Stress Cardiac MRI for Evaluation of Nonspecific Allograft Dysfunction
Condition: Heart Transplant; Acute Graft Rejection; Chronic Graft Rejection
Intervention: Regadenoson; Gadolinium; Cardiac MRI
Intervention description: For use in stress myocardial perfusion imaging.; For use in both perfusion imaging and late gadolinium enhancement.; Cardiac MRI will be the imaging modality for perfusion imaging, late gadolinium enhancement and obtaining mean T1 segmental values of the heart.
Intervention MeSH terms: Regadenoson
Phase: Phase 4
Study type: Interventional
Primary purpose: Diagnostic
Allocation: Non-Randomized
Intervention model: Parallel Assignment
Masking: Single (Outcomes Assessor)
Enrollment: 14.0
Sex: All
Minimum age: 18 Years
Healthy volunteers: No
Keywords: heart transplantation; cardiac MRI; graft rejection; nonspecific allograft dysfunction; allograft vasculopathy

Summary:

      The investigators will use cardiac MRI to measure the myocardial perfusion reserve and amount
      of myocardial edema and fibrosis in heart-transplant patients with nonspecific allograft
      dysfunction in contrast to those with normal graft function. The investigators hypothesize
      that patients with nonspecific allograft dysfunction will demonstrate decreased myocardial
      perfusion reserve, related to microvascular allograft vasculopathy, compared to those with
      normal graft function.
    

Eligibility criteria:

        Inclusion Criteria:

          -  Age greater than or equal to 18 years old.

          -  At least three months status post heart transplantation.

          -  Heart-transplant patients with normal graft function (left ventricular ejection
             fraction equal to or greater than 55%) and no prior history of clinically significant
             acute rejection episodes that required modification of the immunosuppressive regimen
             or cardiac allograft vasculopathy.

          -  Heart-transplant patients with nonspecific allograft dysfunction (left ventricular
             ejection fraction equal to or less than 50% AND decrease from post-transplant baseline
             ejection fraction by an absolute difference of 10% or greater, no formal diagnosis of
             allograft vasculopathy by coronary angiogram or coronary vascular ultrasonography, and
             no history of prior acute rejection episodes known to have decreased left ventricular
             ejection fraction to or less than 50%).

        Exclusion Criteria:

          -  Biopsy proven acute rejection episode in the past 3 months.

          -  Patients with symptoms or signs of acute myocardial ischemia or recent acute coronary
             syndrome in the past 3 months.

          -  Uncontrolled obstructive ventilatory disease including asthma and COPD.

          -  Second or third degree AV nodal block.

          -  Sinus node dysfunction.

          -  Contraindications to MRI including pacemakers or implantable
             cardioverter-defibrillators.

          -  Renal dysfunction with an estimated GFR less than 30 mL/min/1.73m2.

          -  Prior adverse reaction to either regadenoson or gadolinium contrast. Prior adverse
             reaction to adenosine will be assessed on a case-by-case basis.

          -  Any invasive procedure, including endomyocardial biopsy and left coronary angiogram,
             performed within one week.

          -  Systolic blood pressure greater than 180 or less than 85 mmHg.

          -  Diastolic blood pressure greater than 120 or less than 40 mmHg.

          -  Resting heart rate greater than 120 or less than 45 beats per minute.

          -  Severe claustrophobia.