Phase imaging: a new, noninvasive method for diagnosis, localization of accessory pathways, and serial assessment of therapy in patients with Wolff-Parkinson-White syndrome

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Myocardial activation patterns have been elegantly delineated by Durrer et al1 who showed that ventricular activation, although not completely homogeneous, occurs earliest in the middle third of the left interventricular septum and latest in the basal regions of both ventricles and septum. Similarly, patterns of epicardial activation in patients with ventricular preexcitation with an accessory atrioventricular pathway of the Kent bundle type have been delineated in recent years in an attempt to localize these pathways. Wolff-Parkinson-White syndrome assumes its importance clinically because of the frequently associated paroxysms of tachycardia. Because of the now well-established role of surgical division of accessory atrioventricular pathways, precise localization of these pathways has become mandatory. However, localization of accessory atrioventricular pathways has been achieved utilizing very complex, time-consuming invasive preoperative and intraoperative electrophysiologic studies.

Fourier phase analysis of 99m Tc-gated equilibrium radionuclide scans theoretically provides an opportunity to characterize patterns of myocardial movement by accurately demonstrating the timing of contraction between small segments of the myocardium. Fourier phase and amplitude analysis of technetium cardiac scans has been shown to be an accurate method of assessing regional wall motion2 and quantitating areas of dyskinesia in patients with left ventricular aneurysms.3 However, abnormalities of movement may also result from alterations in myocardial activation. Although the movement of the blood pool is a complex process involving many factors, the patterns of delayed electrical activation seen in left bundle branch block have been accurately assessed by Fourier phase analysis of 99m Tc blood-pool scans.4, 5

Theoretically then, Fourier . . .



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