Onset of left ventricular mechanical contraction as determined by phase analysis of ECG-gated myocardial perfusion SPECT imaging: Development of a diagnostic tool for assessment of cardiac mechanical dyssynchrony

Background. A count-based method using technetium-99m sestamibi electrocardiographygated myocardial perfusion single photon emission computed tomography imaging has been developed to extract the left ventricular (LV) regional phase of contraction (onset of mechanical contraction [OMC]) throughout the cardiac cycle. This study was performed to develop ONIC normal databases and dynamic ONIC displays for assessment of cardiac mechanic dyssynchrony. Methods and Results. LV regional phases were extracted from 90 enrolled normal subjects (45 men and 45 women) by use of the Emory Cardiac Toolbox and then submitted to statistical analysis to generate the normal databases. The LV ONIC wave was dynamically propagated over the perfusion polar map by blackening either sequential phase bins or all past phases. The developed ONIC normal databases consisted of peak phase (134.5 degrees +/- 14.3 degrees for men and 140.2 degrees +/- 14.9 degrees for women), phase SD (14.2 degrees +/- 5.1 degrees for men and 11.8 degrees +/- 5.2 degrees for women), and phase histogram bandwidth (38.7 degrees +/- 11.8 degrees for men and 30.6 degrees +/- 9.6 degrees for women), skewness (4.19 +/- 0.68 for men and 4.60 +/- 0.72 for women), and kurtosis (19.72 +/- 7.68 for men and 23.21 +/- 8.16 for women). Both statistical analysis and dynamic ONIC displays were incorporated into a user interface as a diagnostic tool. Conclusion. The ONIC normal databases and dynamic ONIC displays should help clinicians evaluate cardiac mechanic dyssynchrony. Prospective clinical trials are needed to validate whether this tool can be used to select patients with severe heart failure symptoms who might benefit from cardiac resynchronization therapy.