Caswell S A, Jenkins J M, DiCarlo L A
Department of Electrical Engineering and Computer Science, University of Michigan and Michigan Heart and Vascular Institute, Ann Arbor, USA.
J Electrocardiol. 1998;30 Suppl:131-6. doi: 10.1016/s0022-0736(98)80060-5.
Implantable cardioverter defibrillators (ICDs) detect and defibrillate ventricular fibrillation (VF) and ventricular tachycardia (VT). Other therapies which use less energy are also available to terminate VT. Previous studies have shown that ICD rate schemes often misdiagnose VT as VF. In this study, an improved VF classification scheme was designed and tested, which employs the classic rate criteria plus paired signal concordance (PSC); PSC uniquely detects VF where VT and VF rates overlap (220-340 ms). Two signals from a bipolar pair (1 cm) recorded in a unipolar sense exhibit similar signal shape for concordant rhythms, such as sinus rhythm and VT, and disconcordance for VF. Once the rate criterion is met, PSC is measured by the peak normalized cross-correlation coefficient calculated over the depolarization. Variability, measured by a modified range, determined the contextual diagnosis over a passage. Sinus rhythm (20), VT (12), VF (22), atrial fibrillation (10), sinus rhythm with ventricular premature depolarizations (7), and polymorphic VT (4) passages were recorded from 38 patients. Rate-PSC was tested with unfiltered, digitized signals (1-500 Hz, 1,000 samples per second) and with filtered, downsampled signals (1-50 Hz, 100 samples per second). Sensitivity values, or percentage of correct VF detection, and specificity values, or detection of all other rhythms, were generated and compared with simulations of three commercial ICDs programmed to similar settings as rate-PSC and to nominal settings. The sensitivity values for rate-PSC with unfiltered and with filtered signals and for ICDs with 220 ms and with nominal settings were 100%, 100%, 48-80%, and 100%, respectively; the corresponding specificity values were 95%, 83%, 93%, and 7-13%, respectively. It was concluded that the rate-PSC scheme was able to reliably separate VF from other rhythms, even rhythms that have a variable morphology or variable rate. With the confidence of accurate VF detection, use of low-energy therapies for non-VF rhythms will increase device longevity and enhance patient comfort.
植入式心脏复律除颤器（ICD）可检测并除颤心室颤动（VF）和室性心动过速（VT）。也有其他能量较低的治疗方法可用于终止VT。既往研究表明，ICD的心率方案常将VT误诊为VF。在本研究中，设计并测试了一种改进的VF分类方案，该方案采用经典心率标准加配对信号一致性（PSC）；PSC能独特地检测出VT和VF心率重叠（220 - 340毫秒）时的VF。在单极感知中记录的来自一对双极电极（1厘米）的两个信号，对于协调一致的节律（如窦性节律和VT）呈现相似的信号形状，而对于VF则呈现不一致。一旦满足心率标准，PSC通过在去极化过程中计算的峰值归一化互相关系数来测量。通过修正范围测量的变异性决定了一段时间内的情境诊断。从38例患者记录了窦性节律（20段）、VT（12段）、VF（22段）、心房颤动（10段）、伴有室性早搏去极化的窦性节律（7段）和多形性VT（4段）的心电信号段。对未经滤波的数字化信号（1 - 500赫兹，每秒1000个样本）以及经过滤波、下采样的信号（1 - 50赫兹，每秒100个样本）进行了心率 - PSC测试。生成了灵敏度值（即正确检测VF的百分比）和特异度值（即检测所有其他节律的能力），并与三款编程设置与心率 - PSC相似以及标称设置的商用ICD的模拟结果进行比较。未经滤波信号和经滤波信号的心率 - PSC的灵敏度值以及设置为220毫秒和标称设置的ICD的灵敏度值分别为100%、100%、48 - 80%和100%；相应的特异度值分别为95%、83%、93%和7 - 13%。得出的结论是，心率 - PSC方案能够可靠地将VF与其他节律区分开来，即使是形态或心率可变的节律。有了准确检测VF的信心，对非VF节律使用低能量治疗将增加设备使用寿命并提高患者舒适度。
