Percutaneous Pulmonary Balloon Valvuloplasty Provides Good Long-Term Outcomes in Adults With Pulmonary Valve Stenosis

Abstract: Background. Percutaneous balloon pulmonary valvuloplasty (PBPV) is well described in children, but data on the efficacy and long-term outcomes in adult patients with pulmonary valve stenosis (PVS) are limited. Objective. To estimate the long-term outcomes of PBPV in adult PVS patients. Methods. We performed a retrospective analysis of 41 consecutive adult cases (18 females, 23 males) with moderate to severe PVS who underwent PBPV at the First Affiliated Hospital of Soochow University between January 1999 and December 2005. Follow-up was available for all patients (mean follow-up of 11.3 ± 2.1 years; range, 9-15 years). Results. Before intervention, the peak systolic gradient (PSG) was 71.3 ± 27.8 mm Hg. Immediately after intervention, the PSG was reduced to 30.9 ± 10.9 mm Hg (P<.001). At short-term, mid-term, and long-term follow-up, the mean echocardiographic PSGs were 30.6 ± 11.9 mm Hg, 31.1 ± 16.8 mm Hg, and 27.9 ± 7.6 mm Hg, respectively (P<.001 compared with preintervention PSG). At the last follow-up, 37 of 41 patients (90.2%) had a PSG <36 mm Hg. Four patients (9.8%) underwent a second PBPV. Patients with immediate postintervention PSG ≥36 mm Hg were more likely to need a second PBPV. Two cases with immediate postintervention PSG ≥36 mm Hg experienced a spontaneous PSG reduction to <36 mm Hg. No serious adverse complications happened during or after the procedure. Conclusions. PBPV as a treatment for PVS was safe, and provided good long-term outcomes. Some patients with less-optimal immediate results may experience a spontaneous PSG reduction. A small proportion of patients required a second PBPV, especially those with poor immediate results. Close follow-up is necessary.

 J INVASIVE CARDIOL 2015;27(12)E291-E296. Epub 2015 August 25.

Key words: structural heart disease, pulmonary valve stenosis, percutaneous balloon valvuloplasty, follow-up

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Pulmonary valve stenosis (PVS) is a relatively common congenital defect, occurring in 10% of children with congenital heart disease, with an incidence of 0.50 per 1000 newborns; PVS may also be diagnosed in adults, with an incidence of 0.12 per 1000 adults.¹ PVS is graded into mild (mostly asymptomatic or non-specific symptoms), moderate (dyspnea on exertion and fatigue), and severe stenosis (right ventricular failure and cyanosis). Mild and moderate PVS are associated with a benign clinical course, and only the symptomatic moderate and severe stenosis cases undergo intervention during childhood.^2,3 Therefore, a large number of patients enter adulthood without stenosis correction. However, fibrous thickening and valve calcification may occur with aging, and symptoms may appear, ranging from simple mild exertional dyspnea to symptoms of right heart failure.⁴

When an intervention is required to alleviate symptoms, percutaneous balloon pulmonary valvuloplasty (PBPV) is the procedure of choice, and is associated with a mortality rate of 0.2%.^3,5,6 Indications for PBPV at our clinic are: (1) asymptomatic, domed valve, moderate pulmonic valve regurgitation, and peak instantaneous Doppler gradient >50 mm Hg or mean Doppler gradient >40 mm Hg; or (2) symptomatic, domed valve, and peak instantaneous Doppler gradient >36 mm Hg or mean Doppler gradient >30 mm Hg. Surgical intervention is usually preferred for severe stenosis with complicating features (eg, hypoplastic pulmonary annulus, severe regurgitation, subvalvular stenosis, or supravalvular stenosis). The effects of PBPV in children have been well documented,^7-11 but only a few studies assessed the long-term outcomes of adolescents and adults who underwent PBPV,^12-15 reporting favorable outcomes in most patients. 

Therefore, data about the outcomes of PBPV in adult PVS patients are limited. The purpose of this study was to evaluate the short-term, mid-term, and long-term outcomes of PBPV performed in adult PVS patients. The results will provide a better understanding of PVS correction by PBPV in adults.

