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.
RR interval variability in the evaluation of ventricular tachycardia and effects of implantable cardioverter defibrillator therapy
