Fleisher L A, Pincus S M, Rosenbaum S H
Yale University School of Medicine, Yale-New Haven Hospital, Connecticut.
Anesthesiology. 1993 Apr;78(4):683-92. doi: 10.1097/00000542-199304000-00011.
Instantaneous changes in the heart rate, i.e., heart rate variation, traditionally have been quantified by the standard deviation of a series of intervals between successive heart beats. Approximate entropy provides another measure of variability by calculating the logarithmic likelihood that patterns that are similar remain similar on the next incremental comparisons. Approximate entropy is a nonnegative number that will distinguish data sets by their amount of regularity, with larger numbers indicating more randomness. We hypothesized that a decrease in the approximate entropy of heart rate would be associated with postoperative ventricular dysfunction (e.g., myocardial infarction, unstable angina, congestive heart failure, prolonged inotropic support).
Twenty-three high-risk noncardiac patients were continuously monitored by ambulatory electrocardiographic recorders from the evening before surgery up to 80 h during the postoperative period: 9 demonstrated postoperative ventricular dysfunction, and 14 had an uncomplicated postoperative course. Hourly approximate entropy average values were calculated.
Approximate entropy was high (> 0.7) in all but two patients preoperatively. Postoperative approximate entropy <0.55 had a sensitivity of 88% and a specificity of 71% for being associated with postoperative ventricular dysfunction; preoperative approximate entropy values were not significantly different between the two groups.
These results suggest that changes in approximate entropy can distinguish between patients who sustained poor outcome and those who had an uncomplicated course.
心率的瞬间变化，即心率变异性，传统上通过连续心跳之间一系列间期的标准差来量化。近似熵通过计算在后续增量比较中相似模式保持相似的对数似然性，提供了另一种变异性度量。近似熵是一个非负数，它将根据数据集的规则程度来区分它们，数值越大表明随机性越高。我们假设心率近似熵的降低与术后心室功能障碍（如心肌梗死、不稳定型心绞痛、充血性心力衰竭、延长的正性肌力支持）有关。
23例高危非心脏手术患者从术前晚开始通过动态心电图记录仪进行连续监测，直至术后80小时：9例出现术后心室功能障碍，14例术后过程顺利。计算每小时的近似熵平均值。
除两名患者外，术前所有患者的近似熵均较高（>0.7）。术后近似熵<0.55与术后心室功能障碍相关的敏感性为88%，特异性为71%；两组术前近似熵值无显著差异。
这些结果表明，近似熵的变化可以区分预后不良的患者和术后过程顺利的患者。
