The clinical impact of RR-NSVT in DCM patients
RR-NSVT, which meets detection criteria but terminates itself before the delivery of defibrillator therapy, is not rare in routine ICD/CRT-D interrogation of DCM patients. Of note, the definition of RR-NSVT is not the same as NSVT episodes identified on a 24-hour holter. RR-NSVT is based on the continuous recording of a patient’s heart rhythm and can provide more accurate detection of NSVT above the lowest detection rate. In a study enrolling patients with hypertrophic cardiomyopathy, Wang et al. reported that 38% of patients without NSVT detected by preimplant Holter had an NSVT detected by ICD during follow-up14. To the best of our knowledge, 2 studies examined the clinical influence of RR-NSVT and reported that RR-NSVT was a predictor for future ICD therapy and mortality 8, 9. Chen et al. examined the occurrence of RR-NSVT and its association with ICD shocks and mortality in a SCD-HeFT population, in which ICD therapy was set only for a VF zone ≥188 beats/min 8. Recently, Zhou et al. explored the predictive value of RR-NSVT on appropriate ICD therapy in a real-world setting, in which they set the monitor zone of 140–170 bpm and VT therapy zone above 170–210 bpm as well as the VF zone 9. In the present study, we focused on DCM patients and evaluated the clinical impact of RR-NSVT in DCM patients with a practical setting of ICD/CRT-D. We demonstrated that any RR-NSVT was associated with a higher incidence of VTAs in both primary and secondary prevention. On the other hand, RR-NSVT did not show a significant association with cardiac mortality. One possible explanation for the difference in influence of RR-NSVT on mortality between prior studies and the current study is the background heart diseases included; prior studies included approximately 50% of patients with other structural heart disease than non-ischemic cardiomyopathy8,9. Further studies are needed to evaluate the clinical influence of RR-NSVT in specific patient populations.