Left ventricular phase entropy: Novel prognostic predictor in patients with dilated cardiomyopathy and narrow QRS

Background The prognostic impact and pathophysiology of global left ventricular mechanical dyssynchrony (LVMD), namely mechanical dyssynchrony of whole left ventricle, as assessed by phase analysis of electrocardiographically gated (ECG-gated) myocardial perfusion SPECT has not been clearly elucidated in patients with dilated cardiomyopathy (DCM) and narrow QRS complex (<120 ms). Methods and Results Forty-six patients with DCM underwent ECG-gated myocardial 99m Tc-sestamibi perfusion SPECT and endomyocardial biopsy. LV phase entropy was automatically calculated using a phase analysis of ECG-gated myocardial perfusion SPECT. The patients were divided into two groups according to the median phase entropy value: low-phase entropy (<0.61) (N = 23: LE group) and high-phase entropy (≥0.61) (N = 23: HE group). In the Kaplan-Meier survival analysis, the event-free survival rate was significantly lower in the HE group (log-rank P = 0.015). Moreover, high-phase entropy was an independent predictor of adverse cardiac events (hazard ratio, 5.77%; 95% confidence interval, 1.02-108.32; P = 0.047). Interestingly, the mRNA expression levels of sarcoplasmic reticulum Ca 2+ -ATPase (SERCA2a) in endomyocardial biopsy specimens were significantly lower in the HE group ( P = 0.015). Conclusion LV phase entropy, which may reflect impairment of Ca 2+ handling caused by decreased SERCA2a mRNA levels, is a novel prognostic predictor in patients with DCM and narrow QRS complex.