How & Why Q Wave is recorded on the surface ecg !!!

The Q or the q wave on the surface ecg can sometimes proves very dodgy!!!
So let’s look at the normality or how & why q is recorded on the surface ecg !!!!

Here some of my comments consolidated on this aspect of ecg

Normally q is The first or the initial deflection of QRS and results from the rapid depolarisation of the thin walled septum which is occurring from the left to the Right ventricle and this is inscribed in most of the surface ecg leads!!!!

B. Normality
Small Q are defined as less than 0.03 seconds in duration, or two small squares or less in amplitude & Generally should be no larger than 25% of the associated R.
1. Normality in all leads except V1 through V3, where they are always pathological
2. A Q of any size is generally normal in limb lead III (is varying with respiration)
3. laterally in the chest leads, reflecting left-to-right septal depolarization.
4. A large Q May be seen in lead aVR (as it looks at the endocardial of the heart, it registers the endocardial to epicardial spread of depolarization as a Q wave).
5. normal subjects may have nonpathologic wide and deep Q waves in Leads III, aVR, V1!!!

C. Abnormality
1. In some leads like V1, V2, and even V3, usually the presence of a any Q wave should be considered abnormal
2. Chest Lead V4 1 mm deep or at least 0.02 sec or larger than the Q wave in lead V6
3. The loss of small Q waves in leads V5 and V6 should be considered abnormal.
4. and in all other leads (except III and aVR), a “normal” Q wave would be very small

Some of the other terms in use

A. Septal Q waves
These are the small q waves which are normally seen in the left sided leads (I, aVL & V4 to V6) and may be normal variants in one or more of limb leads like II, III, and aVF.
Mechanism ! As described at the top , the ventricle septum depolarises from left to right so the Left sided leads records this spread of voltages toward the right as a small negative deflection (q wave) and as a part of the qR complex in which the R results from the spread of left ventricular voltages toward the these lead then !!!!!

These normally occurring septal q waves must be differentiated from the pathologic Q waves of infarction.
Normal septal q waves are characteristically narrow and of low amplitude.
Generally septal q waves are less than 0.04 sec in duration !!
however this is generally abnormal if
duration is 0.04 sec
sometimes shows a notch as it descends,
ormay be slurred instead of descending and rising abruptly.

B. Positional q waves
One of the relatively common ecg findings which can also lead to lots of confusion is abnormal looking q without underlying heart disease!!!
This can results from abnormal or atypical position of the heart in the chest. Like In short/obese persons !!! They have a high diaphragm position, which then causes a deep Q or a QS deflection in lead III.
(How to disappear them They can be recognized because they disappear during deep inspiration) .

B. non-infarction Q
often a characteristic feature in the ECGs of patients with HCM and can also occur with DCM

C. pathologic Q can be !!!!
1. any Q in leads V2–V3 ≥ 0.02 s or QS complex in leads V2 and V3
2. Q ≥ 0.03 s and > 0.1 mV deep or QS complex in leads I, II, aVL, aVF !!!
3. Or in any two leads of a contiguous lead grouping like (I, aVL) ( V4–V6 ) (II, III, and aVF) !!!!
4. R more than 0.04 s in V1–V2 and R/S equal or more than 1 with a concordant positive T-wave in the absence Conduction defects