Detection of T‐Wave Beat‐By‐Beat Variations prior to Ventricular Arrhythmias Onset in ICD‐Stored Intracardiac Electrograms: The Endocardial T‐Wave Alternans Study (ETWAS)

Abstract

Detection of beat-by-beat repolarization variations in ICD-stored EGMs is feasible in a significant subset of cases and may be used for predicting the onset of ventricular arrhythmias.

Heart Rate–Dependent Hysteresis of T‐Wave Alternans in Primary Prevention ICD Patients

“…Similarly to what found in our previous studies, the best exercise HR for discriminating the two ICD groups was 80 bpm, in correspondence of which ICD_Cases and ICD_Controls were characterized by low but significantly different TWA levels, with the former showing higher TWA than the latter (Table ). Such HR also represents a common HR at which arrhythmias occur, observation that supports the hypothesis of TWA being an arrhythmogenic phenomenon. Another exercise HR in correspondence of which TWA was significantly different between the two ICD groups was 140 bpm (after dropping down from its maximum values) for which, however, TWA was lower in ICD_Cases than ICD_Controls (Table ).…”

Dependency of Exercise‐Induced T‐Wave Alternans Predictive Power for the Occurrence of Ventricular Arrhythmias from Heart Rate

“…Oftentimes, HR increases before the onset of VT/VF, but not above 90 bpm. 33,34 If TWA is arrhythmogenic, then it should be measured at the HR at which arrhythmias occur and not at the HR where is largest.…”

Predictive Power of f99 Repolarization Index for the Occurrence of Ventricular Arrhythmias

“…Indeed, it is commonly observed that HRs immediately preceding arrhythmias are mostly not particularly elevated. Oftentimes, HR increases before the onset of VT/VF, but not above 90 bpm . Since f99 is proposed here as an innovative risk index for the occurrence of VT/VF, then it made sense to initially measure it at the HR at which arrhythmias is more likely to occur.…”