A<unk>  can be diagnosed when the duration of the QRS complex on the ECG exceeds 120 ms. A right<unk>  typically causes prolongation of the last part of the QRS complex and may shift the heart's electrical axis slightly to the right. The ECG will show a terminal R wave in lead V1 and a slurred S wave in lead I. Left<unk>  widens the entire QRS, and in most cases shifts the heart's electrical axis to the left. The ECG will show a QS or rS complex in lead V1 and a monophasic R wave in lead I. Another normal finding with<unk>  is appropriate T wave discordance. In other words, the T wave will be deflected opposite the terminal deflection of the QRS complex.<unk> , especially left<unk> , can lead to cardiac dyssynchrony. The simultaneous occurrence of left and right<unk>  leads to total AV block. Types Image showing the ECG characteristics of a right<unk>  and a left<unk> . In both cases, the late portion of the widened QRS complex arises from an anomalously conducted depolarization impulse. The direction of this delayed depolarization vector differs based on the structure that is blocked; the impulse travels anterior toward the right ventricle in RBBB and lateral toward the left ventricle in LBBB. Depending on the anatomical location of the defect which leads to a<unk> , the blocks are further classified into: *Right<unk>  *Left<unk>  The left<unk>  can be further sub classified into: *Left anterior fascicular block. In this case only the anterior half of the left bundle<unk>  (fascicle) is involved *Left posterior fascicular block. Only the posterior part of the left bundle<unk>  is involved Other classifications of<unk> s are; *Bifascicular block. This is a combination of right<unk>  (RBBB) and either left anterior fascicular block (LAFB) or left posterior fascicular block (LPFB) *Trifascicular block. This is a combination of right<unk>  with either left anterior fascicular block or left posterior fascicular block together with a first degree AV block. *Tachycardia-dependent<unk>  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, its LEFT, a deflection UP indicates RIGHT (RBBB). of course, in both types the QRS is long (>.12 seconds).
Bundle branch block
Right bundle branch block
Left bundle branch block
Sinoatrial block
Pre-excitation syndrome
Sinoatrial arrest
Left anterior fascicular block
Atrioventricular block