[Partial interauricular block. Apropos of a case].

An observation of an inter-auricular conduction disorder is reported. This disorder concerned the median part of the left atrium as shown by evidence provided by stepped oesophageal recordings, which suggest an auricular depolarisation normally descending in the upper part of the left atrium but abnormally retrograded into the lower part. This suggests that interauricular conduction is blocked at the median inter-auricular passage but that it occurs by the tract of Bachmann at the upper part of the left atrium and by retrograde passage to the lower part. On the surface electrocardiogram, the wave P is diphasic + - in D2, D3 and aVF, of normal duration with a normal PR space.