In the
electrocardiogram, the intrinsicoid deflection is the downstroke of the
QRS complex, from its highest amplitude until it reaches the baseline or lower.
Since the
ventricles normally
depolarize from inside to outside, this deflection reflects the depolarization vector from the
endocardium to the
epicardium. The ''time of the onset of the intrinsicoid deflection'', also referred to as the ''ventricular activation time'' or ''R wave peak time'', is measured from the beginning of the QRS complex to the peak of the R wave.
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 or ventricular hypertrophy. Time of onset of intrinsicoid deflection > 0.04 seconds (just over one small box) is used as a non-voltage related criterion to diagnose
left ventricular hypertrophy.
[The Complete Guide to ECGs 2009]
References
Cardiac electrophysiology
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