Association between myocardial hypoxia and fibrosis in hypertrophic cardiomyopathy: analysis by T2* BOLD and T1 mapping MRI.

Abstract

We assessed whether an association exists between myocardial oxygenation and myocardial fibrosis in patients with hypertrophic cardiomyopathy (HCM), using blood-oxygen-level-dependent (BOLD) T2* cardiac magnetic resonance imaging (T2*-CMR) and T1 mapping. T1 mapping and T2*-CMR data were collected from 55 HCM patients using a 3-T MR and were prospectively analyzed. T2*-CMR was conducted using the black blood, breath-hold, multi-echo, and gradient echo sequence. Over 10 min, inhalation of oxygen at the flow rate of 10 L/min, T2* for mid-septum was measured following room-air and oxygen inhalation, and ΔT2* ratio (T2*oxy-T2*air/T2*air, %) was calculated. During pre- and post-gadolinium enhancement, native T1 (ms) and extracellular volume fractions (ECV, %) were calculated at sites same as the T2* measurement. Hypoxia was defined as the segment with an absolute value of the ΔT2* ratio ≥ 10%. ΔT2* ratio was significantly higher for segments with native T1 ≥ 1290 ms than those with native T1 < 1290 ms (21 ± 32% vs. 8 ± 6%, p = 0.005). ΔT2* ratio was also significantly higher for segments with ECV ≥ 28% than those with ECV < 28% (21 ± 32% vs. 8 ± 8%, p = 0.0003). ROC curve analysis revealed that ΔT2* ratio could detect segments with native T1 ≥ 1290 ms and ECV ≥ 28% and c-statistics of 0.72 and 0.79. According to the multivariate logistic regression analysis results, ECV is an independent factor in hypoxia (odds ratio, 1.47; 95% confidence interval, 1.02-2.13; p < 0.05). Analysis of BOLD T2*-CMR and T1 mapping revealed that ECV is strongly associated with ΔT2* ratio, suggesting that the onset of myocardial fibrosis is related to hypoxia in HCM patients. Our study was approved by the ethics committee of our institute (#4036, registered on 21 July 2016) KEY POINTS: • Analysis of ΔT2* ratio and ECV with BOLD-T2* and T1 mapping revealed a strong association between myocardial fibrosis and hypoxia in HCM patients.