Fei L, Gill J S, Katritsis D, Camm A J
Department of Cardiological Sciences, St George's Hospital Medical School, London.
Br Heart J. 1993 Apr;69(4):311-4. doi: 10.1136/hrt.69.4.311.
Idiopathic ventricular tachycardia (VT) occurs in a small but important subset of patients without clinically overt heart disease. The mechanism of the arrhythmogenesis remains unclear in these patients. This study examines modulation of the QT interval by the autonomic nervous system in a group of patients with idiopathic ventricular tachycardia.
Cardiac autonomic activity and ventricular repolarisation were studied in 27 patients with VT associated with a clinically normal heart (NHVT) and in 20 normal subjects. All the patients were in sinus rhythm, had normal atrioventricular conduction, and were in a drug free state. Cardiac efferent autonomic activity was measured by spectral analysis of heart rate variability from 24 hour ambulatory electrocardiograms on a Holter analysis system (Marquette). Ventricular repolarisation was evaluated by measuring the QT intervals from the same 24 hour Holter tapes at one hour intervals.
There was no difference in any of the QT interval variables including the maximum, minimum, and mean of both the QT interval and its corrected value (Bazett's formula) between patients with NHVT and normal subjects. The high frequency component (0.04-0.15 Hz) of heart rate variability was significantly decreased in patients with NHVT compared with normal subjects (16 (8) v 21 (12) ms, p < 0.05). There was a significant correlation between the spectral variables of heart rate variability and the mean, maximal, and minimal QT intervals in normal subjects, whereas the relation was lost in patients with NHVT. No difference was found in mean heart rate between normal subjects and patients with NHVT (70 (9) v 72 (13) beats/min, NS).
The high frequency component of heart rate variability is significantly decreased and the relation of QT interval to heart rate variability is significantly altered in patients with NHVT as compared with normal subjects. These findings suggest that abnormal modulation of the QT interval by the autonomic nervous system may play an important part in the arrhythmogenesis of NHVT. This might result from impaired vagal efferent cardiac activity in these patients.
特发性室性心动过速（VT）发生于一小部分但很重要的无明显临床心脏病的患者中。这些患者心律失常的发生机制仍不清楚。本研究探讨自主神经系统对一组特发性室性心动过速患者QT间期的调节作用。
对27例伴有临床心脏正常的室性心动过速患者（NHVT）和20名正常受试者进行心脏自主神经活动和心室复极研究。所有患者均为窦性心律，房室传导正常，且处于无药物状态。通过在动态心电图分析系统（Marquette）上对24小时动态心电图进行心率变异性频谱分析来测量心脏传出自主神经活动。通过以1小时为间隔从同一24小时动态心电图磁带中测量QT间期来评估心室复极。
NHVT患者与正常受试者之间在任何QT间期变量上均无差异，包括QT间期及其校正值（Bazett公式）的最大值、最小值和平均值。与正常受试者相比，NHVT患者心率变异性的高频成分（0.04 - 0.15Hz）显著降低（16（8）对21（12）ms，p < 0.05）。正常受试者心率变异性的频谱变量与平均、最大和最小QT间期之间存在显著相关性，而在NHVT患者中这种关系消失。正常受试者与NHVT患者之间的平均心率无差异（70（9）对72（13）次/分钟，无显著性差异）。
与正常受试者相比，NHVT患者心率变异性的高频成分显著降低，且QT间期与心率变异性的关系显著改变。这些发现提示自主神经系统对QT间期的异常调节可能在NHVT的心律失常发生中起重要作用。这可能是由于这些患者迷走神经传出心脏活动受损所致。
