T wave morphological changes before onset of ventricular arrhythmia are poorly known. ICD-stored intracardiac electrograms (EGM) present a unique opportunity for detecting temporal changes in repolarisation before initiation of VT/VF.

57 implanted patients with St Jude Medical ICDs (45 men, 64±12 yo, mean EF 34±15%) were prospectively enrolled. Eleven different T wave parameters were extracted from EGM (T amplitude, T peak time, T end time, T duration between baseline crossing and between points of maximal slopes, T peak to T end, maximal ascending and descending slopes, timing of points of maximal slopes and T wave area). Values of each parameter in recordings prior to VT/VF were compared to control recordings sharing comparable QRS and T wave morphology and similar heart rate in the same pts.

23 VT/VF episodes (24±13 beats) and 13 baseline (25±9 beats) (ns) were analyzed in 12 pts (1,9 episode/pt). Mean heart rate was 71±17 bpm for episodes and 66±16 bpm for baseline recordings (ns). Significant differences were found in T wave amplitude, T wave maximal slopes, T peak time and timing of the T wave maximal ascending slope (although ns when corrected by the heart rate).

T wave amplitude is higher, T wave slopes are steeper and initial parts of the T wave are earlier before ventricular arrhythmia compared to baseline. Detection of T wave changes prior to VT/VF might be useful in predicting imminent arrhythmia occurrence.