Balloon Pulmonary Valvuloplasty in Children

Congenital pulmonary valve stenosis comprises 7.5% to 9% of all congenital heart defects. The pathologic features of the stenotic pulmonary valve vary; the most commonly observed pathology is what is described as a “dome-shaped” pulmonary valve. The fused pulmonary valve leaflets protrude from their attachment into the pulmonary artery as a conical, windsock-like structure. The size of the pulmonary valve orifice varies from a pinhole to several millimeters, most usually central in location, but can be eccentric. Raphae presumably fused valve commissures extending from the stenotic orifice to a variable distance down into the base of the dome-shaped valve. The number of the raphae may vary from zero to seven. Less common variants are unicommissural, bicuspid and tricuspid valves. Pulmonary valve ring hypoplasia and dysplastic pulmonary valves may be present in a small percentage of patients. In the past, surgical valvotomy was the treatment of choice; however, more recently, balloon valvuloplasty has gained acceptance as the first option in the management of congenital pulmonary valve stenosis. The first attempt to relieve pulmonary valve obstruction by transcatheter methodology, to my knowledge, was in the early 1950s by Rubio-Alverez et al.^1,2 They used a ureteral catheter with a wire to cut open the stenotic pulmonary valve. In 1979, Semb and associates³ employed a balloon-tipped angiographic (Berman) catheter to produce rupture of pulmonary valve commissures by rapidly withdrawing the inflated balloon across the pulmonary valve. More recently, Kan and her associates4 applied the technique of Gruentzig et al.⁵ to relieve pulmonary valve obstruction by the radial forces of balloon inflation of a balloon catheter positioned across the pulmonic valve. This static balloon dilatation technique is currently employed throughout the world to relieve pulmonary valve obstruction. Subsequent to Kan’s report, a large number of cardiologists have adopted this technique and reported immediate and intermediate-term results of this procedure. We have extensively investigated a number of issues related to balloon pulmonary valvuloplasty including immediate results,^6,7 short-term follow-up results,⁸ electrocardiographic changes,⁹ echo-Doppler evaluation,^10,11 influence of the size of balloon used on the results,^12–14 role of double balloon technique,¹⁵ causes of restenosis,¹⁶ indications,¹⁷ role of balloon dilatation in dysplastic pulmonary valves,¹⁸ significance of infundibular stenosis following balloon dilatation and its treatment,^19,20 application of balloon valvuloplasty to pulmonary stenosis in cyanotic congenital heart defects^21,22 and in the neonate,^23–25 right ventricular filling changes following balloon dilatation,²⁶ feasibility and effectiveness of repeat balloon valvuloplasty in treating recurrent stenosis,²⁷ and long-term results.²⁸ Based on the experience gained from these studies, a number of reviews and book chapters^29–41 were contributed to the literature. In this issue of the Journal, Garty et al.⁴² present long-term follow-up results of balloon pulmonary valvuloplasty in infants and children, with particular attention to late outcomes. One-hundred fifty children between the ages of 1 day to 16.9 years underwent balloon pulmonary valvuloplasty between 1984 and 1992. Single balloon technique was utilized in most patients and double balloon technique was used in 11 (7%) patients. The final balloon/annulus ratio was 1.3 ± 0.2. Immediate reduction in peak-to-peak pulmonary valve gradient from 62 ± 29 to 23 ± 20 mmHg (p Garty, et al. is well-written and contains information on a large cohort of patients followed for an ample length of time, as well as useful data on late outcome of balloon pulmonary valvuloplasty for congenital pulmonary stenosis. The demonstration of growth of the right heart structures, confirmation of development of PI, and a long follow-up period are good attributes of this study. The retrospective nature of the review, lack of definition of indications for initial balloon valvuloplasty, and lack of recognition of works of other investigators with relatively long follow-up periods are some of the limitations of this paper. Despite the limitations, the study by Garty and colleagues is of value and gives us the opportunity to discuss several issues pertaining to balloon pulmonary valvuloplasty in children. Long-term follow-up. We reviewed the long-term results of balloon pulmonary valvuloplasty in late 1990s⁴³ and stated that while there was extensive reporting in the literature of immediate and intermediate-term results of balloon pulmonary valvuloplasty, long-term follow-up results are scanty. At that time the longest follow-up results are those published by McCrindle,⁴⁴ O'Conner,⁴⁵ and Masura46 and their colleagues as well as ours.28 McCrindle, O'Conner, and Masura reported 4.9, 5.3 and 5.2 year (mean) follow-up results in 46, 20 and 34 patients, respectively. McCrindle and Kan44 report a residual peak instantaneous Doppler gradient of 20 ± 13 mmHg, O'Conner et al.⁴⁵ found a gradient of 24 ± 3 mmHg, and Masura’s⁴⁶ patients had residual gradient of 19 ± 10 mmHg. All three groups^44–46 found high prevalence of PI at late follow-up. We undertook a study to review five-to-ten year follow-up results.²⁸ During an 11-year period ending August 1994, 85 children, ages 1 day to 20 years (7.0 ± 6.5 years) underwent balloon pulmonary valvuloplasty with resultant reduction in peak-to-peak gradient from 87 ± 38 to 26 ± 22 mmHg (p . None required immediate surgical intervention. Catheterization (N = 47) and echo-Doppler (N = 82) data at intermediate-term (= 50 mmHg, was observed in 9 (11%) of 82 patients; seven of these underwent successful repeat balloon valvuloplasty. Clinical and echo-Doppler data in 80 patients 2 to 10 (median 7) years after initial valvuloplasty revealed instantaneous Doppler gradients of 17 ± 15 mmHg with evidence for late restenosis in one (1.3%) patient. Surgical intervention to relieve fixed infundibular stenosis (N = 3) or supravalvar pulmonary stenosis (N = 1) and repeat balloon dilatation (N = 2) to relieve restenosis were undertaken during late follow-up. Actuarial reintervention-free rates at 1, 2, 5, and 10 years, respectively were 93%, 89%, 88% and 84%, not too dissimilar to the figures reported by Garty et al.