Clinical features of the systolic anterior motion of the mitral valve among patients without hypertrophic cardiomyopathy.

Background: The prevalence and clinical features of the systolic anterior motion of the mitral valve (SAM) without hypertrophic cardiomyopathy (HCM) have not been studied well.

Methods: Records of 9180 sequential patients who underwent echocardiography at Tokyo Women's Medical University Hospital were reviewed. SAM patients were divided into those with HCM (HCM; n=60, 68%) and those without HCM (non-HCM; n=28, 32%). To assess SAM morphology, non-HCM patients were divided into the valvular and chordal groups.

Results: The prevalence of non-HCM SAM was 0.3%. Non-HCM patients showed older age (65.7±15.0 years vs. 56.9±16.8 years, p=0.02), higher prevalence of sigmoid septum (75% vs. 50%, p=0.03), and lower left ventricular outflow tract pressure gradient (LVOT-PG) (27±31mmHg vs. 43±41mmHg, p=0.03) than HCM patients. However, 8 of 28 non-HCM patients showed a LVOT-PG >30mmHg. Valvular SAM showed higher dyspnea prevalence (29% vs. 0%, p=0.04), higher LVOT-PG (39±36mmHg vs. 6±2mmHg, p<0.001), longer anterior mitral leaflet (28±2mm vs. 26±3mm, p=0.04) and more pronounced mitral regurgitation than chordal SAM.

Conclusion: Non-HCM SAM prevalence was 0.3% in the Japanese population. Non-HCM SAM correlated with older age, sigmoid septum, and a lower LVOT-PG compared with HCM SAM. Among non-HCM SAM, valvular SAM showed a significant symptom, higher LVOT-PG, and more pronounced mitral regurgitation than chordal SAM.