Increased left Ventricular mass increases the leftward and posterior electrical forces. This increases the amplitude of the R waves in leads facing the left ventricule (l, aVL,V5 and V6) and amplitude of S waves in leads facing the right ventricule (V1 AND V2).
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Delay in completion of subendocardial to subepicardial Depolarization may result in repolarization beginning in the subendocardium instead of the subepicardium.
Most often the ST segment slopes downward from a depressed J point and the T wave are asymmetricaly inverted ( secondary ST-T changes or strain pattern.
These repolarization changes usually occur in patients with QRS changes but can appear alone.
They are most topical of left Ventricular Hypertrophy induced by pressure overload. Volume overload can produce Deep Q (>2mm) and tall upright T wave in lead facing the left ventricule.
The ST-T segment abnormalities may also reflect a primary disorder of repolarization that accompanies the cellular process of hypertrophy or subendocardial ischemia induced by the combination of high oxygen demand caused by high wall tension and limited subendocardial blood flow of the thickned wall.
Various diagnostic criteria for Left Ventricular Hypertrophy have been developed are following:
1. Romhilt-estes Point Score System:
1. Any limb lead R or S => 20mm here score points is 3
2. S in v1 or S in v2 > 20 mm points 3
3. R in V5 or V6 > 30 mm points 3
4. ST-T wave abnormalities ( no digits therapy) points 3
5. ST-T WAVE Abnormalities ( digitalis therapy) point 1
6. P terminal force in V1 >0.4 mm.sec X 1 mm points 3
7. Left axis deviation ( => -30) points 2
8. Intrinsicoid deflection in V5 or V6 >50 msec point 1
9. QRS duration > 90 msec point 1
Five or more points indicate definite Left Ventricular Hypertrophy and 4 points indicate probable Left Ventricular Hypertrophy.
2. Cornell Voltage Criteria are following:
- 1. S v3 + R aVL=> 28 mm for men
- 2. S V3 + R aVL => 20 mm for women.
3. Sokolow-Lyion Index:
- S v1 + R V5 or R v6 > 35 mm ( after age of 30 years),
- More than 40 mm ( between 20 to 30 years) and
- More than 60 mm ( between 16 to 20 years).