PATHOLOGICAL Q WAVES CRITERIA AND CAUSES OF PATHOLOGICAL Q WAVES

1. Q WAVE
Dr.G.VENKATA RAMANA
MBBS DNB FAMILY MEDICINE

2. • Q Wave
• Any negative deflection that precedes an R wave
• Represents the normal left-to-right depolarisation of the
interventricular septum
• Small ‘septal’ Q waves are typically seen in the left-sided leads (I, II
aVL, V5 and V6)
• A small Q wave may be normal in lead III, and is often associated
with an inverted T wave
• Q waves are also normal in lead aVR

3. • Q waves in different leads
• Small Q waves are normal in most leads
• Deeper Q waves (>2 mm) may be seen in leads
III and aVR as a normal variant
• Under normal circumstances, Q waves are not
seen in the right-sided leads (V1-3)

6. • Pathological Q Waves
• Q waves are considered pathological if:
• >2 small squares deep, or
• >25 per cent of the height of the following R
wave in depth, and/or
• >1 small square wide
• Seen in leads V1-3
• Usually indicate current or prior myocardial
infarction

7. • Differential diagnosis
• ST Segment elevation Myocardial infarction
• Left ventricular hypertrophy
• Bundle branch block
• Wolff–Parkinson–White syndrome
• Pulmonary embolism
• Cardiomyopathies - Hypertrophic (HCM), infiltrative
myocardial disease
• Rotation of the heart - Extreme clockwise or counter-
clockwise rotation
• Lead placement errors - e.g. upper limb leads placed on
lower limbs
• Loss of normal Q waves
• The absence of small septal Q waves in leads V5-6
should be considered abnormal
• Absent Q waves in V5-6 is most commonly due to LBBB

8. Example 1
•Inferior Q waves (II, III, aVF) with ST elevation due to acute MI

9. Example 2
•Inferior Q waves (II, III, aVF) with T-wave inversion due to previous MI

10. Example 3
•Lateral Q waves (I, aVL) with ST elevation due to acute MI

11. Example 4
•Anterior Q waves (V1-4) with ST elevation due to acute MI

12. Example 5
Anterior Q waves (V1-4) with T-wave inversion due to recent MI

13. Example 6
Classic HCM pattern with asymmetrical septal hypertrophy:
•Voltage criteria for left ventricular hypertrophy.
•Deep narrow Q waves < 40 ms wide in the lateral leads I, aVL and V5-6

14. • Wolff–Parkinson–White syndrome
• The delta waves seen when there is a Wolff–
Parkinson–White pattern on the ECG, indicating
ventricular pre-excitation, can be negative in
some leads(depending on the location of the
accessory pathway)
• As such, these negative delta waves can be
mistaken for Q waves, particularly when they are
seen inferiorly

17. • LA/RA reversal
• With reversal of the LA and RA electrodes, Einthoven’s
triangle flips 180 degrees horizontally around an axis
formed by lead aVF
• This has the following effects on the ECG:
• Lead I becomes inverted
• Leads II and III switch places
• Leads aVL and aVR switch places
• Lead aVF remains unchanged

18. Example 7
LA/RA reversal