Short-Term Variability Of The Qt Interval Can Be Used For The Prediction Of Imminent Ventricular Arrhythmias In Patients With Primary Prophylactic Implantable Cardioverter Defibrillators

Background: Short-term variability of the QT interval (STVQT) has been proposed as a novel electrophysiological marker for the prediction of imminent ventricular arrhythmias in animal models. Our aim is to study whether STVQT 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). STVQT was determined from 31 beats with fiducial segment averaging and calculated as , where D-n represents the QT interval. STVQT was determined before the ventricular arrhythmia or 8:00 am in the control group and between 1:30 and 4:30 am as baseline. STVQT 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 STVQT 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). STVQT 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 STVQT 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: STVQT increases before imminent ventricular arrhythmias in patients, and the extent of the increase is associated with the severity of the ventricular arrhythmia.