Background:The substrate for ventricular tachycardia (VT) in left ventricular (LV) nonischemic cardiomyopathy may be epicardial. We assessed the prevalence, location, endocardial electrograms, and VT ablation outcomes in LV nonischemic cardiomyopathy with isolated epicardial substrate.Methods:Forty-seven of 531 (9%) patients with LV nonischemic cardiomyopathy and VT demonstrated normal endocardial (>1.5 mV)/abnormal epicardial bipolar low-voltage area (LVA, <1.0 mV and signal abnormality). Abnormal endocardial unipolar LVA (≤8.3 mV) and endocardial bipolar split electrograms and predictors of ablation success were assessed.Results:Epicardial bipolar LVA (27.3 cm² [interquartile range, 15.8–50.0]) localized to basal (40), mid (8), and apical (3) LV with basal inferolateral LV most common (28/47, 60%). Of 44 endocardial maps available, 40 (91%) had endocardial unipolar LVA (24.5 cm² [interquartile range, 9.4–68.5]) and 29 (67%) had characteristic normal amplitude endocardial split electrograms opposite the epicardial LVA. At mean of 34 months, the VT-free survival was 55% after one and 72% after multiple procedures. Greater endocardial unipolar LVA than epicardial bipolar LVA (hazard ratio, 10.66 [CI, 2.63–43.12], P=0.001) and number of inducible VTs (hazard ratio, 1.96 [CI, 1.27–3.00], P=0.002) were associated with VT recurrence.Conclusions:In patients with LV nonischemic cardiomyopathy and VT, the substrate may be confined to epicardial and commonly basal inferolateral. LV endocardial unipolar LVA and normal amplitude bipolar split electrograms identify epicardial LVA. Ablation targeting epicardial VT and substrate achieves good long-term VT-free survival. Greater endocardial unipolar than epicardial bipolar LVA and more inducible VTs predict VT recurrence.

中文翻译：

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非缺血性心肌病和孤立性心外膜瘢痕患者室性心动过速导管消融的基质特征和结果

背景：左心室（LV）非缺血性心肌病室性心动过速（VT）的底物可能是心外膜。我们评估了分离心外膜基质的 LV 非缺血性心肌病的患病率、位置、心内膜电图和 VT 消融结果。方法：531 名 LV 非缺血性心肌病和 VT 患者中有 47 名（>1.5 mV）显示正常心内膜（>1.5 mV）/心外膜双极低电压区异常（LVA，<1.0 mV 和信号异常）。对异常心内膜单极 LVA (≤8.3 mV) 和心内膜双极分裂电图和消融成功的预测因素进行了评估。结果：心外膜双极 LVA (27.3 cm ²[四分位距，15.8–50.0]) 局限于左室基底 (40)、中部 (8) 和顶端 (3)，其中基底下外侧 LV 最常见 (28/47, 60%)。在可用的 44 个心内膜图中，40 个（91%）有心内膜单极左心室（24.5 cm ² [四分位距，9.4-68.5]），29 个（67%）有与心外膜左心室相对的特征性正常振幅心内膜分裂电图。平均 34 个月时，一次手术后无 VT 生存率为 55%，多次手术后为 72%。心内膜单极左心室比心外膜双极左心室更大（风险比，10.66 [CI，2.63–43.12]，P = 0.001）和可诱导 VT 的数量（风险比，1.96 [CI，1.27–3.00]，P=0.002）与室速复发有关。结论：在左室非缺血性心肌病合并室速的患者中，底物可能局限于心外膜，通常是基底下外侧。LV 心内膜单极 LVA 和正常振幅双极分裂电图可识别心外膜 LVA。针对心外膜 VT 和基质的消融可实现良好的长期无 VT 生存。心内膜单极比心外膜双极 LVA 更大，且更易诱发的 VT 可预测 VT 复发。