Application of two novel electrical restitution based ECG markers of
ventricular arrhythmia to patients with non-ischemic cardiomyopathy
Abstract
Introduction: Sudden Cardiac Death (SCD) risk assessment is limited,
particularly in patients with non-ischemic cardiomyopathies. This is the
first application, in patients with non-ischemic cardiomyopathies, of
two novel risk markers, Regional Restitution Instability Index (R2I2)
and Peak Electrocardiogram Restitution Slope (PERS), which have been
shown to be predictive of ventricular arrhythmias (VA) or death in
ischemic cardiomyopathy patients. Methods and Results: Blinded
retrospective study of 50 patients: 33 dilated cardiomyopathy and 17
other; undergoing electrophysiological study (EPS) for SCD risk
stratification, and 29 controls with structurally normal hearts
undergoing EPS. R2I2 was calculated from an EPS using ECG surrogates for
action potential duration and diastolic interval. Cut-offs for high and
low R2I2/PERS were predefined. R2I2 was significantly higher in study
than control patients (0.99±0.05 vs. 0.63±0.04, <0.001). PERS
showed a trend to higher values in the study group (1.18[0.63] vs.
1.09[0.54], p=0.07). During median follow up of 5.6 years [IQR 1.9
years] 9 study patients reached the endpoint of ventricular
arrhythmia(VA)/death. Patients who experienced VA/death showed trends to
higher mean R2I2 (1.14±0.07vs.0.95±0.05, p=0.12) and PERS
(1.46[0.49] vs. 1.13[0.62], p=0.22). A Cox proportional hazards
model using grouped markers: R2I2<1.03+PERS<1.21 /
either R2I2≥1.03 or PERS≥1.21 / R2I2≥1.03+PERS≥1.21; significantly
predicted VA/death (p=0.02) with a hazard ratio per positive component
of 3.2 (95% confidence interval 1.2 to 8.8). Conclusion:
R2I2≥1.03+PERS≥1.21 predict VA/death in patients with non-ischemic
cardiomyopathies. R2I2≥1.03+PERS≥1.21 have the potential to play an
important role in SCD risk stratification in non-ischemic
cardiomyopathies but their validity should be confirmed in a larger
study.