A 14-year-old, 5.8 kg (12.7 lb) male castrated Jack Russell Terrier was referred for investigation of syncope and an arrhythmia. Electrocardiogram showed pronounced variation in the sinus rate including long periods of sinus arrest and an inconsistent escape rhythm. Sick sinus syndrome was the presumptive diagnosis. A single lead permanent transvenous pacemaker was implanted and was programmed to perform ventricular-demand pacing. Postoperative pacemaker interrogation revealed undersensing and asynchronous pacing during episodes of supraventricular tachycardia (SVT). This intermittent pacemaker malfunction was attributed to a specific pacemaker programming feature called quiet timer blanking. Adjustment of pacemaker parameters did not restore normal function. Treatment with sotalol (5 mg per os q 12 h) was used to medically treat the SVT, and asynchronous pacing was not observed during follow-up visits. To the authors’ knowledge, this is the first documented case of quiet timer blanking causing paroxysmal undersensing and asynchronous pacing in a dog with a permanent pacemaker.

一名 14 岁、5.8 公斤（12.7 磅）的雄性去势杰克罗素梗被转诊接受晕厥和心律失常的调查。心电图显示窦性频率的显着变化，包括长时间的窦性停搏和不一致的逃逸节律。病窦综合征是推定的诊断。植入了一个单导永久性经静脉起搏器，并被编程为执行心室需求起搏。术后起搏器检查显示室上性心动过速 (SVT) 发作期间感觉不足和不同步起搏。这种间歇性起搏器故障归因于称为安静计时器消隐的特定起搏器编程功能。调整起搏器参数未恢复正常功能。用索他洛尔（5 mg per os q 12 h）治疗用于药物治疗 SVT，在随访期间未观察到异步起搏。据作者所知，这是第一个记录在案的安静计时器消隐案例，导致带有永久性起搏器的狗出现阵发性感知不足和异步起搏。