Native T₁ Mapping in the Diagnosis of Cardiac Allograft Rejection: A Prospective Histologically Validated Study

This study aimed to determine the role of T₁ mapping in identifying cardiac allograft rejection.

Endomyocardial biopsy (EMBx), the current gold standard to diagnose cardiac allograft rejection, is associated with potentially serious complications. Cardiac magnetic resonance (CMR)-based T₁ mapping detects interstitial edema and fibrosis, which are important markers of acute and chronic rejection. Therefore, T₁ mapping can potentially diagnose cardiac allograft rejection noninvasively.

Patients underwent CMR within 24 h of EMBx. T₁ maps were acquired at 1.5-T. EMBx-determined rejection was graded according to International Society of Heart and Lung Transplant (ISHLT) criteria.

Of 112 biopsies with simultaneous CMR, 60 were classified as group 0 (ISHLT grade 0), 35 as group 1 (ISHLT grade 1R), and 17 as group 2 (2R, 3R, clinically diagnosed rejection, antibody-mediated rejection). Native T₁ values in patients with grade 0 biopsies and left ventricular ejection fraction >60% (983 ± 42 ms; 95% confidence interval: 972 to 994 ms) were comparable to values in nontransplant healthy control subjects (974 ± 45 ms; 95% confidence interval: 962 to 987 ms). T₁ values were significantly higher in group 2 (1,066 ± 78 ms) versus group 0 (984 ± 42 ms; p = 0.0001) and versus group 1 (1,001 ± 54 ms; p = 0.001). After excluding patients with an estimated glomerular filtration rate <50 ml/min/m², there was a moderate correlation of log-transformed native T₁ with high-sensitivity troponin T (r = 0.54, p < 0.0001) and pro-B-type natriuretic peptide (r = 0.67, p < 0.0001). Using a T₁ cutoff value of 1,029 ms, the sensitivity, specificity, and negative predictive value were 93%, 79%, and 99%, respectively.

Myocardial tissue characterization with T₁ mapping displays excellent negative predictive capacity for the noninvasive detection of cardiac allograft rejection and holds promise to reduce substantially the EMBx requirement in cardiac transplant rejection surveillance.