Peds ECG (McMaster Guide)

Question 1

Name 8 differences between pediatric and adult ECGs that you may see

Answer 1

1. Faster heart rate
2. Sinus arrhythmia is more common
3. Right QRS axis (up to 3 months and again in adolescence)
4. T wave inversions in the right precordial leads
5. Dominant R wave in V1
6. RSR’ pattern in V1
7. Shorter PR interval and QRS duration
8. Slightly longer QTc

Question 2

How many seconds is each small box on an ECG?

Answer 2

0. 04 seconds (40 ms)

- thus one large box is 5 small boxes = 0.2 seconds (200 ms)

Question 3

How do you count heart rate on an ECG the quick method?

Answer 3

300-150-100-75-60-50 (for each large square) between 2 consecutive R waves

Question 4

How do you calculate heart rate for an irregular rhythm?

Answer 4

Multiply the number of QRS complexes on the rhythm strip by 6.

Question 5

What are causes of left axis deviation? (7)

Answer 5

1. LBBB
2. LVH
3. AVSD
4. Tricuspid atresia
5. WPW
6. TGA

Question 6

What are causes of right axis deviation? (2)

Answer 6

1. RVH

2. RBBB

Question 7

What are the components of “normal sinus rhythm”?

Answer 7

1. Upright P waves in leads I and AVF

2. P wave before every QRS complex

Question 8

What does the P wave represent?

Answer 8

Atrial depolarization

Question 9

What does the PR interval represent?

Answer 9

Reflects transit time of electrical impulse through the AV node (ie. in AV block, you see prolonged PR intervals)

Question 10

What are signs of left atrial enlargement on an ECG?

Answer 10

1. Bifid P wave in Lead II
2. Biphasic P wave in lead V1

**BOTH must also have prolonged P wave duration > 80 msec in infants and > 100 msec in children to qualify for left atrial enlargement

Question 11

What are signs of right atrial enlargement

Answer 11

1. P wave > 3 mm in lead II

2. P wave > 1.5 mm in lead V1

Question 12

What are the 3 types of AV block?

Answer 12

1. 1st degree AV block: Fixed prolongation of the PR interval
2. 2nd degree AV block:
   - Mobitz Type 1 (Wenckebach): Progressive prolongation of the PR interval culminating in a non-conducted P wave. Can have atypical Wenckebach where the is no progressive PR interval prolongation but instead the PR interval of the first conducted P wave is shorter compared to the last conducted P wave
   - Mobitz Type 2: Intermittent non-conducted P waves without progressive prolongation of the PR interval
3. 3rd degree (complete) AV block: independent atrial and ventricular activities; the P wave and QRS complexes are not at all associated.

Question 13

What is a Q wave?

• when is a Q wave considered pathological?
• what is the clinical significance of a pathological Q wave?

Answer 13

A Q wave is any negative deflection that PRECEDES an R wave

• Pathological Q waves:
  1. > 40 ms (1 mm) wide
  2. > 2 mm deep
  3. > 25% of depth of QRS complex
  4. Seen in leads V1-V3
• pathological Q waves usually indicate current or prior myocardial infarction

Question 14

What is the difference between a complete vs incomplete RBBB?

Answer 14

Complete RBBB - always abnormal, QRS duration > 100 ms in children ages 4-16 yo, > 90 ms in children < 4 yo

Incomplete RBBB - can be completely normal in the pediatric population and athletes - QRS duration 90-100 ms in children 4-16 yo, 86-90 ms in children < 4 yo

Question 15

What are the causes of a complete RBBB?

Answer 15

1. Post-intracardiac surgery (ie. repair of VSD and TOF
2. Post cardiac catheterization
3. ASD
4. Ebstein anomaly

Question 16

What are possible causes of a wide QRS complexes?

Answer 16

1. RBBB
2. LBBB
3. Pre-excitation (eg. WPW syndrome)
4. Ventricular rhythm (ie. premature ventricular contraction, V tach or V fib)
5. Intraventricular block seen in hyperkalemia, TCA poisoning

Question 17

What are causes of large QRS voltages? (3)

Answer 17

1. RVH or LVH
2. BBB
3. WPW syndrome

Question 18

What are causes of low QRS voltages? (5)

Answer 18

1. Obesity
2. Pericarditis
3. Myocarditis
4. Neonates (heart is less muscular)
5. Hypothyroidism

Question 19

What is the normal progression of T waves in pediatric population?

