Left Axis Deviation: Axis Illusion of Emphysema

Report:

Sinus rhythm 92/min

Left axis deviation –80o

Right atrial abnormality (RAA)

Q waves in 3, aVF

Comment:

Although it is not an abnormality per se, the QRS complexes in emphysema are often characteristically slender.

The P waves are pointed and make the voltage criteria for the RAA (0.25 mV) in Lead 2; furthermore, their axis in the frontal plane exceeds +70o – the earliest ECG sign of emphysema30. Another sign of RAA is P > 2mm in V1.

The characteristic abnormality of the trace is its left axis deviation with S2 larger than S3. In other causes of abnormal LAD – LAHB, inferior MI, LBBB - S3 is invariably deeper than S2. The mechanism of this uncommon appearance is the QRS vector, almost perpendicular to the frontal plane in emphysema, shifting slightly upwards and projecting onto the left superior quadrant of the frontal plane. This is held not to represent a true left axis deviation, but rather an “axis illusion”31. The inferior (3, aVF) Q waves are not due to inferior infarction (there is, importantly, no Q in 2) but are a recognised expression of emphysema.

The R/S ratio of 1.0 in V5-6 also supports emphysema here.

Below (Fig 54a) is a similar ECG, from a different patient, with a known cor pulmonale. The axis here is indeterminate – the ventricular complexes are equiphasic in all 6 frontal leads. The QRS is even thinner and the P wave axis more positive – almost +90o. Poor R wave progression is also characteristic.