Methods

Patients. This was a retrospective analysis performed in 45 consecutive PVS patients from the Suzhou area, Jiangsu province, China, diagnosed between January 1999 and December 2005 at the First Affiliated Hospital of Soochow University. PVS diagnosis was based on two-dimensional echocardiography and peak-to-peak pressure gradient difference between the pulmonary artery and the right ventricle.^4,16,17 PBPV was performed on a standard basis for any patient with peak systolic gradient (PSG) >50 mm Hg or >36 mm Hg with symptoms such as chest tightness and shortness of breath. All patients who underwent PBPV for PVS were included in the present study. Exclusion criteria were: (1) concomitant congenital heart disease requiring surgical intervention; or (2) failure to advance balloon catheter to the pulmonary valve. Therefore, 2 patients were excluded because of large atrial septal defects >35 mm (ages 18 years and 23 years), and 2 patients because of failure to advance balloon catheter (ages 19 years and 33 years). These 4 cases underwent surgery. Finally, 41 cases were included and analyzed. The study protocol was approved by the ethics committee of the Soochow University. Written informed consent was obtained for all patients before PBPV.

Percutaneous balloon pulmonary valvuloplasty. All patients underwent routine preoperative preparation (liver and kidney functions, blood routine examination, and blood coagulation dysfunction), and all the patients were suitable for the procedure. Local anesthesia was performed. A 6 Fr pigtail catheter was inserted using the Seldinger technique¹⁸ in the right or left femoral vein to the right heart. Right ventriculography was performed in the anteroposterior and left lateral views (Figure 1). The diameter of the pulmonary valve annulus was measured from hinge point to hinge point during systole using the lateral view of the right ventriculography. A Baxter balloon (38.9 ± 6.8 mm in length) was selected according to the diameter of the pulmonary valve annulus to be 3%-43% larger than the pulmonary valve annulus.¹⁹ A single dilatation of 18-25 mm in diameter was performed on a 7-9 Fr catheter. After a single balloon expansion, if PSG was still >50 mm Hg, a second balloon was used. Eight patients required two simultaneous balloons because their pulmonary valve annulus was >25 mm. When two balloons were used simultaneously, the total balloon diameter was calculated according to the following formula: (D1 + D2)/π + (D1 + D2)/2, where D1 and D2 are the diameters of the balloons used.²⁰ The mean balloon annulus diameter ratio was 1.2 ± 0.1 (range, 1.03-1.43). The balloon catheter was positioned across the pulmonary valve and inflated to the maximum pressure using diluted contrast medium. We monitored the inflation using the disappearance of the “waist” of the balloon as a measure that full inflation was achieved (Figures 1B and 1C). The balloon was then deflated quickly. Inflations were repeated until a satisfactory reduction in the gradient was detected. Hemodynamic assessment was repeated after valve dilatation. Patients were asked to stay in bed for 8-12 hours.

Data collection. Patients were classified according to their degree of stenosis into the following groups: 36-49 mm Hg stenosis; 50-99 mm Hg stenosis; and ≥100 mm Hg stenosis. All patients were followed by clinical examination and Doppler ultrasound. Outcomes (survival, symptoms, and need for a second intervention) were assessed during follow-up. Follow-up was performed within 3 months of PBPV (short-term follow-up), between 3-12 months after PBPV (mid-term follow-up), and then yearly thereafter (mean long-term follow-up, 11.3 ± 2.1 years; range, 9-15 years). Symptoms, signs, and two-dimensional echocardiogram with color Doppler to measure transvalvular pressure gradient were assessed during each follow-up visit. Data were retrospectively collected by reviewing the medical records, cardiac catheterization reports, and non-invasive studies. PSGs were obtained by both echocardiogram and catheterization hemodynamics before and immediately after the procedure; for comparison with other time points (short-term, mid-term, long-term follow-up data), we used the preoperative and immediate postoperative echocardiographic data. PSG <36 mm Hg (1 mm Hg = 0.133 kPa) was considered an optimal result.²¹

Statistical analysis. All data are presented as mean ± standard deviation for continuous variables, and as proportions for categorical variables. SPSS version 19.0 (SPSS, Inc) was used to perform statistical analyses. Continuous variables were analyzed using ANOVA with Tukey’s post hoc test. Categorical variables were analyzed using the Chi-squared or Fisher’s exact test, as appropriate. All P-values are two-sided and P<.05 was considered significant.

