Large Right Precordial R Waves in LBBB

Report:

Sinus tachycardia 120/min

Left atrial abnormality (LAA)

Left bundle branch block

Probable old anterior infarction

Comment:

The right precordial are waves look typically thin, like antennæ or unipolar pacing spikes. There is also a loss of R amplitude in V4-5. This was not positional: other ECGs consistently showed this pattern (Fig 35a below). She had the same pattern while in incomplete LBBB one year earlier.

While suggestive of anterior infarction – even in the presence of LBBB17 – this pattern occurs, as in this patient, in primary congestive cardiomyopathy (COCM). She had marked 4-chamber enlargement and moderate mitral incompetence, with LV ejection fraction of only 20%.

Marked R wave notching in leads 1 and aVL also suggests previous infarction. It should be remembered that primary congestive cardiomyopathy may mimic infarction not just electrocardiographically, but also in showing segmental wall motion abnormalities or localised deficits in thallium uptake! This leaves coronary angiography and myocardial biopsy, but even these can be misleading at times. Autopsy is best, but by then it’s rather late.