Published Online
on March 6, 2009

A more recent version of this article appeared on June 1, 2009

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Original Article

Prediction of Ventricular Tachyarrhythmias by Intracardiac Repolarization Variability Analysis

Larisa G. Tereshchenko^1,5; Barry J. Fetics²; Peter P. Domitrovich³; Bruce D. Lindsay⁴ and Ronald D. Berger²

¹ Johns Hopkins Hospital and Washington University;
² Johns Hopkins Hospital;
³ Washington University;
⁴ Washington University and Cleveland Clinic

⁵ E-mail: lteresh1{at}jhmi.edu

Background—Arrhythmic sudden cardiac death (SCD) is generally mediated by ventricular fibrillation (VF) or fast ventricular tachycardia (FVT). We studied the predictive value of temporal QT variability detected from various sources of cardiac electrical signal: surface ECG, far-field (FF) and near-field (NF) intracardiac electrograms (EGMs) in ICD patients.

Methods and Results—Surface ECG and FF and NF intracardiac EGMs were simultaneously recorded at rest (mean heart rate 74±15 bpm) for 4.5±1.3 minutes in 298 patients (mean age 59±14; 216 male [73%]) with structural heart disease and implanted Medtronic ICD for primary (231 patients, 78%) or secondary (67 patients, 22%) prevention of SCD. During mean follow-up of 16±8 months, 52 (13.1% per person-year of follow-up) patients sustained VT/VF and received appropriate ICD therapies, but only 19 (4.8% per person-year of follow-up) patients sustained FVT/VF with cycle length 240 msec. The Kaplan-Meier survival analysis showed that the highest QT variability index (QTVI) quartile from all cardiac sources (surface ECG; NF and FF EGMs) is associated with event-free survival (p=0.038 for ECG; p=0.024 for FF EGM; p=0.012 for NF EGM). QTVI was a predictor of all VT/VF events and FVT/VF in the multivariate Cox model (including ischemic or nonischemic cardiomyopathy, history of revascularization procedures, LVEF, NYHA class). Strong significant correlation among QTVI determined from all three sources was found.

Conclusion—Repolarization lability is present throughout the ventricular myocardium. Increased intracardiac QT variability predicts VT/VF events in patients with structural heart disease.

Key Words: defibrillation • electrophysiology • heart arrest • prognosis • tachyarrhythmias