A 51-year-old woman with a medical history of treated primary hypothyroidism was admitted to the emergency department because of a syncopal episode preceded by palpitations with no other prodromal symptoms. The patient experienced occasional episodes of palpitations in the past without loss of consciousness that coincided with febrile episodes and were resolved once the fever was controlled. Upon arrival at the hospital, she referred a 2-day history of sore throat and was found to be febrile at 101.3°F with otherwise normal vital signs. Physical examination revealed the presence of tonsillopharyngeal erythema and cervical lymphadenopathy. Cardiac examination was unremarkable except for the presence of an irregular heart rhythm upon auscultation, with no murmurs, rubs, or gallops. Laboratory work was normal including normal thyroid levels. A chest X-ray showed no infiltrates or consolidations. An electrocardiogram was performed (Figure 1). A transthoracic echocardiogram ruled out the presence of structural heart disease. What is the most likely cause for the syncopal episode? How should the patient be managed?

Figure 1. Twelve-lead electrocardiogram on presentation. Short coupling interval premature ventricular complexes showing left bundle branch block morphology and left superior frontal plane axis are evident.

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Acute streptococcal pharyngitis was diagnosed and antibiotics and ibuprofen were started. She was placed on telemetry monitoring while complaining of palpitations related to monomorphic premature ventricular complexes (PVCs). The presenting ECG (Figure 1) shows sinus rhythm at 100 beats per minute, with frequent short coupling interval PVCs (230 ms). These had left bundle-branch block morphology and a left superior frontal plane axis with a negative concordance pattern in precordial leads which suggested an origin in the right ventricle.

Shortly after arrival and after a period of bigeminism, the patient experienced a loss of consciousness with documentation of ventricular fibrillation (VF) that required external defibrillation (Figure 2). She presented many subsequent episodes even after intravenous lidocaine and amiodarone. Finally, deep sedation and endotracheal intubation were required. During the next 48 hours, she presented new VF episodes triggered by the same PVC morphology, always coinciding with fever. Only once the patient became afebrile was the burden of PVCs drastically reduced, with no additional VF episodes. A coronary angiography revealed no coronary lesions.

Figure 2. Telemetry strip for the first recorded episode of premature ventricular complexes-related sustained malignant ventricular arrhythmia. Initially, a torsade de pointes is induced after a premature ventricular complex with an initiating coupling interval of 230 ms that subsequently degenerates into ventricular fibrillation. The episode is preceded by a period of ventricular bigeminy and terminated by an external 200J shock.

The presence of recurrent syncope and documentation of short coupling interval PVCs in patients without structural heart disease have been well described as a potential source for sudden cardiac death related to what is called idiopathic VF.¹ That entity is considered a diagnosis of exclusion in patients who have survived a VF episode without any identifiable structural or metabolic cause. Predominantly, VF initiates by PVCs from the left or right Purkinje system in more than 90% of the cases.¹ The mechanisms for these PVCs are usually abnormal automaticity, triggered activity, or, less frequently, reentry. More rarely, the PVCs can be originated in the ventricular myocardium including the right ventricular outflow tract, the papillary muscle, or the moderator band of the right ventricle. Catheter ablation of the PVCs that initiate VF is associated with high rates of success.² However, implantation of a cardioverter-defibrillator is advised in all cases because some patients who have a VF recurrence present a new morphology of PVC triggering VF.² In patients with Brugada syndrome, the relationship between VF and fever as a trigger has been well established. Although less common, such a relationship has also been described for patients with idiopathic VF.³ The mechanism may be related to temperature-dependent modifications of ion channel properties or expression that facilitate spontaneous activity within the Purkinje system as triggers of VF.

In our patient, an electrophysiological study was performed 3 days later. Isolated PVCs were recorded at the beginning of the study. The apical free wall of the right ventricle was the site of earliest ventricular activation during spontaneous PVCs. At that point, a Purkinje potential was recorded preceding ventricular activation and perfect-matched morphology by pace-mapping was obtained as well (Figure 3). Catheter ablation at that point and surrounding points with preceding Purkinje potentials was performed. Spontaneous PVCs were completely abolished. Before discharge, Brugada syndrome was ruled out after a negative drug challenge with flecainide and a cardioverter-defibrillator was implanted. After 7 years of follow-up, no VF recurrence has occurred, and the patient remains completely asymptomatic.

Figure 3. Electrocardiogram and leads with intracardiac recordings.A, Electrocardiogram for a spontaneous premature ventricular complex during the electrophysiological study and exact pace-mapping at the site of the earliest ventricular activation. The premature ventricular complexes showed the same short coupling interval but discrete morphological changes (precordial lead transition in V5) in comparison with those recorded at admission probably related to changes in electrode placement or slightly different exit sites for the same premature ventricular complex. B, Electrocardiographic leads II, V1, V3 and V5 and intracardiac recordings during a spontaneous premature ventricular complex at the site of earliest ventricular activation (30 ms) and exact pace-mapping. A sharp signal (Purkinje potential) preceding the local ventricular activation at the distal ablation catheter electrogram (Abl d) is evident (*). Abl p indicates proximal ablation catheter electrogram; Abl u, unipolar ablation catheter electrogram; HBE, His bundle electrogram; PVC, premature ventricular complex; and RV, right ventricular electrogram.

