Myocardial T1-mapping and extracellular volume in pulmonary arterial hypertension : a systematic review and meta-analysis

Introduction

Elevated myocardial T1-mapping and extracellular volume (ECV) measured on cardiac MR (CMR) imaging is associated with myocardial abnormalities such as oedema or fibrosis. This meta-analysis aims to provide a summary of T1-mapping and ECV values in pulmonary arterial hypertension (PAH) and compare their values with controls.

Methods

We searched CENTRAL, MEDLINE, Embase, and Web of Science in August 2020. We included CMR studies reporting T1-mapping or ECV values in adults with any type of PAH. We calculated the mean difference of T1-values and ECV between PAH and controls.

Results

We included 12 studies with 674 participants. T1-values were significantly higher in PAH with the highest mean difference (MD) recorded at the RV insertion points (RVIP) (108 milliseconds (ms), 95% confidence intervals (CI) 89 to 128), followed by the RV free wall (MD 91 ms, 95% CI 56 to 126). The pooled mean T1-value in PAH at the RVIP was 1084, 95% CI (1071 to 1097) measured using 1.5 Tesla Siemens systems. ECV was also higher in PAH with an MD of 7.5%, 95% CI (5.9 to 9.1) at the RV free wall.

Conclusion

T1 mapping values in PAH patients are on average 9% higher than healthy controls when assessed under the same conditions including the same MRI system, magnetic field strength or sequence used for acquisition. The highest T1 and ECV values are at the RVIP. T1 mapping and ECV values in PH are higher than the values reported in cardiomyopathies and were associated with poor RV function and RV dilatation.