Answer 19

• 1st week of life: T waves in V1 MAY be positive, usually negative in V2-V4, V5 usually positive, V6 always positive
• after first week of life: T waves become inverted normally in V1-V4! As the child ages, you will see T waves become upright starting in V4–> V1. This does NOT skip leads so if you see negative T waves that are out of sequence, this is abnormal! Usually this is due to lead misplacement. T waves should be positive in V5 and V6

**T wave inversion in leads V1-V4 in black/African athletes is normal

Question 20

What is the diagnosis for a pediatric patient (age < 7 yo) if you see upright T waves in V1?

Answer 20

Suggestive of RVH - such as pulmonary stenosis or TOF

Question 21

What is a U wave?

-differential diagnosis for a U wave?

Answer 21

An additional positive deflection after the T wave

DDx:

1. Can be normal IF the voltage is < 25% of the T wave voltage, is in the same direction as the T wave, is more visible with slower heart rates
2. Hypokalemia
3. Bradycardia
4. Digitalis toxicity
5. Amiodarone toxicity

Question 22

What does the QT interval represent?

Answer 22

Time taken for both depolarization and repolarization of the ventricles

Question 23

How do you calculate the corrected QTc?

Answer 23

QT/square root of R-R

-remember to take the R-R interval between the R waves PRIOR to the measured QT interval

Question 24

What is the upper limit of the normal QTc range in boys vs. girls, pre puberty vs post puberty?
-what is considered a “borderline prolonged QTc”?

Answer 24

<15 years old:

• boys: 450 ms
• girls: 460 ms

> 15 years old:

• boys: 440 ms
• girls: 450 ms

***Borderline prolonged QTc is considered to be up to 480 ms. Anything above 480 ms is for sure prolonged!

Question 25

What is a quick way to eyeball whether QTc is prolonged?

Answer 25

QT interval should be less than half the preceding R-R interval

Question 26

What are the 4 stages of ECG changes seen in pericarditis?

Answer 26

1. During first two weeks: diffuse ST elevation and PR depression with opposite seen in aVR 2. Between 1-3 weeks: generalized T wave flattening 3. After 3 weeks: flattened T waves become inverted 4. Several weeks later: ECG returns to normal

Question 27

What are possible ECG findings in myocarditis?(7)

Answer 27

1. AV conduction disturbances: PR prolongation, AV block, etc. 2. Low QRS voltages (5 mm or less in all limb leads) 3. Decreased T wave amplitude, negative or flat T waves 4. QT prolongation 5. Tachyarrhythmias - SVT or VT for example 6. Pseudoinfarction pattern with deep Q waves and poor R wave progression in precordial leads 7. ST segment elevation

Question 28

What are ECG findings of RVH?

Answer 28

1. RAD 2. Tall R waves in right sided leads: V1, V2, aVR 3. Deep S waves in left sided leads: V5, V6, I 4. R/S ratio in V1 and V2 is more than the upper limits of normal for age 5. Upright T waves in V1 in children > 7 days to < 7 years (this is enough to diagnose RVH

Question 29

What are ECG findings of LVH?

Answer 29

1. LAD 2. Tall R waves in left sided leads: V5, V6, I 3. Deep S waves in right sided leads: V1, V2, aVR 4. R/S ratio in V1 and V2 less than lower limits of normal for age 5. Inverted T waves in lead I and aVL AND left precordial leads (LV strain pattern)

Question 30

What is the ECG finding for hypocalcemia?

Answer 30

1. ST segment prolongation | 2. QTc prolongation

Question 31

What is the ECG finding for hypercalcemia?

Answer 31

1. ST segment shortening | 2. QTc shortening

Question 32

What are ECG findings for hyperkalemia?

Answer 32

1. K > 6 - peaked tall T waves 2. K > 7.5 - long PR interval, wide QRS duration, tall T wave 3. K > 9 - absent P wave, sinusoidal wave

Question 33

What are ECG findings for hypokalemia?

Answer 33

K < 2.5 - depressed ST segment, biphasic T wave, prominent U wave

Question 34

What are ECG findings for WPW syndrome?

Answer 34

1. Shortened PR interval 2. Delta wave = slurring slow rise of the initial portion of the QRS 3. QRS prolongation