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.