INTRODUCTION
Non-sustained ventricular tachycardia (NSVT) is defined as more than 3
consecutive beats arising below the atrioventricular node with a rate
>100 beats/min and lasting less than 30 seconds1. In clinical practice, NSVT is recorded in a wide
range of conditions from apparently healthy, young individuals to
patients with significant heart disease 2. Prior
studies suggested that NSVT is a marker for increased risk of subsequent
sustained tachyarrhythmias and sudden cardiac death. However, its role
in patients with dilated cardiomyopathy (DCM) remains controversial3. Zecchin et al. reported that frequent NSVT (≥3
runs/day) was associated with an increased risk of mortality and
ventricular tachyarrhythmias (VTAs), but only in the subgroup of
patients with severe LV impairment and idiopathic DCM4. Spezzacatene et al. reported that 38.2% of DCM
patients showed an arrhythmogenic phenotype and that rapid NSVTs (≥ 5
beats, ≥ 150 bpm) increased the risk of sudden cardiac death5. On the other hand, other researchers suggested that
NSVT may merely be a surrogate marker of poor left ventricular ejection
fraction (LVEF) and electrical instability 6 or severe
HF 7 in such patients. Whereas NSVT was generally
recorded on ambulatory monitoring (usually 24-hour holter), the
prognostic influence of NSVT recorded in defibrillator devices, referred
to as rapid rate-NSVT (RR-NSVT), has only been discussed in limited
studies 8, 9. Defibrillators can provide the
continuous recordings of heart rhythm and, therefore, could be useful to
clarify the incidence and clinical impact of NSVT with heart rates above
the detection zones.
The current study was sought to explore the incidence of RR-NSVT and its
prognostic impacts in DCM patients with defibrillator treatment.