Results

Patient characteristics. Forty-one patients underwent PBPV, including 18 females and 23 males, ages 17-46 years (mean age, 27.6 ± 6.4 years). In the 41 cases, 39 had a dome-like pulmonary valve stenosis and 2 had dysplastic morphology. All patients were followed every year after the intervention. The mean long-term follow-up was 11.3 ± 2.1 years (range, 9-15 years) (Table 1).

Intervention results. Before PBPV, all 41 patients were confirmed to have PVS by right heart catheterization and right ventriculography. The preoperative PSG was 71.3 ± 27.8 mm Hg (range, 40-135 mm Hg). After the procedure, it was reduced to 30.9 ± 10.9 mm Hg (range, 14-70 mm Hg) (P<.001). The procedure was unsuccessful in 2 patients (4.65%). 

Two of the 41 cases had atrial septal defect (28 mm and 24 mm, respectively). They successfully underwent transcatheter occlusion with an Amplatzer double umbrella (32 mm and 28 mm diameters, respectively) after PBPV (100% success rate). 

Follow-up outcomes. Thirty-three patients (80.5%, defined as group A) showed optimal immediate results (immediate postoperative PSG <36 mm Hg). The mean postoperative PSG of these patients was 26.6 ± 4.9 mm Hg (range, 14-35 mm Hg). The remaining 8 cases (19.5%, defined as group B) had suboptimal immediate results (immediate postoperative PSG ≥36 mm Hg), and their mean postoperative PSG was 48.5 ± 11.2 mm Hg (range, 38-70 mm Hg). 

At short-term follow-up, the mean PSG was 30.6 ± 11.9 mm Hg (range, 13-74 mm Hg), which was significantly lower compared with baseline (P<.001) (Table 2). 

No patient in group A suffered from restenosis (PSG ≥36 mm Hg) within 3 months. All patients in group B had PSG >36 mm Hg at short-term follow-up, and their mean PSG was 49.4 ± 13.5 mm Hg (range, 37-74 mm Hg), which was similar to baseline PSG (P>.05). One patient in group A suffered from restenosis 12 months after PBPV (PSG increased from 27 mm Hg immediately after the procedure to 55 mm Hg). He underwent a second PBPV, and PSG decreased from 55 mm Hg to 33 mm Hg. 

Two patients in group B showed significant residual PSG increment (PSG from 60 mm Hg and 70 mm Hg immediately after the procedure to 105 mm Hg and 78 mm Hg, respectively, at mid-term follow-up), and they successfully underwent second PBPVs at 9 months and 11 months, respectively. After the second PBPV, the PSG of these 2 patients decreased from 105 mm Hg to 35 mm Hg and 78 mm Hg to 33 mm Hg. 

At mid-term follow-up, the mean PSG was 31.1 ± 16.8 mm Hg (range, 10-105 mm Hg), which was significantly lower compared with baseline (P<.001), but similar to immediately after PBPV (P>.05) or short-term follow-up (P>.05) (Table 2). At mid-term follow-up, 2 patients in group B had subsequent spontaneous PSG reduction to <36 mm Hg (from 40 mm Hg to 30 mm Hg, and from 39 mm Hg to 20 mm Hg), and these 2 patients still had good outcomes at long-term follow-up (32 mm Hg and 23 mm Hg at last follow-up, respectively). 

The mean PSG of all 41 patients at the last follow-up was 27.9 ± 7.6 mm Hg (range, 12-47 mm Hg), and it was significantly lower compared with baseline (P<.001), but not compared with the other time points (P>.05) (Table 2). Thirty-seven cases (90.2%) at long-term follow-up showed a PSG <36 mm Hg. One patient in group B underwent a second PBPV 5 years after the initial procedure because of significant PSG increment (PSG from 47 mm Hg immediately after the procedure to 92 mm Hg at 5-year follow-up). After repeat PBPV, her PSG decreased from 92 mm Hg to 34 mm Hg immediately, and was 35 mm Hg at the last follow-up. 

