SEX DIFFERENCES IN REPOLARIZATION AND EARLY REPOLARIZATION (AIM 3)

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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. In this project, we hypothesize that the level of sex hormones is a major determinant of myocardial repolarization (ST height). The rationale supporting this study is that there are important sex differences in susceptibility to certain arrhtyhmias (irregular heartbeats), suggesting the existence of fundamental electrophysiologic distinctions between males and females. To test our hypothesis, we will examine the relationship between ST height and sex hormone levels in a mixed population of subjects (young and old men and women) without heart disease undergoing hormonal replacement therapy and in subjects not undergoing hormal replacement therapy. Specifically, subjects will be given an echocardiogram (a test using a sound wave that outlines the size of the heart and determines how well the heart is functioning), asked to do an exercise test on a stationary bicycle (which records the heart's electrical activity while the subject is pedaling), undergo, if females with regular menstrual cycles, a urinary ovulation predictor test and give 20 ccs of blood to determine several sex hormone levels. We will seek to determine the magnitude of changes in ST variables according to hormone levels changes occuring during the different phases of a normal menstrual cycle and following a long-term sex hormones therapy.