Balloon pulmonary valvuloplasty.

Abstract

Since the initial description of balloon pulmonary valvuloplasty in 1982 by Kan and her associates, the procedure has been extensively used by several groups of workers for relief of pulmonary valve stenosis. It is generally recommended that the procedure be performed for peak-to-peak gradients in excess of 50 mmHg. Severe and critical obstructions, irrespective of age and pulmonary valve dysplasia, are amenable to balloon dilatation. The technique involves positioning one or more balloon catheters across the stenotic valve, usually over an extra-stiff guidewire and inflating the balloons, thus producing valvotomy. The recommended balloon:annulus ratio is 1.2 to 1.4. Immediate reduction of gradient, increase in jet width, and free motion of the pulmonary valve leaflets with less doming have been observed following balloon dilatation. Improvement of right ventricular function, tricuspid insufficiency, and right-to-left shunt has also occurred. At intermediate-term follow-up, both catheterization measured peak-to-peak gradients and Doppler-measured peak instantaneous gradients remain improved for the group as a whole. However, restenosis, defined as gradient ≥ 50 mmHg, has been observed in nearly 10% of children. Predictors of restenosis include balloon:annulus ratio ≥ 1.2 and immediate postvalvuloplasty gradient ≥ 30 mmHg. Small pulmonary valve annulus, earlier study year, and postsurgical complex pulmonary stenosis have also been identified as factors predictive of restenosis. Redilatation with balloons that are larger than those used at the time of initial balloon valvuloplasty produces excellent results, and redilatation is the procedure of choice in the management of restenosis after previous balloon pulmonary valvuloplasty. Regression of right ventricular hypertrophy on ECG following balloon dilatation has been well documented; ECG is a useful adjunct in the evaluation of results of balloon dilatation. However, ECG evidence for hemodynamic improvement does not become apparent until 6 months after balloon dilatation. Doppler gradient is generally reflective of residual obstruction and is a useful and reliable noninvasive monitoring tool. Infundibular gradients occur in nearly 30% of patients: the older the age and higher the severity of obstruction, the higher the prevalence of infundibular reaction. When residual infundibular gradient is ≥ 50 mmHg, beta blockade therapy is generally recommended. The infundibular obstruction regresses to a great degree at follow-up with the rare patient requiring surgical intervention. While there is some controversy with regard to use of balloon dilatation in patients with dysplastic pulmonary valves, based on our own observations and those of others, the results of balloon valvuloplasty with dysplastic pulmonary valves are comparable to those without. Dysplastic valves did not seem to be responsible for recurrence, and balloons large enough to produce balloon:annulus ratio of 1.4:1.5 may be needed to produce a satisfactory result. Comparison with surgical valvotomy has limitations, but generally there is greater reduction of gradient following surgery, but the degree and frequency of pulmonary insufficiency may be higher following surgery than after balloon therapy. Long-term follow-up results are scanty, but the data from our cohort reveal minimal additional restenosis, event-free rates of 88% and 84% at 5 and 10 years, respectively, and significant increase in the prevalence of pulmonary insufficiency. But, no surgical intervention was warranted for pulmonary insufficiency in any patient following balloon dilatation. In conclusion, balloon pulmonary valvuloplasty is the treatment of choice for relief of pulmonary valve stenosis. Use of balloons 1.2-1.4 times larger than pulmonary valve annulus may produce optimal results. Ten- to 20-year follow-up to identify the significance of residual pulmonary insufficiency is indicated.