[Evaluation of the interventricular septum in left bundle branch block using basal echocardiography (M-mode) and myocardial stress scintigraphy (thallium-201)].

In thirty-six consecutive subjects, with left bundle branch block (LBBB) of the interventricular septum (IS), septal perfusion and/or viability was verified by M-mode echocardiography and by stress redistribution 201 TI-scintigraphy. After the early systolic "dip", a characteristic pattern of interventricular septum in left bundle branch block, we observed: a) an anterior paradoxical movement (A-type) during the ejection phase in 5 subjects; b) hypokinetic posterior movement (B-type) in 10 subjects and c) a normal motion (C-type) in 21 subjects. All the subjects with an A-type paradoxical anterior motion of the interventricular septum, showed a persistent defect of T1 uptake both during exercise and after redistribution. Of 31 patients with posterior interventricular septum motion (B and C types), 21 showed normal septal TI uptake and 10 reversible, exercise-induced perfusion defect, with complete redistribution on scintigrams at rest. In conclusion the analysis of our data demonstrates that in patients with left bundle branch block 1) the motion of the interventricular septum is not merely due to the anomalous electrical activation, but to other different factors, such as the anatomical and functional changes underlying the conduction pathology, 2) an A-type motion by M-mode echocardiography is highly predictive of interventricular septum damage.