【正文】 TWave Alternans ? A number of observational cohort studies have been published that suggest that microvolt Twave alternans may work at least as well as electrophysiological testing for prediction of SCD or major arrhythmic events. ? Recent cohort studies that involved at least 100 pts found that Twave alternans was associated with substantially increased risk and predicted events as well as or better than other markers, including LVEF, EP testing, SAECG, BRS, and HRV. [1,2,3 ] ? Furthermore, Twave alternans predicted risk in pts with coronary artery disease and in pts with dilated cardiomyopathy.[2] MR, et al. J Am Coll Cardiol. 2020。由于其陰性預(yù)測值高，因此它在識別低危患者方面非常有效。為了明確心率變異性在心臟性猝死危險分層中是否有價值，還需要進(jìn)一步的研究。143:1085–1091. （二）室性早搏和非持續(xù)性室速 ? Patients with nonischemic cardiomyopathy are at increased risk of SCD and frequently have highgrade ventricular ectopy and NSVT [] ? In GESICA trial, which included a majority of pts with nonischemic cardiomyopathy, confirmed the prevalence of ventricular arrhythmias on AECG in pts with heart failure and LVEF 35%. NSVT was an independent predictor of mortality, but ventricular couplets appeared to be equally predictive.[3] Couplets and/or NSVT were detected in % of the study population, with a % mortality rate. The remaining %, without couplets or NSVT, had a lower mortality rate of %. J,et al. Chest. 1988。s de Luna A. Am Heart J. 1989。44:820–826. （四）心率變異性 ? 定義 : 心率變異性（ heart rate variability,HRV）是指逐次心動周期之間 的細(xì)微的時間變化及其規(guī)律。85:I77I91. （六）心室晚電位 ? 定義 :心室晚電位（ ventricular late potential， VLP）是指出現(xiàn)在 QRS波群終末部、 ST段內(nèi)的一種高頻、低振幅、多形性碎裂電活動。以往 TWA幅度為毫伏級（ mV），而新近 TWA幅度為微伏級（181。119:e391e479 2020 ACC/AHA 心衰指南 ? Approximately 50% to 70% of patients with low EF and symptomatic HF have episodes of nonsustained VT on routine ambulatory electrocardiographic monitoring。尚需進(jìn)一步的研究來確定這些參數(shù)的在 SCD危險性分層中的臨床意義。但尚需更多資料進(jìn)一步明確其臨床應(yīng)用價值。104:1911–1916. ? A phenomenon related to heart rate recovery is ventricular ectopy during recovery, which has also been hypothesized to reflect parasympathetic activity. Occurrence of frequent or severe ventricular ectopy during the first 5 minutes of recovery after exercise has been linked to risk of death in pts without and with heart failure and/or coronary artery disease.[1,2] JP, et al. N Engl J Med. 2020。 2020. 2 Adapted from Heikki et al. N Engl J Med, Vol. 345, No. 20, 2020. 3 Myerberg RJ. Heart Disease, A Textbook of Cardiovascular Medicine. 6th ed. P. 895. 一、心臟猝死的概況 Albert CM. Circulation. 2020。51:507–512. HC, et al. Circulation. 1996。107: 565–570. 長程心率變異性 ? In DINAMIT, 15 675 postMI pts who had decreased LVEF and low HRV (or elevated heart rate) were randomized to receive or not receive an was no significant difference in survival between the groups. ? Cammetal [147]studied 3717 postMi pts with left ventricular dysfunction and characterized them into low and highrisk groups on the basis of the triangular index of HRV. Although the trial was designed to examine the effects of an antiarrhythmic drug (azimilide) on survival, data on the prognostic importance of HRV were also reported. By multivariate analysis, low HRV increased risk of allcause mortality with a hazard ratio of (95% CI to )。 （七） QT 離散度 ? 定義 : QT間期離散度（