At the last follow-up, 1 patient in group A had a PSG increase from 35 mm Hg to 38 mm Hg, and she was followed closely. The other 3 patients in group B had similar PSG at the last follow-up compared with the PSG immediately after initial PBPV (45 mm Hg, 38 mm Hg, and 49 mm Hg immediately after the procedure, respectively; 43 mm Hg, 39 mm Hg, and 47 mm Hg at the last follow-up). They were not willing to undergo a second PBPV and were followed; these patients remained asymptomatic. The natural history of the 41 patients is presented in Figure 2.

In total, 1 of 33 patients (3.0%) in group A underwent a second PBPV, compared with 3 of 8 patients (37.5%) in group B (P=.02). 

PSG in different pulmonary stenosis degrees. The 41 patients were divided into three groups: 11 cases with 36-49 mm Hg stenosis, 20 cases with 50-99 mm Hg stenosis, and 10 cases with ≥100 mm Hg stenosis. In all three groups, PSGs immediately after the procedure and during follow-up were different from baseline (all P<.001) (Table 3).

Complications. During balloon dilatation, all 41 patients had premature ventricular complex, and non-sustained ventricular tachycardia. One patient suffered from a vasovagal reaction, which was relieved by intravenous atropine. One patient had right ventricular flow spasm during balloon dilation; transient stenosis of the right ventricular outflow tract was discovered by echocardiography, and it resolved by itself within 10 minutes. Pulmonary regurgitation was absent in 27 patients (65.9%), mild in 11 patients (26.8%), and moderate in 3 patients (7.3%) at the last follow-up. No case had severe pulmonary valve or tricuspid regurgitation. Surgical or transcatheter pulmonary valve replacement for treatment of pulmonary regurgitation was not required. No case had pericardial tamponade during or after the procedure. No patient died.

Discussion

Treatment outcomes of PVS in adults are not well known. Therefore, the aim of the present study was to assess the long-term outcomes of PBPV in adult PVS patients. Results showed that PSG was reduced immediately after the procedure, and that it remained reduced during follow-up in most patients (90.2%). Four patients (9.8%) underwent a second PBPV. Patients with immediate postoperative PSG ≥36 mm Hg were more likely to need a second PBPV. Two cases with immediate PSG ≥36 mm Hg experienced a spontaneous PSG reduction to <36 mm Hg. No serious adverse complications occurred during or after the procedures.

Some studies have reported the successful use of PBPV in adult PVS patients,^12-15 but there was a lack of data about its long-term efficacy. The present study clearly demonstrated that PBPV was as effective in adults as in children. Furthermore, the beneficial effects of PBPV were well maintained during follow-up, for as long as 15 years after the procedure. Patients with poor immediate results were more likely to undergo a second PBPV, probably due to pulmonary valve dysplasia.²² Taggart et al¹⁵ claimed good outcomes from PBPV in adults, but their mean follow-up was only 1.9 years. A study by Chen et al¹² reported excellent outcomes in adolescent and adult PVS patients who underwent PBPV and who were followed for 0.2-9.8 years. Finally, a study by Rao et al¹⁴ reported actuarial reintervention-free survival rates of 94%, 89%, 88%, and 84% at 1 year, 2 years, 5 years, and 10 years. These previous studies support the conclusions of the present study.

The goal of performing PBPV is the prevention and relief of symptoms, the prevention of secondary changes in the right ventricle and pulmonary artery, and the prevention of progression to more severe degrees of obstruction. However, the majority of patients are asymptomatic, including most patients with severe stenosis. The indications for PVS treatment are still controversial. It is now widely recognized that patients with moderate to severe stenosis should undergo treatment even if asymptomatic because of the possibility of dangerous complications such as hypoxia, dyspnea, and syncope.²³ Some physicians recommend that patients with mild PVS should not be exposed to the risks and expenses of the procedure, that they should undergo a long-term echocardiographic monitoring of PSG, and that the procedure should be performed when the PSG is >50 mm Hg.^24,25 However, some studies also reported that even in mild or moderate stenosis cases, a very fast progression of symptoms may be observed.^8,26 Therefore, Santoro et al²⁷ and McCrindle et al²⁸ advocated a gradient cut-point of 36 mm Hg for intervention. In our series, 11 cases (26.8%) suffered from stenosis between 36-49 mm Hg before PBPV, and these cases showed a significantly decreased PSG immediately after PBPV and during follow-up. Therefore, we infer that PBPV might be an optional treatment for adult PVS patients with stenosis <50 mm Hg, but that these patients can also benefit from PBPV. 

