ICD Shock, Not Ventricular Fibrillation, Causes Elevation of High Sensitive Troponin T after Defibrillation Threshold Testing—The Prospective, Randomized, Multicentre TropShock-Trial

Background
The placement of an implantable cardioverter defibrillator (ICD) has become routine practice to protect high risk patients from sudden cardiac death. However, implantation-related myocardial micro-damage and its relation to different implantation strategies are poorly characterized.
Methods
A total of 194 ICD recipients (64±12 years, 83% male, 95% primary prevention of sudden cardiac death, 35% cardiac resynchronization therapy) were randomly assigned to one of three implantation strategies: (1) ICD implantation without any defibrillation threshold (DFT) testing, (2) estimation of the DFT without arrhythmia induction (modified “upper limit of vulnerability (ULV) testing”) or (3) traditional safety margin testing including ventricular arrhythmia induction. High-sensitive Troponin T (hsTnT) levels were determined prior to the implantation and 6 hours after.
Results
All three groups showed a postoperative increase of hsTnT. The mean delta was 0.031±0.032 ng/ml for patients without DFT testing, 0.080±0.067 ng/ml for the modified ULV-testing and 0.064±0.056 ng/ml for patients with traditional safety margin testing. Delta hsTnT was significantly larger in both of the groups with intraoperative ICD testing compared to the non-testing strategy (p≤0.001 each). There was no statistical difference in delta hsTnT between the two groups with intraoperative ICD testing (p = 0.179).
Conclusion
High-sensitive Troponin T release during ICD implantation is significantly higher in patients with intraoperative ICD testing using shock applications compared to those without testing. Shock applications, with or without arrhythmia induction, did not result in a significantly different delta hsTnT. Hence, the ICD shock itself and not ventricular fibrillation seems to cause myocardial micro-damage.
Trial Registration
ClinicalTrials.gov NCT01230086

背景
植入式心脏复律除颤器（implantable cardioverter defibrillator, ICD）已成为保护高危患者免于心源性猝死的常规临床操作。然而，与植入相关的心肌微损伤及其与不同植入策略的关联，目前尚未得到充分表征。

方法
共计194名ICD植入患者（年龄64±12岁，男性占比83%，95%为心源性猝死一级预防人群，35%接受心脏再同步治疗）被随机分配至三种植入策略之一：(1) 未行任何除颤阈值（defibrillation threshold, DFT）测试的ICD植入；(2) 不诱导心律失常的DFT评估（改良“安全上限（upper limit of vulnerability, ULV）测试”）；(3) 包含室性心律失常诱导的传统安全边界测试。分别于植入前及植入后6小时检测高敏肌钙蛋白T（high-sensitive Troponin T, hsTnT）水平。

结果
三组患者术后均出现hsTnT水平升高。未行DFT测试组的平均hsTnT变化值为0.031±0.032 ng/ml，改良ULV测试组为0.080±0.067 ng/ml，传统安全边界测试组为0.064±0.056 ng/ml。术中行ICD测试的两组患者的hsTnT变化值均显著高于未测试组（两组均p≤0.001）；而术中行ICD测试的两组之间，hsTnT变化值无统计学差异（p=0.179）。

结论
与未行测试的患者相比，术中使用电击操作进行ICD测试的患者，其ICD植入期间的高敏肌钙蛋白T释放量显著更高。无论是否诱导心律失常，电击操作均未导致hsTnT变化值出现显著差异。由此可见，引发心肌微损伤的因素似乎是ICD电击本身，而非室性颤动。

临床试验注册
ClinicalTrials.gov NCT01230086