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

Objectives 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. Methods 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 Delta T2* 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 Delta T2* ratio >= 10%. Results Delta T2* 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). Delta T2* 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 Delta T2* 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). Conclusions Analysis of BOLD T2*-CMR and T1 mapping revealed that ECV is strongly associated with Delta T2* ratio, suggesting that the onset of myocardial fibrosis is related to hypoxia in HCM patients.