated with severe defects of the heart and related abnormalities including pulmonary hypoplasia. Dextrocardia situs solitus Dextrocardia refers to a heart positioned in the right side of the chest. Situs solitus describes viscera that are in the normal position, with the stomach on the left side. Dextrocardia situs inversus Dextrocardia situs inversus refers to the heart being a mirror image situated on the right side. For all visceral ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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Chronic Obstructive Pulmonary Disease
Chronic obstructive pulmonary disease (COPD) is a type of progressive lung disease characterized by chronic respiratory symptoms and airflow limitation. GOLD defines COPD as a heterogeneous lung condition characterized by chronic respiratory symptoms (shortness of breath, cough, sputum production or exacerbations) due to abnormalities of the airways (bronchitis, bronchiolitis) or alveoli ( emphysema) that cause persistent, often progressive, airflow obstruction. The main symptoms of COPD include shortness of breath and a cough, which may or may not produce mucus. COPD progressively worsens, with everyday activities such as walking or dressing becoming difficult. While COPD is incurable, it is preventable and treatable. The two most common types of COPD are emphysema and chronic bronchitis and have been the two classic COPD phenotypes. However, this basic dogma has been challenged as varying degrees of co-existing emphysema, chronic bronchitis, and potentially significan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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Right Ventricular Hypertrophy
Right ventricular hypertrophy (RVH) is a condition defined by an abnormal enlargement of the cardiac muscle surrounding the right ventricle. The right ventricle is one of the four chambers of the heart. It is located towards the right lower chamber of the heart and it receives deoxygenated blood from the right upper chamber (right atrium) and pumps blood into the lungs. Since RVH is an enlargement of muscle it arises when the muscle is required to work harder. Therefore, the main causes of RVH are pathologies of systems related to the right ventricle such as the pulmonary artery, the tricuspid valve or the airways. RVH can be benign and have little impact on day-to-day life or it can lead to conditions such as heart failure, which has a poor prognosis. Signs and symptoms Symptoms Although presentations vary, individuals with right ventricular hypertrophy can experience symptoms that are associated with pulmonary hypertension, heart failure and/or a reduced cardiac output. These i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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Electrocardiography
Electrocardiography is the process of producing an electrocardiogram (ECG or EKG), a recording of the heart's electrical activity through repeated cardiac cycles. It is an electrogram of the heart which is a graph of voltage versus time of the electrical activity of the heart using electrodes placed on the skin. These electrodes detect the small electrical changes that are a consequence of cardiac muscle depolarization followed by repolarization during each cardiac cycle (heartbeat). Changes in the normal ECG pattern occur in numerous cardiac abnormalities, including: * Cardiac rhythmicity, Cardiac rhythm disturbances, such as atrial fibrillation and ventricular tachycardia; * Inadequate coronary artery blood flow, such as myocardial ischemia and myocardial infarction; * and electrolyte disturbances, such as hypokalemia. Traditionally, "ECG" usually means a 12-lead ECG taken while lying down as discussed below. However, other devices can record the electrical activity of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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Ectopic Beat
Ectopic beat is a disturbance of the cardiac rhythm frequently related to the electrical conduction system of the heart, in which beats arise from fibers or group of fibers outside the region in the heart muscle ordinarily responsible for impulse formation (''i.e.'', the sinoatrial node). An ectopic beat can be further classified as either a premature ventricular contraction (PVC), or a premature atrial contraction (PAC). Some patients describe this experience as a "flip" or a "jolt" in the chest, or a "heart hiccup", while others report dropped or missed beats. Ectopic beats are more common during periods of psychological stress, exercise or debility; they may also be triggered by consumption of some food like carbohydrates, strong cheese, or chocolate. It is a form of cardiac arrhythmia in which ectopic foci within either ventricular or atrial myocardium, or from finer branches of the electric transduction system, cause additional beats of the heart. Some medications may wor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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Wolff Parkinson White Syndrome
Wolff is a variant of the Wolf surname which is derived from the baptismal names Wolfgang or Wolfram. List of people surnamed Wolff A * Albert Wolff (other), several people * Alex Wolff, American actor * Alexander Wolff, American writer * Alexander Wolff (soldier), (1788–1863), British officer who served under the Duke of Wellington * Andreas Wolff (born 1991), German handball player * Auguste Wolff (1821–1887), French piano maker B * Betje Wolff (1738–1804), Dutch writer * Bernard Wolff (1811–1879), German media mogul * Bernard Wolff Beffie (1872–1943), Dutch chess master and dermatologist * Beverly Wolff (1928–2005), American mezzo-soprano * Bobby Wolff (born 1932), American bridge player C * Carl Gustaf Wolff, a prominent Finnish shipowner and businessman * Caspar Friedrich Wolff (1734–1794), founder of embryology * Christian Wolff (other), several people * Christina Wolff, American politician * Christoph Wolff (born 1940), German-born mus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |