Medtronic, Minneapolis, Minnesota, USA.
J Card Fail. 2011 Jul;17(7):569-76. doi: 10.1016/j.cardfail.2011.03.002. Epub 2011 Apr 22.
Intrathoracic impedance fluid monitoring has been shown to predict worsening congestive heart failure (CHF) in patients with implantable devices. We developed and externally validated a modified algorithm to identify worsening heart failure (HF) by using intrathoracic impedance.
The modified algorithm was developed by using published data from 81 CHF subjects averaging 259 days of follow-up. Device-measured daily impedance was input to both the existing and the modified intrathoracic impedance fluid monitoring algorithms to determine a reference impedance and a fluid index (FI). Separate validation sets included 326 cardiac resynchronization therapy device (CRT-D) patients with an average 333 days of follow-up (group 1) and 104 CRT-D/implantable cardioverter/defibrillator (ICD) patients followed for an average of 520 days (group 2). Clinicians and patients in group 2 were blinded to impedance and FI data. HF events included adjudicated HF hospitalizations or emergency room visits. Sensitivity was defined as the percentage of HF events preceded by FI exceeding the predefined threshold (60 Ω-d) within the last 2 weeks. Unexplained detections were FI threshold crossing events not followed by a HF event within 2 weeks. The modified algorithm significantly decreased unexplained detections by 30% (P = .01; GEE) in the development set, 30% (P < .001) in the group 1 validation set, and 43% (P < .001) in group 2. Sensitivity did not change significantly in any group. Simulated monthly review of FI threshold crossings identified subjects at significantly greater risk of worsening HF within the next 30 days.
A modified intrathoracic impedance based fluid detection algorithm lowered the number of unexplained FI threshold crossings and identified patients at significantly increased immediate risk of worsening HF.
已有研究表明，胸腔内阻抗液体监测可预测植入式设备患者充血性心力衰竭（CHF）的恶化情况。我们开发并外部验证了一种改良算法，通过使用胸腔内阻抗来识别心力衰竭（HF）恶化。
改良算法是利用 81 例 CHF 患者的已发表数据开发的，平均随访时间为 259 天。将设备测量的每日阻抗输入到现有的和改良的胸腔内阻抗液体监测算法中，以确定参考阻抗和液体指数（FI）。单独的验证集包括 326 例心脏再同步治疗设备（CRT-D）患者，平均随访时间为 333 天（组 1）和 104 例 CRT-D/植入式心脏复律除颤器（ICD）患者，平均随访时间为 520 天（组 2）。组 2 中的临床医生和患者对阻抗和 FI 数据均不知情。HF 事件包括经裁决的 HF 住院或急诊就诊。敏感性定义为在最后 2 周内 FI 超过预定阈值（60 Ω-d）的 HF 事件百分比。未解释的检测是指 FI 阈值交叉事件在 2 周内未出现 HF 事件。在开发组中，改良算法显著减少了 30%的未解释检测（P =.01；GEE），在组 1 的验证组中减少了 30%（P <.001），在组 2 中减少了 43%（P <.001）。在任何一组中，敏感性均无显著变化。FI 阈值交叉的模拟每月回顾确定了在接下来的 30 天内 HF 恶化风险显著增加的患者。
一种改良的基于胸腔内阻抗的液体检测算法降低了未解释的 FI 阈值交叉的数量，并确定了 HF 恶化风险显著增加的患者。