In our group of 41 patients, the mean balloon annulus ratio was 1.23 ± 0.08 (range, 1.03-1.43). Saad et al²⁹ found that the factor closely associated with immediate postoperative efficacy was the balloon annulus ratio. Rao et al¹⁹ observed that when the balloon annulus ratio was between 1.0-1.4, there was no significant correlation between immediate postoperative PSG and balloon annulus ratio. A too-small balloon diameter will result in poor immediate postoperative results, but there is no evidence showing that using an oversized balloon can result in better long-term efficacy. However, oversized balloons can result in greater damage to the heart and valve, potentially causing pulmonary and tricuspid regurgitation, right heart failure, and even uncontrollable pleural hemorrhage and rupture of the heart.^30,31 

Among our 41 cases, 8 had suboptimal immediate results, with postoperative PSG ≥36 mm Hg. Among these patients, there were 2 cases whose PSG decreased to <36 mm Hg spontaneously at mid-term follow-up. This phenomenon was observed in previous studies.^12,32 This delayed reduction of the gradient may also occur after surgical pulmonary valvotomy,³³ and suggests that the measurement of the systolic gradient immediately after PBPV probably underestimates the long-term efficacy of the procedure. The possible mechanism explaining this phenomenon is infundibular gradient caused by infundibular stenosis.³⁴ It is unclear whether infundibular stenosis is due to subvalvular muscular hypertrophy that subsequently resolves after successful treatment of the valvular stenosis or to infundibular spasm.³⁵ Some studies recommend the use of beta-blockers for patients after valvuloplasty,³⁶ but we did not prescribe them to any of our patients. 

In our series, no severe complications occurred. The incidence of pulmonary regurgitation was low immediately after PBPV (34.1%) and at long-term follow-up (29.3%). Rupture of the right ventricular outflow tract has been observed to be the major fatal complication of PBPV.³⁷ It usually occurs in neonates or infants with critical pulmonary stenosis and hypoplastic pulmonary valve.^11,38,39 However, this complication seems to be extremely rare in adults.^12-15

Study limitations. The present study suffered from some limitations. Indeed, the small sample size prevented us from making any firm conclusions. However, our results, supported by previous studies, suggest that PBPV is safe and effective in adult PVS patients. Larger studies are required to reach firm conclusions. A randomized clinical trial might even be performed in mild stenosis patients.

Conclusion

PBPV is safe and effective for adult PVS patients, with good long-term efficacy. Mild stenosis may also benefit from PBPV. Some patients, especially those with poor immediate postoperative effect, may need a second PBPV. Therefore, follow-up is necessary after PBPV.

Acknowledgments. The authors acknowledge the invaluable participation of the patients.

