Effects of hypertrophy and fibrosis on regional and global functional heterogeneity in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a disease that typically has heterogeneous hypertrophy and dysfunction of the myocardium. Cardiac magnetic resonance imaging (CMR) can be used to accurately assess ventricular wall thickness and regional fibrosis. We investigated the effects of hypertrophy and fibrosis on the heterogeneity of regional and global myocardial function in HCM. Forty patients who were diagnosed with HCM were consecutively enrolled. Echocardiography and CMR with delayed hyper-enhancement imaging (DHE) was performed for each patient. Left ventricular (LV) regional and global longitudinal strain (SLR and SLG) were obtained by two-dimensional speckle tracking method on echocardiography. With CMR, regional myocardial wall thickness was measured, and the amount of DHE was calculated semi-quantitatively in each segment. Overall, 720 segments were analyzed. SLR was significantly decreased in the hypertrophied segments (thickness[ 11 mm) and segments with DHE (P < 0.001). SLR was correlated with myocardial wall thickness (r = 0.47, P = 0.001) and amount of regional DHE (r = 0.39, P < 0.001). On multivariate analysis, regional LV wall thickness and amount of DHE were the only independent determinants of SLR. SLG was associated with LV diastolic functional parameters in echocardiography, total DHE volume, and LV mass index. Total DHE volume and LV mass index were independent determinants of SLG on multivariate analysis. The extent of regional myocardial fibrosis is associated with regional myocardial function independently of morphological changes of the myocardium, and the correlation extended to global LV function. In this context, DHE may be a useful parameter to discover early myocardial dysfunction independently of LV hypertrophy.