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Figure 3 Multiple VT Exit Sites: RBBB/LBBB Patterns
Shown in the "best-septal" left anterior oblique projection are phase images, in sinus rhythm, and during 2 different induced VT patterns, imaged at a similar rate, one with a RBBB and another with a LBBB, in patient OH. Below each phase image is the regional ejection fraction (EF) image, where green, yellow, and red indicate high values and blue reflects akinetic to dyskinetic segments, as in the color scale at right. At rest, earliest Ø, green (white arrow) was confined to septal and adjacent LV regions with an RV contraction and conduction delay (yellow). On the related EF image, ventricular function is preserved only at the bases. The RBBB VT relates to a gross distal RV Ø delay, pink (white arrow), with earliest Ø at the mid- and basal LV, green-blue (thick white arrow), confirmed at electrophysiologic study. The function of both ventricles was modestly reduced. The LBBB VT related to a distal septal or RV apical exit site, green, with great delay in basal LV contraction, pink (white arrow). A gross Ø delay in the distal LV with aneurysm formation is evident in blue and on the EF image. LBBB = left bundle branch block; RBBB = right bundle branch block; other abbreviations as in Figure 2.
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