School of Medicine, The University of Queensland, Brisbane, Australia.
J Cardiovasc Electrophysiol. 2013 Mar;24(3):305-13. doi: 10.1111/jce.12039. Epub 2012 Dec 4.
QT Variability and Sympathetic Dysinnervation.
The mechanism of adverse prognosis attributable to proarrhythmic cardiac sympathetic dysinnervation in patients with type 2 diabetes is incompletely understood. This study sought the association of cardiac sympathetic dysinnervation with temporal instability of ventricular repolarization assessed by beat-to-beat QT interval variability.
(123) I-metaiodobenzylguanidine ((123) I-MIBG) scintigraphy was analyzed in 31 type 2 diabetic patients for cardiac sympathetic dysinnervation (4-hour heart-to-mediastinum ratio <1.8) and regional sympathetic integrity and washout rate (from 15-minute (123) I-MIBG uptake). Relative QT variability was defined from a continuous 5-minute ECG in the supine position (n = 31) and standing position (subgroup; n = 15) by the log ratio of absolute QT variability (QT variance divided by the mean QT interval squared) to heart rate (HR) variability (HR variance divided by the mean HR squared). Patients with (n = 16; 52%) versus without cardiac sympathetic dysinnervation demonstrated higher relative QT variability in the supine position (P < 0.001), owing to lower HR variability. However, on standing, absolute QT variability was significantly raised in these patients (P = 0.009) despite similar HR variability in the 2 groups. Correlations of heart-to-mediastinum ratio with standing QT variability (relative [r =-0.63, P = 0.013] and absolute [r =-0.79, P = 0.001]) were superior to corresponding supine measures (relative [r =-0.47, P = 0.008] and absolute [P = NS]). No associations of QT variability with washout rate or regional (123) I-MIBG uptake were identified.
Elevated QT variability is associated with cardiac sympathetic dysinnervation in type 2 diabetes and may contribute to adverse prognosis. Moreover, QT variability may be more specific for cardiac sympathetic innervation when measured in the context of sympathetic activation. (J Cardiovasc Electrophysiol, Vol. 24, pp. 305-313, March 2013).
QT 可变性和交感神经功能障碍。
导致 2 型糖尿病患者心律失常性心脏交感神经支配不良的不良预后机制尚不完全清楚。本研究旨在探讨心脏交感神经支配不良与通过逐搏 QT 间期变异性评估的心室复极时间的瞬时不稳定性之间的关系。
对 31 例 2 型糖尿病患者进行了 123I-间位碘苄胍（123I-MIBG）闪烁显像分析，以评估心脏交感神经支配不良（4 小时心脏与纵隔比值＜1.8）和区域性交感神经完整性及洗脱率（从 15 分钟摄取的 123I-MIBG）。通过在仰卧位（n=31）和直立位（亚组；n=15）连续 5 分钟心电图，以绝对 QT 变异性（QT 方差除以 QT 间期平方的均值）与心率（HR）变异性（HR 方差除以 HR 平方的均值）的对数比来定义相对 QT 变异性。与无心脏交感神经支配不良的患者（n=16；52%）相比，这些患者在仰卧位时的相对 QT 变异性更高（P＜0.001），这是由于 HR 变异性降低所致。然而，在站立位时，尽管两组的 HR 变异性相似，但这些患者的绝对 QT 变异性明显升高（P=0.009）。心脏与纵隔比值与站立时 QT 变异性的相关性（相对[ r=-0.63，P=0.013]和绝对[ r=-0.79，P=0.001]）优于仰卧位时的相应测量值（相对[ r=-0.47，P=0.008]和绝对[P=NS]）。QT 变异性与洗脱率或区域性 123I-MIBG 摄取之间没有相关性。
在 2 型糖尿病中，QT 变异性升高与心脏交感神经支配不良有关，可能导致不良预后。此外，当在交感神经激活的情况下测量时，QT 变异性可能更能特异性地反映心脏交感神经支配。（J 心血管电生理学，第 24 卷，第 305-313 页，2013 年 3 月）。
