Native T1 mapping versus myocardial perfusion reserve index for coronary microvascular dysfunction detection in patients with ischaemia and nonobstructive coronary artery disease: positron emission tomography/magnetic resonance imaging validation.

Aim

Native T1 mapping has not been systematically compared with the myocardial perfusion reserve index (MPRI) for detecting coronary microvascular dysfunction (CMVD) in patients with ischaemia and nonobstructive coronary artery disease (INOCA). The aim of this study was to investigate the diagnostic performance of native T1 mapping and MPRI for detecting CMVD compared with positron emission tomography (PET)-derived myocardial flow reserve (MFR).

Materials And Methods

Seventy-seven INOCA patients underwent stress/rest PET/magnetic resonance imaging (MRI), including 3-T native T1 mapping and gadopentetate dimeglumine perfusion MRI. CMVD was defined as PET-derived MFR <2.0. MPRI was calculated using CVI42 software, with native T1 values analysed via endocardial/epicardial contouring.

Results

CMVD patients had significantly higher mean global native T1 values (1238 ± 25 milliseconds vs 1200 ± 21 milliseconds; P < .001) and lower MPRI (1.68 ± 0.34 vs 2.14 ± 0.36; P < .001). Native T1 inversely correlated with global (r = -0.57; P < .001) and regional MFR (r = -0.53; P < .001), and MPRI significantly correlated with global (r = 0.58; P < .001) and regional MFR (r = 0.46; P < .001). Receiver operating characteristic analysis showed comparable diagnostic accuracy between native T1 and MPRI (P = .310). At a cutoff of 1225 milliseconds, native T1 mapping showed 72.7% sensitivity and 93.2% specificity, while MPRI (cutoff <1.99) demonstrated 84.9% sensitivity and 70.5% specificity.

Conclusion

Native T1 mapping correlates inversely with MFR and matches MPRI for CMVD detection in INOCA. This gadolinium-free technique enables safe serial monitoring, particularly for renal-impaired patients, and may serve as a robust surrogate for CMVD severity.