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The operative results in our first 100 consecutive patients treated for a partial form of atrioventricular canal have been reviewed. There were sixteen hospital deaths. Seventy-eight of the remaining 84 have been followed for an average of 55.6 months. An attempt was made to compare surgical results with the natural history as assessed from the literature in order to define criteria for surgery. The degree of mitral incompetence influenced the operative mortality rate: The operative risk was 53.8 per cent in 13 patients with severe mitral incompetence as compared to 10.34 per cent in 87 with moderate or no mitral incompetence. Operative heart block occurred in 19 patients. In 7 cases the heart block persisted and was followed by two deaths. In view of the poor prognosis for patients with partial persistent atrioventricular canal treated medically, the reduction of the operative mortality rate (5.4 per cent during the last 4 years), and of the incidence of operative heart block, surgical management of the condition is warranted. The degree of mitral incompetence is a critical determinant in the selection of surgical candidates, since those with little or no incompetence do extremely well whereas those with a severe degree of incompetence still bear a high operative risk.

A systematic study of congenital mitral valve malformations was undertaken on a surgical basis in an attempt to develop techniques of valvular reconstruction adapted to the various lesions. Forty-seven children between the ages of 4 months and 12 years (average 6 years, 4 months) have been operated upon between January, 1970, and March, 1976. Valvular lesions were classified into four groups: Group I, mitral insufficiency owing to valvular lesions; Group II, mitral insufficiency with subvalvular lesions; Group III, mitral insufficiency and stenosis; Group IV, stenosis. Associated lesions (ventricular or atrial septal defects, coarctation, or aortic valve stenosis) were present in 31 patients (65 per cent) and were corrected during the same operation. Valve reconstruction was possible in 38 patients whereas valve replacement was necessary in 9 patients. In the valve repair group there were three operative deaths (8 per cent), no late deaths, one reoperation for residual ventricular septal defect, and one myocardial infarction. In the valve replacement group of 9 patients, there were three operative deaths, three late deaths, and one ease of repeated embolization. Thirty-one of 38 patients in the valve repair group were classified into Functional Class I after the operation (86 per cent), 2 were in Class II, and one in Class III. Minimal or moderate regurgitation and cardiomegaly persisted in the majority of the patients. Pulmonary artery pressure significantly decreased, however, as demonstrated by postoperative catheterization in 17 patients.

Between January, 1969, and January, 1978, 551 patients with mitral incompetence were treated by a system of reconstructive techniques. Mitral valve incompetence was classified into three types according to leaflet pliability; type I normal leaflet motion, 150 cases; type II, leaflet prolapse, 213 cases; and type III, restricted leaflet motion, 188 cases. Associated tricuspid valvular disease was present in 174 cases (31.5%) and was treated by prosthetic ring annuloplasty. The operative mortality rate was 4.2% (16/377) in the mitral group and 14% (25/174) in the mitral-tricuspid group. Follow-up data are available in 341 patients from 1 year to 10 years (average 4 1/2 years). The late mortality rate was 7% (24/341). Actuarial curves including hospital mortality rate show an 82% survival rate at 9 years in the mitral group and a 79% rate in the mitral-tricuspid group. Thirty-seven patients (11%) underwent reoperation mainly for residual (17) or recurrent (16) mitral incompetence. Thromboembolism occurred in 12 patients for an embolic rate of 0.6% per patient-year, even though 48% were not given anticoagulants. According to the New York Heart Association (N.Y.H.A.) classification, 76% (207/270) of the patients were in Class I, 19% (51/270) were in Class II, 4% (10/270) were in Class III, and 0.7% were in Class IV (2/270). Results of postoperative catheterization and angiocardiography are available in 52 patients. Comparison between the various groups shows that the best results were obtained in type II mitral incompetence, followed by type I and type III mitral incompetence. This experience demonstrates that predictable and stable long-term results have been achieved by techniques of valvular reconstruction with a low incidence of thromboembolism. Reproducibility of the techniques is a limiting factor which can be overcome by adequate training and progressive experience. Patient selection is based on the valvular disease rather than age, physical condition, or cause of valvular disease.