Tetralogy of Fallot with subarterial ventricular septal defect

Tetralogy of Fallot with subarterial ventricular septal defect is frequently seen among Asians. Compared with infracristal ventricular septal defect, postoperative right ventricular outflow obstruction is more likely because of subpulmonary extension of the defect. Moreover the incidence of aortic regurgitation is a concern because of the absence of a supporting infundibulum.

Four hundred cases of classic tetralogy were reviewed, 61 of which had subarterial ventricular septal defect.

Aortic regurgitation (of more than mild degree) was identified in 7 cases with subarterial and 7 with infracristal ventricular septal defects. The mechanism of infracristal defect was predominantly an annular dilation before surgery. In contrast 5 cases with subarterial defect had progression of aortic regurgitation after operation yielding an actuarial incidence of 29.7% at 20 years. In 2 patients the cause seemed to be fixation or plication of the aortic valve annulus by the ventricular septal patch. Compared with infracristal defect, subarterial defect was associated with increased incidence of reoperation (12.0% versus 1.9% at 10 years, p = 0.01), frequent use of transannular patch (70.5% versus 45.7%, p = 0.0004), and worse New York Heart Association (NYHA) functional class (p = 0.007). Right ventricular outflow obstruction was the reason for reoperation in 3 patients with subarterial defect and was associated with worse NYHA classification in the long-term, on multivariate analysis (p = 0.0002).

Tetralogy with subarterial ventricular septal defect was associated with worse functional outcome. To prevent adverse outcomes, precise suturing of the distal ventricular septal patch, extensive infundibulectomy, lower threshold for transannular incision, and smaller-sized ventricular septal patch placement are warranted.