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Tachycardia-dependent bundle branch block; 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).
Ashman beats are described as wide complex QRS complexes that follow a short R-R interval preceded by a long R-R interval. [3] This short QRS complex typically has a right bundle branch block morphology and represents an aberrantly conducted complex that originates above the AV node, rather than a complex that originates in either the right or left ventricle.
An incomplete right bundle branch block (IRBBB) is a conduction abnormality in the right bundle branch block. While a complete RBBB has a QRS duration of 120 ms or more, an incomplete RBBB has a wave duration between 100 and 120 ms.
Electrocardiogram showing left bundle branch block and irregular rhythm due to supraventricular extrasystoles. A left bundle branch block. LBBB is diagnosed on a 12-lead ECG. 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]
Any abnormality of conduction takes longer and causes "widened" QRS complexes. In bundle branch block, there can be an abnormal second upward deflection within the QRS complex. In this case, such a second upward deflection is referred to as R′ (pronounced "R prime"). This would be described as an RSR′ pattern.
IVCD can be caused by abnormalities in the structures of bundle of His, Purkinje fibers or ventricular myocardium. [5] [6] Nonspecific intraventricular conduction delay (NICD) is a delay with widened QRS complex but without a specific intraventricular block present. [7]
Since now one of the ventricles is contracting late, a QRS complex longer than 120 ms is common to see in a bundle branch block. Okay, so far we’ve been looking a relatively common view of the heart, called lead two, which is a type of limb lead, since we get it by attaching leads to the right arm and left leg, both of which are limbs.
In the presence of bundle branch block or ventricular hypertrophy, the depolarization impulse takes a longer than normal period of time to reach the recording electrode. This delays the onset of the intrinsicoid deflection. This prolongation or delay is an important criterion for diagnosing bundle branch block or ventricular hypertrophy.