Today our topic of discussion is Electrocardiogram for Axis.
Electrocardiogram for Axis
Axis
- It refers to the direction of depolarization which spreads throughout the heart to stimulate the myocardium to contract
- Vector: It shows the direction in which most of the stimulus is traveling. QRS vector is always AV node. QRS vector- normally points downwards and to the patients left side
- We can locate the position of the QRS vector with in a large cycle around the heart. The center point is AV node. QRS vector changes in hypertrophy (Vector is less than 90″) and infarction (Vector is more than 90 degree)
- Normal axis: QRS vector shows left downwards points in 0 to 90″. Lead I QRS vector right side called positive vector and left side called negative vector. Lead I positive called normal axis
- AVE lead shows lower half is positive and upper half is negative. The AVF positive vector is the normal axis
- Normal axis defined as lead I positive and AVF lead positive. Left axis deviation defines lead .I positive and AVF lead negative
- Right axis deviation defines as lead I negative and AVF lead positive.Extreme right axis deviation defines defined as lead I negative and AVF negative.
Myocardial Infarction
- Anterioseptal (anterior) myocardial infarction causes ECG changes are abnormal Q wave in lead 1, AVL and VI-V3. Reciprocal changes are depressed ST segment in lead II. III and AVF
- Anteriolateral (lateral) myocardial infarction causes abnormal Q-wave in lead 1, AVL and V5-V6. Reciprocal changes are depressed ST in lead II, III and AVF
- Inferior myocardial infarction causes abnormal Q wave in lead II, III, and AVF Posterior myocardial infarction causes often large dominant R in lead VI and V2. 12 Lead ECG
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