Abstract 15065: Detection of Interstitial Fibrosis in Hypertrophic Cardiomyopathy by Post-gadolinium Bolus CMR T1 Mapping
Background: Fibrosis is an important pathogenic driver of adverse cardiac events in hypertrophic cardiomyopathy (HCM). Post-gadolinium cardiovascular magnetic resonance (CMR) T1 mapping holds promise as a means of assessing diffuse myocardial fibrosis not detected by late gadolinium enhancement (LGE) imaging. Accurate assessment requires contrast equilibrium; however, there is no consensus about when this occurs. We aimed to determine the time point at which equilibrium occurs after a gadolinium bolus and to assess the utility of T1 mapping for identifying both manifest and latent fibrosis in HCM.
Methods: Eight HCM patients free of significant comorbidity and 22 controls were studied. Short-axis T1 maps were acquired using the Modified Look Locker Inversion Recovery sequence at the base,mid-ventricle and apex for HCM patients and at the mid-ventricle for controls pre-gadolinium bolus and then at 2, 5, 7, 9, 11, 15, 20 and 25 minutes. Signal intensity-time curves for myocardial and blood pool regions of interest were used to determine T1 relaxation times through a non-linear curve-fit (CMR42, Circle Cardiovascular Imaging, Calgary, Canada). Plots of T1 times for the myocardium and blood pool against time were used to determine the point of equilibrium. The gadolinium partition coefficient (λ) at equilibrium, an index of fibrosis, was determined by plotting the reciprocal of myocardial T1 times against that of T1 times for the blood pool at various time points once contrast equilibrium was reached, and calculating the slope of the resultant linear regression line.
Results: Contrast equilibrium occurred within 5 minutes of gadolinium injection in both groups. The λ was significantly elevated in HCM(mean±SD: 0.42±0.13 versus 0.24±0.03; p=0.006). This remained true even for slices not exhibiting LGE (0.38±0.10 versus 0.24±0.03; p=0.02) suggesting the presence of interstitial fibrosis.
Conclusion: Contrast equilibrium occurs quickly after a gadolinium bolus making early post-contrast T1 mapping a clinically feasible protocol. We found λ to be significantly raised in HCM both in regions with and without LGE. It may therefore provide a novel means of non-invasively detecting diffuse myocardial fibrosis which is not currently visualised by LGE CMR.
- © 2011 by American Heart Association, Inc.