Intrinsicoid deflection

In ECG nomenclature it is the downward deflection after the peak of the R wave.

The time of the onset of the intrinsicoid deflection, also referred to as the R wave peak time, is measured from the beginning of the QRS complex to the peak of the R wave.

Diagnostic significance: In the presence of bundle branch block or ventricular hypertrophy, the depolarization impulse takes a longer than normal period of time to reach the recording electrode. This delays the onset of the intrinsicoid deflection. This prolongation or delay is an important criterion for diagnosing bundle branch block and ventricular hypertrophy.