A 41-year-old woman was assessed for recurrent intermittent irregular palpitations, associated with dizziness and shortness of breath. She had a negative electrophysiology study 12 years earlier, for similar symptoms. In addition, β-blockers, calcium-channel blockers (Verapamil), and flecainide did not result in significant improvement of her arrhythmia. A recent echocardiogram disclosed a structurally normal heart. Following the electrocardiogram recorded during one of her latest emergency department visits (Figure 1), oral anticoagulation was started and a referral for electrophysiology opinion was made. What is the arrhythmia displayed in Figure 1, and what is the explanation of the irregularity in the rhythm?

Figure 1. Twelve-lead ECG of the presenting arrhythmia.

Please turn the page to read the diagnosis.

This irregular arrhythmia results from a complex interplay of junctional ectopic tachycardia (JET) at 103 beats per minute, and sinus tachycardia at 108 beats per minute.

There is stable sinus rhythm throughout the trace, with some P waves hidden inside QRS complexes (P and (P) in Figure 2, respectively). All QRS complexes are narrow, with some resulting from conducted P waves, whereas others are dissociated. This finding of atrioventricular dissociation with narrow QRS complexes is suggestive of JET (* in Figure 2). The JET QRS morphology is slightly different compared with the conducted beats: they lack septal q waves in lateral leads, they are ever-so-slightly broader, and the ST segment is shifted opposite to the QRS complex. This slight difference in the QRS morphology and initial QRS forces between the JET and the normal beats suggests that the origin of the JET beats maybe infranodal and below the first ramifications of the His bundle, or that they conduct with minor degrees of aberrancy in the proximal His-Purkinje system.¹ The interval between some JET beats is twice as long as between others (Figure 2, horizontal double arrow vs single arrow, respectively), suggesting that some JET beats are not manifest on the ECG. This longer interval between the JET beats is occupied by 2 conducted QRS beats with a coupling interval which is shorter (ie, faster) than the sinus rate. This results from concealed retrograde conduction of the JET beats into the atrioventricular node (Figure 3, red arrows). The sinus beat hidden in the JET QRS is thus conducted with a longer atrioventricular delay (Figure 3, blue arrows), with subsequent shortening of the next RR interval (Figure 3, gray vs black arrows). Also, this delay of the atrioventricular conduction, with subsequent RR shortening, results in the next JET beat falling in His-Purkinje and ventricular refractoriness of the previously conducted beat, explaining why it is not manifest on the ECG even if the JET continues (Figure 3, empty star).

Figure 2. Key features on the 12-lead ECG. There is stable sinus rhythm throughout the trace, but only some P waves are clearly visible, whereas others are hidden inside QRS complexes (P and (P), respectively). All QRS complexes are narrow, but some are dissociated from the P waves; these are junctional ectopic tachycardia (JET) beats (*). The interval between some JET beats is twice as long as between others (horizontal double arrow vs single arrow, respectively), suggesting that some JET beats are not manifest on the ECG.

Figure 3. Ladder diagram with the proposed mechanism of the arrhythmia. For simplicity, only lead II is displayed. At the atrial level (A), dark green arrows denote visible P waves, and lighter arrows denote P waves hidden by QRS complexes. At the atrioventricular nodal (AVN) level, dashed green arrows denote normal atrioventricular conduction, dashed blue arrows denote prolonged atrioventricular conduction of sinus beats caused by retrograde concealed conduction of junctional ectopic tachycardia (JET) beats (designated by dashed red arrows). At the His bundle level, JET beats are represented by stars (black for conducted JET beats, empty for nonconducted JET beats that fall in the ventricular refractoriness). At ventricular (V) level, the green arrows represent normally conducted QRS complexes, while red arrows denote JET QRS complexes. The shaded areas represent presumed ventricular refractoriness (according to the QRST complex duration on the ECG). In addition, the RR interval between 2 consecutively conducted sinus beats is shown below the ladder diagram, with the black arrow denoting RR interval similar to sinus rate (because of normal atrioventricular conduction), and the gray arrows denoting shortened RR interval because of prolonged atrioventricular conduction of the sinus beat hidden in the earlier JET beat.

JET is mostly encountered in children or after cardiac surgery. It is notable for being resistant to medical therapy, and possibly incessant. If fast, it can lead to tachycardiomyopathy, heart failure, and death, especially in children.² In our case, JET is rather slow (approximately 103 beats per minute) and nonsustained, which likely explains why the cardiac function is completely normal. Symptoms, however, can be quite significant, either because of the irregular rhythm, “cannon waves” because of overlap between P waves and JET beats, or both. Catheter ablation may provide definitive cure, but is associated with high risk of iatrogenic atrioventricular block and requirement of life-long pacing, so it is usually performed as a last resort in refractory cases.³ Meanwhile, careful analysis of ECG should be performed to avoid mislabeling any irregular arrhythmia as atrial tachycardia or atrial fibrillation, and provide unnecessary anticoagulation.

