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    • The requirements for establishing this

    2019-07-01

    The requirements for establishing this arrhythmia are as follows: (1) a slow pathway (or maybe a fast pathway) should not have retrograde conduction; and (2) the refractory Protease Inhibitor Cocktail (EDTA-Free, 100X in DMSO) of of the distal common pathway must be shorter than the difference in the conduction times over the fast and slow pathways so that the impulses of these pathways reach the His bundle and ventricles after refractoriness of the previous impulse [2]. The most important differential diagnosis for DAVNNT is Hisian bigeminal extrasystoles. Differentiating between these two phenomena is difficult. In our patient, there were some clues that ruled out Hisian extrasystoles. Retrograde His activation (i.e., activation of the proximal His after the distal His) and shortening of the HV interval are indicative of parahisian extrasystole [3]. However, in our case, His was activated antegradely with an equal HV interval compared to the sinus rhythm (Fig. 1). Prolongation of the AH1 and AH2 interval with a Wenckebach pattern, as shown in our case, is much more compatible with decremental conduction from the fast and slow pathway [4]. These criteria increase the likelihood of dual AV node physiology, but complete disappearance of the arrhythmia after performing slow pathway ablation is the strongest reason for making this diagnosis. Until recently, very rare cases of tachycardia-induced cardiomyopathy due to this arrhythmia have resolved by slow pathway ablation similar to our case [1]. Thus, it seems that the early detection of this arrhythmia and definitive treatment, especially in cases of tachycardiomyopathy, is important to prevent or minimize the effects of persistent tachycardia on cardiac function.
    Conclusions
    Conflict of interest
    Acknowledgments This work was supported by the Cardiovascular Research Center, Shahid Beheshti University of Medical Sciences and the Department of Pacemaker and Cardiac Electrophysiology, Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences.
    Introduction Persistent left superior vena cava (PLSVC) is often encountered in the electrophysiology laboratory and can be accompanied by other venous anomalies [1]. Implantation of transvenous pacemaker or implantable cardioverter-defibrillator (ICD) leads through the PLSVC is challenging, with prolonged procedural times. ICD lead placement with a defibrillation coil through the PLSVC may be difficult because it often requires looping the lead in the right atrium (RA) for the lead to cross the tricuspid valve [2]. This can increase the mechanical stress on the lead, making it prone to future complications. We describe a patient with a PLSVC who underwent a successful left pectoral implantation of an ICD lead through an alternative approach.
    Case A 52-year-old woman with a history of congestive heart failure secondary to non-ischemic cardiomyopathy and sinus bradycardia underwent a left pectoral implantation of a dual-chamber ICD for primary prophylaxis. She had no history of congenital anomalies. A cephalic venous access was obtained via the standard approach. When a guidewire was advanced through the cephalic vein, a possible PLSVC was observed (Fig. 1A). Venography confirmed the PLSVC and revealed a small branch that allowed the PLSVC to communicate with the right-sided venous drainage (Fig. 1B). A 0.035-in hydrophilic-coated guidewire was introduced through the cephalic vein and carefully manipulated through the communicating branch into the RA and back up to the PLSVC (Fig. 1C), providing good support for introducing a 7-Fr-long sheath into the RA over the guidewire. Another guidewire was introduced into the RA through the long sheath and was used to advance the second long sheath. Atrial (2088TC-46, St. Jude Medical, Saint Paul, MN, USA) and ICD leads (7122Q-58, St. Jude Medical) were successfully placed through the communicating branch in the RA appendage and right ventricular apex, respectively (Fig. 2). An ICD pulse generator (St. Jude Medical CD2357-40Q) was placed in the left subcutaneous pocket. Defibrillation threshold testing was performed with successful defibrillation with 15-J biphasic shock. On postprocedural enhanced computed tomography, other congenital anomalies were ruled out, and the PLSVC and its communicating branch with a right-sided venous system were clearly identified (Fig. 1D). No complications occurred.