Sinus at 100/minute
Axis: right axis deviation
Intervals: QRS prolonged at 160ms with a tall R in V₁ – RBBB

Now, chamber enlargement?
With a RBBB the usual criteria for both right and left ventricular chamber enlargement are somewhat altered.

R wave in lead V₁ > 15mm suggests RVH, especially with rightward deviation of the axis

LVH criteria become less sensitive (eg not seen as reliably), but if voltage criteria for LVH are met with a RBBB they are quite specific.

In this week’s tracing, the very tall T in V₁ is 18mm, and with the right axis deviation is diagnostic of right ventricular hypertrophy.