心率震荡  Heart Rate Turbulence

作者：方 宇

What is HRT?什么是 心率震荡？

HRT - Heart Rate Turbulence - is the physiological, bi-phasic response of the sinus node to premature ventricular contractions. It consists of a short initial acceleration followed by a deceleration of the heart rate. HRT can be quantified by two numerical parameters, namely the Turbulence Onset and the Turbulence Slope. The underlying mechanisms of HRT have not been fully identified. HRT is most probably an autonomous baro-reflex. The premature ventricular contraction causes a brief disturbance of the arterial blood pressure (low amplitude of the premature beat, high amplitude of the ensuing normal beat). When the autonomic control system is intact, this fleeting change is registered immediately with an instantaneous response in the form of HRT. If the autonomic control system is impaired, this reaction is either weakened or entirely missing.

    HRT－ 心率震荡－是窦房结对于室性期前收缩的一种双向的生理反应，它表现为一个短暂的初期心率加速和紧接着的心率减速，HRT可以由2个参数进行定量的表达，这2个参数是振荡阶跃（TO）和振荡斜率（TS）。虽然HRT的内在机理尚不十分清楚，但是HRT极有可能是一种自然存在的生理指数。室性早搏引起动脉血压短暂的紊乱（低振幅的早搏和紧随其后的高振幅的正常心搏），当人体的自主调节功能完好时，这种短暂的变化会以心率震荡HRT的形式立即得到体现，当人体的自主调节功能受损时，这种变化会减弱甚至消失。

HRT is suitable for assessing the risk following myocardial infarction. After analysis of the data of more than 3,000 post-infarction patients it was established that HRT is - independent of other risk predictors - the most powerful ECG-related risk predictor. The predictive value of HRT is comparable with that of the ejection fraction of the left ventricle.

    HRT适用于心梗之后的危险度评估。在研究了多达3000例心梗恢复期患者的资料之后，可以确认，HRT是独立于其他危险预测指标的一个强有力的心电预测指标， HRT的预测价值可以与左室射血指数相比。

Calculation计算

Quantification of HRT定量计算HRT

Turbulence Onset (TO) is the percentage difference between the heart rate immediately following PVC and the heart rate immediately preceding PVC. It is calculated using the equation

TO = ((RR1 + RR2) - (RR-2 + RR-1)) / (RR-2 + RR-1) * 100

with RR-2 and RR-1 being the first two normal intervals preceding the PVC and RR1 and RR2 the first two normal intervals following the PVC. Initially, TO is determined for each individual PVC, followed by the determination of the average value of all individual measurements. Positive values for Turbulence Onset indicate deceleration, negative values indicate acceleration of the sinus rhythm.

The Turbulence Slope (TS) corresponds to the steepest slope of the linear regression line for each sequence of five consecutive normal intervals in the local tachogram. The Turbulence Slope calculations are based on the averaged tachogram and expressed in ms per RR interval.

    振荡阶跃TO指数是用百分比表示的室性早搏之后的正常心搏的间期与室性早搏之前的正常心搏的间期之差，计算公式如下：

TO = ((RR1 + RR2) - (RR-2 + RR-1)) / (RR-2 + RR-1) * 100

    其中，RR-2和RR-1代表室性早搏之前的2个正常心搏的RR间期，RR1和RR2代表室性早搏之后的2个正常心搏的RR间期，先计算出单个室性早搏的TO值，然后对所有室性早搏的TO值进行平均，HRT为正时，代表窦性心率减缓，HRT为付时，代表窦性心率加快。

    振荡斜率TS指数是对连续的5个正常心搏的RR间期的阶梯图进行线性回归处理，取其中最大的斜率。计算振荡斜率TS时，以平均的阶梯图为基础，TS值以每个RR间期多少毫秒（ms）为计量单位。

Filters选择过滤

The algorithm for HRT quantificationcan only deliver usable results if the triggering event was a true PVC (and not an artefact, T-wave or similar). In addition it must be ensured that the sinus rhythm immediately preceding and following the PVC is free from arrhythmia, artefacts and false classifications. In order to fulfill these requirements, we use filters which exclude RR intervals with the following characteristics from the HRT calculation:

• < 300 ms

• > 2000 ms

• > 200 ms difference to the preceding sinus interval

• > 20% difference to the reference interval (mean of the 5 last sinus intervals)

In addition, we limit the HRT calculations to PVCs with:

• a minimum prematurity of 20% and

• a post-extrasystole interval which is at least 20% longer than the normal interval.

• 　

    只有对真正的室性早搏（排除把伪差、T波等当作室性早搏的情况）作为研究对象时，使用HRT算法才能得到有用的结果，同时，选定的这个室性早搏之前的心搏必须是一个正常的窦性心搏，为了满足这些要求，在进行HRT计算时，有必要排除具有以下特征的RR间期：

• < 300 ms

• > 2000 ms

• > 200 ms （与前一窦性心搏的间期之差）

• > 20%（与前5个窦性心搏的平均间期之差）

另外，只采用具有以下特征的室性早搏:

• 最小提早率为20%，并且

• 早搏之后的代偿间期至少超过正常间期的20%

Turbulence Onset振荡阶跃

Turbulence Onset 振荡阶跃

is the percentage difference between the average value of the first two normal intervals following the PVC and of the last two normal intervals preceding the PVC. Initially, TO is determined for each individual PVC, followed by the determination of the average value of all individual measurements.

    振荡阶跃TO：是室性早搏之后的前2个正常心搏间期与室性早搏之前的后2个正常心搏间期之差，用百分比表示。先计算出单个室性早搏的TO值，然后对所有室性早搏的TO值进行平均。

Turbulence Slope振荡斜率

Turbulence Slope 振荡斜率

is the steepest slope of a linear regression line through five consecutive measurement points in the averaged tachogram. The Turbulence Slope calculations are based on the averaged tachogram and expressed in ms per RR interval.

    振荡斜率TS：是对连续的5个正常心搏的RR间期的阶梯图进行线性回归处理，取其中最大的斜率。计算振荡斜率TS时，以平均的阶梯图为基础，TS值以每个RR间期多少毫秒（ms）为计量单位。

Case病例

Cas1 病例1

    Holter心电图片断，急性心梗2周后，患者状况良好，无并发症。“阶梯图”上，室性早搏之后的RR间期缩短，几个心搏之后，发生了相反的变化，第6至第12个心搏的RR间期逐渐延长。最终回归初始状态。

Cas2 病例2

    Holter心电图片断，急性心梗3月后死亡。“阶梯图”上几乎看不到 心率震荡。

    注：美高仪公司2004年3月升级的ECGLAB TOP版HOLTER软件具有“心率震荡”功能。