This document provides an overview of QRS complexes and abnormalities seen on electrocardiograms (ECGs). It defines the components of the QRS complex and discusses causes of low or high voltage QRS complexes. Specific conditions that can cause left or right ventricular hypertrophy are described. Various conduction abnormalities are also summarized, including right and left bundle branch blocks, fascicular blocks, and bifascicular blocks. Causes of wide QRS complexes like hyperkalemia and certain drugs are mentioned. The document aims to educate on interpreting and analyzing QRS complexes on ECGs.

1. ECG BASICSECG BASICS
33rdrd
LectureLecture
QRS complexQRS complex
By
Salah Mabruok Khalaf
South Egypt Cancer Institute
2017
Course of Medical Oncology
Medical Oncology department

2. • Definitions of QRS:
• Q wave – first downward deflection after P
wave
• R wave – first upward deflection after Q
wave
• R` wave – any second upward deflection
• S wave – first downward deflection after the
R wave
• QRS duration :
0.06 to 0.12 msec= 3 ss

3. • Nomenclature of QRS

4. Ventricular Depolarization
Occurs in 2 stagesOccurs in 2 stages:
1- septal depolarization:
direction from stronger
left bundle to the right bundle
V1 +ve wave = septal r
V6 -ve wave = septal q
V1
V6

5. Ventricular Depolarization
2- wall depolarization:
directed mainly to the left
due to stronger left ventricle
V1 -ve wave = deep S
V6 +ve wave = Tall R
V1 V6

6. Lead Septal Wall Total
V1
V6

7. Are the QRS complexes normal?
• Voltage?
• Duration?
• Pathological Q waves?
• QRS axis?

8. Voltage of QRS
Low Voltage
• Diagnostic Criteria
1. Voltage of entire QRS complex in all limb leads <
5mm(≤ 1 Ls).
2. Voltage of entire QRS complex in all chest leads <
10mm(≤ 2 Ls).
3. Either criteria may be met to qualify as "low
voltage".

9. ECG on presentation with low QRS voltages compatible
with pericardial effusion
After two months of treatment and disappearance of
pericardial effusion and normalisation of ECG

10. Differential Diagnosis of low QRS voltages
1) Increased Distance
1) Pericardial effusion
2) Obesity
3) COPD with hyperinflation
4) Pleural effusion
5) Constrictive pericarditis
2) Infiltrative Heart and Diseased myocardium
1) Amyloidosis
2) Scleroderma
3) Hemachromatosis
4) Cardiomyopathy
5) Myocardial Ischemia or infarction
3) Decreased Metabolic activity
1) Myxoedema
2) Hypothermia

11. High voltage
Ventricular Hypertrophy
• Conditions that increase the load, pressure
or volume, on either the left or right ventricle,
cause a compensatory increase in the
ventricular muscle massmuscle mass.
• This increase in muscle mass is seen on the
surface electrocardiogram as an increase in
QRS voltage.

12. 1- Left Ventricular Hypertrophy
V1 V6

13. 1- Left Ventricular Hypertrophy:
ESTES Criteria for LVH
("diagnostic", ≥5 points; "probable", 4 points)
ECG Criteria Points
Voltage Criteria (any of):
Tall R in V5 or V6 >30 mm (≥ 6 Ls)
Deep S in V1 or V2 > 30 mm (≥ 6 Ls)
Tall R in V5 or V6 + Deep S in V1 > 35 mm (≥ 7 Ls)
3 points
Left Atrial Enlargement in V1 (p mitrale) 3 points
ST-T Abnormalities:
Without digitalis
With digitalis
3 points
1 point
Left axis deviation 2 points
QRS duration 0.09 sec 1 point
Delayed intrinsicoid deflection in V5 or V6 (>0.05 sec)
(i.e., time from QRS onset to peak R is >0.05 sec)
1 point

14. S in V1 or V2 > 30 mm (≥ 6 Ls)
R in V5 or V6 > 30 mm (≥ 6 Ls)
Left Atrial Enlargement in V1
ST-T Abnormalities
S in V1 + R in V5 or V6 > 35 mm (≥ 7 Ls)

