Sex Differences in Early Myocardial Repolarization

描述（由申请方提供）：自20世纪初以来，已知QT间期存在性别差异。 相比之下，ST段的性别差异包括较高的ST段高度和升高的J点，只是最近才被详细研究。 临床心律失常存在性别差异，这可能与性别ECG差异有关。 室性心动过速在35 - 40%的男性中是可诱导的，但在患有冠状动脉疾病和左室功能障碍的女性中只有20%是可诱导的。 女性发展VF作为心脏骤停原因的可能性只有男性的一半。 某些心律失常的易感性存在重要的性别差异，这一事实表明男性和女性之间存在基本的电生理学差异，这些差异仍有待阐明。 本研究的总体假设是，早期心肌复极的性别差异是频率依赖性的，是由于性激素的影响，并改变临床心律失常的倾向。 将检验以下具体假设。 1)ST段高度的一个主要决定因素是性激素水平。 我们还将试图确定ST段抬高最常见于运动男性有时被称为“早期复极”是否是一个遥远的临床综合征。 2)心肌复极的性别差异取决于心率和自主神经张力。 这一目标将通过检查男性和女性自主神经操作前后ST段高度的心率依赖性来实现。 3)雄激素而不是雌激素或孕酮调节早期复极。 这一目标将通过研究将接受性激素治疗的受试者来实现。 4)先前根据不完整数据被定性为良性的ST段抬高改变了适当病理条件下心律失常的倾向。 为此，将检查静息ECG上ST段抬高和室性心动过速和室颤之间的关系。 研究将在急性和已愈合心肌梗死患者以及非缺血性扩张型心肌病患者中进行。 希望本研究的结果将通过揭示重要的性别相关差异来提高对心肌生理学的理解，并改善心律失常的风险分层和治疗。

DESCRIPTION (provided by applicant): Sex differences in the QT interval have been known since the early 1900s. In contrast, sex differences in the ST segment consisting of a higher ST height and elevated J point have only recently been studied in detail. There are sex differences in clinical arrhythmias that may be associated with the sex ECG differences. Ventricular tachycardia is inducible in 35-40 percent of men but only 20 percent of women with coronary artery disease and LV dysfunction. Women are only half as likely as men to develop VF as a cause of cardiac arrest are. The fact that there are important sex differences in susceptibility to certain arrhythmias suggests the existence of fundamental electrophysiologic distinctions between males and females that remain to be elucidated. The overall hypothesis of the present study is that sex differences in early myocardial repolarization are rate dependent, are due to effects of sex hormones and alter the propensity to clinical arrhythmias. The following specific hypotheses will be tested. 1) A major determinant of ST height is the level of sex hormones. We will also seek to determine whether the ST elevation seen most often in athletic males sometimes called "early repolarization" is a distant clinical syndrome. 2) Sexrelated differences in myocardial repolarization are dependent on both heart rate and autonomic tone. This aim will be accomplished by examining the heart rate dependence of ST height before and after autonomic manipulations in both men and women. 3) Androgens but not estrogens or progesterone modulate early repolarization. This aim will be accomplished by studying subjects who will undergo sex hormone therapy. 4) ST elevation that has previously been characterized as benign based on incomplete data alters the propensity to arrhythmias under appropriate pathologic conditions. In this aim, the relationship between ST elevation on the resting ECG and ventricular tachycardia and ventricular fibrillation will be examined. Studies will be performed in patients with acute and healed myocardial infarction and in patients with non-ischemic dilated cardiomyopathy. It is hoped that the results of this study will improve the understanding of myocardial physiology and improve risk stratification and therapy for arrhythmias by uncovering important sex related differences.