Secundum atrial septal defect and significant mitral regurgitation: incidence, management and morphologic basis.

To better understand the association between mitral regurgitation and secundum atrial septal defect and to clarify the evaluation and management of these patients, the records of 235 adult patients with atrial septal defect were reviewed. Ten patients (4 percent) had significant mitral regurgitation defined by clinical, hemodynamic and angiographic criteria. Three patients required mitral valve replacement at the time of closure of the atrial septal defect and four patients had closure alone, one of whom required mitral valve replacement after five years. Three patients did not undergo closure of the atrial septal defect or mitral valve replacement because of severe coexisting medical problems. In six patients, the mitral valves were studied pathologically and all had thick, fibrotic leaflets and short, thick, fibrotic chordae tendineae. Three of these valves also had scattered areas of patchy myxomatous degeneration and three had areas of vascular ingrowth suggestive of rheumatic disease. Although both invasive and noninvasive studies have high-lighted the coincidence between atrial septal defect and mitral regurgitation, particularly the frequent association of mitral valve prolapse, our data indicate that this association rarely has clinical significance. Furthermore, the morphologic basis for mitral regurgitation in patients with atrial septal defect consists of leaflet and chordal thickening fibrosis and deformity rather than attenuation and ballooning as would be expected in mitral valve prolapse.