True statement about 'instantaneous mean vector' a) Equal & same as mean QRS vectorb) It is drawn through the centre of vector in a direction from base toward apexc) Summated vector of generated potential at particular instant caused by inflowing septal depolarizationd) When a vector is exactly horizontal and directed toward the person's left side, the vector is said to extend in the direction of 0 degrees
In a normal heart, the current flows from the base towards apex. So the vector is pointed towards the apex at an angle of +59o. The angle is calculated from a vector running horizontally towards left, which is 0o. Instantaneous mean vector is the summated vector of general potential at a given instant due to septal depolarization.
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