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Abstract
Objective To investigate whether cardiac magnetic resonance (CMR) can assess the progression and regression of myocardial fibrosis in patients with aortic stenosis (AS).
Methods Sixty-three patients with aortic stenosis were followed up for 2 years with serial CMR and echocardiography: 28 patients (63±13 years, 68% male, 50% asymptomatic severe AS) did not undergo intervention (natural history cohort) and 35 patients (67±8 years, 73% male, 83% symptomatic severe AS) underwent aortic valve replacement (AVR) within the first year (AVR cohort). Replacement and diffuse myocardial fibrosis were assessed using the late gadolinium enhancement (LGE) and T1 mapping techniques respectively. Annualised change was calculated for all measures.
Results In the natural history cohort, left ventricular mass index (LVMi) increased over time (6%±1%, p<0.0001) and was accompanied by a fall in longitudinal systolic function (−4%±2% p=0.03). The indexed extracellular volume (iECV, a measure of diffuse fibrosis) also increased over time (7%±2%, p<0.0001). However, no changes were observed in native T1, post-contrast T1 or extracellular volume (ECV) fraction on serial imaging. Mid-wall LGE was observed in nine patients (32%). Absolute LGE mass increased by 3.8±0.8g (p<0.0001) amongst all the patients with baseline mid-wall LGE. Four patients with mid-wall LGE at baseline developed new areas of LGE in different myocardial segments. No patients without pre-existing mid-wall LGE developed new LGE during follow up.
The AVR cohort displayed a fall in LVMi following surgery (−15%±2%, p<0.0001) mirrored by a reduction in diffuse fibrosis (iECV, −9%±2%, p<0.0001). The ECV fraction however was observed to increase (5% [2, 11], p<0.0001), with no change in native T1. Mid-wall LGE was present in 9 patients (26%). No patient went on to develop new LGE nor did existing LGE resolve in any patient and LGE mass did not change. Longitudinal systolic function increased following AVR (16%±6%, p=0.01).
Conclusion Changes in diffuse fibrosis can be tracked using iECV and increase with time in patients with AS alongside LV mass and replacement fibrosis. Following AVR there is a fall in LV mass driven predominantly by regression of cellular hypertrophy with more gradual reduction in diffuse fibrosis burden but no change in replacement fibrosis.
Mid-wall LGE is present on baseline scan (white arrow) and new areas are seen on 1 year scan (red arrows). Following AVR there is no change in mid-wall LGE (white arrows). Annualised change in imaging measures is presented below in the natural history (black) and AVR (red) groups.
Main Figure: Serial cardiac magnetic resonance imaging in a patient with severe aortic stenosis.