Centre for Heart Rhythm Disorders, The University of Adelaide and Royal Adelaide Hospital, Adelaide, South Australia, Australia;
Am J Physiol Heart Circ Physiol. 2013 Oct 15;305(8):H1181-8. doi: 10.1152/ajpheart.00448.2013. Epub 2013 Aug 9.
QT variability (QTV) signifies repolarization lability, and increased QTV is a risk predictor for sudden cardiac death. The aim of the present study was to investigate the role of autonomic nervous system activity on QTV. This study was performed in 29 subjects: 10 heart failure (HF) patients with spontaneous ventricular tachycardia [HFVT(+)], 10 HF patients without spontaneous VT [HFVT(-)], and 9 subjects with structurally normal hearts (HNorm). The beat-to-beat QT interval was measured on 3-min records of surface ECGs at baseline and during interventions (atrial pacing and esmolol, isoprenaline, and atropine infusion). Variability in QT intervals was expressed as the SD of all QT intervals (SDQT). The ratio of the SDQT to SD of RR intervals (SDRR) was calculated as an index of QTV normalized to heart rate variability. There was a trend toward a higher baseline SDQT-to-SDRR ratio in the HFVT(+) group compared with the HFVT(-) and HNorm groups (P = 0.09). SDQT increased significantly in the HFVT(+) and HFVT(-) groups compared with the HNorm group during fixed-rate atrial pacing (P = 0.008). Compared with baseline, isoprenaline infusion increased SDQT in HNorm subjects (P = 0.02) but not in HF patients. SDQT remained elevated in the HFVT(+) group relative to the HNorm group despite acute β-adrenoceptor blockade with esmolol (P = 0.02). In conclusion, patients with HF and spontaneous VT have larger fluctuations in beat-to-beat QT intervals. This appears to be a genuine effect that is not solely a consequence of heart rate variation. The effect of acute autonomic nervous system modulation on QTV appears to be limited in HF patients.
QT 变异（QTV）表示复极不稳定，增加 QTV 是心脏性猝死的风险预测因子。本研究旨在探讨自主神经系统活动对 QTV 的作用。该研究在 29 名受试者中进行：10 名心力衰竭（HF）伴有自发性室性心动过速的患者[HFVT（+）]、10 名无自发性 VT 的 HF 患者[HFVT（-）]和 9 名结构正常心脏的受试者（HNorm）。在基线和干预期间（心房起搏和艾司洛尔、异丙肾上腺素和阿托品输注），在 3 分钟的体表心电图记录中测量逐搏 QT 间期。QT 间期变异性用 QT 间期的标准差（SDQT）表示。QT 间期标准差与 RR 间期标准差的比值（SDRR）被计算为 QT 变异性归一化至心率变异性的指数。与 HFVT（-）和 HNorm 组相比，HFVT（+）组的基线 SDQT-to-SDRR 比值有升高的趋势（P = 0.09）。与 HNorm 组相比，HFVT（+）和 HFVT（-）组在固定频率心房起搏时 SDQT 显著增加（P = 0.008）。与基线相比，异丙肾上腺素输注使 HNorm 组的 SDQT 增加（P = 0.02），但 HF 患者没有增加。尽管用艾司洛尔进行急性β肾上腺素能受体阻断，但 HFVT（+）组的 SDQT 仍高于 HNorm 组（P = 0.02）。结论：HF 伴自发性 VT 的患者存在逐搏 QT 间期更大的波动。这似乎是一种真实的效应，不仅仅是心率变化的结果。急性自主神经系统调节对 QTV 的影响在 HF 患者中似乎是有限的。
