Background: Monitoring arrhythmic risk may improve management of patients with implantable cardioverter-defibrillators (ICD) and prevent ICD shocks. Changes in repolarization duration between subsequent beats quantified as short-term variability (STV) is associated with ventricular arrhythmias in several animal models. Objective: We evaluated STV of QT from right ventricular intracardiac ICD electrograms in patients with structural heart disease and compared its predictive value with the QT variability index (QTVI). Methods: In 233 patients, STV over 60 beats for QT and RR intervals and their ratio was calculated (STV QT, STV RR, STV Ratio, respectively). QTVI was derived from mean and SD of QT and heart rate. Follow-up duration was 26 ± 15 months. Predictive value was determined for sudden arrhythmic death (SAD) defined as sudden cardiac death or fast ventricular tachycardia/fibrillation [CL <240 ms]. Results: In univariate analysis, STV Ratio, but not STV QT or STV RR, was predictive of SAD. Hazard ratios for highest quartile STV Ratio and QTVI were comparable (STV Ratio: 1.9, 95% confidence interval [CI] 1.1 to 3.3, P =.038, QTVI: 2.2, 95% CI 1.2 to 3.8, P =.010). In a multivariate model, highest quartile STV Ratio was predictive of SAD after adjustment for New York Heart Association class, history of ischemia, ICD indication, and use of class I antiarrhythmics (hazard ratio 1.8, 95% CI 1.0 to 3.4, P Ratio and QTVI identified patients at highest risk (hazard ratio 2.4, 95% CI 1.3 to 4.3, P =.005, positive predictive value 38%, negative predictive value 82%). Conclusion: STV Ratio from ICD electrograms is predictive of SAD. Predictive value is similar for order-based STV Ratio and distribution-based QTVI, but the combination of both parameters can further improve results.
- intracardiac electrogram
- Risk stratification
- Structural heart disease
- Variability or repolarization
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine
- Physiology (medical)