CTICasesHypertrophic Cardiomyopathy with Chordal Systolic Anterior Motion (SAM)
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Imaging findings
Cardiac MRI demonstrates severe hypertrophy of the basilar septum. During systole, the ventricular outflow tract is severely narrowed (measuring approximately 8 mm) due to a Venturi effect that pulls the chordae portion of the mitral valve anteriorly into the outflow tract, causing systolic anterior motion (SAM). This is associated with an eccentric, laterally and inferiorly directed mitral regurgitant jet. Late gadolinium enhancement (LGE) imaging shows patchy, hazy mid-myocardial enhancement throughout the septum, along with prominent enhancement at both the superior and inferior right ventricular insertion points.
Key takeaways
Systolic anterior motion (SAM) can involve the chordae tendineae (chordal SAM) as well as the anterior leaflet of the mitral valve in patients with hypertrophic obstructive cardiomyopathy (HOCM). SAM causes left ventricular outflow tract (LVOT) obstruction and classic eccentric mitral regurgitation. Myocardial late gadolinium enhancement and the severity of LVOT obstruction are key independent predictors of adverse clinical outcomes, including sudden cardiac death.
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