The assumption rather, has no sound theoretical basis, vet surprisingly, it is a very good working rule.

ds the R wave gradually becomes taller and taller from V7 lo V5 and S becomes smaller and smaller from VI 10 V5 . 0 is present in VS and V6 but absent in V1 4. In all leads P wave, PR intervals, QRS complex have normal values and ST segment is isoelectric 5. The electric axis (see below) is normal The electrical bus Clinical electro cardiographists traditiooally assume that for some specific purposes, the electircal events of the ventricle can be represented by a single resultant dipole (and I he moment to momenl change of the direction of me resultant dipole need not be considered). The assumption rather, has no sound theoretical basis, vet surprisingly, it is a very good working rule. This single resultant dipole is called the etectrical axis [fig 6.11 7 a) Fig 571,7 Upper- normal heart, middle - left ventricular hypertrophy (boot shaped enlargement of heart) left axis deviation; lower - right ventricular hypertrophy (right am deviation) Normal hearts have a normal axis (fig.5 11 7a) If The axis rotates (deviates) anticlockwise it is called left axis deviation (5 11.7b). Left axjs deviation is due is such conditions like left ventricular hypertrophy (which causes a boot shaped enlargement of the heart) and others Conversely if there is a clockwise rotation there is right axis deviation (5 11 7c) which may be due to right ventricular hypertrophy.