15. • ESTES Criteria: 3 points for voltage in V5, 3
points for ST-T changes (more than 5 points
• Note
– LAD - P mitrale in V1

16. 2-Right Ventricular Hypertrophy:
V1
V6

17. 2-Right Ventricular Hypertrophy
11 ss
7 ss

18. RAD R in v1 > 7 mm
R/S ratio > 1 and
negative T wave
RAE

19. RVHRVH

20. 3-Biventricular Hypertrophy:
• Biventricular Hypertrophy (difficult ECG
diagnosis to make)
In the presence of LAELAE any one of the following
suggests this diagnosis:
• R/S ratio in V5 or V6 < 1
• S in V5 or V6 > 6 mm
• RAD (>90 degrees)
Other suggestive ECG findings:
• Criteria for LVH and RVH both met
• LVH criteria met and RAD or RAE present

21. Tall R wave in lead V1
1. Right Ventricular Hypertrophy.
2. Posterior infarction
3. Muscular dystrophy.
4. Wolff-Parkinson-White syndrome.
5. Right bundle branch block.

22. • Poor R Wave Progression – defined as loss of, or no
R waves in leads V1-3 (R ≤ 2mm):
1. Normal variant (if the rest of the ECG is normal)
2. LVH (look for voltage criteria and ST-T changes of
LV "strain")
3. Complete or incomplete LBBB (increased QRS
duration)
4. Left anterior fascicular block (should see LAD in
frontal plane)
5. Anterior or anteroseptal MI
6. Emphysema and COPD (look for R/S ratio in V5-6
<1)
7. Diffuse infiltrative or myopathic processes

23. Poor R Wave ProgressionPoor R Wave Progression

24. QRS duration=3 ssQRS duration=3 ss

25. QRS duration=3 ss
• Causes of wide QRS:
I- Intrinsic intraventricular delay:
• Right BBB.
• Left BBB.
• pacemaker.
II- Extrinsic (toxic) intraventricular delay:
• Hyperkalemia.
• Drugs.
III- Ventricular ectopy: premature, escape, or paced
IV- Wolf-Parkinson-White syndrome
V- Myocardial infarction.

26. Right Bundle Branch Block (RBBB):
Ventricular Depolari Occurs in
3 stages:
1- septal depolarization:
direction from left bundle
to the right.
V1 +ve wave = septal r
V6 -ve wave = septal q
V1 V6

27. 2- Lt vent. depolarization:
directed to the left
V1 deep -ve wave = S
V6 tall +ve wave = R
V1 V6

28. 3- Rt vent. depolarization:
directed to the right from
the Lt vent
V1 deep -ve wave = R'
V6 tall +ve wave = S
V1 V6

29. Lead Septal Lt vent Rt vent Total
V1 R S R' RSR'
V6 q R S qRS

30. Character of RBBB
1. Terminal R' wave in lead V1 (rSR' complex)
2. Terminal S waves in leads I, aVL, V6 (qRS).
3. "Complete" RBBB has a QRS duration >0.12s
4. "Incomplete" RBBB has a QRS duration of
0.10 - 0.12s with the same terminal QRS
features. This is often a normal variant.

31. Character of RBBB
5. The ST-T waves in RBBB should be oriented
opposite to the direction of the terminal QRS
forces
– In leads with terminal R or R' forces the ST-T should be
negative or downwards
– In leads with terminal S forces the ST-T should be
positive or upwards.
5. If the ST-T waves are in the same direction as the
terminal QRS forces, they should be labeled
primary ST-T wave abnormalities.

32. RBBBRBBB

33. • The ECG below illustrates primary ST-T wave
abnormalities (leads I, II, aVR, V5, V6) in a
patient with RBBB.

34. Character of RBBB
6. The frontal plane QRS axis in RBBB should be in
the normal range (i.e., -30 to +90 degrees).
– If left axis deviation is present, think about left anterior
fascicular block in addition to the RBBB
– If right axis deviation is present, think about left
posterior fascicular block in addition to the RBBB.

