Central Circulatory Changes Accompanying Mitral Commissurotomy

The flow-pressure relationships within the pulmonary circuit and left side of the heart were measured in 24 patients immediately before and just after mitral commissurotomy. The diastolic pressure gradient across the mitral valve was decreased in all cases, but was rarely obliterated completely. No significant change occurred in cardiac output; a shorter ventricular filling period and a consequent increase in mitral valve flow per unit of filling time was consistently observed. A decrease in mean pulmonary artery pressure generally occurred with valve fracture, but it was almost always less than the decrease in left atrial pressure. The result was an immediate postoperative increase in the pressure gradient and in the calculated resistance across the pulmonary circuit. These observations suggest that the reduction in left atrial pressure following mitral commissurotomy has no immediate effect on pulmonary vasomotor tone.