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

Abstract

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 ^99mTc-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 Ca²⁺-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 Ca²⁺ handling caused by decreased SERCA2a mRNA levels, is a novel prognostic predictor in patients with DCM and narrow QRS complex.

Keywords: SERCA2a; cardiomyopathy; dyssynchrony; gated SPECT; outcomes research.