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  • In normal embryogenesis the left cardinal vein involutes to

    2019-04-24

    In normal embryogenesis, the left cardinal vein involutes to form the ligament of Marshall, the right cardinal vein and the superior connection between the left and right cardinal veins persist to form the superior vena cava and the brachiocephalic vein, respectively. PLSVC is when involution of the anterior cardinal vein does not occur. It is more frequently connected to the coronary sinus (92%) rather than the left atrium (8%). In most cases, a normal right-sided SVC is present, as well as a left brachiocephalic vein [2]. Associated cardiac abnormalities such as atrial septal defect and bicuspid aortic valve commonly occur. PLSVC is even more frequent (12%) in the presence of other congenital arginase inhibitor abnormalities [2]. Jiang et al. recommended that in such cases, a PLSVC should be identified preoperatively, to avoid the cephalic vein, as the lead may be short and not reach the target site [3].
    Conflict of interest statement
    Introduction A double ventricular response to a single atrial depolarization is described as a dual atrioventricular (AV) nodal nonreentrant tachycardia (DAVNNT), which is a rare form of arrhythmia that is being reported at an increasing frequency. To our knowledge, few cases of this arrhythmia with tachycardia-mediated cardiomyopathy have been reported [1,2]. We describe a 45-year-old female who presented with congestive heart failure and incessant DAVNNT that was completely resolved by performing radiofrequency (RF) ablation of the slow pathway.
    Case report A 45-year-old female was referred to our hospital from another center because of symptomatic congestive heart failure and drug-resistant incessant nonsustained supraventricular tachycardia. In the last 6 months, she had aggravated dyspnea on exertion. On admission, she had dyspnea at rest, distended jugular veins, and pulmonary rales. She denied sudden onset palpitation. A dilated left ventricle with an ejection fraction of approximately 30% was detected on echocardiography. Electrocardiogram (ECG) showed frequent supraventricular premature beats or junctional ectopic beats with an average heart rate of 130beats/min. In the last 3 months, several drugs such as a beta blocker (i.e., sotalol) and digoxin failed to control her arrhythmia and symptoms. During sinus rhythm, the atrio-His (AH) and His-ventricle (HV) intervals measured 62ms and 40ms, respectively. During incremental atrial pacing, a 2:1 atrioventricular block developed at a pacing cycle length of 220ms. However, because of frequent double responses, standard evaluation of the AV node with premature atrial extrastimuli could not be performed. During ventricular pacing, retrograde VA conduction was absent. Three surface ECG leads and intracardiac recordings of spontaneous tachycardia are shown in Fig. 1. A 1:2 AV relationship was noted. A His deflection was visible before every ventricular activity with a constant and normal HV interval. Interestingly, a pattern of group beating was obvious with progressive prolongation of AH1 (fast pathway conduction) and AH2 (slow pathway conduction) that ended with a complete block of the slow pathway conduction, which was compatible with decremental properties of the AV node. The postulated mechanism is suggested in the ladder diagram of Fig. 1. A good slow pathway potential and appropriate A/V ratio was obtained via an anatomical approach in the right atrial posteroseptal region. Subsequently, RF application at this site (55°C, 60s) resulted in a junctional rhythm (Fig. 2) and the successful elimination of tachycardia and non-inducibility of arrhythmia during the electrophysiology study. During the post-ablation study, no sign of dual conduction was detected. AV conduction was occurring only along the fast pathway, and the effective refractory period of AVN was reached at 330ms without an AH jump (Fig. 3). The rhythm was sinus with stable PR intervals.
    Discussion We present a rare case of supraventricular tachycardia based on a dual AV nodal physiology. Although typical and atypical AV nodal reentrant tachycardias are common arrhythmias due to this physiology, DAVNNT is also reported with a nonreentrant pattern based on the existence of a dual AV nodal pathway. A dual ventricular response to a single atrial impulse due to simultaneous fast and slow pathway conduction can be observed during an electrophysiology study (i.e., each ventricular activation is preceded by a His bundle deflection) [1,2]. This arrhythmia is sometimes misinterpreted as atrial fibrillation, and some of these cases were detected in the electrophysiology laboratories when they were referred for pulmonary vein isolation [2].