Left posterior hemiblock related to an interventricular septum tumour. First case in the literature.

A 22-year-old man who engaged in intense and regular physical exercise complained of atypical chest pain. The only remarkable abnormality found in the routine clinical work-up was a left posterior hemiblock. The echocardiogram and the magnetic resonance imaging (MRI) study showed a tumour in the posterior and superior aspect of the interventricular septum where the posterior fascicle of the left bundle is located. It was interpreted that the left posterior hemiblock was produced by the tumour.