The QRS complex is the name for a combination of three of the graphical deflections seen in a typical electrocardiogram (ECG or ECG). This is usually the most visually visible part of the search, in other words, this is the major spike seen on the ECG line. This corresponds to the depolarization of the right and left ventricle of the human heart and the contraction of the large ventricular muscles.
In adults, the QRS complex usually lasts 0.06-0.10 s; in children and during physical activity, it may be shorter. The Q, R, and S waves occur sequentially, not all of them appearing in all directions, and reflect one event and are therefore usually considered shared. Q wave is any downward deflection immediately after P wave . The wave R follows as an upward deflection, and wave S is any downward deflection after wave R. The wave T follows the S wave, and in some case, the wave U follows the T wave.
Video QRS complex
Formation
Cardiac ventricular depolarization occurs almost simultaneously, through bundles of fibers and Purkinje. If they work efficiently, QRS complexes are 80 to 120 ms . These are represented by three small squares or less at a standard paper speed of 25 mm/s.
Maps QRS complex
Clinical interests
Any conduction abnormality takes longer and causes the QRS complex to "widen". In the branch block bundle, an abnormal second upward deflection in the QRS complex may occur. In this case, the second upward deflection is referred to as R '(pronounced "R prime"). This will be described as an RSR pattern.
The ventricles contain more muscle mass than atria. Therefore, the QRS complex is much greater than the wave P. The QRS complex is often used to determine the electrocardiogram axis, though it is also possible to determine the separate P wave axis.
The duration, amplitude, and complex morphology of QRS are useful in diagnosing cardiac arrhythmias, conduction abnormalities, ventricular hypertrophy, myocardial infarction, electrolyte disorders, and other disease states.
Components
The QRS complex is also included in estimating QT intervals.
Wave Q
The normal Q wave, at present, represents the interventricular septum depolarization. For this reason, they are referred to as the Q wave of the septum and can be appreciated on the lateral rings of I, aVL, V5 and V6.
Pathological Q waves occur when electrical signals pass through a stunned or injured heart muscle; thus, they are usually markers of previous myocardial infarction, with subsequent fibrosis. Pathological Q waves are defined as having a deflection amplitude of 25% or more of the next R wave, or being & gt; 0.04 s (40Ã, ms) with width and & gt; 2 mm in amplitude. However, the diagnosis requires the presence of this pattern in more than one corresponding lead.
Myocardial infarction with pathological Q waves is referred to as MI elevation ST.
R wave progression
Looking at the precordial leads, the R wave usually develops from showing the complex type of rS in V 1 with increasing R and decreasing S wave as it moves toward the left side. There is usually a type of qR-complex in V 5 and V 6 with a R-wave amplitude usually higher in V 5 than in V 6 . It is normal to have a narrow QS and rSr pattern in V 1 , and this also applies to the qR and R patterns in V 5 and V 6 . The transition zone is where the QRS complex changes from predominantly negative to positive dominant (R/S ratio becomes & gt; 1), and this usually occurs at V 3 or V < sub> 4 . It is normal to have a transition zone on V 2 (called "initial transition") and on V 5 (called "delayed transition"). In biomedical engineering, the maximum amplitude in R waves is usually called "R peak amplitude", or simply "peak R". Accurate R peak detection is essential in signal processing equipment for heart rate measurement and is a key feature used to detect arrhythmias.
The definition of poor R wave progression (PRWP) varies in literature, but the common one is when R waves are less than 2-4 mm in leads V 3 or V 4 and/or the presence of inverted R waveform development, defined as R in V 4 & lt; R in V 3 or R in V 3 & lt; R in V 2 or R in V 2 & lt; R in V 1 , or a combination of these. Improvement of poor R wave is generally associated with anterior myocardial infarction, but may also be caused by left bundle branch block, Wolff-Parkinson-White syndrome, right ventricular and left ventricular hypertrophy, or incorrect ECG recording technique..
J-point
The point at which the QRS complex meets the ST segment is the J-point. The A-point is easily identified when the ST segment is horizontal and forms a sharp angle with the last part of the QRS complex. However, when the ST segment is angled or the QRS complex is wide, the two features do not form a sharp angle and the location of the J-point is less clear. There is no consensus about the precise location of the J-point under these circumstances. Two possible definitions are:
- The first "inflection point of the S wave ride style"
- The point at which ECG traces become more horizontal than vertical
Terminology
Not every QRS complex contains Q waves, R waves, and S waves. By convention, any combination of these waves can be referred to as QRS complexes. However, the correct interpretation of a difficult ECG requires proper labeling of the various waves. Some authors use lowercase and uppercase letters, depending on the relative size of each wave. For example, the Rs complex will be positively deflected, while the rS complex will be deflected negatively. If both complexes are labeled RS, it is impossible to appreciate this difference without looking at the actual ECG.
Monomorphic or polymorphic
Monomorphine refers to all QRS waves in a lead having a similar shape. Polymorphic means that QRS changes from complex to complex. These terms are used in the description of ventricular tachycardia.
Algorithm
The common algorithm used for QRS complex detection is the Pan-Tompkins algorithm (or method); another is based on Hilbert's transformation. Many other algorithms have been proposed and investigated.
See also
- Electrophysiology
References
Source of the article : Wikipedia
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