Shown, for 4 patients (AP, PB, AP, and LS), are maps of the 15 endocardial regions initially sampled in VT at electrophysiologic study and those more thoroughly sampled (circled). Shaded circles represent regions of earliest activation, sometimes multiple. X marks the site of earliest phase angle, the scintigraphic VT exit site. Electrophysiologic and scintigraphic exit disagreed only in AP, upper left, where phase analysis identified an adjacent segment. See Online Video 1. VT = ventricular tachycardia.

Analyzed are the phase images in sinus rhythm (A) and VT (B) in the "best-septal" left anterior oblique projection in patient PB, who is illustrated in Figure 1. The phase images are displayed above their related LV (white) and RV (black) histograms, relating the phase angle, Ø, of each pixel, increasing from left to right on the abscissa, to the number of pixels with a given Ø, on the ordinate. The pixels with Ø spanned by the gray histogram sampling window are highlighted in white on the phase image, above. (C) and (D) are enlargements of the serially highlighted phase images shown in (A) and (B), respectively. In sinus rhythm (A), earliest Ø is evident at the septal base (black arrow, panel 2) here projecting to the right, with an accompanying early LV site, a normal pattern. Initiation of both histograms is near simultaneous but the late histogram peak of localized LVØ delay (white arrow, panel 2) corresponds to an apical aneurysm (black arrow, panel 5). In VT (B), the RV histogram (white arrow, panel 2) precedes the LV. Earliest Ø is now in the distal RV, at sites highlighted in phase panels 2 and 3 (black arrow, phase panel 3). The late peaks on both histograms (black arrows, panel 3) correspond to an expanded LV aneurysm and a "new" RV apical aneurysm (black arrow, panel 4), distal to the VT exit site, which lies on its proximal border. (E) The lower panels present ungated blood pool images in the "best-septal" left anterior oblique projection for reference in interpreting the color phase images in sinus rhythm, sinus, and VT shown in preceding panels. These phase images present a color summary of sequential contraction, where the site of earliest Ø (in green) marks the septum and proximal RV (arrow in sinus rhythm), and the mid-RV in VT (arrowhead). The paradoxical motion of the apical LV aneurysm is featured in blue in sinus rhythm (arrowhead), and the new apical RV aneurysm is seen in blue in VT (arrow). Apical LV and RV scars, both supplied by an occluded left anterior descending coronary artery and a distal RV VT exit site, were confirmed at surgery. See Online Video 2. LV = left ventricular; RV = right ventricular; VT = ventricular tachycardia.

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.

Click on image to view video

Shown are the amplitude (top row), and the phase images (bottom row) generated from the equilibrium radionuclide angiograms acquired in patient GW in sinus rhythm and with 3 VT exit sites VT-1, VT-2, and VT-3. Intensity above is proportional to amplitude, and the phase image gray scale, below, parallels the contraction sequence. Regional amplitude and function were near normal in normal sinus rhythm; amplitude was moderately reduced with VT-1, with earliest Ø in the LV (black arrow), and a RBBB pattern; amplitude was well preserved with VT-2, with earliest Ø, black, in the RV (white arrow), and a LBBB pattern; The patient was intolerant to VT-3, with much-reduced amplitude and an LV septal exit site (black arrow), but with delayed RV and LVØ, in gray shades. The heart rate in each of these VT rhythms was similar. See Online Videos 3 and 4. Abbreviations as in Figures 2 and 3.