Background
Short‐term variability of the QT interval (STV
QT
) has been proposed as a novel electrophysiological marker for the prediction of imminent ventricular arrhythmias in animal models. Our aim is to study whether STV
QT
can predict imminent ventricular arrhythmias in patients.
Methods and Results
In 2331 patients with primary prophylactic implantable cardioverter defibrillators, 24‐hour ECG Holter recordings were obtained as part of the EU‐CERT‐ICD (European Comparative Effectiveness Research to Assess the Use of Primary Prophylactic Implantable Cardioverter Defibrillators) study. ECG Holter recordings showing ventricular arrhythmias of >4 consecutive complexes were selected for the arrhythmic groups (n=170), whereas a control group was randomly selected from the remaining Holter recordings (n=37). STV
QT
was determined from 31 beats with fiducial segment averaging and calculated as
, where
D
n
represents the QT interval. STV
QT
was determined before the ventricular arrhythmia or 8:00
am
in the control group and between 1:30 and 4:30
am
as baseline. STV
QT
at baseline was 0.84±0.47 ms and increased to 1.18±0.74 ms (
P
<0.05) before the ventricular arrhythmia, whereas the STV
QT
in the control group remained unchanged. The arrhythmic patients were divided into three groups based on the severity of the arrhythmia: (1) nonsustained ventricular arrhythmia (n=32), (2) nonsustained ventricular tachycardia (n=134), (3) sustained ventricular tachycardia (n=4). STV
QT
increased before nonsustained ventricular arrhythmia, nonsustained ventricular tachycardia, and sustained ventricular tachycardia from 0.80±0.43 ms to 1.18±0.78 ms (
P
<0.05), from 0.90±0.49 ms to 1.14±0.70 ms (
P
<0.05), and from 1.05±0.22 ms to 2.33±1.25 ms (
P
<0.05). This rise in STV
QT
was significantly higher in sustained ventricular tachycardia compared with nonsustained ventricular arrhythmia (+1.28±1.05 ms versus +0.24±0.57 ms [
P
<0.05]) and compared with nonsustained ventricular arrhythmia (+0.34±0.87 ms [
P
<0.05]).
Conclusions
STV
QT
increases before imminent ventricular arrhythmias in patients, and the extent of the increase is associated with the severity of the ventricular arrhythmia.
Efficacy of Antitachycardia Pacing for Very Fast Ventricular Tachycardia (200–250ms Cycle Length) and Low Energy Shock (5J) for Ventricular Arrhythmias in Patients with Implantable Cardioverter Defibrillators
