Matching Perfusion and Metabolic Activity in HFpEF

This study is investigating a type of heart failure called HFpEF (heart failure with preserved ejection fraction), where the heart pumps normally but is too stiff. Researchers are looking at how blood flow and energy use in the heart muscle are matched or mismatched. **You may be eligible if:** - You have moderate heart failure symptoms (breathlessness or fatigue with activity) - Your heart's pumping function is at least 50% (relatively normal) - Your condition has been stable for at least 2 weeks - You have evidence of increased pressure inside your heart (based on echocardiogram or prior testing) - You are 18 or older **You may NOT be eligible if:** - You are pregnant - You take certain heart medications (nitrates or phosphodiesterase inhibitors) that cannot be stopped - Your heart rate is uncontrolled (resting rate above 100 beats per minute due to atrial fibrillation) - You have severe anemia, significant heart valve disease, hypertrophic cardiomyopathy, or serious lung disease - Your kidney function is severely impaired (eGFR below 30) - You are unable or unwilling to exercise Talk to your doctor to see if this trial is right for you.