[The endocardial ventricular activation map in a case of intermittent BBS in phase III (author's transl)]

To obtain information on endocardial activation-sequence, unipolar recordings at seven left ventricular and six right ventricular points were performed in a 37-year-old man suffering from cardiomyopathy and tachycardia-dependent left bundle branch block (LBBB). Results were as follows: 1) the recovery time was longer in anterior than in posterior portion of left bundle branch fibers; 2) an high posterior left ventricular point was directly activated via posterior left bundle branch fibers; 3) the directly activated left ventricular zone was too small and relatively too late excited in respect of the right interventricular septum, from which the stimulus reached the left septum, to mask the LBBB electrocardiographic pattern; 4) in the presence of tachycardia-dependent LBBB the duration of left ventricular endocardial activation was about twice (62 msec) that found in the absence of tachycardia-dependent LBBB (28 msec).