Baumert Mathias, Lambert Gavin W, Dawood Tye, Lambert Elisabeth A, Esler Murray D, McGrane Mariee, Barton David, Nalivaiko Eugene
School of Electrical and Electronic Engineering, Centre for Biomedical Engineering, University of Adelaide, Adelaide, Australia.
Am J Physiol Heart Circ Physiol. 2008 Sep;295(3):H962-H968. doi: 10.1152/ajpheart.00301.2008. Epub 2008 Jul 3.
Suggestions were made that increased myocardial sympathetic activity is reflected by elevated QT variability (dynamic changes in QT interval duration). However, the relationship between QT variability and the amount of norepinephrine released from the cardiac sympathetic terminals is unknown. We thus attempted to assess this relationship. The study was performed in 17 subjects (12 with major depressive disorder and 5 with panic disorder). Cardiac norepinephrine spillover (measured by direct catheter technique coupled with norepinephrine isotope dilution methodology) was assessed before and 4 mo after treatment with selective serotonin reuptake inhibitor (SSRI) antidepressants. The distribution of the cardiac norepinephrine spillover was bimodal, with the majority of patients having values of < or =10 ng/min. There was a positive correlation between cardiac norepinephrine spillover and corrected QT interval (r = 0.7, P = 0.03) but not with any of the QT variability measures. However, in a subgroup of five patients who had high levels of cardiac norepinephrine spillover (>20 ng/min) a tendency for a strong positive correlation with variance of QT intervals (r = 0.9, P = 0.08) was observed. There were significant correlations between the severity of depression and QT variability indexes normalized to the heart rate [QTVi and QT interval/R-R interval (QT/RR) coherence] and between the severity of anxiety and the QT/RR residual and regression coefficient, respectively. Treatment with SSRI antidepressants substantially reduced depression score but did not affect any of the QT variability indexes. We conclude that in depression/panic disorder patients with near-normal cardiac norepinephrine levels QT variability is not correlated with cardiac norepinephrine spillover and is not affected by treatment with SSRI.
有人提出，QT变异性增加（QT间期持续时间的动态变化）反映了心肌交感神经活动增强。然而，QT变异性与心脏交感神经末梢释放的去甲肾上腺素量之间的关系尚不清楚。因此，我们试图评估这种关系。该研究对17名受试者进行（12名患有重度抑郁症，5名患有惊恐障碍）。在用选择性5-羟色胺再摄取抑制剂（SSRI）抗抑郁药治疗前及治疗4个月后，评估心脏去甲肾上腺素溢出（通过直接导管技术结合去甲肾上腺素同位素稀释法测量）。心脏去甲肾上腺素溢出的分布呈双峰状，大多数患者的值≤10 ng/分钟。心脏去甲肾上腺素溢出与校正QT间期呈正相关（r = 0.7，P = 0.03），但与任何QT变异性测量指标均无相关性。然而，在5名心脏去甲肾上腺素溢出水平较高（>20 ng/分钟）的患者亚组中，观察到与QT间期方差呈强正相关的趋势（r = 0.9，P = 0.08）。抑郁严重程度与心率标准化的QT变异性指标[QT变异指数（QTVi）和QT间期/R-R间期（QT/RR）相干性]之间，以及焦虑严重程度与QT/RR残差和回归系数之间分别存在显著相关性。用SSRI抗抑郁药治疗可显著降低抑郁评分，但不影响任何QT变异性指标。我们得出结论，在心脏去甲肾上腺素水平接近正常的抑郁症/惊恐障碍患者中，QT变异性与心脏去甲肾上腺素溢出无关，且不受SSRI治疗的影响。