None.

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

评估了一名41岁妇女的周期性间歇性不规则心pit，并伴有头晕和呼吸急促。12年前，她因类似症状接受了负电生理学研究。此外，β受体阻滞剂，钙通道阻滞剂（维拉帕米）和氟卡尼胺未导致心律不齐的明显改善。最近的超声心动图显示心脏结构正常。在她最近一次急诊就诊期间记录的心电图（图1）之后，开始口服抗凝治疗，并转介了电生理学意见。图1中显示的心律不齐是什么？对节律不规则的解释是什么？

图1. 出现心律不齐的十二导联心电图。

请翻页阅读诊断。

这种不规则的心律失常是由于交界性异位心动过速（JET）以每分钟103次搏动和窦性心动过速以每分钟108次搏动的复杂相互作用造成的。

整个迹线都有稳定的窦性心律，QRS波群内隐藏着一些P波（P和分别在图2中的（P））。所有QRS络合物都很窄，其中一些是由传导P波产生的，而另一些则是离解的。房室分离与狭窄QRS复合体的发现提示JET（图2中的*）。与传导节拍相比，JET QRS形态略有不同：它们在横向导线中缺少间隔q波，它们的宽度略微偏宽，并且ST段向QRS复合物的相反方向移动。JET和正常搏动之间QRS形态和初始QRS力的细微差异表明，JET搏动的起源可能在下节律且在His束的第一个分支以下，或它们在近端的异常程度较小His-Purkinje系统。^1个某些JET搏动之间的间隔是其他JET搏动之间的两倍（分别是图2，水平双箭头与单箭头），这表明某些JET搏动在ECG上不明显。JET搏动之间的较长间隔被2次传导QRS搏动所占据，其耦合间隔短于（即快于）窦率。这是由于JET搏动的隐性逆行传导进入房室结所致（图3，红色箭头）。隐藏在JET QRS中的窦性搏动因此以更长的房室延迟进行（图3，蓝色箭头），随后缩短下一个RR间隔（图3，灰色vs黑色箭头）。此外，房室传导的这种延迟以及随后的RR缩短，

图2. 12导联心电图的主要功能。整个迹线都有稳定的窦性心律，但只有一些P波清晰可见，而另一些则隐藏在QRS复合波内（分别为P和（P））。所有QRS络合物都很窄，但有些与P波分离。这些是交界性异位心动过速（JET）搏动（*）。某些JET搏动之间的间隔是其他JET搏动之间的间隔的两倍（分别是水平双箭头和单箭头），这表明某些JET搏动在ECG上不明显。

图3。 梯形图与心律失常的建议机制。为简单起见，仅显示线索II。在心房水平（A），深绿色箭头表示可见的P波，较浅的箭头表示QRS复合波所隐藏的P波。在房室结（AVN）级别，绿色虚线箭头表示正常的房室传导，蓝色虚线箭头表示由结节性异位心动过速（JET）搏动的逆行隐蔽传导引起的窦性搏动的延长房室传导（由虚线红色箭头表示）。在希氏束水平上，JET搏动以星号表示（黑色代表传导性JET搏动，空表示不传导性JET搏动，其落在心室耐火度中）。在心室（V）级别，绿色箭头表示正常进行的QRS复合波，而红色箭头表示JET QRS复合波。阴影区域表示假定的心室难治性（根据ECG上的QRST复杂时间）。此外，梯形图下方显示了两个连续进行的窦性心跳之间的RR间隔，黑色箭头表示RR间隔与窦率相似（由于正常的房室传导），灰色箭头表示RR间隔缩短是由于房室时间延长隐藏在较早的JET搏动中的窦性搏动的传导。

JET多见于儿童或心脏手术后。值得注意的是它对药物治​​疗有抵抗力，而且可能持续不断。如果速度很快，则可能导致心动过速，心力衰竭和死亡，尤其是在儿童中。²在我们的案例中，JET相当慢（每分钟约103次跳动）并且没有持续，这可能解释了为什么心功能完全正常。但是，由于节奏不规则，或者由于P波和JET拍之间的重叠而导致的“大炮波”，或者两者兼而有之，症状可能非常明显。导管消融术可以提供确定的治愈方法，但与医源性房室传导阻滞的高风险和终身起搏的要求相关，因此通常在难治性病例中作为最后的手段进行。³ 同时，应进行仔细的心电图分析，以免将任何不规则的心律失常错误地标记为心动过速或房颤，并提供不必要的抗凝治疗。

没有。

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