Early post-contrast T1 mapping yields maximal discriminatory capacity for detection of cardiac amyloid - influence of temporal T1 differences on MOLLI imaging

Abstract

Methods Myocardial T1 mapping was performed in two cohorts (1) “amyloid +” subjects, defined by biopsy-proven systemic amyloid with associated remodeling suggestive of cardiac involvement (left ventricular [LV] hypertrophy and/or atrial dilation); (2) normative controls without risk factors for amyloid or cardiovascular disease. CMR (1.5T) included 2 components cine-CMR (SSFP) for cardiac structure/function, and T1 mapping for myocardial tissue characterization. T1 mapping was performed using a conventional modified look locker inversion recovery (MOLLI) sequence (flip angle = 30°; matrix 256 × 128; parallel imaging reduction factor =1.5; linear view ordering; 6 Kaiser-Bessel ramp preparation; 17 heart beat acquisition), with T1 calculated using an established formula (T1 = T1* (B/A-1), T1*, A, and B obtained via three-parameter exponential fit). To test time dependent differences in myocardial T1, MOLLI was acquired at sequential time points (3,5,10,14, 20 minutes) following intravenous administration of gadolinium (0.2 mmol/kg). Results 10 subjects (5 amyloid, 5 controls) were studied (44 ± 21 years, 40% male); all amyloid affected subjects had biopsyconfirmed disease (4 light chain type, 1 transthyretin). Amyloid subjects had higher LV mass (200 ± 34 vs. 101 ± 34 gm, p = 0.004), lower myocardial contraction fraction (32 ± 8 vs. 88 ± 27, p = 0.002), and larger left atrial area (26 ± 5 vs. 18 ± 5 cm2, p = 0.03) than controls, but similar LV end-diastolic volume (120 ± 24 vs. 133 ± 45 ml, p = 0.61), stroke volume (66 ± 10 vs. 86 ± 30 ml, p = 0.20), and LVEF (56 ± 10 vs. 65 ± 4%, p = 0.11). MOLLI was successfully acquired in all subjects at each time point: T1 differed significantly (all p ≤ 0.05) between amyloid and control groups at all times (Figure 1). However, magnitude of difference temporally decreased following gadolinium administration (Figure 2): T1 differences between patients and controls were maximal at 3 minutes post-contrast (135 ± 15 vs. 310 ± 61 msec, p = 0.004) with progressive decrements thereafter, as evidenced by 57% relative difference between groups at 3 minutes and only a 36% difference at 20 minutes following gadolinium infusion.