Abstract 2851: Temporal QT Variability from Bipolar Ventricular Tip-to-Ring Electrograms Predicts Sustained Ventricular Tachyarrhythmia.
We assessed the hypothesis that ventricular tachycardia / ventricular fibrillation (VT/VF) risk stratification based on the repolarization assessment of intracardiac electrograms (EGMs) from implantable devices is feasible.
Methods: Bipolar right ventricular tip-to-ring EGMs were recorded at rest (mean heart rate 66 ± 16 bpm) for 5.5 ± 2.6 minutes in 75 patients (58 ± 14 years, 72% men) with ischemic (60%) and non-ischemic (40%) cardiomyopathy who underwent single-chamber Medtronic ICD implantation for primary (77%) or secondary (23%) prevention of SCD. QT variability index (QTVI), variability of Tpeak-Tend area index, and T-wave alternans (TWA) were calculated as previously described elsewhere. Only 41 out of 75 recordings (55%) were eligible for analysis as determined by data quality requirements of the custom software (less than 10% non-analyzable beats or 5% ectopic beats). The endpoint was appropriate ICD therapy for VT/VF during follow-up > 6 months.
Results: During mean follow-up of 12 months (range 6–19 months), 12 patients had appropriate ICD therapy. The survival analysis showed that the top quartile of QTVI (> - 0.5) predicts an event-free survival rate from appropriate ICD therapies (p = 0.027). Neither increased Tpeak-Tend area variability nor TWA was associated with a significant increased risk for VT/VF.
Conclusions: In this prospective study, temporal QT variability measured from right ventricular tip-to-ring EGMs is associated with increased risk of sustained VT/VF events. Repolarization lability may be present throughout the ventricular myocardium, such that single-site EGMs may provide an effective means for VT/VF risk stratification.