MRI Characteristics, Prevalence, and Outcomes of Hypertrophic Cardiomyopathy with Restrictive Phenotype

Purpose To investigate the MRI characteristics, prevalence, and outcomes of hypertrophic cardiomyopathy (HCM) with restrictive phenotype. Materials and Methods A total of 2592 consecutive patients with HCM were evaluated to identify individuals who fulfilled the diagnostic criteria of restrictive phenotype. Thirty-four patients with HCM (mean age, 41 years ± 16 [standard deviation]; range, 21–62 years, 16 men) with restrictive phenotype were retrospectively identified. Thirty-four patients with HCM with the same age and sex distributions were randomly selected as a control group. Kaplan-Meier survival curves were compared using log-rank statistics for survival analysis. Results The anteroposterior diameters of the left and right atria were 55 mm ± 5 and 61 mm ± 9, respectively, which were larger than those of the control group (P < .001). The maximum wall thickness in the restrictive group was lower than that in the control group (16 mm ± 2 vs 19 mm ± 3, P < .001). No significant difference was found in late gadolinium enhancement fraction between the restricted phenotype and the control group (15% ± 8 vs 13% ± 7, P = .376). The 5-year event-free survival from any cause of death and cardiac transplantation was 81% in the restrictive group, compared with 94% in the control group (log-rank P = .018). Conclusion Restrictive phenotype is a rare subtype of HCM and is associated with severe clinical symptoms and poor prognosis. The MRI features of this phenotype include mild to moderate left ventricular hypertrophy, markedly enlarged atria, moderate myocardial fibrosis, and pericardial effusion.