Clinical impact of NSVT in DCM patients
DCM consists of a heterogeneous group of diseases and affects the myocardium without the presence of any significant coronary artery disease 13. The incidence of NSVT in DCM patients has been reported to widely range between 43% and 66.5%4, 7, and the role of NSVT in DCM remains controversial. Whereas some prior studies suggested that NSVT is a marker for the increased risk of subsequent sustained tachyarrhythmias and SCD 3, others described NSVT as a potential surrogate marker of poor LVEF and electrical instability6 or severe HF 7 in DCM patients. In our study, 50.0% of study patients experienced ≥ 1 episode of RR-NSVT and any NSVT showed a positive association with VTA occurrence. Of note, there was no significant difference in the incidence of HF symptoms and BNP levels between patients with and without RR-NSVT. In addition, the accumulative incidence of cardiac death and heart failure admission was comparable between groups. Recently, Spezzacatene et al. reported that 38.2% of DCM patients meet the criteria of an arrhythmogenic phenotype defined by the presence of ≥1 of the following: rapid NSVT (≥5 beats, ≥150 bpm), ≥1000 PVCs/day, ≥50 couplets/day, and syncope and that NSVT and VTAs may occur without signs and symptoms of overt HF and may not be related to the severity of LV dysfunction 5. Furthermore, they described that a DCM arrhythmogenic phenotype and family history of sudden cardiac death (SCD)/VTAs are predictors for the occurrence of SCD/VTAs. As most patients with RR-NSVT defined in our study corresponds with the definition of an arrrhythmogenic phenotype, our findings may highlight the clinical impact of such phenotypes in DCM patients.