A 59-year-old man with no history of cardiovascular disease was admitted to the emergency department with sudden onset of rapid palpitations and dizziness 2 hours before admission. ECG (Figure 1) revealed a rapid irregular wide QRS complex tachycardia with right bundle-branch block morphology and alternating QRS width. Because the patient was hemodynamically unstable, immediate direct current cardioversion was performed, restoring normal sinus rhythm (Figure 2). After that, physical examination was unremarkable and transthoracic echocardiogram ruled out overt structural heart disease. Ionic disturbances were ruled out as well. The patient denied history of syncope or palpitations and was not on any medication. He was referred for electrophysiologic study. The tachycardia shown in Figure 3 was reproducibly induced. What is the most likely diagnosis for the patient? What mechanism would explain the exclusive changes in ventricular repolarization during tachycardia? What is the appropriate management of the patient?

Figure 1. Twelve-lead ECG on admission. The shortest RR interval was 180 ms (high risk accessory pathway). Delta wave and QRS were positive in leads V1 and V2 and negative in leads II, III, and aVF.

Figure 2. Twelve-lead ECG once sinus rhythm was restored after electrical cardioversion.

Figure 3. Twelve-lead ECG of the induced tachycardia. ST segment and T-wave alternans are evident on leads V1 and V2.

Please turn the page to read the diagnosis.

ECG on admission is consistent with pre-excited atrial fibrillation presumably attributable to a left posterior accessory pathway (AP; irregular rhythm, wide QRS complexes with change in shape and morphology, delta wave positive in V1 and negative in inferior leads). Orthodromic tachycardia mediated by a left AP was reproducibly induced by ventricular pacing (Figure 4) and confirmed by diagnostic pacing maneuvers. Close observation of the tachycardia (Figure 3) demonstrated substantial changes in repolarization in the right precordial leads, with lead V1 showing a coved-type ST-segment elevation followed by a negative T wave consistent with the Brugada type 1 electrocardiographic pattern. Moreover, ST segment and T-wave alternans were evident in leads V1 and V2 (arrows). After tachycardia termination, type 1 Brugada electrocardiographic pattern disappeared and morphology of QRS complexes returned to basal. A saddleback-type ST-segment elevation was present on lead V2 for the sinus beats (Figures 2 and 3), fitting with nondiagnostic type 2 Brugada electrocardiographic pattern, and there was no visible delta wave. This was a case of inapparent pre-excitation in which, despite the presence of an anterogradely conducting AP, conduction over the normal conduction system reached the ventricle faster than that over the AP. Occurrence of type 1 Brugada electrocardiographic pattern was reproducible in every induction of orthodromic tachycardia. The AP was found at the posterolateral mitral annulus and ablation of the AP was successful. After that, rapid atrial pacing (120 bpm) again elicited the Brugada type 1 electrocardiographic pattern (Figure 5).

Figure 4. Electrocardiographic leads aVL, aVF, V1, and V4 and intracardiac electrograms during induced regular tachycardia. Eccentric retrograde atrial activation at the coronary sinus (CS) was observed. CS 3-4 was located at the posterolateral region. The shorter His-ventricular interval (HV) during sinus rhythm denotes the existence of subtle ventricular pre-excitation (inapparent pre-excitation; see text). HBE indicates His bundle electrogram; and RVA, right ventricular apex.

Figure 5. Twelve-lead ECG during drive-train stimulation (500 ms) and early extrastimulation (330 ms) atrial pacing from the coronary sinus.

It is well known that patients with Brugada syndrome usually have arrhythmic events at rest attributable to preponderance in vagal activity. Augmented ST-segment elevation just in early recovery of exercise has been identified as an independent predictor for ventricular arrhythmias in patients with this entity.¹ However, ST-segment elevation at faster rates is uncommon and has unknown prognostic implications. An additional I_Na reduction in certain subgroups of patients with Brugada syndrome at faster rates represents a plausible mechanism explaining the appearance of type 1 Brugada electrocardiographic pattern because the diastolic interval becomes extremely short to allow the sodium channels to recover completely from the slow inactivated state.² ST segment and T-wave alternans were only evident at faster rates in the present case (Figure 3), probably reflecting a larger I_NA function reduction.

A drug challenge with intravenous flecainide confirmed the diagnosis of Brugada syndrome (Figure 6). Because ST segment and T-wave alternans in Brugada syndrome has been postulated as a potential risk factor for spontaneous malignant ventricular arrhythmias,³ and despite lack of spontaneous type 1 Brugada pattern, programmed ventricular stimulation was performed with no induction of ventricular arrhythmias. A cardiac defibrillator was not implanted. The patient refused genetic testing and was discharged after being advised not to take the drugs listed at brugadadrugs.org, to avoid excessive alcohol intake, and to treat fever early. During a follow-up of 5 years, the patient was asymptomatic. Despite the well-established association between Brugada syndrome and atrial fibrillation, no further episodes of arrhythmia have occurred, favoring the main role of the anterograde conducting AP in the genesis of atrial fibrillation in our patient.

