[Surgical mitral valvuloplasty and dynamic left ventricular obstruction syndrome]

The "dynamic" left ventricular outflow obstruction syndrome, which is found in 4.5 to 11 p. 100 of patients who underwent mitral valve repair by Carpentier's technique, seems to be due to the association of two different sets of circumstances. The first set is anatomical; the syndrome is thought to result from the implantation of a semi-rigid valve ring, from the excessive length of the mitral valve system in relation to the size of the ventricular cavity, and from excessive correction of mitral regurgitation with subsequent excessive reduction in caliber of the left ventricular outflow tract, change in the interrelation between outflow tract and ventricular filling and strongly anterior position of the mitral valve. The second set is functional; it is due to a more than 20 p. 100 reduction in caliber of the left ventricular outflow tract on the one hand, and to a more than 2.5 m/s increase in blood flow velocity on the other hand. These two phenomena may be produced by a decrease in left ventricular volume as a result of hypovolaemia, tachycardia or more rapid circulation. Treatment of the syndrome consists of correcting the associated abnormalities by prescribing a diet with a normal sodium content, together with an appropriate anti-arrhythmic agent and a beta-blocker.