[The left posterior fascicular block: is the diagnosis possible only by ECG? (author's transl)].

The diagnosis of Left Posterior Fascicular Block based on clinical ECG and VCG tracings alone is possible when ECG and VCG allow to recognize asynchronous left ventricular activation. The delayed inscription time of the intrinsecoid deflection in aVF (or V6) in absolute and relative to aVL permits the diagnosis if intrinsecond deflection in aVL exceeds 0,035". Il more premature, a further control is required to distinguish Left Ventricular Hypertrophy from Left Posterior Fascicular Block, both in anatomically vertical heart.