Texas Cardiac Arrhythmia Institute, St David's Medical Center, Austin, TX 78705, USA.
Circ Arrhythm Electrophysiol. 2012 Jun 1;5(3):475-83. doi: 10.1161/CIRCEP.111.967893. Epub 2012 Mar 15.
The differential diagnosis between idiopathic and cardiomyopathy-related right ventricular outflow tract (RVOT) ventricular arrhythmias (VAs) is crucial. Signal-averaged ECG (SAECG) abnormalities are frequent in cardiomyopathy-related RVOT-VAs, although their pathophysiologic basis and diagnostic value in this setting are undefined. We tested the association between SAECG and the myocardial substrate underlying RVOT-VAs.
Twenty-four consecutive patients (median age, 50 years [42-59]; 12 men) with RVOT-VAs (10 with frequent [>1000/24 hours] premature ventricular contractions, 14 with ventricular tachycardias) underwent SAECG with 40-Hz filtering and electroanatomic mapping (EAM) with EAM-guided biopsy for characterization of the RVOT-VAs substrate. A filtered averaged QRS (fQRS) was obtained and analyzed for fQRS duration, low amplitude signal duration<40 mV (LAS40), and root-mean-square voltage in the last 40 ms of the QRS (RMS40). Standard definition of EAM scar was used. EAM-guided biopsy diagnosed ARVC in 11 (46%), myocarditis in 8 (33%), and idiopathic RVOT-VAs in 5 (21%) patients. Patients with cardiomyopathy-related RVOT-VAs had ≥1 EAM scar (median, 2 [1-2]; all with RVOT scar). EAM of patients with idiopathic RVOT-VAs was normal. Patients with cardiomyopathy-related RVOT-VAs had significantly longer fQRS (106 ms [92-132] versus 83 ms [82-84], P=0.01) and LAS40 (39 ms [36-51] versus 19 ms [18-21], P=0.02), and lower RMS40 (18 µV [9-26] versus 33 µV [32-33], P=0.04). A significant linear correlation was found between the extension (cm2) of the RVOT scar and all 3 SAECG parameters (rs=0.76, P<0.001 for the fQRSd; rs=0.73, P<0.001 for the LAS40; and rs=-0.72, P<0.001 for the RMS40). Using the established 2 of 3 criteria (ie, late potentials), SAECG diagnosed cardiomyopathy-related RVOT-VAs with high positive (100%) but low negative (38%) predictive values and missed 7 of 9 (78%) patients with RVOT scar<8 cm2.
In patients with RVOT-VAs, abnormal SAECG parameters reflect the presence of extensive cardiomyopathic involvement of the RVOT. However, a negative SAECG does not reliably rule out cardiomyopathy-related RVOT-VAs in the presence of a small RVOT scar.
特发性与心肌病相关的右心室流出道（RVOT）室性心律失常（VA）的鉴别诊断至关重要。尽管信号平均心电图（SAECG）异常在心肌病相关 RVOT-VA 中很常见，但它们在这种情况下的病理生理基础和诊断价值尚未确定。我们检验了 SAECG 与 RVOT-VA 下心肌基质之间的关联。
24 例连续 RVOT-VA 患者（中位数年龄 50 岁[42-59]；男性 12 例）进行了 SAECG 检查，包括 40Hz 滤波和电解剖标测（EAM），并进行 EAM 指导下的 RVOT-VA 基质活检。获得滤波后的 QRS 波（fQRS），并分析 fQRS 持续时间、低振幅信号持续时间<40mV（LAS40）和 QRS 波最后 40ms 的均方根电压（RMS40）。采用标准的 EAM 瘢痕定义。EAM 指导下的活检诊断为 ARVC 11 例（46%）、心肌炎 8 例（33%）和特发性 RVOT-VA 5 例（21%）。心肌病相关 RVOT-VA 患者有≥1 个 EAM 瘢痕（中位数，2[1-2]；均为 RVOT 瘢痕）。特发性 RVOT-VA 患者的 EAM 正常。心肌病相关 RVOT-VA 患者的 fQRS 明显延长（106ms[92-132]比 83ms[82-84]，P=0.01）和 LAS40 延长（39ms[36-51]比 19ms[18-21]，P=0.02），而 RMS40 降低（18µV[9-26]比 33µV[32-33]，P=0.04）。RVOT 瘢痕的延伸（cm2）与所有 3 项 SAECG 参数之间存在显著的线性相关性（rs=0.76，P<0.001 用于 fQRSd；rs=0.73，P<0.001 用于 LAS40；rs=-0.72，P<0.001 用于 RMS40）。使用既定的 2/3 标准（即晚电位），SAECG 诊断出与心肌病相关的 RVOT-VA 阳性预测值高（100%）但阴性预测值低（38%），漏诊了 9 例 RVOT 瘢痕<8cm2 的患者中的 7 例（78%）。
在 RVOT-VA 患者中，异常的 SAECG 参数反映了 RVOT 广泛的心肌病受累。然而，在存在小 RVOT 瘢痕的情况下，阴性的 SAECG 并不能可靠地排除与心肌病相关的 RVOT-VA。
