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J Thorac Cardiovasc Surg 2000;120:755-763
© 2000 The American Association for Thoracic Surgery

Surgery for Congenital Heart Disease

Surgery for bilateral outflow tract obstruction in elastin arteriopathy

From the Departments of Cardiac Surgery,^a Cardiology,^b and Biostatistics,^c Children's Hospital Boston, Harvard Medical School, Boston, Mass.

During the time of this investigation, Dr C. Stamm was supported by a grant from the German Research Foundation (STA 497/2-2).

Address for reprints: Pedro J. del Nido, MD, The Children's Hospital Boston, Cardiac Surgery, 300 Longwood Ave, Boston, MA 02115 (E-mail: delnido{at}a1.tch.harvard.edu).

	Abstract

Top Abstract Introduction Methods Results Discussion Conclusion References

 
Objective: A number of patients with Williams syndrome or other forms of elastin arteriopathy have stenoses of pulmonary arteries in addition to supravalvular aortic stenosis. We sought to investigate the effect of the degree of pulmonary arterial stenosis on the prognosis after an operation for supravalvular aortic stenosis to help define the optimal treatment strategy for patients with severe forms of elastin arteriopathy.
Methods: Between 1960 and 1999, 33 patients underwent operations for supravalvular aortic stenosis while having significant stenoses of the pulmonary arteries. We retrospectively reviewed patient charts, obtained current follow-up information, and determined risk factors for survival and reoperation.
Results: Fifteen patients with moderate right-sided obstructions (confirmed by pulmonary artery Z-scores and right ventricular/descending aortic pressure ratio) underwent operations for supravalvular aortic stenosis only. Eighteen patients had more severe right-sided obstructions and underwent surgical relief of pulmonary arterial stenoses or right ventricular outflow tract obstruction in addition to operations for supravalvular aortic stenosis. Eight patients had undergone preoperative balloon dilations of stenotic pulmonary arteries. There were 6 early deaths and 1 late death in our series. Survival at 10 and 20 years was 76% (70% confidence interval, 68%-84%) and freedom from reintervention was 59% (70% confidence interval, 46%-71%) at 10 years and 49% (70% confidence interval, 35%-62%) at 20 years. Multivariate analysis revealed that patients with a right ventricular/descending aortic pressure ratio of 1.0 or more were at higher risk for reintervention but not for death.
Conclusions: Surgical treatment of pulmonary artery obstructions in elastin arteriopathy is palliative but, in conjunction with balloon dilation of peripheral pulmonary arteries, offers good long-term survival to patients with the severest form of elastin arteriopathy.

	Introduction

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The underlying cause for congenital supravalvular aortic stenosis (SVAS) in patients with Williams syndrome, familial SVAS, and probably also sporadic SVAS has been identified as a chromosomal microdeletion at 7q11.23, including the elastin gene. ¹ The resulting decrease in elastin expression during development is associated with an increased number of elastin lamellae and excessive accumulation of collagen and smooth muscle cells in the vascular wall, resulting in formation of severely thickened and rigid arterial vessels. ^2-4 This elastin arteriopathy is not a localized process but rather a generalized disease of both the systemic and pulmonary arterial systems. ^5-7 Although in many patients with SVAS only the aortic obstruction is of clinical relevance, obstructions of the pulmonary vasculature are frequently observed. ^8-11 Peripheral pulmonary arterial stenosis has long been acknowledged as part of Williams syndrome, and central pulmonary artery stenosis is often found. ¹² Patients with elastin arteriopathy may also have pulmonary artery stenoses without having relevant SVAS. ^9,13 Localized supravalvular pulmonary stenosis has also been described, ^14,15 although it is the least frequent type of pulmonary artery stenosis in elastin arteriopathy. Depending on the degree of stenosis, right ventricular pressure overload and biventricular hypertrophy may develop. Several reports indicate that in the natural course of the disease, the severity of pulmonary artery stenoses, and thus right ventricular pressure load, decrease throughout childhood and adolescence. ^10,13,16-18 However, there are a number of patients with severe pulmonary artery stenoses who require surgical treatment for SVAS while also having significant right ventricular pressure overload, and these patients may have a higher operative risk.