None.

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

一名患有原发性甲状腺功能减退病史的51岁妇女因晕厥发作，心无其他前驱症状而入院急诊科。过去，患者偶尔会出现心pit发作，而不会出现与高热发作相伴的意识丧失，一旦发烧得到控制，病情就会得到缓解。到达医院后，她转诊了2天的咽喉痛史，发现她在101.3°F时发热，并且生命体征正常。体格检查发现扁桃体咽部红斑和宫颈淋巴结肿大。心脏检查无异常，除了听诊时出现不规则的心律，无杂音，摩擦或疾驰。实验室工作正常，包括甲状腺水平正常。胸部X光片未见浸润或巩固。进行了心电图检查（图1）。经胸超声心动图排除了结构性心脏病的存在。晕厥发作的最可能原因是什么？应该如何管理患者？

图1. 十二导联心电图。短的耦合间隔早搏心室复合体显示左束支传导阻滞形态和左上额叶平面轴很明显。

请翻页阅读诊断。

诊断为急性链球菌性咽炎，并开始使用抗生素和布洛芬。她被放置在遥测监测中，同时抱怨与单形性早发性心室复合体（PVC）有关的心pit。呈现的心电图（图1）显示每分钟100次搏动的窦性心律，频繁出现短的PVC耦合间隔（230毫秒）。它们具有左束支传导阻滞形态和左前额叶上轴，在心前区导联中呈负一致模式，提示起源于右心室。

到达后不久，经过一段时间的女性霸权主义后，患者出现意识丧失，需要室颤（VF）记录，需要进行体外除颤（图2）。即使静脉注射利多卡因和胺碘酮，她也出现了许多随后的发作。最后，需要进行深度镇静和气管插管。在接下来的48小时内，她展示了由相同的PVC形态触发的新的VF发作，并总是与发烧同时发生。仅当患者出现发热时，PVC的负担才能大大减轻，而无其他VF发作。冠状动脉造影未发现冠状动脉病变。

图2. 记录的早发性室性早搏相关的持续性恶性室性心律失常的遥测带。最初，在过早的心室复合体之后，以230 ms的起始耦合间隔诱发扭转点，随后退化为心室纤颤。发作之前有一段心室重婚期，并因外部200J休克而终止。

在没有结构性心脏病的患者中，反复出现晕厥和短时间间隔PVC的记录已被很好地描述为与特发性VF相关的心源性猝死的潜在来源。¹该实体被认为是在没有任何可识别的结构或代谢原因的VF发作中幸存的患者的排除诊断。在超过90％的病例中，VF主要由左或右浦肯野系统的PVC引发。^1个这些PVC的机制通常是异常的自动性，触发的活动，或者（较不常见的）重入机制。很少会有PVCs起源于心室心肌，包括右心室流出道，乳头肌或右心室的缓和带。启动VF的PVC的导管消融与高成功率相关。²但是，在所有情况下都建议植入心脏复律除颤器，因为一些具有室颤复发的患者表现出一种新的PVC触发室颤形态。²在患有Brugada综合征的患者中，VF和发烧之间的关系已经得到了很好的确立。尽管不常见，但对于特发性VF患者也描述了这种关系。³该机制可能与离子通道性质或表达的温度依赖性修饰有关，该修饰促进Purkinje系统内自发活性作为VF触发。

在我们的患者中，三天后进行了电生理研究。在研究开始时记录了孤立的PVC。右心室的顶部游离壁是自发性PVC期间最早的心室激活部位。在这一点上，记录了浦肯野电位，随后激活了心室，并通过起搏图获得了完美匹配的形态（图3）。用先前的浦肯野电位在该点和周围点进行导管消融。自发的PVC被完全废除。在出院前，使用氟卡尼对药物进行了阴性攻击并植入了心脏复律除颤器后，排除了Brugada综合征。经过7年的随访，没有发生VF复发，并且患者完全没有症状。

图3. 心电图和带心内记录的导线。A，在电生理研究过程中自发性早发性心室复合体的心电图，以及在最早的心室激活部位的精确起搏图。与入院时记录的那些相比，早发性脑室复合物显示出相同的短耦合间隔，但具有不连续的形态学变化（V5的心前导联转变），可能与同一早发性脑室复合物的电极位置变化或出口位置略有不同。乙，心电图导联II，V1，V3和V5以及自发性早发性心室复合体在最早的心室激活（30毫秒）和准确的步速映射部位出现的心内记录。在远端消融导管电描记图（Abl d）处的局部心室激活之前，有一个清晰的信号（浦肯野电位）是明显的（*）。Abl p表示近端消融导管电描记图；单极消融导管电描记图；HBE，他的束电描记图；PVC，室性早搏；和RV，右心室电描记图。

没有。

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