Figure 6. Twelve-lead ECG just after drug challenge with intravenous flecainide. Typical type 1 Brugada electrocardiographic pattern is evident on leads V1 and V2.

None.

https://www.ahajournals.org/journal/circ

一名无心血管疾病史的59岁男子在入院前2小时突然进入急诊室并出现头晕和头晕。心电图（图1）显示快速不规则宽QRS复杂性心动过速，具有右束支传导阻滞形态和交替的QRS宽度。由于患者血液动力学不稳定，应立即进行直流电复律，以恢复正常的窦性心律（图2）。此后，体格检查无异常，经胸超声心动图排除了明显的结构性心脏病。离子干扰也被排除。该患者否认有晕厥或心史，且未服用任何药物。他被转介进行电生理研究。图3所示的心动过速是可重现的。对患者最可能的诊断是什么？什么机制可以解释心动过速期间心室复极的排他性变化？对患者的适当管理是什么？

图1. 十二导联心电图。RR间隔最短为180毫秒（高风险辅助途径）。V1和V2导线中的Delta波和QRS阳性，II，III和aVF导线中的Delta波和QRS阴性。

图2. 心脏电复律后窦性心律恢复后的十二导联心电图。

图3。 十二导联心电图诱发的心动过速。在导线V1和V2上可见ST段和T波交变。

请翻页阅读诊断。

入院时的心电图与可能由左后副途径引起的预激性房颤一致（AP；不规则节律，形状和形态改变的宽QRS波群，V1中的三角波为正，下铅为负）。左心室起搏可重复地诱导左心室AP引起的原发性心动过速（图4），并通过诊断性起搏手法得到证实。对心动过速的近距离观察（图3）表明右心前导联的复极化发生了实质性变化，导联V1显示凹型ST段抬高，然后出现负T波，与Brugada 1型心电图模式一致。此外，在导线V1和V2中（箭头）明显存在ST段和T波交替现象。心动过速终止后，1型Brugada心电图模式消失，QRS复合体形态恢复为基础。对于窦性搏动，V2导联上出现了鞍背型ST段抬高（图2和图3），与非诊断性2型Brugada心电图模式相符，并且没有可见的三角波。这是一种无明显预激励的情况，其中，尽管存在顺行传导性AP，但正常传导系统上的传导到达心室的速度比AP上传导的快。在每次正畸性心动过速的诱导中，都可以重现1型Brugada心电图模式的发生。AP位于二尖瓣后外侧环，成功消融。此后，快速心房起搏（120 bpm）再次引发了Brugada 1型心电图模式（图5）。

图4. 诱发规则性心动过速期间的心电图导联aVL，aVF，V1和V4以及心内电描记图。观察到冠状窦（CS）的偏心逆行性房颤激活。CS 3-4位于后外侧区域。窦性心律期间较短的组室间隔（HV）表示存在微妙的室性预激（无明显的预激；见正文）。HBE表示他的束电描记图；和RVA，右心室先端。

图5. 十二指肠心电图在驱动系统刺激（500毫秒）和早期超刺激（330毫秒）期间从冠状窦心房起搏。

众所周知，患有Brugada综合征的患者通常在静息时会出现心律不齐事件，这归因于迷走神经活动的优势。仅在运动的早期恢复中，增强的ST段抬高已被确定为该病患室性心律失常的独立预测因子。¹然而，ST段抬高速度较快并不常见，其预后影响未知。一个额外的我_的Na在患有以更快的速率Brugada综合征某些亚组减少代表一个可行的机制解释类型1布鲁格达心电图图案的外观，因为舒张间隔变得极短，以允许钠通道从慢失活状态完全恢复。²在本例中，ST段和T波交替蛋白仅以较快的速率出现（图3），这可能反映了较大的I _NA功能降低。

静脉注射氟卡尼的药物攻击证实了Brugada综合征的诊断（图6）。因为已经假定Brugada综合征的ST段和T波交替蛋白是自发性恶性室性心律失常的潜在危险因素，³尽管缺乏自发的1型Brugada模式，在没有诱发心律失常的情况下进行了程序性心室刺激。未植入心脏除颤器。该患者被建议不要服用brugadadrugs.org上列出的药物，以避免过量饮酒，及早治疗发烧，因此拒绝了基因检测，并已出院。在5年的随访中，该患者无症状。尽管Brugada综合征和房颤之间已建立了良好的联系，但未发生心律失常的进一步发作，这有利于顺行传导性AP在我们患者房颤的起源中的主要作用。

图6. 用氟卡尼静脉注射药物攻击后的十二导联心电图。在导线V1和V2上可以看到典型的1型Brugada心电图。

没有。

https://www.ahajournals.org/journal/circ