Woo M A, Moser D K, Stevenson L W, Stevenson W G
School of Nursing, University of California, Los Angeles, USA.
Am J Crit Care. 1997 Sep;6(5):348-54.
The 6-minute walk and heart rate variability have been used to assess mortality risk in patients with heart failure, but their relationship to each other and their usefulness for predicting mortality at 1 year are unknown.
To assess the relationships between the 6-minute walk test, heart rate variability, and 1-year mortality.
A sample of 113 patients in advanced stages of heart failure (New York Heart Association Functional Class III-IV, left ventricular ejection < 0.25) were studied. All 6-minute walks took place in an enclosed, level, measured corridor and were supervised by the same nurse. Heart rate variability was measured by using (1) a standard-deviation method and (2) Poincaré plots. Data on RR intervals obtained by using 24-hour Holter monitoring were analyzed. Survival was determined at 1 year after the Holter recording.
The results showed no significant associations between the results of the 6-minute walk and the two measures of heart rate variability. The results of the walk were related to 1-year mortality but not to the risk of sudden death. Both measures of heart rate variability had significant associations with 1-year mortality and with sudden death. However, only heart rate variability measured by using Poincaré plots was a predictor of total mortality and risk of sudden death, independent of left ventricular ejection fraction, serum levels of sodium, results of the 6-minute walk test, and the standard-deviation measure of heart rate variability.
Results of the 6-minute walk have poor association with mortality and the two measures of heart rate variability in patients with advanced-stage heart failure and a low ejection fraction. Further studies are needed to determine the optimal clinical usefulness of the 6-minute walk and heart rate variability in patients with advanced-stage heart failure.
6分钟步行试验和心率变异性已被用于评估心力衰竭患者的死亡风险，但它们之间的关系以及对预测1年死亡率的作用尚不清楚。
评估6分钟步行试验、心率变异性与1年死亡率之间的关系。
对113例晚期心力衰竭患者（纽约心脏协会心功能分级III-IV级，左心室射血分数<0.25）进行研究。所有6分钟步行试验均在封闭、平坦、有测量标记的走廊内进行，并由同一名护士监督。心率变异性采用（1）标准差法和（2）庞加莱图进行测量。对使用24小时动态心电图监测获得的RR间期数据进行分析。在动态心电图记录后1年确定生存率。
结果显示，6分钟步行试验结果与两种心率变异性测量方法之间无显著相关性。步行试验结果与1年死亡率相关，但与猝死风险无关。两种心率变异性测量方法均与1年死亡率和猝死显著相关。然而，只有采用庞加莱图测量的心率变异性是总死亡率和猝死风险的预测指标，独立于左心室射血分数、血清钠水平、6分钟步行试验结果以及心率变异性的标准差测量值。
在晚期心力衰竭且射血分数低的患者中，6分钟步行试验结果与死亡率及两种心率变异性测量方法的相关性较差。需要进一步研究以确定6分钟步行试验和心率变异性在晚期心力衰竭患者中的最佳临床应用价值。
