Abstract 2127: Increased Beat-to-beat QT Variability In Surface ECG And Intracardiac Electrograms Predicts Fast Ventricular Tachycardia And Ventricular Fibrillation
Introduction: Arrhythmic sudden cardiac death is generally mediated by ventricular fibrillation (VF) or fast ventricular tachycardia (VT). We studied the predictive value of temporal QT variability detected from various sources of cardiac electrical signal (surface ECG, far-field and near-field intracardiac electrograms) for fast VT/VF events in ICD patients.
Methods: Surface ECG, far-field (FF) and near-field bipolar tip to ring (NF) intracardiac electrograms (EGMs) were simultaneously recorded at rest (mean heart rate 65 ± 15 bpm) for 4.5 ± 1.3 minutes in 448 patients (mean age 58 ± 14; 329 male [74%]) with ischemic (268 patients, 60%) and non-ischemic (180 patients, 40%) cardiomyopathy and implanted single- or dual-chamber Medtronic ICD for primary (339 patients, 76%) or secondary (109 patients, 24%) prevention of SCD. Patients were followed prospectively at least 12 months; sustained fast VT/VF events (cycle length (CL) less than 240 msec) and appropriate ICD shocks served as endpoints for analysis. The QT variability index (QTVI) was calculated as the logarithm of the ratio of normalized QT variance to heart rate variance.
Results: During mean follow-up of 15 ± 8 months, 55 (12.3%) patients sustained VT/VF and received appropriate ICD therapies, but only 17 (9.1%) patients sustained fast VT/VF and appropriate ICD shocks. The Kaplan-Meier survival analysis showed that the highest QTVI quartile predicts fast VT/VF event-free rate (p=0.044 on ECG; p=0.032 on FF EGM; p=0.008 on NF EGM). QTVI was an independent predictor of fast VT/VF in a generalized linear model (the model included age, race, gender, NYHA class, and ejection fraction (EF)), NF EGM QTVI highest quartile hazard ratio [HR], 2.99; 95% CI, 1.2 to 5.2; P=0.021). Determined by ROC curve analysis cut-off for NF EGM QTVI > 0.5 has 99% specificity and 90% sensitivity.
Conclusion: In this prospective study, temporal beat-to-beat QT variability measured from both intracardiac electrograms and surface ECG is associated with increased risk of fast VT/VF events.