Modern noninvasive risk stratification in primary prevention of sudden cardiac death.

OBJECTIVE: Since the publication of MADIT II and SCD-HeFT, an implantable cardioverter defibrillator (ICD) for primary prevention represents an established, guideline-implemented therapeutic strategy. Facing such an enormous amount of potential ICD recipients, the identification of an effective risk stratification remains crucial.
METHODS: This article reviews the tools of noninvasive risk stratification which are currently used and defines an optimal test configuration. This analysis focuses on the capacity of the tests regarding to the negative predictive value to reduce unneeded devices.
RESULTS: Presently, no marker exists in terms of risk stratification which qualifies itself as gold standard. However, encouraging results can be stated for microvolt T-wave alternans (mTWA) providing a high negative predictive value. An increased QT variability (QTv) and an impaired deceleration capacity are associated with an excellent positive predictive value. Currently, only mTWA and QTv seem to be suitable in ischemic and non-ischemic disease, but available data, especially in non-ischemic patients, are too small to provide clear recommendations.
CONCLUSION: The most hopeful tools at hand in modern noninvasive risk evaluation of sudden cardiac death in primary prevention seem to be mTWA and QTv. These noninvasive methods provide the best negative predictive or positive predictive value of all known parameters, while a higher rate of complete coronary revascularizations in acute coronary syndromes might also reduce the number of fatal arrhythmic events and therefore complicate the invention of an ideal risk marker.