Q: What is 'venturi' effect or SAM?
A: Hypertrophic cardiomyopathy (HCM) is a disease characterized by hypertrophy of the left ventricle.
In a subset of patients, the inward movement of the hypertrophied septum during systole further narrows the LV outflow tract resulting in high left ventricular outflow tract (LVOT) blood velocities that pull the mitral valve leaflet toward the interventricular septum - call Venturi effect or SAM.
In the classic form of hypertrophic obstructive cardiomyopathy (HOCM), patients manifest asymmetric septal hypertrophy (ASH), systolic anterior motion (SAM) of the anterior leaflet of the mitral valve and, in most cases, mitral regurgitation.
Site and extent of cardiac hypertrophy results in obstruction to left ventricular outflow tract (LVOT). This may be present at rest but,also occurs under conditions that tend to reduce ventricular pre-load (dehydration, sudden adoption of the upright posture and the Valsalva maneuvre) or increase ventricular contractility particularly exercise.
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