The performance of free-breathing multiparametric SAturation-recovery single-SHot acquisition T1 and T2 mapping in cardiac allograft rejection

Cardiovascular magnetic resonance (CMR) has been studied as an alternative to endomyocardial biopsy (EMB) in orthotopic heart transplant recipients (OHTRs), particularly through breath-hold myocardial T1 and T2 mapping sequences. We aimed to assess the diagnostic performance of the novel free-breathing multiparametric saturation-recovery single-shot acquisition (mSASHA) mapping technique to identify acute cardiac allograft rejection (ACAR) non-invasively against EMB. This retrospective study included n = 21 consecutive OHTRs with suspected ACAR who underwent both a 1.5T CMR scan with mSASHA mapping and an EMB within 5.4 (1.2-14.8) days, and n = 20 healthy controls who underwent CMR with mSASHA mapping. Conventional breath-holding T2-prepared balanced steady-state free precession (T2p-bSSFP) T2 mapping was also acquired. CAR was EMB defined as histological rejection (HR) (acute cellular rejection of ≥ 1 R or acute antibody-mediated rejection of ≥ 1). Overall, n = 21 OHTRs (9 females) with a mean age of 43.2 ± 16.2 years and a median time of 5.4 (1.2-14.8) years since transplantation were included in the study, alongside n = 20 healthy controls. HR was present in n = 9 patients. The HR group showed significantly higher septal mSASHA T2 values compared to the non-HR (n = 12) group (53 ± 6 ms vs. 47 ± 4 ms, p = 0.014). Receiver operator characteristics analysis showed an area under the curve of 0.79 (95% confidence interval 0.59-0.98, p = 0.028) and an optimal cut-off value of 50 ms (sensitivity of 67%, specificity of 75%) for identifying patients with HR using septal mSASHA T2 values. There was at least a moderate correlation of septal and global mSASHA T1 and T2 values (n = 21) with MOLLI T1 (n = 17) and T2p-bSSFP T2 (n = 18) values (r > 0.6, p ≤ 0.003). OHTR patients without HR showed higher septal (T1: 1256 ± 42 ms vs. 1201 ± 46 ms, p = 0.002; T2: 47 ± 4 ms vs. 43 ± 2 ms, p = 0.003) and global mSASHA (T1: 1250 ± 58 ms vs. 1201 ± 45 ms, p = 0.013; T2: 48 ± 5 ms vs. 43 ± 2 ms, p = 0.009) values compared to normal controls (n = 20). In the control group, native mSASHA T1 and T2 values were higher in females (n = 9) than in males. Free-breathing mSASHA T2 mapping may be useful in identifying histological changes associated with ACAR, overcoming the challenges of breath holding and with good diagnostic performance.