Abstract
BackgroundMyocardial fibrosis is a major determinant of outcome in aortic stenosis (AS). Novel fast real-time (RT) cardiovascular magnetic resonance (CMR) mapping techniques allow comprehensive quantification of fibrosis but have not yet been compared against standard techniques and histology.MethodsPatients with severe AS underwent CMR before (n = 110) and left ventricular (LV) endomyocardial biopsy (n = 46) at transcatheter aortic valve replacement (TAVR). Midventricular short axis (SAX) native, post-contrast T1 and extracellular volume fraction (ECV) maps were generated using commercially available modified Look-Locker Inversion recovery (MOLLI) (native: 5(3)3, post-contrast: 4(1)3(1)2) and RT single-shot inversion recovery Fast Low-Angle Shot (FLASH) with radial undersampling. Focal late gadolinium enhancement was excluded from T1 and ECV regions of interest. ECV and LV mass were used to calculate LV matrix volumes. Variability and agreements were assessed between RT, MOLLI and histology using intraclass correlation coefficients, coefficients of variation and Bland Altman analyses.ResultsRT and MOLLI derived ECV were similar for midventricular SAX slice coverage (26.2 vs. 26.5, p = 0.073) and septal region of interest (26.2 vs. 26.5, p = 0.216). MOLLI native T1 time was in median 20 ms longer compared to RT (p < 0.001). Agreement between RT and MOLLI was best for ECV (ICC > 0.91), excellent for post-contrast T1 times (ICC > 0.81) and good for native T1 times (ICC > 0.62). Diffuse collagen volume fraction by biopsies was in median 7.8%. ECV (RT r = 0.345, p = 0.039; MOLLI r = 0.40, p = 0.010) and LV matrix volumes (RT r = 0.45, p = 0.005; MOLLI r = 0.43, p = 0.007) were the only parameters associated with histology.ConclusionsRT mapping offers fast and sufficient ECV and LV matrix volume calculation in AS patients. ECV and LV matrix volume represent robust and universally comparable parameters with associations to histologically assessed fibrosis and may emerge as potential targets for clinical decision making.
Highlights
Left ventricular (LV) remodelling including hypertrophy, interstitial volume alteration and expansion is a common feature in cardiac diseases [1]
Severe aortic stenosis (AS) is the most prevalent valvular heart disease in the Western world with 7 million people aged above 75 years thought to be affected [2, 3]
Cardiovascular magnetic resonance (CMR) imaging allows quantification of myocardial remodelling using T1 mapping and extracellular volume (ECV) fraction calculation based on pre- and post-contrast T1 maps [10]
Summary
Left ventricular (LV) remodelling including hypertrophy, interstitial volume alteration and expansion is a common feature in cardiac diseases [1]. Severe symptomatic AS is associated with worse prognosis in the absence of aortic valve replacement [4,5,6]. Current guidelines recommend aortic valve replacement in symptomatic severe AS [12] irrespective of cardiac remodelling. Notwithstanding, there is evidence to suggest reverse myocardial remodelling following valve replacement with regression of diffuse fibrosis in some patients and the quantification of its extent could represent a novel endpoint for patient selection [13]. Cardiovascular magnetic resonance (CMR) imaging allows quantification of myocardial remodelling using T1 mapping and extracellular volume (ECV) fraction calculation based on pre- and post-contrast T1 maps [10]. Novel fast real-time (RT) cardiovascular magnetic resonance (CMR) mapping techniques allow comprehensive quantification of fibrosis but have not yet been compared against standard techniques and histology
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