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QRS duration: 75 to 105 ms [3] Shorter in children [4] Prolonged duration could indicate hyperkalemia [5] or intraventricular conduction delay such as bundle branch block. QRS amplitude: S amplitude in V1 + R amplitude in V5 < 3.5 millivolt (mV) [4] R+S in a precordial lead < 4.5 mV [4] R in V5 or V6 < 2.6 mV; Increased amplitude indicates ...
The QRS duration must be more than 100 ms (incomplete block) or more than 120 ms (complete block). [9] There should be a terminal R wave in lead V 1 (often called "R prime," and denoted by R, rR', rsR', rSR', or qR). There must be a prolonged S wave in leads I and V 6 (sometimes referred to as a "slurred" S wave).
A simple way to quickly differentiate between the two types is to note the deflection of the QRS complex in the V1 lead. A (V1) QRS segment deflected down indicates left bundle branch block, while a deflection up indicates right bundle branch block. In both types, the QRS is wide (> 0.12 seconds).
Ventricular tachycardia is a regular rhythm with a rate of 140-250 bpm, there are no P waves and the main feature is a wide QRS complex (0.12 and greater) Ventricular fibrillation has no p waves or QRS complexes, there are only wavy irregular deflections throughout the heart rhythm, at this point the heart would have a rate of 0 and be ...
In adults, it is seen as wide QRS complexes lasting ≥120ms with characteristic QRS shapes in the precordial leads, although narrower complexes are seen in children. [4] In lead V 1 , the QRS complex is often entirely negative (QS morphology), although a small initial R wave may be seen (rS morphology).
They may be classified into narrow and wide complex based on the QRS complex. [10] Equal or less than 0.1s for narrow complex. [11] Presented in order of most to least common, they are: [10] Narrow complex Sinus tachycardia, which originates from the sino-atrial (SA) node, near the base of the superior vena cava; Atrial fibrillation; Atrial flutter
A wide QRS complex (because the ectopics for the generation of the cardiac impulse originate in the ventricular myocyte and are propagated via the intermyocyte conduction, which is a delayed conduction) A Josephson's sign where there is the notch in the downsloping of the S wave near its nadir (considered very specific for the VT)
Furthermore, tall or wide QRS complex with an upright T wave is further suggestive of the posterior infarction. [ 5 ] Wellens' syndrome is caused by the injury or blockage of the left anterior descending artery , therefore resulting in symmetrical T wave inversions from V2 to V4 with depth more than 5 mm in 75% of the cases.