⁴² At late follow-up, PI was noted in 70 (87%) of 80 patients, which represents significant increase in its prevalence at late follow-up. However, right ventricular dilatation did not occur nor did any patient develop paradoxical septal motion. Based on these observations, it was recommended that balloon valvuloplasty is the treatment of choice in the management of isolated valvar pulmonary stenosis and that longer-term (10 to 20 years) follow-up studies, to clarify the significance of PI, should be undertaken.²⁸ Since that review,⁴³ Bader⁴⁷ and Jarrar⁴⁸ and their associates as well Garty et al.⁴² in this issue reported long-term results. Bader examined long term follow-up data of 50 patients who underwent balloon pulmonary valvuloplasty between August 1984 and June 1985 and found mild residual Doppler gradients at 5 (15 ± 10 mmHg), 10 (14 ± 6 mmHg) and 15 (13 ± 6 mmHg) years after the procedure.⁴⁷ Jarrar et al.⁴⁸ analyzed follow-up data on 62 patients and found a residual gradient of 18 ± 9 mmHg one to ten years (6.4 ± 3.4) following balloon pulmonary valvuloplasty. Mild-to-moderate PI was in 39% of patients at follow-up. These data²⁸,^42–48 suggest that the late follow-up results indicate mild residual gradients, but with a high prevalence of PI. Pulmonary insufficiency. Our detailed echocardiographic analysis²⁸ revealed gradual increase in the incidence of PI; 70 of 80 (88%) had PI at long term follow-up while only 10% had PI prior to balloon valvuloplasty. There was gradual increase in severity of PI. There was also increase in incidence of flat inter-ventricular septal motion, although none had paradoxical septal motion or right ventricular dilatation, indicating that there was no right ventricular volume overload, which implies that the PI was not severe. Also, none of our patients required pulmonary valve replacement. Despite this we were concerned about PI, leading us to recommend longer term follow-up for 10 to 20 years to evaluate the significance of PI. Subsequent to publication of our papers,^28,43 Berman et al.⁴⁹ reported development of significant PI in 6 of 107 (6%) patients at late follow-up and some of these patients required pulmonary valve replacement. In an accompanying editorial, Mullins50 stated that he did not find the need for consideration of pulmonary valve replacement among 390 balloon pulmonary valve procedures, although this is an anecdotal observation. None of our patients28 or patients reported by Garty et al.⁴² required pulmonary valve replacement for PI. Review of the available data⁵¹ led me to conclude that development of substantial PI at late follow-up, reported by Berman, is an important observation and that attempts to discern causes of late PI, devise methods to prevent such problem and careful long term follow-up studies to confirm Berman’s observations are warranted. Causes of pulmonary insufficiency and their implications. Berman’s observations⁴⁹ suggested young age, higher degrees of obstruction, large balloon/annulus ratio, use of non-compliant balloons and low post-dilatation peak-to-peak systolic pressure gradients as factors that may have a role in the development of late PI. Abu Haweleh and Hakim⁵² reported results of balloon pulmonary valvuloplasty, performed between January 1995 and January 2002 in 68 children. They detected mild (29%) and moderate (12%) pulmonary insufficiency (PI) in 41% patients; their analysis suggested that use of large balloons (balloon/annulus ratio > 1.3:1) for valvuloplasty may be associated with development of PI at follow-up. Garty et al.⁴² report pulmonary regurgitation in 57% (moderate = 40%; severe = 17%) patients at late follow-up. Multivariate analysis suggested that younger age and smaller body surface area at the time balloon dilatation and non-syndromic children are likely to be associated with development of late PI. My independent analysis⁵¹ suggested a balloon annulus ratio between 1.2 and 1.25, not too different than that proposed by Abu Haweleh and Hakim,⁵² may be most appropriate for balloon pulmonary valvuloplasty. The usefulness of balloons larger than 1.2 times the pulmonary valve annulus in effectively relieving pulmonary stenosis acutely⁵³ and both acutely and at follow-up^12–14 is well recognized. Also, balloons larger than 1.5 times the valve annulus tend to damage right ventricular outflow tract.⁵⁴ In addition, such large balloons did not have advantage beyond that produced by balloons that are 1.2 to 1.4 times the annular size.^13,14 Therefore, I recommended that we strive for a balloon/annulus ratio of 1.2 to 1.25 instead of the previously recommended 1.2 to 1.4.^12–14,53 Such lower ratios are likely to result in good relief of pulmonary valve obstruction while at the same time may help to prevent significant PI at late follow-up. Summary and conclusions. In summary, long term follow-up studies such as that reported by Garty⁴² are welcome additions to the existing data. Based on these data and those by several groups workers reporting on long-term results,^28,43–49 it is concluded that late follow-up results of balloon pulmonary valvuloplasty are excellent, requiring repeat balloon dilatation or surgical intervention in the minority of patients with actuarial re-intervention-free rates in mid-80s at 10 years and high-70s at 15 years.^28,42 Residual PI is present in the majority of patients which does not require surgical intervention in most patients. Reduction of balloon/annulus ratio to 1.2 to 1.25 for balloon pulmonary valvuloplasty may reduce the PI at follow-up. We continue to believe that balloon valvuloplasty is the treatment of choice in the management of valvar pulmonic stenosis of moderate to severe degree. Further longer-term follow-up studies^28,43,51 and life-long clinical follow-up⁴² to evaluate the significance of residual PI should be undertaken.

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