Abstract:

Objective · To investigate the difference in myocardial strain of left ventricle between obstructive hypertrophy cardiomyopathy (HCM) and nonobstructive HCM. Methods · Cardiac magnetic resonance imaging (MRI) exam was performed on 48 sequential enrolled patients with HCM (18 with obstructive HCM, and 30 with nonobstructive HCM), whose left ventricular ejection fractions (LVEF) were over 50%. Twenty-five healthy volunteers were examined as normal controls. Global longitudinal strain (GLS), global radial strain (GRS), global circumferential strain (GCS), LVEF, left ventricular end diastolic volume (LVEDV), left ventricular mass (LVM), left ventricular end diastolic volume index (LVEDVI), and left ventricular mass index (LVMI) were collected and compared. Radial strain, circumferential strain and peak radial displacement were also measured in medial segment of left ventricle according to American Heart Association (AHA) 17-segment model. Results · ① LVEF of the patients with obstructive HCM was bigger than those of nonobstructive HCM patients and control group (P<0.05). LVM and LVMI of the HCM groups were bigger than those of control group (P<0.01). ② Left ventricle GLS, GRS, and GCS significantly decreased in the patients with nonobstructive HCM compared to those with obstructive HCM (P<0.05). The three parameters of two HCM groups were significantly lower than those of healthy volunteers (P<0.05). ③ Compared with obstructive HCM patients, he segmental parameters of left ventricule, the medial segment circumferential strain and radial strain of nonobstructive HCM patients significantly decreased (P<0.05), and the two parameters of both HCM groups were lower than those in healthy volunteers. Compared with obstructive HCM patients and healthy volunteers, peak radial displacement of left ventricule medial segment in nonobstructive HCM witnessed a significant decrease, while no significant difference was observed between obstructive HCM patients and healthy volunteers. Conclusion · In the LVEF preserved HCM patients, the myocardial strain of left ventricle in nonobstructive HCM patients decrease significantly than that in obstructive HCM patients, which may result in the different clinical outcomes in two types of HCM patients. It is suggested that the myocardial strain is more sensitive than ejection fraction in the evaluation of myocardial performance of HCM patients.

Key words: hypertrophy cardiomyopathy, obstructive type, nonobstructive type, strain, cardiac magnetic resonance imaging