Introduction:
Pediatric heart transplant recipients (PHTx) undergo frequent surveillance endomyocardial biopsies (EMB). Non-invasive screening for acute rejection (AR) could decrease morbidity, improve quality of life, and decrease healthcare costs.
Hypothesis:
We hypothesized that cardiac magnetic resonance (CMR) extracellular volume (ECV), native T1, and T2 mapping can detect AR in PHTx.
Methods:
PHTx (n=29) were prospectively enrolled at two sites at time of surveillance EMB or EMB for AR. AR was defined as a clinical change or positive EMB requiring intensification of immunosuppression. Subjects with cardiac allograft vasculopathy (n=3) were excluded; ECV was not measured in 2 subjects without rejection (no IV, poor breathholds). CMR without sedation included standard volumetrics, modified Look-Locker inversion recovery before and after contrast, and T2 mapping. A Wilcoxon rank sum was used to assess for a difference between groups.
Results:
Median age was 17 y/o (range 9-19). There were 9 subjects with and 17 subjects without AR. Base ECV, mid ECV, 4-ch ECV, and average ECV were increased in AR vs non-rejection (Table 1, Fig 1). Native T1 and T2 times were also increased in patients with AR (Table 1). A cut-off of 29% for mid ECV and 1070ms for mid native T1 identifies all patients with rejection with 6 false positive results in non-rejection (Fig 1) and could potentially decrease the need for EMB by 65%.
Conclusions:
ECV, native T1, and T2 mapping can non-invasively distinguish between PHTx with and without AR and have potential to decrease the required number of surveillance EMBs.
Cardiovascular magnetic resonance in heart transplant patients: diagnostic value of quantitative tissue markers: T2 mapping and extracellular volume fraction, for acute rejection diagnosis