Cohen Richard J
Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge 02142, USA.
Card Electrophysiol Rev. 2003 Dec;7(4):438-42. doi: 10.1023/B:CEPR.0000023161.35685.68.
The MADIT-II study (Moss et al., N Engl J Med 2002;346:877-883) demonstrated that implantation of a cardioverter/defibrillator (ICD) reduced mortality from 19.8% to 14.2% during 20 months of follow-up in patients with prior myocardial infarction and left ventricular ejection fraction <or=0.30. Concerns have been raised both about the cost and potential morbidity of implanting ICDs in a large group of patients when only a small fraction of the patients would be expected to benefit from the treatment. This concern has given rise to the hope that an effective means of risk stratifying the MADIT-II population might be developed so that ICD therapy can be directed to only those patients who are at significant risk and thus likely to benefit from treatment for purposes of primary prevention of arrhythmic death. Electrophysiology study (EPS) is probably not suitable for this purpose because of its established relatively high false negative rate and because it is itself an invasive procedure. QRS width has been proposed for this purpose but prospective data demonstrating its effectiveness in stratifying the MADIT-II population for risk of arrhythmic death are absent. Initial data suggest that microvolt T-wave alternans (MTWA) testing does appear to be a suitable candidate for risk stratifying the MADIT-II population. These data indicate that approximately 30% of the MADIT-II population test negative for MTWA and that these patients are at extremely low risk for sudden cardiac death and cardiac arrest. Furthermore, MTWA is an inexpensive non-invasive test which can be repeated over time to monitor whether a patient who initially tests negative develops arrhythmic risk with the progression of the underlying disease. As studies of MTWA testing in the MADIT-II population come to publication, a database will likely be formed which will establish MTWA as an effective means of stratifying the MADIT-II population. ICD therapy may not be indicated in patients who test MTWA negative, and conversely the remaining patients may enjoy a greater mortality benefit than that observed in the MADIT-II trial. Furthermore, widespread MTWA testing might have the further benefit in those patients who do not test negative of serving as a call to action to referring physicians to direct those patients to ICD therapy, thereby greatly increasing the number of appropriate patients who actually receive potentially life saving therapy.
MADIT-II研究（莫斯等人，《新英格兰医学杂志》2002年；346:877 - 883）表明，对于既往有心肌梗死且左心室射血分数≤0.30的患者，植入心脏复律除颤器（ICD）可使20个月随访期间的死亡率从19.8%降至14.2%。当预计只有一小部分患者能从治疗中获益时，在一大群患者中植入ICD的成本和潜在发病率引发了人们的担忧。这种担忧促使人们希望能开发出一种对MADIT-II研究人群进行风险分层的有效方法，以便ICD治疗仅针对那些有显著风险、因而可能从心律失常性死亡一级预防治疗中获益的患者。由于其既定的相对较高的假阴性率且本身是一种侵入性操作，电生理检查（EPS）可能不适合用于此目的。有人提出用QRS波宽度来进行此操作，但缺乏前瞻性数据证明其在对MADIT-II研究人群进行心律失常性死亡风险分层方面的有效性。初步数据表明，微伏级T波交替（MTWA）检测似乎确实是对MADIT-II研究人群进行风险分层的合适选择。这些数据表明，MADIT-II研究人群中约30%的患者MTWA检测呈阴性，这些患者发生心源性猝死和心脏骤停的风险极低。此外，MTWA是一种廉价的非侵入性检测方法，可随时间重复进行，以监测最初检测为阴性的患者是否会随着基础疾病的进展而出现心律失常风险。随着在MADIT-II研究人群中进行MTWA检测的研究成果发表，可能会形成一个数据库，这将确立MTWA作为对MADIT-II研究人群进行分层的有效方法。MTWA检测呈阴性的患者可能无需进行ICD治疗，相反，其余患者可能比MADIT-II试验中观察到的有更大的死亡率获益。此外，广泛开展MTWA检测可能对那些检测结果为非阴性的患者还有进一步的益处，即促使转诊医生采取行动，指导这些患者接受ICD治疗，从而大幅增加实际接受可能挽救生命治疗的合适患者数量。
