Department of Cardiology, Congenital Heart Diseases and Electrotherapy, Medical University of Silesia, Zabrze, Poland.
Kardiol Pol. 2012;70(5):447-55.
Prediction of recurrent malignant ventricular tachyarrhythmias after insertion of a implantable cardioverter-defibrillator (ICD) is challenging. Microvolt T-wave alternans (MTWA) seems to be a promising marker of such events in ICD recipients.
To assess prognostic significance of MTWA and other noninvasive parameters in the prediction of major arrhythmic events after ICD implantation.
This prospective study included 155 patients (121 male, age 59 ± 11 years) in whom ICD was implanted for secondary prevention of a sudden cardiac death. In all patients, clinical evaluation along with estimation of ejection fraction, MTWA measurement using the HearTwave Cambridge Heart system, and determination of the corrected QT interval (QTc) and QT dispersion (QTd) based on resting ECG were performed 3 days before ICD implantation. Using 24-h Holter monitoring, cardiac arrhythmias, QT interval, QT dynamicity, QT variability (QTSD) and heart rate variability (HRV) time domain parameters were determined. MTWA results were categorised, based on the accepted criteria, as positive, negative or indeterminate. In further analyses, positive and indeterminate MTWA results were grouped together as abnormal or non-negative tests [MTWA+], while negative MTWA results were considered normal [MTWA-]. During the follow-up (mean duration 21.6 ± 11.6 months), major arrhythmic cardiac events (MACE), defined as death and/or the need for ablation and/or heart transplantation due to malignant ventricular tachyarrhythmias, were recorded.
During the follow-up, MACE occurred in 17 (11%) patients. Abnormal MTWA before ICD implantation was found significantly more frequently in patients with MACE as compared to patients without MACE. Multivariate Cox regression analysis identified abnormal MTWA and QTSD as independent risk factors for MACE, with hazard ratios of 10.82 (95% CI 9.76-11.88; p〈 0.05) and 1.08 (95% CI 1.05-1.08), respectively. Significant differences in MACE-free survival rate with regard to MTWA results (abnormal vs normal MTWA) were shown during the follow-up (p〈 0.001). The negative predictive value of normal MTWA for MACE was 98.6%. When both MTWA and QTSD were combined, the positive predictive value increased to 35%, with a sensitivity of 82% and specificity of 81%. The probability of MACE with normal results of both these tests was 2.3%.
Abnormal MTWA is a strong independent predictor of MACE in ICD recipients, and QTSD is a weaker predictor. In the prediction of MACE after ICD implantation, the highest predictive value was noted for abnormal MTWA combined with QTSD. Normal values of these two parameters were associated with a low probability of MACE. These results suggest that standardised MTWA evaluation can be useful for risk stratification in the clinical practice.
预测植入式心脏复律除颤器（ICD）后复发性恶性室性心律失常具有挑战性。微伏 T 波交替（MTWA）似乎是 ICD 受者发生此类事件的有希望的标志物。
评估 MTWA 和其他无创参数在预测 ICD 植入后主要心律失常事件中的预后意义。
这项前瞻性研究纳入了 155 名患者（121 名男性，年龄 59±11 岁），他们因心脏性猝死的二级预防而植入 ICD。所有患者在 ICD 植入前 3 天进行临床评估，包括估计射血分数、使用剑桥心脏 HearTwave 系统测量 MTWA、基于静息心电图确定校正 QT 间期（QTc）和 QT 离散度（QTd）。使用 24 小时动态心电图监测，确定心律失常、QT 间期、QT 动态、QT 变异性（QTSD）和心率变异性（HRV）时域参数。根据公认标准对 MTWA 结果进行分类，分为阳性、阴性或不确定。在进一步的分析中，将阳性和不确定的 MTWA 结果组合为异常或非阴性测试[MTWA+]，而阴性 MTWA 结果被认为是正常的[MTWA-]。在随访期间（平均 21.6±11.6 个月），记录主要心律失常心脏事件（MACE），定义为因恶性室性心律失常而死亡和/或需要消融和/或心脏移植。
在随访期间，17 名（11%）患者发生 MACE。与无 MACE 患者相比，植入 ICD 前出现异常 MTWA 的患者明显更多。多变量 Cox 回归分析确定异常 MTWA 和 QTSD 是 MACE 的独立危险因素，风险比分别为 10.82（95%CI 9.76-11.88；p〈0.05）和 1.08（95%CI 1.05-1.08）。在随访期间，MTWA 结果（异常与正常 MTWA）显示出显著的 MACE 无事件生存率差异（p〈0.001）。正常 MTWA 对 MACE 的阴性预测值为 98.6%。当同时结合 MTWA 和 QTSD 时，阳性预测值增加至 35%，灵敏度为 82%，特异性为 81%。这两项检查结果正常的 MACE 概率为 2.3%。
异常 MTWA 是 ICD 受者 MACE 的强独立预测因子，而 QTSD 是较弱的预测因子。在预测 ICD 植入后 MACE 时，异常 MTWA 结合 QTSD 的预测价值最高。这两个参数的正常值与 MACE 的低概率相关。这些结果表明，标准化的 MTWA 评估可用于临床实践中的风险分层。
