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In the usual type of obstructive hypertrophic cardiomyopathy the
patient's mitral valve is pushed by the force of flow into a wall
of the heart, the interventricular septum. (The mitral valve is
a normal cardiac structure that prevents blood from flowing backwards
from the main pumping chamber, the left ventricle, into the left
atrium.) The abnormal movement of the mitral valve can be easily
detected on echocardiography. It is called systolic anterior motion
(SAM) of the mitral valve. The obstruction caused by mitral-septal
contact causes a pressure difference similar to the one that occurs
when the nozzle of a hose is tightened. Obstruction makes HCM
symptoms worse because the heart must work harder to pump blood
to the body.
The diagram below shows what the heart looks like on echocardiography
as the mitral valve is pushed into the septum. As the heart begins
to eject blood (the two pictures on the left) the mitral valve
is swept by the flow towards the heart wall itself. When the valve
touches the septum, which is a wall of the heart (third picture)
a pressure difference or gradient occurs. This pressure difference
drives the mitral valve further into the septum, worsening the
pressure difference. Obstruction begets further obstruction.
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 |
 |
 |
| Coaptation |
Just Before
Contact |
Contact |
After Contact |
Medical treatment of obstruction uses drugs called negative inotropes.
These medicines slow the ejection of blood out of the heart, decrease
the force on the mitral valve and may thereby eliminate mitral-septal
contact. |
