[Fascicular block of the His bundle: critical approach for its identification].

The correct identification of the left and right fascicles blocks of the His bundle will permit to explain different patterns of the ECG and VCG. The differentiation between the right peripheral bundle branch and the left bundle branch division is not only important in anatomic and physiologic grounds, but also in a clinic viewpoint. So, trying to refine the diagnostic criteria and improve the recognition of these intraventricular conduction disturbances, we developed this study. Eighty five patients were evaluated and divided into two groups. Group I included 65 patients with cardiac disease; group II consisted of 20 normal subjects taken as a control. Some classic ECG and VCG criteria were tested as well as new ones. We confirmed the significance of the S2/S3 relation to distinguish the right superior divisional block (RSDB) from the left anterior hemiblock (LAH), and added some new criteria: 1) C morphology in horizontal plane (HP) to the right divisional block (RDB); 2) assessment of aVL lead to separate RSDB from LAH--qR pattern in the last, and different one to RSDB; 3) the qR' pattern in L2, L3 and aVF leads associated with left ventricular hypertrophy (LVH) pattern screened the left posterior hemiblock (LPH). We found no significance in R3/R2 relation to the right inferior divisional block (RIDB). Similarly to what happened to the left bundle branch block in the 70's decade, we expect that an adequate assessment of the RDB can permit a better understanding of its real clinical value.