Traditionally, evaluation of patients with suspected coronary artery disease has focused on the epicardial coronary system. More recently, investigators have come to appreciate better that the status of the coronary microcirculation can influence significantly long-term morbidity and mortality. Although cardiac transplant recipients commonly develop microcirculatory dysfunction, its timing and its effect on outcomes is unclear. Patients with acute myocardial infarction, despite successful recanalization of an occluded epicardial artery, suffer from microcirculatory dysfunction, both in the infarcted region, as well as in myocardium remote from the infarction. However, the incidence and implications of micro-circulatory dysfunction in areas remote from an acutely infarcted territory are poorly understood. To date, evaluation of the coronary microcirculation has been limited by techniques which incorporate the epicardial system into their assessment. Additionally, most methods require specialized equipment and/or analyses. Others are limited by their qualitative nature. Finally, the majority of methods are noninvasive, yet many patients first present for evaluation of their coronary arterial system in the cardiac catheterization laboratory. The first goal of this project is to demonstrate that an invasive, coronary wire-based method for evaluating the coronary microcirculation is easy to perform and interpret, quantitative, and correlates well with standard methods for assessing the microcirculation. The technique will be validated in a porcine model of epicardial artery and microcirculatory disease. It's correlation with PET imaging, the current gold standard noninvasive method of evaluating the microcirculation, will then be tested in patients with and without microcirculatory dysfunction. The second and third goals of this study will be to apply this technique to gain a better understanding of the role of the microcirculation in the outcomes of cardiac transplant patients and those suffering from acute myocardial infarction.
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