Unique scintigraphic parameters for the evaluation of ventricular synchrony were derived, and their added value was determine compared with established measures. Indications for pacemaker therapy now include the treatment of severe congestive heart failure (CHF). Atrial triggered biventricular pacemakers reduce CHF symptoms and prolong life in patients with cardiomyopathy, severe CHF, left ventricular (LV) ejection fraction (EF) lower than 35%, and QRS greater than 120 milliseconds. Such pacing, or cardiac resynchronization therapy (CRT), seeks to reduce the heterogeneity and increase the synchrony of ventricular activation, conduction, and contraction. CRT has improved hemodynamics, increased exercise tolerance, reduced symptoms and the need for hospitalization, reversed ventricular remodeling, and reduced the all-cause mortality rate in CHF. However, CRT is costly, fails to improve symptoms or activity level in more than 30% of patients, and is applied blindly without individualization or consideration of lead placement sight. A variety of echocardiographic methods have sought to measure synchrony and its serial changes with CRT. A recent study presented evidence of the poor reproducibility of several widely applied echocardiographic measurements by which to determine ventricular synchrony. Magnetic resonance imaging has excellent resolution of regional wall motion and has been applied to assess ventricular synchrony and its response to pacing therapy. However, these methods are complex and are not well established or widely available, and magnetic resonance imaging has not been widely applied after pacing. An accurate and reproducible method is needed by which to objectively measure regional ventricular synchrony. Phase image analysis, a functional method based on the first Fourier harmonic fit of the gated blood pool time versus radioactivity curve, generates the parameters of amplitude (A), which parallels the extent of regional ventricular contraction or stroke volume, and phase angle (Ø), which represents the timing of regional contraction. It was applied early with demonstrated reproducibility to show the linkage between electrical and mechanical dyssynchrony and to characterize the contraction pattern in heart failure and its alteration with CRT. The SD of ventricular Ø, applied as a marker of synchrony, has been shown to demonstrate the beneficial effects of biventricular pacing, and its strong prognostic value has been shown in patients with congestive cardiomyopathy and CHF, superior to LVEF. The SD Ø may not be optimal for synchrony evaluation. We sought improved, more sensitive parameters to better differentiate synchrony among the spectrum of possible patterns of dyssynergy. We derived, initially evaluated, and here present new synchrony (S) and entropy (E) parameters, based on the phase method, to quantitate regional and global ventricular synchrony and applied them in simulation and clinical protocols.