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Prognostic value of rubidium-82 positron emission tomography in patients after heart transplant
Brian A Mc Ardle1, Ross A Davies1, Li Chen1
1From the Division of Cardiology, Department of Medicine (B.A.M.A., R.A.D., G.R.S., T.D.R., G.D., Y.Y., H.H., L.M.M., E.S., R.H., R.S.B., B.J.W.C.), National Cardiac PET Center (B.A.M.A., R.A.D., T.D.R., R.H., A.G., R.S.B., R.A.d., B.J.W.C.), and Division of Cardiology, Department of Medicine, Cardiovascular Research Methods Center (L.C.), University of Ottawa Heart Institute. Ottawa, Canada.
Insights
Rubidium-82 positron emission tomography can identify cardiac allograft vasculopathy after heart transplant. Abnormalities in myocardial flow reserve and blood flow predict adverse events in these patients.
Area of Science:
- Cardiology
- Nuclear Medicine
- Transplantation
Background:
- Cardiac allograft vasculopathy (CAV) significantly impacts prognosis after heart transplantation.
- Accurate detection and risk stratification of CAV remain challenging.
- Rubidium-82 positron emission tomography (Rb-82 PET) offers quantitative myocardial blood flow (MBF) assessment, potentially aiding risk stratification.
Purpose of the Study:
- To evaluate the utility of dipyridamole Rb-82 PET for risk stratification in heart transplant recipients.
- To determine if quantitative MBF parameters predict adverse clinical outcomes in this population.
Main Methods:
- Prospective enrollment of 140 heart transplant patients undergoing dipyridamole Rb-82 PET.
- Quantification of absolute MBF at rest and stress, and calculation of myocardial flow reserve (MFR).
- Follow-up for all-cause death, acute coronary syndrome, and heart failure hospitalization.
Main Results:
- 14 adverse events occurred during a median follow-up of 18.2 months.
- Lower MFR and reduced mean stress MBF were significant predictors of adverse outcomes.
- Relative perfusion defects also correlated with adverse events.
Conclusions:
- Abnormalities detected by Rb-82 PET, including reduced MFR and stress MBF, predict adverse events in heart transplant patients.
- These findings suggest Rb-82 PET's potential role in managing CAV.
- Larger studies are needed to validate these results.
Background:
Cardiac allograft vasculopathy is a key prognostic determinant after heart transplant. Detection and risk stratification of patients with cardiac allograft vasculopathy are problematic. Positron emission tomography using rubidium-82 allows quantification of absolute myocardial blood flow and may have utility for risk stratification in this population.
Methods And Results:
Patients with a history of heart transplant undergoing dipyridamole rubidium-82 positron emission tomography were prospectively enrolled. Myocardial perfusion and left ventricular ejection fraction were recorded. Absolute flow quantification at rest and after dipyridamole stress as well as the ratio of mean global flow at stress and at rest, termed myocardial flow reserve, were calculated. Patients were followed for all-cause death, acute coronary syndrome, and heart failure hospitalization. A total of 140 patients (81% men; median age, 62 years; median follow-up, 18.2 months) were included. There were 14 events during follow-up (9 deaths, 1 acute coronary syndrome, and 4 heart failure admissions). In addition to baseline clinical variables (estimated glomerular filtration rate, previously documented cardiac allograft vasculopathy), relative perfusion defects, mean myocardial flow reserve, and mean stress myocardial blood flow were significant predictors of adverse outcome.
Conclusions:
Abnormalities on rubidium-82 positron emission tomography were predictors of adverse events in heart transplant patients. Larger prospective studies are required to confirm these findings.
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