2.9 ECG of Atrial Enlargement

Question 1

Describe the morphology and voltage of the normal P wave.

Answer 1

• <0.12s in duration, i.e. less than 3 small boxes
• Upright in Lead 1 and Lead 2
• Negative deflection <1 box wide and <1 box deep in V1

Question 2

Describe P-wave morphology in V1.

How is this affected by atrial enlargement?

Answer 2

In most leads (e.g. lead II), the right and left atrial waveforms move in the same direction, forming a monophasic P wave.

However, in lead V1 the right and left atrial waveforms move in opposite directions. This produces a biphasic P wave with the initial positive deflection corresponding to right atrial activation and the subsequent negative deflection denoting left atrial activation.

• RAE causes increased height (> 1.5mm) in V1 of the initial positive deflection of the P wave.
• LAE causes widening (> 40ms wide) and deepening (> 1mm deep) in V1 of the terminal negative portion of the P wave.

Question 3

Describe P-wave changes of RAE in Lead II.

Answer 3

• P-wave is enlarged, >2.5mm tall.
• In V1, you could also notice upward deflection of P-wave (tall, spikey) >1.5mm.

Question 4

Describe P-wave changes of LAE in Lead II.

Answer 4

• P wave is longer, >120ms
• In V1, you could also notice downward deflection in lead V1 > 40 ms and > 1 mm

Question 5

Describe the changes suggestive of LAE specific to mitral valve stenosis.

Answer 5

Note the elongated P-wave spells ‘M’ for mitral valve disease.

Question 6

A 52M presents to ED with SOB. He has untreated HTN. O/E has signs of heart failure. BP 190/108. HR 96.

ECG is attached.

What does he have?

Answer 6

Left ventricular hypertrophy.

Question 7

44F visits doctor complaining of fatigue and increasing SOB over the last year. O/E Loud pulmonic component of S2. Swelling of lower legs.

ECG is attached.

What is the diagnosis?

Answer 7

The diagnosis is right ventricular hypertrophy, secondary to pulmonary hypertension.