Clinical and MRI characteristics of hypertrophic cardiomyopathy with restrictive phenotype

Objective: To investigate the clinical and MR characteristics of hypertrophic cardiomyopathy (HCM) with restrictive phenotype. Methods: Nineteen patients of HCM with obviously restrictive characteristics (HCM with restrictive phenotype) and 19 typical patients with non obstructive HCM, matched with age, gender and suffering time, were retrospectively collected. A short-axis stack, one 4-chamber and 2-chamber views were acquired using black blood sequence and bright blood cine sequence. Ten to 15 minutes after injection of contrast medium late gadolinium enhancement images were acquired. The clinical features, the wall thickness and segments of delayed enhancement, and the MR function parameters of the two groups were compared retrospectively. The paired sample t test and Fisher exact probability method were used for the analysis of quantitative data and categorical data respectively. Results: Eleven of patients of HCM with restrictive phenotype suffered sustained atrial fibrillation and pericardial effusion, whereas only 0 and 1 cases was found had the same two symptoms in HCM(all P < 0.01). The heart function classification was worse compared with controls (P < 0.01); The left and right atrium diameter were (55.8 ± 5.3) mm and (61.3 ± 11.0) mm in case group, which were significantly greater than the controls[(37.0 ± 7.8) and (39.3 ± 5.3) mm respectively](t = 8.82 and 25.55, P < 0.01); HCM with restrictive phenotype showed obvious right ventricular long axis shortening, similar to restrictive cardiomyopathy. The segments with late gadolinium enhancement were 7.7 ± 3.0 in patients with restrictive phenotype, which were significantly greater than controls (5.1 ± 2.8, t = 2.80, P < 0.01). The left ventricular end-diastolic volume index, the cardiac index, and the Left heart ejection fraction of patients with restrictive phenotype were all significantly less than those of the controls. Conclusions: HCM with restrictive phenotype is a subtype of HCM. The patients often have severe clinical symptoms. MRI has important application value in the diagnosis and evaluation of the disease. (authors)