Investigating the Utility of Remote Index of Microvascular Resistance in Patients With Chronic Total Occlusion

The study will enroll subjects who have been scheduled for a clinically-indicated cardiac catheterization, and will evaluate coronary microvascular function in all subjects meeting inclusion criteria with a coronary flow wire. Evaluation of coronary microvascular function may be performed using indirect methods, however the rationale behind the present study is to directly measure microvascular function using direct coronary flow measurements, since the subjects in the study are to undergo a clinically-indicated cardiac catheterization. The overall purpose of the study is to define the presence and severity of coronary microvascular dysfunction subjects with CTO.