Isolated left<unk><unk>  block is often an uncommon finding  owing to the fact that the left<unk>  fascicle has a dual blood supply, and it is exposed to lower pressures and turbulence, hence, it is rarely damaged.  It usually accompanies right bundle branch block (RBBB) or in the setting of arteriosclerotic heart diseases such as myocardial infarction.  Other less common causes include: infectious (e.g. diphteritic myocarditis, Chagas disease); genetic (e.g. myotonic dystrophy).
Left posterior fascicular block causes
Sinoatrial arrest causes
Left bundle branch block causes
Right bundle branch block causes
Third degree AV block causes
Atrial flutter causes
Stress cardiomyopathy causes
Supraventricular tachycardia causes