Arrhythmias & electrophysiology

Combined Analysis of Cardiac Repolarization Entropy and Magnetic Resonance Imaging Enhances Risk Stratification of Patients Receiving a Primary-Prevention Implantable Cardioverter-defibrillator (ICD)

JACC Clin ElectrophysiolPublished Prospective Observational Study

Authors' conclusion

EntropyXQT and CMR gray zone mass complement each other and conventional risk factors, improving risk stratification for appropriate ICD shock and mortality, and together may enhance the selection of primary prevention ICD recipients. (Prospective Observational Study of the ICD in Sudden Cardiac Death Prevention (PROSe-ICD; NCT00733590).

Study context

Population
Patients with a left ventricular ejection fraction ≤35% in sinus rhythm receiving a primary prevention ICD
Participants
230 consecutive patients
Exposure
EntropyXQT and CMR gray zone mass added to a model composed of conventional clinical predictors, left ventricular end-systolic volume (LVESV) and prescribed diuretics
Outcome
ICD shock for VT
Follow-up
6.1 ± 3.3 years
Methodological detailsconsecutive patients
  • Consecutive patients

Main finding

As reported in the abstract

Adjusted hazard ratio (per SD change)

1.8

95% CI 1.4–2.3

EntropyXQT

Adjusted hazard ratio (per SD change)

1.5

95% CI 1.2–1.8

CMR gray zone mass

Patients who received appropriate ICD shocks
62 patients (27%)

Observational data: associations, not effects.

Secondary outcomes

Model discrimination (Harrell's C-statistic)

Harrell's C-statistic improved with EntropyXQT and CMR gray zone mass, from
0.59
Harrell's C-statistic improved to
0.73

Predictor strength over time

EntropyXQT was the strongest predictor in years 1-3, whereas CMR and LVESV were stronger in years >3

Secondary endpoints (all-cause events, including mortality)

EntropyXQT independently predicted the secondary endpoints

Original publication

Combined Analysis of Cardiac Repolarization Entropy and Magnetic Resonance Imaging Enhances Risk Stratification of Patients Receiving a Primary-Prevention ICD. JACC Clin Electrophysiol. Published 14 March 2026. doi:10.1016/j.jacep.2026.01.051

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