[Estimation of ventricular activation by scintigraphic phase image analysis].

We examined the capabilities of scintigraphic phase imaging in detecting the site of the onset of ventricular activation and the pattern of ventricular activation sequence. ECG-gated equilibrium cardiac blood pool scintigraphy was obtained in the left anterior oblique (LAO) and right anterior oblique (RAO) projections. The standard 12-lead electrocardiograms (ECG) were recorded in 29 cases with various conditions. These included seven normal subjects as controls, eight patients (pts) with complete right bundle branch block (CRBBB), one with CRBBB and left axis deviation (LAD), two with complete left bundle branch block (CLBBB), one with the Wolff-Parkinson-White (WPW) syndrome (B-type), six with right ventricular apical endocardial pacemakers, one with a right ventricular anterior wall myocardial pacemaker, and three with left ventricular apical myocardial pacemakers. Phase image analysis was performed using the first harmonic of the Fourier transform to fit a cosine curve to the time-activity curve of each pixel in the cardiac blood pool study. The results were as follows: In pts with WPW syndrome (B-type) and artificial pacemakers, the site of the earliest phase angle corresponded to the site of the onset of ventricular activation as predicted by ECG and chest radiographs, respectively. However, in normal subjects and in pts with CRBBB, the site of the earliest phase angle was observed at the basal (upper) interventricular septum, which was different from the site of the onset of ventricular activation previously reported by Sodi-Pallares et al and Durrer et al. This discrepancy may have been caused by the paradoxical motion of the basal (upper) interventricular septum in those cases. A similar discrepancy was also observed in pts with CLBBB. Although the site of onset of ventricular activation was predicted to be near the insertion of the anterior papillary muscle of the right ventricle by ECG and electrophysiology, the pixels showing early phase angle were distributed widely along the interventricular septum in those pts with CLBBB. This error in the phase image may have been caused by the extensive paradoxical motion of the interventricular septum. Thus, caution should be exercised in estimating the site of the onset of ventricular activation by phase images. The main direction of phase changes corresponded well to the ventricular activation sequence estimated using ECG in all subjects.(ABSTRACT TRUNCATED AT 400 WORDS)