References

1. Marelli AJ, Mackie AS, Ionescu-Ittu R, Rahme E, Pilote L. Congenital heart disease in the general population: changing prevalence and age distribution. Circulation. 2007;115:163-172.
2. Warnes CA, Williams RG, Bashore TM, et al. ACC/AHA 2008 guidelines for the management of adults with congenital heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (writing committee to develop guidelines on the management of adults with congenital heart disease). Circulation. 2008;118:e714-e833.
3. Hayes CJ, Gersony WM, Driscoll DJ, et al. Second natural history study of congenital heart defects. Results of treatment of patients with pulmonary valvar stenosis. Circulation. 1993;87(2 Suppl):I28-I37.
4. Bonow RO, Carabello BA, Chatterjee K, et al. 2008 focused update incorporated into the ACC/AHA 2006 guidelines for the management of patients with valvular heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (writing committee to revise the 1998 guidelines for the management of patients with valvular heart disease): endorsed by the Society of Cardiovascular Anesthesiologists, Society for Cardiovascular Angiography and Interventions, and Society of Thoracic Surgeons. Circulation. 2008;118:e523-e661.
5. Stanger P, Cassidy SC, Girod DA, Kan JS, Lababidi Z, Shapiro SR. Balloon pulmonary valvuloplasty: results of the Valvuloplasty and Angioplasty of Congenital Anomalies Registry. Am J Cardiol. 1990;65:775-783.
6. Kan JS, White RI Jr, Mitchell SE, Gardner TJ. Percutaneous balloon valvuloplasty: a new method for treating congenital pulmonary-valve stenosis. N Engl J Med. 1982;307:540-542.
7. Ahmadi A, Sabri M. Percutaneous balloon valvuloplasty inpatients with pulmonary valve stenosis: a single center experiment. J Pak Med Assoc. 2012;62(3 Suppl 2):S58-S61.
8. Werynski P, Rudzinski A, Krol-Jawien W, Kuzma J. Percutaneous balloon valvuloplasty for the treatment of pulmonary valve stenosis in children — a single-centre experience. Kardiol Pol. 2009;67:369-375.
9. Maostafa BA, Seyed-Hossien M, Shahrokh R. Long-term results of balloon pulmonary valvuloplasty in children with congenital pulmonary valve stenosis. Iran J Ped. 2013;23:32-36.
10. Ghaffari S, Ghaffari MR, Ghaffari AR, Sagafy S. Pulmonary valve balloon valvuloplasty compared across three age groups of children. Int J Gen Med. 2012;5:479-482.
11. Luo F, Xu WZ, Xia CS, et al. Percutaneous balloon pulmonary valvuloplasty for critical pulmonary stenosis in infants under 6 months of age and short and medium term follow-up. Zhonghua Er Ke Za Zhi. 2011;49:17-20.
12. Chen CR, Cheng TO, Huang T, et al. Percutaneous balloon valvuloplasty for pulmonic stenosis in adolescents and adults. N Engl J Med. 1996;335:21-25.
13. Roos-Hesselink JW, Meijboom FJ, Spitaels SE, et al. Long-term outcome after surgery for pulmonary stenosis (a longitudinal study of 22-33 years). Eur Heart J. 2006;27:482-488.
14. Rao PS, Galal O, Patnana M, Buck SH, Wilson AD. Results of three to 10 year follow-up of balloon dilatation of the pulmonary valve. Heart. 1998;80:591-595.
15. Taggart NW, Cetta F, Cabalka AK, Hagler DJ. Outcomes for balloon pulmonary valvuloplasty in adults: comparison with a concurrent pediatric cohort. Catheter Cardiovasc Interv. 2013;82:811-815.
16. Baumgartner H, Bonhoeffer P, De Groot NM, et al. ESC guidelines for the management of grown-up congenital heart disease (new version 2010). Eur Heart J. 2010;31:2915-2957.
17. Baumgartner H, Hung J, Bermejo J, et al. Echocardiographic assessment of valve stenosis: EAE/ASE recommendations for clinical practice. J Am Soc Echocardiog. 2009;22:1-23; quiz 101-102.
18. Seldinger SI. Catheter replacement of the needle in percutaneous arteriography; a new technique. Acta Radiol. 1953;39:368-376.
19. Rao PS. Percutaneous balloon pulmonary valvuloplasty: state of the art. Catheter Cardiovasc Interv. 2007;69:747-763.
20. Rao PS. Influence of balloon size on short-term and long-term results of balloon pulmonary valvuloplasty. Tex Heart Inst J. 1987;14:57-61.
21. McCrindle BW, Kan JS. Long-term results after balloon pulmonary valvuloplasty. Circulation. 1991;83:1915-1922.
22. Gardiner HM, Belmar C, Tulzer G, et al. Morphologic and functional predictors of eventual circulation in the fetus with pulmonary atresia or critical pulmonary stenosis with intact septum. J Am Coll Cardiol. 2008;51:1299-1308.
