[Left axis deviation investigated by body surface mapping and phase image analysis].

Relationship between left axis deviation and left anterior fascicular block (LAFB) was investigated by estimating the ventricular excitation and contraction sequence using body surface potential mapping and phase image analysis by radionuclide ventriculography. This study included seven normal persons, eight patients with complete right bundle branch block (RBBB) without left axis deviation (LAD), twelve with RBBB and unblocked axis (determined by the first half of the QRS complex) of 0 degrees or farther deviated to the left (RBBB with LAD), and three with isolated LAD. The isochrone ventricular activation maps (VAT maps) were obtained by body surface mapping technique. Planar phase images in the left anterior oblique projection and short-axis ventricular tomographic phase images using a seven-pinhole collimator were constructed by ECG-gated equilibrium blood pool scintigrams. On the VAT maps of RBBB, there was a markedly delayed conduction to the right ventricle, however, in the left ventricle, the excitation was initiated in the anterior paraseptal region, and it proceeded rapidly toward the lateral and posterior walls, and in the same direction as normal. The VAT maps of RBBB with LAD were categorized in three types according to the activation sequence in the left ventricle. Type I, the same as maps of RBBB, consisted of three cases. Type II, four cases, showed excitation starting from the apex and ascending in the anterior wall. There were five cases of type III, which showed the earliest excitation in the basal posteroparaseptal region, proceeding toward the apex and ascending in the anterior wall. Type II was considered compatible with block of the left anterosuperior fascicle, and type III was that of left anterosuperior and midseptal fascicles. In types II and III, the phase delay in the left anterior wall was recognized in tomographic phase images, and the difference between right and left ventricular mean phase angles in planar phase images was significantly smaller than in cases of isolated RBBB, These were thought to support the existence of LAFB. The range of the unblocked axis of RBBB with LAD was -3 degrees approximately 13 degrees (-7.7 +/- 5.0 degrees) in type I, -8 degrees approximately -30 degrees (-19.8 +/- 9.1 degrees) in type II, and -33 degrees approximately -60 degrees (-51.0 +/- 10.9 degrees) in type III. All cases with left axis deviation beyond -30 degrees were of type III, and suspected to have extensive damage, including the midseptal fascicle.(ABSTRACT TRUNCATED AT 400 WORDS)