Fabry disease (FD) is a rare, lysosomal storage disorder with myocardial sphingolipid accumulation detectable by CMR native T1 mapping. Myocardial native T1 is affected by intramyocardial blood, and as blood has a longer and more variable T1 compared to myocardial T1, blood correction of myocardial T1 has been proposed.
To investigate whether blood correction of native T1 values increases the detection of myocardial sphingolipid accumulation (low native T1) in FD patients.
A retrospective multinational multicenter study, FD patients (n=218, age 47±16 years) and healthy volunteers (n=117, age 29±5 years) underwent CMR at 1.5T (Siemens) at three different sites with a comparison set of non-FD patients (n=200, age 51 ± 18 years) at a fourth site. Native T1 maps used MOLLI. T1 was measured with a single region of interest in the LV septum, and both LV and RV blood pools. A linear correction model using mean R1 (1/T1 average LV + RV blood) was developed at the fourth site as previously described (1), and applied to the FD population and healthy volunteers. Sphingolipid accumulation in FD patients was defined as a native myocardial T1 value below the site specific 95% limits of agreement in healthy volunteers, both for corrected and uncorrected measures.
Prior to blood correction, 134 FD patients (61%) had low myocardial native T1 indicating sphingolipid accumulation (84 (39%) normal myocardial native T1). Of the 84 patients with normal native T1 prior to blood correction, 25 (30%) were reclassified as having low myocardial native T1 following blood correction. Of these 25 reclassified patients, 14 (56%) did not have any CMR signs of cardiac involvement by late gadolinium enhancement or left ventricular hypertrophy. Thus, 14/84 (17%) were reclassified as having cardiac involvement following blood correction. By comparison, 4/134 (3%) of patients with low native T1 prior to blood correction were reclassified to normal myocardial native T1 following blood correction.
Blood correction of myocardial native T1 increases the detection of low myocardial native T1 in 17% of patients with Fabry disease that otherwise had no CMR signs of cardiac involvement. Blood correction of myocardial native T1 has the potential to impact the ability to detect and track cardiac involvement in Fabry disease, and merits prospective studies and histological validation.