Evaluating the Effectiveness of Sildenafil at Improving Health Outcomes and Exercise Ability in People With Diastolic Heart Failure (The RELAX Study)

DHF is a condition in which one of the chambers of the heart, the left ventricle, loses its
ability to relax completely because the muscle has become too stiff. When this occurs, the
heart is unable to properly fill with blood, which can lead to decreased blood circulation.
People with DHF may experience shortness of breath and pulmonary congestion, which is an
abnormal build-up of fluid in the lungs. Current treatment for DHF includes
guidelines/recommendations to lower blood pressure, stop smoking, and lose weight, but there
are no medications available to specifically treat DHF. Sildenafil, commonly known as
Revatio or Viagra, is a medication that increases the supply of blood to the lungs and
reduces the workload of the heart. Preliminary studies have shown that sildenafil may be
beneficial at improving heart and lung function in people with DHF, but more research is
needed to confirm these findings. The purpose of this study is to determine if sildenafil
can improve exercise ability and health outcomes in people with DHF.

This 24-week study will enroll people with DHF. Participants will be randomly assigned to
receive either sildenafil or placebo three times a day for 24 weeks. Participants will
attend study visits at baseline and Weeks 1, 4, 12, 13, and 24. At most study visits, the
following procedures will occur: physical exam, medical history review, questionnaires,
blood collection, 6-minute walk test to measure endurance, and an exercise test. At baseline
and Week 24, participants will also undergo an electrocardiogram, which will measure the
electrical activity of the heart, and a cardiac magnetic resonance imaging (MRI) procedure
and an echocardiogram, which will both obtain pictures of the heart. At Weeks 3, 8, 16, and
20, study researchers will call participants to collect health information.