Abstract
Introduction:An implantable cardioverter defibrillator (ICD) is the most reliable
therapeutic device for preventing sudden cardiac death in patients with
sustained ventricular tachycardia
(VT). Regarding the effectiveness of the ICD, targeted VT is defined
based on the tachyarrhythmia cycle length. However, variation of the RR
interval variability of VTs does occur. A few studies reported on VT
characteristics and effects of ICD therapy according to RR interval
variability. This study aimed to identify the clinical characteristics
of VTs and effects of ICD therapy according to RR interval variability.
Methods: We analyzed 821 VT episodes in 69 of 185 patients
treated with ICDs or cardiac resynchronization therapy defibrillators.
VTs were classified as regular or irregular based on RR interval
variability. We evaluated successful termination using anti-tachycardia
pacing (ATP)/shock therapy, spontaneous termination, and acceleration
between regular and irregular VTs. Reproducibility of the RR interval
variability in one VT episode and within an individual with recurrent VT
episodes was evaluated.
Results: Regular VT was significantly more successfully
terminated than irregular VT by ATP therapy. There was no significant
difference in shock therapy or VT acceleration, irrespective of the
variability of the VT cycle length. Spontaneous termination of VT
occurred significantly more often in irregular than in regular VT.
Reproducibility of RR interval variability in an episode and individual
was 89% and 73%, respectively.
Conclusion: ATP therapy showed greater effectiveness for
regular than for irregular VT. Spontaneous termination was more common
in irregular than in regular VT. RR interval variability of VTs is
reproducible.
Keywords: ventricular tachycardia, implantable cardioverter
defibrillator, RR interval variability, shock therapy, anti-tachycardia
pacing therapy