We have previously reported our institutional experience with surgical treatment of SVAS with respect to aortic valve function. ¹¹ In this study we sought to (1) examine the nature of pulmonary artery stenosis in these patients in greater detail, (2) determine the effect of different degrees of pulmonary artery stenosis on the prognosis after surgical treatment of SVAS, and (3) help define the optimal treatment strategy on the basis of the results of surgical relief of pulmonary artery obstructions as part of a generalized elastin arteriopathy.

	Methods

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This study is confined to patients who underwent an operation for SVAS at Children's Hospital Boston between 1960 and 1999 and had concomitant pulmonary artery stenoses indicating generalized elastin arteriopathy. Patients operated on before August 1998 were also included in a study that analyzed the results of different techniques for reconstruction of the aortic root in SVAS. ¹¹ The patients' charts were reviewed, and questionnaires were sent to physicians and cardiologists. All available reports of cardiac catheterization, echocardiography, and lung perfusion scans were reviewed. Patients or parents were contacted and sent a questionnaire when no recent follow-up information was available. The protocol was approved by the Children's Hospital Institutional Review Board. The follow-up period ranged from between 5 months and 34 years (mean 9.2 years), and cross-sectional follow-up was complete for all patients as of June 1999.

Hemodynamic and morphometric measurements
Data were obtained during routine clinical follow-up and reviewed retrospectively. Preoperative left ventricular and aortic pressure measurements were performed by cardiac catheterization in 31 patients; the left ventricular–aortic pressure gradient at follow-up was assessed by Doppler echocardiography in 16 patients and cardiac catheterization in 13. Right ventricular pressure was measured by means of preoperative cardiac catheterization in 27 patients. Right heart catheterization during follow-up was performed in 13 patients (3.2 ± 2.8, median 1.5 years postoperatively). In 15 patients right ventricular pressure at follow-up was derived from the peak velocity of the tricuspid regurgitation jet, as measured by Doppler echocardiography (performed 6.9 ± 3.1, median 5.4 years postoperatively). The right ventricle/descending thoracic aorta (RV/AoDT) pressure ratio was calculated to assess right ventricular pressure load. The pulmonary artery diameter was measured on anteroposterior angiograms in 24 patients preoperatively and in 13 patients at follow-up. Two-dimensional echocardiography was used to measure the diameter of the central pulmonary arteries at follow-up in 16 patients. Z-scores of pulmonary artery size for a given body surface area were calculated by use of the diameter measured midway between the origin and first branching point. Calculations were based on the normal ranges reported by Sievers and colleagues ¹⁹ for measurements obtained from angiograms and on an institutional database representative of the local patient demographics for echocardiographic measurements. ²⁰

Definitions
Central pulmonary artery stenosis was defined as greater than 50% narrowing in diameter of the main, left, or right pulmonary artery, as demonstrated by angiography or echocardiography. Peripheral pulmonary artery stenosis was defined as greater than 50% narrowing distal to the pulmonary artery branching point at the hilum, as demonstrated by angiography. Diffuse pulmonary artery stenosis was defined as an angiographically diagnosed bilateral hypoplasia involving the central and peripheral pulmonary arteries. Discrete SVAS was defined as an hourglass-shaped narrowing of the aorta at the level of the sinutubular junction. A tubular narrowing involving the ascending aorta or beyond was termed diffuse.

Statistical analysis
Estimated rates of survival and freedom from reoperation with 70% confidence intervals (CI) were determined by the Kaplan-Meier product-limit method, and survival curves were compared by the log-rank test. The Cox proportional-hazards regression model was used to establish the variables independently associated with each outcome, with risk measured by the adjusted hazard ratio. ²¹ Variables tested were as follows: surgical, interventional, or both types of treatment of pulmonary artery stenosis; type of SVAS (diffuse or discrete); and presence of diffuse pulmonary artery stenosis. Age at the time of operation, year of operation, and RV/AoDT pressure ratio were investigated as continuous variables. A forward stepwise selection procedure was used to build the final multivariate models by means of the variables stated above. Hemodynamic and morphometric variables were evaluated by the Kolmogorov-Smirnov test to ascertain whether the measurements follow a normal distribution. For variables having a skewed distribution, the Mann-Whitney U test was used for between-group comparisons, and the Wilcoxon signed-rank test was used for comparisons of preoperative and follow-up data. Variables following a normal distribution (including Z-scores) were analyzed by means of the appropriate parametric t test. The correlation between patient age and the RV/AoDT pressure ratio was tested by fitting the data to a nonlinear decay function of the first order. Data were analyzed with the SPSS software package (version 9.0; SPSS Inc, Chicago, Ill).

