In BBB and LVH we see prolongation of intrinsicoid deflection on ECG. But many times this deflection is defectively calculated in leads like v1, v2,v3 etc.
the reality is INTRINSICOID deflection should be measured only in LATERAL LEADS v5,v6, I, and Avl.
why?.
intrinsic deflection is the time taken for the depolarization wave to spread from endocardium to epicardium when the lead is placed directly on the heart. But on surface ECG these leads are placed on chest wall far away from the myocardium. Hence the deflection is called intrinsicoid (=intrinsic like) deflection.
As the lateral leads look the electrical activity of the heart from a vantage point and are least influenced by the elctrical forces from the other parts of the heart, these are the ideal leads to measure the intrinsicoid deflection.
usually it takes 45msec to reach the electrical activity from endocardium to epicardium. duration more than thius is considered as prolonged intrinsicoid deflection.
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