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CMR Can Detect Acute Allograft Rejection After Heart Transplant
Study Questions:
What is the sensitivity of multiparametric cardiac magnetic resonance imaging (CMR) for the detection of acute cardiac allograft rejection (ACAR)?
Methods:
The investigators prospectively recruited 58 transplant recipients (age 47.0 ± 14.7 years) and 14 controls (age 47.7 ± 16.7 years) from August 2014 to May 2017, who underwent 97 CMRs (83 transplant, 14 control) for assessment of global left ventricular function and myocardial T2, T1, and extracellular volume fraction (ECV). CMRs were divided into four groups based on biopsy grade: controls (n = 14), No ACAR (no history of ACAR, n = 36), Past ACAR (history of ACAR, n = 24), ACAR+ (active grade ≥1R ACAR, n = 23). CMR parameters that were the strongest independent predictors of ACAR, along with basic demographic information (age at CMR, time since transplant, sex), were evaluated with binary logistic regression to determine if a combination of factors was predictive of ACAR.
Results:
Myocardial T2 was significantly higher in patients with past ACAR compared to No ACAR (51.0 ± 3.8 ms vs. 49.2 ± 4.0 ms, p = 0.02) and in No ACAR patients compared to controls (49.2 ± 4.0 ms vs. 45.2 ± 2.3 ms, p < 0.01). ACAR+ patients demonstrated increased T2 compared to the No ACAR group (52.4 ± 4.7 ms vs. 49.2 ± 4.0 ms, p < 0.01), but not compared to the Past ACAR group. In contrast, ECV was significantly elevated in ACAR+ patients compared to recipients without ACAR regardless of history of ACAR (No ACAR: 31.5 ± 3.9% vs. 26.8 ± 3.3%, p < 0.01; Past ACAR: 31.5 ± 3.9% vs. 26.8 ± 4.0%, p < 0.01). Receiver operating characteristic curve (ROC) analysis revealed that a combined model of age at CMR, global T2, and global ECV was predictive of ACAR (area under the curve = 0.84).
Conclusions:
The authors concluded that a combination of CMR-derived myocardial T2 and ECV has potential as a noninvasive tissue biomarker for ACAR.
Perspective:
This study reports that T2 was elevated in ACAR+ patients compared to patients without a history of ACAR, and ECV was elevated in ACAR+ patients compared to recipients without active ACAR, regardless of ACAR history. Furthermore, ROC analysis confirmed the potential for multiparametric CMR within 3 months of endomyocardial biopsy to differentiate between patients with and without ACAR. These data suggest that CMR may potentially serve as a noninvasive and less expensive alternative to endomyocardial biopsy in patients in whom there is a low to moderate index of suspicion for rejection. Larger studies during acute ACAR are indicated to confirm these findings, and for further development of multiparametric CMR for transplant recipient surveillance.
Keywords: Allografts, Biomarkers, Biopsy, Cardiac Surgical Procedures, Diagnostic Imaging, Graft Rejection, Heart Failure, Heart Transplantation, Magnetic Resonance Imaging, Myocardium, Ventricular Function, Left
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