Systolic anterior motion (SAM) of the mitral valve can cause sudden hypoxemia in during and after surgery.

Presentation: sudden decrease in oxygen saturation


Mechanism: dynamic mitral regurgitation and variable left ventricular outflow obstruction, with pulmonary edema


Risk factors for SAM:

(1) narrow left ventricular outflow tract

(2) anteriorly located mitral coaptation point

(3) small mitral-aortic angle (< 120°)


Clinical features:

(1) absence of severe hypotension

(2) chest X-ray consistent with pulmonary edema.

(3) new onset of systolic murmur peaking late

(4) absence of evidence of myocardial infarction


The diagnosis is made:

(1) with echocardiography

(2) by exclusion of other causes of hypoxemia


Echocardiographic findings:

(1) mitral leaflet contact with ventricular septum during systole on 2D or M mode

(2) shark-tooth velocity contour in the left ventricular outflow tract on continuous Doppler flow

(3) mosaic flow pattern in the left ventricular outflow tract

(4) posteriorly directed mitral regurgitation jet on color-flow Doppler mapping


Therapy with diuretics, vasodilators and inotropes (therapy for cardiogenic edema) may worsen hypoxemia in these patients.

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