Abstract
BackgroundExtent of myocardial fibrosis (MF) determined using late gadolinium enhanced (LGE) predicts outcomes, but gadolinium is contraindicated in advanced renal disease. We assessed the ability of native T1-mapping to identify and quantify MF in aortic stenosis patients (AS) as a model for use in haemodialysis patients.MethodsWe compared the ability to identify areas of replacement-MF using native T1-mapping to LGE in 25 AS patients at 3 T. We assessed agreement between extent of MF defined by LGE full-width-half-maximum (FWHM) and the LGE 3-standard-deviations (3SD) in AS patients and nine T1 thresholding-techniques, with thresholds set 2-to-9 standard-deviations above normal-range (1083 ± 33 ms). A further technique was tested that set an individual T1-threshold for each patient (T11SD). The technique that agreed most strongly with FWHM or 3SD in AS patients was used to compare extent of MF between AS (n = 25) and haemodialysis patients (n = 25).ResultsTwenty-six areas of enhancement were identified on LGE images, with 25 corresponding areas of discretely increased native T1 signal identified on T1 maps. Global T1 was higher in haemodialysis than AS patients (1279 ms ± 5.8 vs 1143 ms ± 12.49, P < 0.01). No signal-threshold technique derived from standard-deviations above normal-range associated with FWHM or 3SD. T11SD correlated with FWHM in AS patients (r = 0.55) with moderate agreement (ICC = 0.64), (but not with 3SD). Extent of MF defined by T11SD was higher in haemodialysis vs AS patients (21.92% ± 1 vs 18.24% ± 1.4, P = 0.038), as was T1 in regions-of-interest defined as scar (1390 ± 8.7 vs 1276 ms ± 20.5, P < 0.01). There was no difference in the relative difference between remote myocardium and regions defined as scar, between groups (111.4 ms ± 7.6 vs 133.2 ms ± 17.5, P = 0.26).ConclusionsAreas of MF are identifiable on native T1 maps, but absolute thresholds to define extent of MF could not be determined. Histological studies are needed to assess the ability of native-T1 signal-thresholding techniques to define extent of MF in haemodialysis patients.Data is taken from the PRIMID-AS (NCT01658345) and CYCLE-HD studies (ISRCTN11299707).
Highlights
Extent of myocardial fibrosis (MF) determined using late gadolinium enhanced (LGE) predicts outcomes, but gadolinium is contraindicated in advanced renal disease
Systolic blood pressure was significantly lower in haemodialysis patients without areas of discretely increased signal on native T1 maps compared to aortic stenosis patients (AS) patients and to haemodialysis patients with areas of discretely increased signal on native T1 maps
Discussion we have shown that areas of discretely increased signal on native T1 mapping are visible and appear to correspond to areas LGE, we were not able to define an absolute native T1 signal threshold to define the extent of MF compared to FWHM or 3SD in AS patients
Summary
Extent of myocardial fibrosis (MF) determined using late gadolinium enhanced (LGE) predicts outcomes, but gadolinium is contraindicated in advanced renal disease. The pathogenesis of MF differs across disease states, but in diseases of pressure or volume overload, patients initially develop diffuse interstitial myocardial fibrosis (DMF) [3]. Over time, increasing levels of DMF lead to decreased capillary density and myocardial ischaemia, with subsequent myocyte apoptosis and development of replacement fibrosis (scar) [4]. Percentage area of LV fibrosis has been shown to be a stronger predictor of cardiovascular outcomes than extent of myocyte hypertrophy in haemodialysis patients and an independent predictor of mortality [8]. The ability to non-invasively detect and define extent of MF in patients with advanced renal disease has significant implications [9, 10]
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