Sverrisdóttir Y B, Rundqvist B, Elam M
Department of Clinical Neurophysiology, Sahlgren University Hospital, Göteborg, Sweden.
Clin Auton Res. 1998 Apr;8(2):95-100. doi: 10.1007/BF02267819.
Microneurographically recorded sympathetic outflow to the human muscle vascular bed is traditionally quantified by identifying pulse-synchronous bursts of impulses in a mean voltage neurogram and expressing them in terms of bursts per minute (burst frequency) or bursts per 100 heart beats (burst incidence). As both these measures show large inter-individual differences in resting healthy subjects, a problem arises when comparing sympathetic traffic in cross-sectional studies, making moderate differences in muscle sympathetic nerve activity (MSA) between groups difficult to identify. Absolute measures of the strength of the sympathetic discharges (burst amplitude or area) can also be evaluated. However, as they critically depend on the proximity of the microelectrode to the recorded fibres, such measures cannot be used for interindividual comparisons. The aim of the present study was to evaluate the use of relative burst amplitude spectra for quantification of MSA, describing the proportion of small vs large bursts in a neurogram. We recorded MSA in 18 patients with mild to moderate congestive heart failure (CHF) (New York Heart Association functional classes I-IIIA) and 18 matched healthy controls. Sympathetic activity was expressed as burst frequency, burst incidence and burst amplitude spectra. When comparing the traditional burst counts between the groups (presented as the median and 25th-75th percentiles) there was a tendency towards higher MSA in CHF patients, but the difference was not significant (42 (34-52) vs 53 (41-63) bursts/min, 62 (51-78) vs 69 (52-84) bursts/100 heart beats, both ns). Relative burst amplitude spectra, on the other hand, were clearly shifted to the right in the CHF group compared to the control group (median burst amplitudes 42 (34-45) vs 30 (28-35), P = 0.0002). Relative burst amplitude spectra thus appear to provide a more sensitive indicator of altered MSA than traditional burst counts. The right-ward shift of these spectra may suggest that sympatho-excitation occurs early in the development of CHF.
传统上，通过在平均电压神经图中识别与脉搏同步的脉冲爆发，并以每分钟爆发次数（爆发频率）或每100次心跳的爆发次数（爆发发生率）来量化通过微神经图记录的人体肌肉血管床的交感神经输出。由于这两种测量方法在静息健康受试者中显示出较大的个体间差异，因此在横断面研究中比较交感神经活动时会出现问题，使得难以识别组间肌肉交感神经活动（MSA）的适度差异。也可以评估交感神经放电强度的绝对测量值（爆发幅度或面积）。然而，由于它们严重依赖于微电极与记录纤维的接近程度，因此这些测量方法不能用于个体间比较。本研究的目的是评估使用相对爆发幅度谱来量化MSA，描述神经图中小爆发与大爆发的比例。我们记录了18例轻度至中度充血性心力衰竭（CHF）（纽约心脏协会功能分级I-IIIA）患者和18例匹配的健康对照者的MSA。交感神经活动以爆发频率、爆发发生率和爆发幅度谱表示。当比较两组之间的传统爆发计数（以中位数和第25-75百分位数表示）时，CHF患者的MSA有升高的趋势，但差异不显著（42（34-52）次/分钟 vs 53（41-63）次/分钟，62（51-78）次/100次心跳 vs 69（52-84）次/100次心跳，均无统计学意义）。另一方面，与对照组相比，CHF组的相对爆发幅度谱明显向右偏移（中位数爆发幅度42（34-45） vs 30（28-35），P = 0.0002）。因此，相对爆发幅度谱似乎比传统的爆发计数提供了更敏感的MSA改变指标。这些谱的向右偏移可能表明交感神经兴奋在CHF发展的早期就已发生。
