Background: Left ventricular (LV) mechanical dyssynchrony by phase analysis has been studied by myocardial perfusion imaging (MPI) gated SPECT in patients with LV dysfunction in various clinical settings. We aimed to investigate the routine use of phase analysis with gated SPECT for predicting cardiac outcome.
Methods: Patients referred to a tertiary medical center in 2010-2011 underwent a comprehensive MPI assessment including gated SPECT with Tc-99m sestamibi and phase analysis, were followed-up for cardiac events. The value of clinical variables, NYHA class, myocardial perfusion, LV function, and phase parameters in predicting cardiac events was tested by univariate and multivariate analyses.
Results: The study group included 787 patients (66.5±11yrs, 81% men) followed for a mean duration of 19.1±5.7 months. There were 45 (6%) cardiac "composite endpoint"; cardiac death occurred in 26 patients, the rest had new-onset or worsening heart failure and life-threatening arrhythmias. Patients with cardiac events were significantly older, have more ICD/CRT , diabetes mellitus , abnormal ECG, CLBBB, wider QRS , higher NYHA functional class, lower LVEF ,more scar and larger scar as well as increased phase SD and histogram bandwidth. In multivariate analysis, it was shown that NYHA class, diabetes mellitus and LVEF< 50% were the independent predictors for composite endpoint. However, the predictors for cardiac mortality were, NYHA class and phase SD. Using an abnormal phase SD as > 40°, It was shown by Cox-proportional hazard survival plots that cardiac mortality significantly stratified by normal and abnormal phase SD adjusted for LVEF <50% ,but it was not stratified for composite endpoint.
Conclusion: Routine gated SPECT MPI with phase analysis is a useful tool to assess mechanical LV dyssynchrony. Together with perfusion and function data, LV dyssynchrony, as measured by phase SD together with NYHA functional class, can predict cardiac death, especially in patients with LV dysfunction.
