Reading the ECG: Axis and Chamber Size

What this deck covers

Reading the ECG: Axis and Chamber Size in twelve illustrated clinical cases with worked explanations – case presentations built around clinical images, radiology, teaching illustrations and real laboratory data, with the reference range beside every value a case quotes. This visual, data-interpretation style of practice suits candidates preparing for MRCPCH AKP in particular, alongside Saudi and Gulf licensing examinations such as the Arab Board, DHA and OMSB. Each case gives you a clinical vignette, four options, the correct answer, and an explanation of why each of the other three is wrong.

The twelve cases, in order

1. An axis, and two leads to read it
2. A right-sided axis in a newborn
3. Pinning the axis down more precisely
4. Negative in both of the two leads
5. A tall pointed P wave
6. A broad P wave with a notch
7. Where the P wave should be measured
8. A tall R wave in the first chest lead
9. A tall R wave in the last chest lead
10. Adult criteria on a child
11. Tall complexes in a very thin boy
12. A pattern that changed between traces

What this deck teaches

• Two perpendicular leads give the quadrant. Leads I and aVF are at right angles, so their two signs place the axis in one of four quadrants in a couple of seconds.
• Negative in both is the quadrant health avoids. An axis between minus 90 and 180 degrees is rare in a normal heart and, in an infant, goes with defects of the atrioventricular septum.
• The newborn axis points right. The right ventricle does the work before birth, so a rightward axis and a dominant R wave in V1 are normal at birth and shift leftward over the first years.
• The isoelectric lead locates, the tallest lead points. A complex is isoelectric when depolarisation runs at right angles to it, and that changes fast as the axis moves. A tall R changes slowly.
• Tall is the right atrium, broad is the left. The atria depolarise in sequence, so the right contributes the first half of the P wave and the left the second. Height and duration answer about different chambers.
• V1 looks right and V6 looks left. Forces towards V1 and away from V6 are the right ventricle; the reverse is the left. Both are read against the range for the age.

Exam pearls from this deck

• Leads I and aVF are perpendicular. Their signs give you the quadrant.
• The newborn axis is to the RIGHT. It walks leftward over the first years.

The twelve worked cases in this deck, with the images and the full explanation of every option, are part of Pediatric Case Review membership. See what is included, or start with the free Pediatric Exam Review Sets.

More from this system: all cardiology illustrated case decks · cardiology board questions for bank-style drilling · the free Pediatric Exam Review Sets · pediatric reference values.