CHANGES IN CARDIAC REPOLARIZATION RESULTING FROM VENTRICULAR PACING

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子项目和研究者（PI）可能从另一个NIH来源获得主要资金，因此可以在其他CRISP条目中表示。所列机构为中心，不一定是研究者所在机构。术语“心脏记忆”已被用于描述在心脏的去极化的矢量（或方向）改变之后在心电图上发生的变化。例如，在心脏起搏一段时间后，T波将改变其形态或形状，尽管返回到正常去极化向量。这种变化将持续很多天。T波代表心脏复极。最近，复极的变化已被证明与死亡率增加有关。复极的措施已经开发量化这些变化。研究者假设，由去极化向量变化引起的T波变化可引起与风险增加相关的复极异常。传统上，患有窦房结功能障碍的患者会接受双腔起搏器，心室起搏是常规操作。此类患者不需要心室起搏，仅需要心房起搏。因此，将比较一组患者在心房起搏和心室起搏后的复极特征。 研究设计为双盲、交叉试验。将评价因窦房结功能障碍而植入双腔起搏器的患者安全接受心房起搏的能力。排除房室传导阻滞患者。随机分配至心房起搏组或双腔起搏组。在此模式下起搏超过40天后，患者将返回并测量复极和去极。所有这些测量都将以非侵入性方式进行。患者的起搏器将重新程控为替代模式，患者将在额外40天后返回进行重复测量。将根据仅从心房起搏的能力选择患者。此外，将通过以相对较高的速率起搏心脏并观察房室传导阻滞来测试从该腔室以正常速率起搏的能力。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The term "cardiac memory" has been used to describe changes that occur on the electrocardiogram after a change in the vector (or direction) of depolarization of the heart. For example, after a period of pacing the heart, the T wave will change its morphology or shape despite a return to the normal depolarization vector. This change will persist for many days. The T wave is representative of cardiac repolarization. Recently, changes in repolarization have been shown to be associated with increased mortality. Measures of repolarization have been developed which quantify these changes. The investigator hypothesizes that T wave changes induced by changes in the vector of depolarization induce repolarization abnormalities associated with increased risk. Patients with sinus node dysfunction traditionally receive dual chamber pacemakers and ventricular pacing is instituted as a matter of routine. Such patients do not need ventricular pacing and only require atrial pacing. Thus repolarization characteristics of a group of patients after atrial pacing as well as after ventricular pacing will be compared. The study design will be a double blinded, crossover trial. Patients with dual chamber pacemakers, implanted for sinus node dysfunction, will be evaluated for the ability to undergo atrial pacing safely. Patients with atrioventricular block are excluded. Assignment to an atrial pacing group or a dual chamber pacing group will be random. After greater than forty days of pacing in this mode, the patient will return and measurement of repolarization and depolarization will be made. All of these measurements will be done noninvasively. The patient's pacemaker will be reprogrammed to the alternative mode and the patient will return for repeat measurements after 40 additional days. Patients will be selected for the ability to be paced only from the atrium. Additionally, the ability to pace at normal rates from this chamber will be tested by pacing the heart at a relatively high rate and observing for AV block.