Bonnet J L, Brusseau E, Limousin M, Cazeau S
Clinical Research Department, Le Plessis Robinson, France.
Pacing Clin Electrophysiol. 1996 Nov;19(11 Pt 2):1724-8. doi: 10.1111/j.1540-8159.1996.tb03214.x.
Mode switching algorithms are commonly used to protect the ventricles against high rates induced by atrial tachycardia. In the case of atrial fibrillation (AF), the response of these algorithms depends on the quality of atrial sensing. The Chorum 7234 DDDR pacemaker uses a new mode switching algorithm, based on a statistical analysis of the atrial rhythm. It includes two criteria of diagnosis: "high" if more than 28 of 32 cycles are abnormally accelerated; and "low" if more than 36 of 64 cycles are abnormally accelerated.
From a taped database of electrophysiological studies, episodes of AF lasting more than 2 minutes were selected. A tape recorder replayed the atrial signals into an external Chorum device. Each episode was replayed eight times with a programmed atrial sensitivity increasing from 0.4-2.0 mV. For each criterion of diagnosis and each programmed sensitivity, the percentage of atrial sensing, the time to switching, and the mean ventricular rate were measured. Ten episodes of AF from 10 patients (9 men and 1 woman; ages 62 +/- 16 years) were included: 1.95 +/- 0.97 mV and 196 +/- 64 ms. The sensitivity of the algorithm to diagnose atrial tachycardia reached 100%, for an atrial sensitivity set between 0.4 and 1.0 mV. The mean percentages of atrial sensed events were 74% +/- 18% and 46% +/- 9% for the "high" and "low" criteria, respectively. The mean diagnostic times were 28 +/- 26 seconds and 68 +/- 27 seconds, respectively. Sensing of < 23% of AF events resulted in failure to diagnose the arrhythmias by both algorithms. In the event of diagnostic failure, the mean ventricular pacing rate was 79 +/- 9 ppm.
Up to an atrial sensitivity of 1 mV, 100% of AF episodes were diagnosed. The Chorum mode switching algorithms are 100% reliable if > 45% of the AF waves are sensed. In the event of switching failure, the ventricle is protected by an average rate remaining below 80 ppm.
模式切换算法通常用于保护心室免受房性心动过速引起的高心率影响。在房颤（AF）的情况下，这些算法的反应取决于心房感知的质量。Chorum 7234 DDDR起搏器使用一种基于心房节律统计分析的新模式切换算法。它包括两个诊断标准：如果32个周期中有超过28个异常加速，则为“高”；如果64个周期中有超过36个异常加速，则为“低”。
从电生理研究的磁带数据库中，选择持续时间超过2分钟的房颤发作。磁带录音机将心房信号重放至外部Chorum设备。每个发作以编程的心房敏感度从0.4 - 2.0 mV递增的方式重放八次。对于每个诊断标准和每个编程的敏感度，测量心房感知的百分比、切换时间和平均心室率。纳入了10名患者（9名男性和1名女性；年龄62±16岁）的10次房颤发作：1.95±0.97 mV和196±64 ms。当心房敏感度设定在0.4至1.0 mV之间时，该算法诊断房性心动过速的敏感度达到100%。“高”和“低”标准下心房感知事件的平均百分比分别为74%±18%和46%±9%。平均诊断时间分别为28±26秒和68±27秒。少于23%的房颤事件被感知导致两种算法均无法诊断心律失常。在诊断失败的情况下，平均心室起搏率为79±9 ppm。
心房敏感度高达1 mV时，100%的房颤发作可被诊断。如果感知到超过45%的房颤波，Chorum模式切换算法100%可靠。在切换失败的情况下，心室受到平均心率保持在80 ppm以下的保护。
