Quantification of cardiac conduction abnormalities using segmental vector fourier analysis of radionuclide gated blood pool scans

Timing abnormalities of myocardial contractility may occur as inter- or intraventricular asynchrony. Gated blood pool scintigraphy was performed on 21 patients with a normal ejection fraction and the following electrocardiograms: six normal, six with left bundle branch block, four with right bundle branch block and five with right ventricular pacemaker rhythm. A phase and amplitude of the first harmonic of the Fourier transform was obtained for each pixel, and left and right ventricles were trisected. A mean vector phase for each region was obtained by vector summation. Regional and global values were analyzed within each group and compared with normal values. The phase differences between the entire left and right ventricles (mean ± standard deviation) were: 9 ± 3 in the normal patients, 38 ± 8 (p < 0.01) in patients with left bundle branch block, - 6 ± 7 (p < 0.05) in patients with right bundle branch block and 15 ± 9 (difference not significant) in patients with pacemaker rhythm. The phase differences between left ventricular posterolateral and septal regions were - 4 ± 2 in the normal patients, 10 ± 5 (p < 0.01) in patients with left bundle branch block, - 7 ± 10 (p < 0.05) in patients with right bundle branch block and 10 ± 5 (p < 0.01) in patients with pacemaker rhythm. Within the right ventricle, phase differences between the apical and septal segments were 14 ± 9 in the normal patients, 14 ± 10 (NS) in patients with left bundle branch block, -2 ± 3 (p < 0.01) in patients with right bundle branch block and - 22 ± 18 (p < 0.01) in patients with pacemaker rhythm. Interventricular phase differences were greatest in patients with left bundle branch block and absent or reversed in right bundle branch block. Intraventricular asynchrony occurred in the left ventricle in patients with left bundle branch block, right bundle branch block and pacemaker rhythm, while right intraventricular asynchrony occurred only in patients with right bundle branch block and pacemaker rhythm. Regional vector summation permits quantification of asynchrony within, as well as between, the right and left ventricles.