Haapalahti Petri, Viitasalo Matti, Perhonen Merja, Mäkijärvi Markku, Väänänen Heikki, Oikarinen Lasse, Hekkala Anna-Mari, Salorinne Yrjö, Swan Heikki, Toivonen Lauri
Department of Cardiology, Helsinki University Hospital, Helsinki, Finland.
Pacing Clin Electrophysiol. 2006 Oct;29(10):1122-9. doi: 10.1111/j.1540-8159.2006.00506.x.
In the most prevalent LQT1 form of inherited long QT syndrome symptoms often occur during abrupt physical or emotional stress. Sympathetic stimulation aggravates repolarization abnormalities in experimental LQT1 models. We hypothesized that autonomic function tests might reveal the abnormal repolarization in asymptomatic LQT1 patients.
We measured heart rates (HRs) and QT intervals in nine asymptomatic carriers of a C-terminal KCNQ1 mutation and 8 unaffected healthy subjects using an approach of global QT values derived from 28 simultaneous electrocardiographic leads on beat-to-beat base during Valsalva maneuver, mental stress, sustained handgrip, and light supine exercise.
LQT1 patients exhibited impaired shortening of both QTpeak and QTend intervals during autonomic interventions but exaggerated lengthening of the intervals--a QT overshoot--during the recovery phases. The number of tests with a QT overshoot was 2.4 +/- 1.7 in LQT1 patients and 0.8 +/- 0.7 in unaffected subjects (P = 0.02). Valsalva strain prolonged T wave peak to T wave end interval (TPE) in LQT1 but not in unaffected patients. LQT1 patients showed diminished HR acceleration in response to adrenergic challenge whereas HR responses to vagal stimuli were similar in both groups.
Standard cardiovascular autonomic provocations induce a QT interval overshoot during recovery in asymptomatic KCNQ1 mutation carriers. Valsalva maneuver causes an exaggerated fluctuation of QT and TPE intervals partly explaining the occurrence of cardiac events during abrupt bursts of autonomic activity in LQT1 patients.
在遗传性长QT综合征最常见的LQT1型中，症状通常在突然的身体或情绪应激期间出现。交感神经刺激会加重实验性LQT1模型中的复极异常。我们推测自主神经功能测试可能会揭示无症状LQT1患者的复极异常。
我们使用一种从28个同步心电图导联逐搏获取整体QT值的方法，在瓦尔萨尔瓦动作、精神应激、持续握力和轻度仰卧运动期间，测量了9名C末端KCNQ1突变的无症状携带者和8名未受影响的健康受试者的心率（HR）和QT间期。
LQT1患者在自主神经干预期间QTpeak和QTend间期的缩短受损，但在恢复阶段间期延长——QT超调现象。LQT1患者出现QT超调的测试次数为2.4±1.7次，未受影响的受试者为0.8±0.7次（P=0.02）。瓦尔萨尔瓦动作使LQT1患者的T波峰到T波末间期（TPE）延长，而未受影响的患者则无此现象。LQT1患者对肾上腺素能刺激的心率加速反应减弱，而两组对迷走神经刺激的心率反应相似。
标准的心血管自主神经激发试验在无症状KCNQ1突变携带者恢复期间会诱发QT间期超调。瓦尔萨尔瓦动作导致QT和TPE间期过度波动，部分解释了LQT1患者在自主神经活动突然发作期间心脏事件的发生。
