CHANGES IN CARDIAC REPOLARIZATION RESULTING FROM VENTRICULAR PACING

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。“心脏记忆”一词被用来描述心脏去极化矢量（或方向）改变后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，尽管它回到了正常的去极化向量。这种变化将持续许多天。T波是心脏复极的代表。最近，重极化的变化已被证明与死亡率增加有关。已经开发出了量化这些变化的复极化测量方法。研究者推测，由去极化矢量的改变引起的T波变化会诱发与风险增加相关的复极化异常。窦房结功能障碍的患者传统上接受双室起搏器和心室起搏作为常规事项。这类患者不需要心室起搏，只需要心房起搏。从而比较一组患者心房起搏后和心室起搏后的复极特征。研究设计为双盲交叉试验。因窦房结功能障碍而植入双室起搏器的患者，将评估其安全进行心房起搏的能力。排除有房室传导阻滞的患者。随机分配到心房起搏组或双室起搏组。在该模式下起搏超过40天后，患者将返回并测量复极化和去极化。所有这些测量都是无创的。患者的起搏器将被重新编程为备用模式，患者将在40天后返回进行重复测量。患者将根据仅从心房起搏的能力进行选择。此外，将通过以相对较高的心率起搏并观察房室传导阻滞来测试该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.