ECG Q wave Causes

1. MBBS, FCPS, MD, FACC, FESC, FRCP, FSCAI,
FCCP,FAPSC, FAPSIC, FAHA,FACP,FASE
Professor and Head of Cardiology
Colonel Malek Medical College , Manikganj.
For under-graduates
drtoufiq19711@yahoo.com21/11/2019
Under graduate version 2019

2. drtoufiq1971@gmail.com
28.11.2019 CMMC-02 ECG Lecture 09
Q wave
Professor Dr Md Toufiqur Rahman
The Q Wave
• A Q wave is any negative deflection
that precedes an R wave
• The Q 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, aVL, V5 and V6)

3. drtoufiq1971@gmail.com
28.11.2019 CMMC-02 ECG Lecture 08
Q wave
Professor Dr Md Toufiqur Rahman

4. drtoufiq1971@gmail.com
28.11.2019 CMMC-02 ECG Lecture 08
Q wave
Professor Dr Md Toufiqur Rahman
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)

5. drtoufiq1971@gmail.com
28.11.2019 CMMC-02 ECG Lecture 08
Q wave
Professor Dr Md Toufiqur Rahman
Pathological Q Waves
Q waves are considered pathological if:
> 40 ms (1 mm) wide
> 2 mm deep
> 25% of depth of QRS complex
Seen in leads V1-3
Pathological Q waves usually indicate
current or prior myocardial infarction.

6. drtoufiq1971@gmail.com
21.11.2019 CMMC-02 ECG Lecture 07
Q wave
Professor Dr Md Toufiqur Rahman
Differential Diagnosis/ Causes of Q waves
• Myocardial infarction
• 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

7. drtoufiq1971@gmail.com
21.11.2019 CMMC-02 ECG Lecture 07
Q wave
Professor Dr Md Toufiqur Rahman
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. drtoufiq1971@gmail.com
21.11.2019 CMMC-02 ECG Lecture 07
Q wave
Professor Dr Md Toufiqur Rahman
Inferior Q waves (II, III, aVF) with ST elevation due to acute MI

9. drtoufiq1971@gmail.com
21.11.2019 CMMC-02 ECG Lecture 07
Q wave
Professor Dr Md Toufiqur Rahman
Inferior Q waves (II, III, aVF) with T-wave inversion due to
previous MI

10. drtoufiq1971@gmail.com
21.11.2019 CMMC-02 ECG Lecture 07
Q wave
Professor Dr Md Toufiqur Rahman
Lateral Q waves (I, aVL) with ST elevation due to acute MI

11. drtoufiq1971@gmail.com
21.11.2019 CMMC-02 ECG Lecture 07
Q wave
Professor Dr Md Toufiqur Rahman
Anterior Q waves (V1-4) with ST elevation due to acute MI

12. drtoufiq1971@gmail.com
21.11.2019 CMMC-02 ECG Lecture 07
Q wave
Professor Dr Md Toufiqur Rahman
Anterior Q waves (V1-4) with T-wave inversion due to recent MI