Patients will be asked to undergo heart angiogram testing to test for abnormalities in their heart arteries. If the heart angiogram shows that the patients do not have blockages in major heart arteries, then the patients will have coronary flow reserve measurement test (as part of the heart angiogram) to determine whether the patients have abnormally functioning of the small heart arteries. This test will be performed by infusing the three drugs: adenosine, acetylcholine and nitroglycerin. The three drugs are naturally occurring substances and have been used for routine heart angiograms.