Guzzetti Stefano, Spyrou Nicos, Rosen Stuart D, Mezzetti Silvia, Martinoli Elena, Foale Rodney A, Camici Paolo G
Università degli Studi Milano, Italy.
Basic Res Cardiol. 2002 Jan;97(1):97-104. doi: 10.1007/s395-002-8392-8.
The low frequency spectral component (LF; 0.04-0.15 Hz) of heart rate variability (HRV) is considered to be an index of sympathetic modulation of sinus node activity under physiological conditions, although the relationship is less clearly defined in non-physiological conditions. Several cardiovascular diseases are characterized by an absent or blunted 24-h pattern of the LF spectral component. The aim of the present study was to investigate the relationship between chronically increased neural sympathetic efferent drive to the heart, quantified in terms of downregulation of myocardial beta-receptors, and the 24-h power of the LF spectral component in patients after acute myocardial infarction.
In 24 patients, HRV was analyzed for a 24-h period, one month after an uncomplicated Q wave myocardial infarction. The following time domain measures and spectral components were calculated: mean RR, SDNN, SDANN, RMSSD, SDNN index, pNN50, and very low frequency (VLF), low frequency (LF) and high frequency (HF) spectral components. The density of beta-adrenoceptors was measured in vivo by positron emission tomography (PET) with 11-CGP-12177.
Post-AMI patients had normal plasma levels of adrenaline and noradrenaline (respectively 1.48 +/- 0.18 and 0.28 +/- 0.03 IU/L) but reduced myocardial beta-adrenoceptor density (6.86 +/- 0.24 pmol/g). Patients had similar heart rates but lower values of SDNN and SDANN compared with control subjects. The absolute and normalized power of the spectral components were similar in the two groups, but the usual day-night oscillation was blunted in patients. Moreover, the day-night change in the power of the LF spectral component was positively related (r = 0.51; p < 0.001) to the myocardial beta-adrenoceptor density.
The loss of the day-night oscillation of the LF spectral component appears to be a significant marker of sustained sympathetic over-activity in post-AMI patients.
心率变异性（HRV）的低频谱成分（LF；0.04 - 0.15赫兹）在生理条件下被认为是窦房结活动交感神经调节的一个指标，尽管在非生理条件下这种关系的界定不太明确。几种心血管疾病的特征是LF谱成分缺乏或减弱的24小时模式。本研究的目的是调查在急性心肌梗死后患者中，以心肌β受体下调来量化的心脏慢性神经交感传出驱动增加与LF谱成分的24小时功率之间的关系。
在24例患者中，于无并发症的Q波心肌梗死后1个月分析其24小时的HRV。计算了以下时域测量值和谱成分：平均RR、SDNN、SDANN、RMSSD、SDNN指数、pNN50，以及极低频（VLF）、低频（LF）和高频（HF）谱成分。通过用11 - CGP - 12177进行正电子发射断层扫描（PET）在体内测量β肾上腺素能受体的密度。
急性心肌梗死后患者的肾上腺素和去甲肾上腺素血浆水平正常（分别为1.48±0.18和0.28±0.03国际单位/升），但心肌β肾上腺素能受体密度降低（6.86±0.24皮摩尔/克）。与对照组相比患者心率相似，但SDNN和SDANN值较低。两组谱成分的绝对功率和标准化功率相似，但患者中通常的昼夜振荡减弱。此外，LF谱成分功率的昼夜变化与心肌β肾上腺素能受体密度呈正相关（r = 0.51；p < 0.001）。
LF谱成分昼夜振荡的丧失似乎是急性心肌梗死后患者持续交感神经过度活动的一个重要标志。