35. Left Bundle Branch Block (LBBB):
Ventricular Depolari Occurs in
3 stages:
1- septal depolarization:
direction from right
to the left
V1 -ve wave = septal q
V6 +ve wave = septal r
V1 V6

36. Left Bundle Branch Block (LBBB):
2- Rt ventr depolarization:
direction to the right
V1 +ve wave
V6 -ve wave
V1 V6

37. Left Bundle Branch Block (LBBB):
3- Lt ventr depolarization:
direction to the left from
Rt vent
V1 -ve wave
V6 +ve wave
V1 V6

38. Lead Septal Lt vent Rt vent Total
V1
W-shaped
V6
M-shaped

39. Character of LBBB
1. Terminal R waves in lead I, aVL, V6 broad
usually M-shaped
2. Poor R progression from V1 to V3 is common.
3. "Complete" LBBB" has a QRS duration
>0.12s .
4. "Incomplete" LBBB looks like LBBB but QRS
duration = 0.10 to 0.12s, with less ST-T
change. This is often a progression of LVH.
5. The "normal" ST-T waves in LBBB should be
oriented opposite to the direction of the
terminal QRS forces;

40. LBBB

42. Left Anterior Fascicular Block
III II
AvF
rS
LAD
AvL qR
V1-3
Poor R wave
progression
V5-6
Tall R wave
Mimic LVH

43. • Criteria of left anterior fascicular block
• I. QRS duration < 0.10 sec.
• II. LAD.
• III. QRS morphology
• Limb leads
– qR in leads I and aVL.
– rS in leads II, III, and aVF.
– R peaks in aVL before aVR.
• Precordial leads
– Poor R wave progression.
– Persistent S wave in V5-V6

44. • In this ECG, note –
• 75 degree QRS axis
• rS complexes in II, III, aVF
• tiny q-wave in aVL
• poor R progression V1-3
• late S waves in leads V5-6.
• QRS duration is normal, and there is a slight slur to
the R wave downstroke in lead aVL.

46. Left posterior Fascicular Block
III II
AvF
rSI
RAD
qR
R in III > R in II

47. • Left Posterior Fascicular Block (LPFB)....
Very rare intraventricular defect!
1. Right axis deviation in the frontal plane (usually >
+100 degrees)
2. rS complex in lead I
3. qR complexes in leads II, III, aVF, with R in lead III
> R in lead II
4. QRS duration usually <0.12s unless coexisting
RBBB
5. Must first exclude (on clinical grounds) other
causes of right axis deviation such as cor
pulmonale, pulmonary heart disease,
pulmonary hypertension, etc., because these
conditions can result in the identical ECG
picture!

48. R in III > R in IIRAD rS

49. Bifascicular Blocks
• RBBB plus either LAFB (common) or LPFB (uncommon)
• Features of RBBB plus frontal plane features of the
fascicular block (axis deviation, etc.)
• The above ECG shows classic RBBB (note rSR' in V1)
plus LAFB (note QRS axis = -45 degrees, rS in II, III, aVF;
and small q in aVL).

50. • Electrocardiogram of a 59-year-old man
showing a bifascicular block (consisting of a
RBBB and LAFB).

51. Bifascicular block.
• Right bundle branch block and left anterior
fascicular block.

52. Causes of wide QRS:
II- Extrinsic (toxic) intraventricular delay:
• Hyperkalemia.
• Drugs.

53. Hyperkalemia
• The following changes may be seen in
hyperkalaemia
1. small or absent P waves
2. shortened or absent ST segment
3. atrial fibrillation
4. ventricular fibrillation
5. wide QRS
6. wide, tall and tented T waves
Potassium
•P wave small or absent
•Oscillation or fibrillation
•T wide and tall
•Absent or shortened ST
segment

54. Hyperkalemia and ECG changesHyperkalemia and ECG changes
according to its levelaccording to its level

55. Drugs
• Antiarrhythmic drugs
• Beta-blockers
• Calcium channel blockers
• Cardiac Digitalis
• Clonidine (Catapres)
• Cholinergic
• Central Tricyclic antidepressant

56. Causes of wide QRS:
III- Ventricular ectopy: see arrhythmia
lecture
IV- WPW syndrome: see 1st
lecture.
V- Myocardial infarction: see 6th
lecture.