Incidence of systemic embolism before and after mitral valvotomy

Mitral valvotomy is of established value in improving the clinical condition and life expectancy of patients with rheumatic mitral stenosis. Its value in preventing or reducing the incidence of systemic arterial embolism is less certain. A comparison of pre- and post-operative embolic incidence can only be accepted if it is clear that the method of assessing the pre-operative figure is reliable. It is shown that the figure varies according to the length of the pre-operative study, and evidence is presented to show a changing incidence with increasing length of chronic rheumatic history. By studying patients in whom the time of onset of rheumatic heart disease is accurately known, a rising embolic incidence with the passage of time is shown. A comparison is made between groups of patients who have experienced the same length of chronic rheumatic history but who differ in respect of mitral valvotomy. We conclude from our comparison that this operation does not diminish the incidence of embolism, though only about a quarter of all our patients had atrial appendagectomy at the time of valvotomy. A reduction in the incidence of recurrent embolism in a given patient after mitral valvotomy is shown but may be more apparent than real. Operative embolism, defined here as that occurring either at or within 48 hours of operation, has an incidence of 3·8%. The factors related to pre-operative, operative, and post-operative embolism are presented.