VENTRICULAR FIBRILLATION AND ITS ALTERATION BY PACING

描述（来自申请人摘要的逐字）：心脏骤停 通常由心室纤维性颤动（VF）引起。本申请 建议使用心脏标测来回答有关心脏的重要问题。 VF如何维持以及VF如何被改变和控制的机制 在病人和动物身上。有三个具体目标。具体目标1： 量化患者的VF组织，并确定 组织预测自发性VF终止和除颤 阈值（DFT）。将在患者中检验以下关于VF的假设 接受心脏手术或心脏复律器/除颤器植入。（一） 心外膜折返是罕见的和短暂的。(2)传导阻滞更多 频繁的激活前沿平行，而不是垂直于长 肌纤维轴(3)需要最小长度的块来启动 再入(4)虽然心肌梗死周围的组织可能是 对于VF启动，它不有助于VF维持。(5)定量 激活前组织的措施预测VF何时停止 自发的(6)一组略有不同的量化指标 识别DFT较低的患者。具体目标2：确定算法， 在猪VF期间通过起搏最大化心肌夺获。光学和 将进行电标测以测试以下假设。（一） 逐渐增加起搏频率会增加 在某些心脏区域被捕获。(2)逐渐减慢起搏频率 允许在其他区域捕获更多组织。(3)交替减速和 增加起搏速率将使捕获的组织量最大化。 (4)从适当间隔的两个部位起搏将捕获比 通过单独从每侧起搏捕获的组织的总和。(5)从上往下走 16个站点同时进行将阻止VF。(6)从那些 除颤冲击电位梯度最弱时DFT会降低。(7)的 心外膜可以被分成多个区域，每个区域具有不同的激活率。 (8)从较快域起搏比从较慢域起搏捕获更多组织 域.具体目标3：确定是否可以通过以下方式夺获心肌： 患者VF期间起搏。最成功的起搏技术和大多数 具体目标2的假设将在患者中进行检验。

DESCRIPTION (Verbatim from Applicant's Abstract): Sudden cardiac arrest frequently is caused by ventricular fibrillation (VF). This application proposes to use cardiac mapping to answer important questions about the mechanisms of how VF is maintained and how VF can be altered and controlled by pacing in patients and animals. There are three specific aims. Specific Aim 1: Quantify VF organization in patients and determine which measures of organization predict spontaneous VF termination and the defibrillation threshold (DFT). The following hypotheses about VF will be tested in patients undergoing cardiac surgery or cardioverter/defibrillator implantation. (1) Epicardial reentry is uncommon and short-lived. (2) Conduction block is more frequent for activation fronts parallel rather than perpendicular to the long axis of myofibers. (3) A minimal length of block is necessary to initiate reentry. (4) While spared tissue around a myocardial infarct may be responsible for VF initiation, it does not contribute to VF maintenance. (5) Quantitative measures of activation front organization predict when VF will stop spontaneously. (6) A slightly different group of quantitative measures identifies patients with a low DFT. Specific Aim 2: Determine algorithms to maximize the capture of myocardium by pacing during VF in pigs. Optical and electrical mapping will be performed to test the following hypotheses. (1) Gradually increasing the pacing rate will increase the amount of tissue captured in some cardiac regions. (2) Gradually slowing the pacing rate will allow the capture of more tissue in other regions. (3) Alternately slowing and increasing the pacing rate will maximize the amount of tissue that is captured. (4) Pacing from two sites spaced appropriately apart will capture more than the sum of the tissue captured by pacing from each side alone. (5) Pacing from up to 16 sites simultaneously will halt VF. (6) Pacing from regions in which the defibrillation shock potential gradient is weakest will lower the DFT. (7) The epicardium can be divided into domains, each with a different activation rate. (8) Pacing from faster domains captures more tissue than pacing from slower domains. Specific Aim 3: Determine if it is possible to capture myocardium by pacing during VF in patients. The most successful pacing techniques and most of the hypotheses of Specific Aim 2 will be tested in patients.