Sosnowski Maciej, Czyz Zbigniew, Tendera Michal
Third Division of Cardiology, Silesian Medical School, Ziolowa 47, 40-635 Katowice, Poland.
Eur J Heart Fail. 2002 Dec;4(6):737-43. doi: 10.1016/s1388-9842(02)00167-8.
Determinants of temporal lability in ventricular repolarisation are not fully recognised. We aimed to analyse the sources of RT variability by comparing normal subjects and patients after myocardial infarction (MI) with either depressed or preserved left ventricular (LV) function.
One hundred and nine patients (27 women, 82 men, aged 51 +/- 9 years) were divided into three groups: 24 patients (pts) with an uncomplicated angiographically proven coronary heart disease (CHD-group), 59 post-MI pts with preserved LV function (LVEF > 40%, PMI-N-group) and 26 post-MI pts with depressed LV function (LVEF < 40%, PMI-L-group). An ECG signal of low-noise 512 heartbeats was recorded using a computer-assisted amplifier (16 bit, 2 kHz). The onset and offset of the R-wave and T-wave were determined automatically. The magnitude of R-R and R-T variability was measured as the standard deviation of all intervals (SD-RR and SD-RT, ms, respectively). Their relationship was quantified by the correlation coefficient r(RT/RR). Power spectral density of RR or RT variability was estimated with the FFT (Welch's averaged periodogram, Hanning window) and frequency relation was quantified using a squared coherence spectrum (SCS). For all spectral and cross-spectral measurements two frequency ranges were considered: high (0.15-0.50 Hz, HF) and low (0.04-0.15 Hz, LF). Spectral power and SCS of RR and RT variability for both ranges (HF(RR), LF(RR), HF(RT), LF(RT), SCS(HF), SCS(LF)), and the ratios LF/HF(RR) and LF/HF(RT) were drawn for comparisons. The central frequency of HF(RR) was considered as the frequency of respiration (f(resp), Hz).
In the PMI-L group the SD-RT was significantly greater compared to the remaining groups and accounted for almost 10% of the SDRR. Also, the coefficient r(RT/RR) was weakest in this group. The spectral indices of RR variability were similar in all groups, while the greatest value of the HFRT was observed in the PMI-L group. The SCS(LF) was insignificant in this group, contrary to the CHD and PMI-N groups. Additionally, there were significant negative relationships between f(resp) and spectral indices of RT variability in PMI-patients with depressed LV function.
A greater beat-to-beat variation in RT interval duration along with increased power of its HF component indicates an important role of respiration in ventricular repolarisation control, while reduced time- and frequency RT-RR relationships seem to relate to an impaired process of ventricular duration adaptation.
心室复极时间变异性的决定因素尚未完全明确。我们旨在通过比较正常受试者以及心肌梗死（MI）后左心室（LV）功能减退或保留的患者，分析RT变异性的来源。
109例患者（27例女性，82例男性，年龄51±9岁）分为三组：24例经血管造影证实无并发症的冠心病患者（CHD组），59例MI后LV功能保留的患者（左心室射血分数[LVEF]>40%，PMI-N组）和26例MI后LV功能减退的患者（LVEF<40%，PMI-L组）。使用计算机辅助放大器（16位，2kHz）记录512次低噪声心跳的心电图信号。自动确定R波和T波的起始和终点。RR和RT变异性的大小分别以所有间期的标准差（SD-RR和SD-RT，毫秒）来衡量。它们之间的关系通过相关系数r（RT/RR）进行量化。RR或RT变异性的功率谱密度通过快速傅里叶变换（FFT，韦尔奇平均周期图，汉宁窗）进行估计，频率关系使用平方相干谱（SCS）进行量化。对于所有频谱和交叉频谱测量，考虑两个频率范围：高频（0.15-0.50Hz，HF）和低频（0.04-0.15Hz，LF）。绘制两个范围（HF（RR）、LF（RR）、HF（RT）、LF（RT）、SCS（HF）、SCS（LF））的RR和RT变异性的频谱功率和SCS，以及LF/HF（RR）和LF/HF（RT）的比值进行比较。HF（RR）的中心频率被视为呼吸频率（f（resp），Hz）。
与其余组相比，PMI-L组的SD-RT显著更大，几乎占SDRR 的10%。此外，该组的系数r（RT/RR）最弱。所有组的RR变异性频谱指数相似，而PMI-L组观察到HFRT的最大值。与CHD组和PMI-N组相反，该组的SCS（LF）无统计学意义。此外，LV功能减退的PMI患者中，f（resp）与RT变异性频谱指数之间存在显著负相关。
RT间期持续时间的逐搏变化更大以及其HF成分的功率增加表明呼吸在心室复极控制中起重要作用，而RT-RR时间和频率关系的减弱似乎与心室间期适应过程受损有关。