23. Voet A, Rega F, de Bruaene AV, et al. Long-term outcome after treatment of isolated pulmonary valve stenosis. Int J Cardiol. 2012;156:11-15.
24. Miyazaki T, Yamagishi M. Re-right ventricular outflow reconstruction. Kyobu Geka. 2013;66(8 Suppl):670-673.
25. Rao PS. Consensus on timing of intervention for common congenital heart diseases: part I — acyanotic heart defects. Indian J Pediatr. 2013;80:32-38.
26. Freedom RM. Congenital pulmonary stenosis and isolated congenital pulmonary insufficiency. In: The Natural and Modified History of Congenital Heart Disease. New York: Futura, Blackwell Publishing; 2004.
27. Santoro G, Formigari R, Di Carlo D, Pasquini L, Ballerini L. Mid-term outcome after pulmonary balloon valvuloplasty in patients younger than one year of age. Am J Cardiol. 1995;75:637-639.
28. McCrindle BW. Independent predictors of long-term results after balloon pulmonary valvuloplasty. Valvuloplasty and Angioplasty of Congenital Anomalies (VACA) Registry Investigators. Circulation. 1994;89:1751-1759.
29. Saad MH, Roushdy AM, Elsayed MH. Immediate- and medium-term effects of balloon pulmonary valvuloplasty in infants with critical pulmonary stenoses during the first year of life: a prospective single center study. J Saudi Heart Assoc. 2010;22:195-201.
30. Cheng HI, Lee PC, Hwang B, Meng CC. Acute pulmonary reperfusion hemorrhage: a rare complication after oversized percutaneous balloon valvuloplasty for pulmonary valve stenosis. J Chin Med Assoc. 2009;72:607-610.
31. Harrild DM, Powell AJ, Tran TX, et al. Long-term pulmonary regurgitation following balloon valvuloplasty for pulmonary stenosis risk factors and relationship to exercise capacity and ventricular volume and function. J Am Coll Cardiol. 2010;55:1041-1047.
32. Parent JJ, Hoyer MH. Delayed success of balloon dilation for coexisting pulmonary valve stenosis and sinotubular narrowing. Congenit Heart Dis. 2014;9:216-220. Epub 2013 Jun 27.
33. Earing MG, Connolly HM, Dearani JA, Ammash NM, Grogan M, Warnes CA. Long-term follow-up of patients after surgical treatment for isolated pulmonary valve stenosis. Mayo Clin Proc. 2005;80:871-876.
34. Thakkar B, Madan T, Ashwal AJ. Transcatheter right ventricular outflow tract stenting in children with postoperative infundibular stenosis and preserved pulmonary valve function. J Invasive Cardiol. 2013;25:E151-E154.
35. Lee ML, Peng JW, Tu GJ, Chen SY, Lee JY, Chang SL. Major determinants and long-term outcomes of successful balloon dilatation for the pediatric patients with isolated native valvular pulmonary stenosis: a 10-year institutional experience. Yonsei Med J. 2008;49:416-421.
36. Khambatta HJ, Velado M, Gaffney JW, Schechter WS, Casta A. Management of right ventricular outflow tract reactivity following pulmonary valve dilatation under general anesthesia: experience of a medical mission. Paediatr Anaesth. 2006;16:1087-1089.
37. Karagoz T, Asoh K, Hickey E, et al. Balloon dilation of pulmonary valve stenosis in infants less than 3 kg: a 20-year experience. Catheter Cardiovasc Interv. 2009;74:753-761.
38. Freund MW, Schouten T, Lemmers P, Schroer C, Strengers J. Successful percutaneous balloon valvuloplasty in a preterm infant weighing 1500 g with critical pulmonary valve stenosis. Neth Heart J. 2008;16:264-266.
39. Behjati-Ardakani M, Forouzannia SK, Abdollahi MH, Sarebanhassanabadi M. Immediate, short, intermediate and long-term results of balloon valvuloplasty in congenital pulmonary valve stenosis. Acta Med Iran. 2013;51:324-328.

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From the Department of Cardiology, the First Affiliated Hospital of Soochow University, Suzhou, China.

Funding: National Natural Science Foundation of China, No. K112213810 and No. 81170174.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.

Manuscript submitted June 30, 2014, provisional acceptance given August 3, 2014, final version accepted December 16, 2014.

Address for correspondence: Xiangjun Yang, Department of Cardiology, The First Affiliated Hospital of Soochow University, No. 188, Shizi Street, Suzhou 215006, Jiangsu, China. Email: medsciyxj@126.com