快速心房起搏后不同时期犬心房肌细胞电生理特性的变化

目的探讨快速心房起搏后不同时期犬心房肌电生理特性的变化,包括动作电位及钙离子通道的变化以及诱发心房颤动(房颤)的情况.方法通过植入420次/min的固定频率起搏器并将电极固定于右心房制成犬快速心房起搏模型,起搏持续时间分别为2,4,6,8周,然后将犬处死,分离单个心房肌细胞,并应用全细胞膜片钳法,记录犬心房肌细胞跨膜动作电位和L型钙离子电流(IcaL)的变化.结果①9只起搏持续时间为4～8周的犬中,有4只出现阵发性房颤,②与对照组(未起搏组)相比,在2,4,6,8周动作电位时程(APD90)分别减少33.4%、48.6%、47.8%和48.3%:动作电位幅度(APA)分别减少9%、15.8%、17.9%和18.4%;IcaL分别减少40.7%、63%、62.8%和61.7%.③起搏4～8周的犬中,出现阵发性房颤(4/9)与无阵发性房颤的犬(5/9)相比,APD90,APA和Ⅰ-caL的数值无明显变化(P＞0.05).结论随着快速起搏时间的延长,动作电位时程,动作电位幅度及L型钙电流密度呈进行性减低,于第四周达到最低水平,然后持续在这一低水平.     

A New Type of Dual Atrioventricular Nodal Nonreentrant Tachycardia

Dual atrioventricular nodal nonreentrant tachycardia (DAVNNT) is very rarely observed clinically. The first review of this arrhythmia was published in 2011 by Wang, where four types of DAVNNT were described. Our case report presents a phenomenon that has never been published before. We revealed a very specific sequence of double fire phenomenon, 1:1 atrioventricular (AV) conduction and AV block.     

Increasing atrial fibrillation: What is the cause?

A 72‐year‐old woman with a history of paroxysmal atrial fibrillation (AF) and sinus node dysfunction is seen in clinic for routine follow‐up.     

Left ventricle automatic pacing threshold management in CRT systems: A comprehensive review

Modern cardiac resynchronization therapy (CRT) device‐based threshold detection enables capture management and voltage output adjusting to combine consistent left ventricular (LV) pacing with acceptable battery drainage. The current technologies available for LV capture automatic confirmation in most cases require the evoked response, as well as “LV pace to right ventricular sense” algorithms. The LV pacing percentage counter may overestimate the CRT delivery which may be reduced due to pacing inhibition (by sensed LV activation) or inadequate capture due to subthreshold current or pacing into refractory tissue. Moreover, the LV threshold at implant and its behavior over time (as a marker of electrical viability) and the ineffective CRT issues (subthreshold stimulation or concealed loss of capture) are discussed. The purpose of the present review is to explore these new challenges regarding LV pacing automatic management.     

Systemic venous atrium stimulation in transvenous pacing after mustard procedure

We present the case of a young woman corrected with a Mustard procedure undergoing successful transvenous double chamber pacemaker implantation with the atrial lead placed in the systemic venous channel. The case presented demonstrates that, when the systemic venous atrium is separate from the left atrial appendage, the lead can be easily and safely placed in the systemic venous left atrium gaining satisfactory sensing and pacing thresholds despite consisting partially of pericardial tissue.