Relationship Between Coronary Microvascular Dysfunction and Improvement of Left Ventricular Systolic Function in Patients With Heart Failure With Reduced Ejection Fraction Caused by Non-ischemic Etiology

This study investigates whether problems with tiny blood vessels in the heart (coronary microvascular dysfunction) affect how well the heart recovers its pumping function in people with heart failure who have a weakened heart NOT caused by blocked arteries. Researchers will assess these small vessel problems during routine heart catheterization. **You may be eligible if...** - You are 19 years of age or older - You have been diagnosed with heart failure with a reduced pumping function (ejection fraction of 40% or less) - You have symptoms such as shortness of breath (NYHA class 2 or higher) - You are already scheduled for a coronary angiogram (heart catheterization) as part of your clinical care **You may NOT be eligible if...** - You have significant coronary artery blockages found during angiogram - You are being evaluated for a heart transplant or a mechanical heart pump (LVAD) - Your heart failure is caused by inflammation of the heart lining (restrictive cardiomyopathy, constrictive pericarditis, or active myocarditis) - You have a severe heart valve problem requiring surgery - You have a serious non-heart illness that is life-threatening Talk to your doctor to see if this trial is right for you.