Introduction
Cardiac magnetic resonance (CMR) is a non-invasive imaging modality capable of
identifying structural and tissular heart pathology and has a particular interest when
myocardial fibrosis is suspected. Images performed after administration of a
Gadolinium-based contrast agent allow to visualize localized, macroscopic myocardial
scar. Specific myocardial mapping-sequences can detect more diffuse and subtle
pathologies. T1-mapping with extracellular volume (ECV) estimation has proven to be
a robust and reproducible method to detect microscopic interstitial fibrosis. In order to
be able to detect pathology, establishment of reference values in normal hearts is
recommended for every specific MR-system and T1-mapping sequence.
Method
Subjects without known cardiovascular risk factors nor heart disease and with a normal
CMR study were retrospectively included. On a 1.5T scanner, an ECG-triggered
modified Look-Locker inversion recovery sequence which is a standard T1-mapping
sequence was acquired on a short-axis basal slice of the left ventricle (LV). Native and
post-contrast myocardial T1 relaxation time was measured, and ECV calculated for six
LV- segments as well as mean values for the whole short-axis slice.
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Results
Fifty patients (age 43 ± 15y, 36% male) were included. Left ventricular end-diastolic
volume and mass were 78±14 ml/m2 and 94 ± 27 g, respectively. Mean native T1-
mapping and ECV values for the left ventricle were 982 ± 35 (range 886-1051 msec)
and 22.9 ± 2.7% (16.6-28.3%), respectively. Women had significantly higher mean T1
and ECV values than men (987 ± 35ms vs 966 ± 31ms, p=0.04; 24 ± 2% vs 21 ± 3%,
p<0.001). Native T1 and ECV values didn’t change with age: <40 years; N=19, 987±
30ms, 23 ±3%; 40-60 years, N=24, 983 ± 33ms, ECV 24 ± 2%; > 60 years, N=5, 969
± 46ms, ECV 22±3%; p=0.23/0.18.
Conclusion
In a low-risk group of subjects with a normal CMR study, native T1 mapping values
were 982 ± 35ms and ECV 22.9 % ± 2.7%. Female subjects had a slightly higher mean
native T1 and ECV value than men, however, T1 and ECV do not appear to change
with age.