Echocardiographic characteristics and outcome of straddling mitral valve

OBJECTIVES This study sought to characterize the echocardiographic features of straddling mitral valve (SMV) and to determine its surgical implications and midterm outcome in a large clinical cohort. BACKGROUND Despite a relatively large body of literature on the postmortem anatomy of SMV, there is a paucity of information regarding its echocardiographic features, surgical implications and preoperative predictors of outcome. METHODS A retrospective review identified 46 patients with SMV between 1982 and 1999 who underwent echocardiography and surgery and had follow-up data. A detailed review of the echocardiograms, surgical reports and all pertinent records was undertaken. RESULTS Review of the echocardiograms revealed a widely varying anatomy among the study patients. However, four distinct groups with relatively uniform morphologic features could be distinguished on the basis of segmental analysis. Cardiac malposition associated with right ventricular hypoplasia, superior-inferior ventricles and criss-cross atrioventricular relations were common among patients with {S,D,L} (S = visceroatrial situs solitus, D = D-ventricular loop, L = L-malposition of the great arteries) (n = 6) and {S,L,D} (n = 5) segmental combinations but were rare among patients with {S,D,D} (n = 26) and {S,L,L} (n = 9) combinations. Surgical management consisted of a functional single-ventricle palliation in 38 patients (83%) and biventricular repair in 8 patients (17%). Overall mortality was 22%, but none of the seven patients who were operated on during the cohort’s last five years (1994 to 1999) has died. By multivariate analysis, noncommitted ventricular septal defect was the strongest independent predictor of death (relative RISK = 10.2), followed by multiple ventricular septal defects (relative RISK = 4.7). CONCLUSIONS This study demonstrates that echocardiography provides detailed noninvasive imaging of the complex anatomic features of SMV and its associated anomalies. Anatomic classification based on segmental analysis allows the distinction of four groups with more uniform morphologic features. Although a biventricular approach is feasible in selected patients, a functional univentricular palliation is indicated in those with major straddling and markedly hypoplastic ventricles.