	Results

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Thirty-three patients with SVAS and pulmonary artery stenosis underwent operations at our institution. Thirteen (39%) of the patients were male, and 20 (61%) were female. Ages at operation ranged between 6 months and 16 years (mean 5.7 years; median 3.7 years). In 23 (70%) patients a diagnosis of Williams syndrome was made by a medical geneticist and supported by fluorescence in situ hybridization analysis of a deletion on chromosome 7q11.23. In 5 (15%) patients a familial history of SVAS, generalized arteriopathy, or both, was known, and the remaining 5 (15%) patients were classified as sporadic cases. Associated cardiovascular anomalies included patent ductus arteriosus (n = 1), atrial septal defect (n = 1), small muscular ventricular septal defect (n = 1), and stenosis of the left main coronary artery (n = 1). Systemic arterial stenoses were demonstrated in 12 (36%) patients and involved renal arteries (n = 6) and aortic arch branches (n = 9). Six patients had previously undergone cardiovascular procedures other than balloon dilations of pulmonary artery stenoses, including repair of aortic coarctation (n = 4), division of a patent ductus arteriosus (n = 1), and balloon dilation of a stenotic left carotid and innominate artery.

Twenty (61%) patients were in New York Heart Association functional class II to IV. One patient had repeated syncopal episodes. Electrocardiographic evidence, echocardiographic evidence, or both, of significant biventricular hypertrophy was present in 28 (85%) patients. Two patients underwent emergency operations while receiving cardiopulmonary resuscitation after cardiac arrest, one during diagnostic coronary angiography and one during induction of anesthesia.

Left ventricular–aortic pressure gradients ranged between 35 and 120 mm Hg, and right ventricular pressures ranged between 30 and 200 mm Hg. The RV/AoDT pressure ratios ranged between 0.3 and 2.8 (mean 0.9; median 0.75) and was greater than 1.0 in 9 patients. There was a nonlinear correlation between age at the time of the investigation and the RV/AoDT pressure ratio(Fig 1). Stenosis of the proximal right pulmonary artery was demonstrated in 26 (79%) patients, and stenosis of the left pulmonary artery was demonstrated in 20 (61%) patients. Peripheral pulmonary artery stenosis was present in all patients, usually involving more than one lobar or segmental pulmonary artery. Diffuse pulmonary artery stenosis was present in 12 (36%) patients. Pulmonary valve stenosis was found in 9 patients, and a supravalvular narrowing of the main pulmonary artery was found in 4. In 1 patient stenosis of the right ventricular infundibulum was noted in addition to a small pulmonary valve and stenoses of both the right and left pulmonary arteries. Lung perfusion scans were performed in 14 patients with more severe pulmonary artery stenosis and demonstrated a marked perfusion mismatch in 7. As indicated by elevated right atrial pressure (>10 mm Hg), 5 patients had evidence of right ventricular failure. A systemic venous oxygen saturation of less than 50%, which indicated insufficient systemic perfusion, was found in 1 patient.

View larger version (10K): [in this window] [in a new window]   Fig. 1. Right ventricular/descending aortic (RV/AoDT) pressure ratio as a function of age at investigation. Measurements were obtained by means of preoperative right and left heart catheterization in 25 patients. Nonlinear regression analysis revealed a negative correlation between the RV/AoDT pressure ratio and patient age (R = 0.65, R2 = 0.43, P = .0003).

View larger version (16K): [in this window] [in a new window]   Fig. 2. Flow chart indicating the number of patients associated with a respective treatment or outcome. SVAS, Supravalvular aortic stenosis; PAS, pulmonary artery stenosis.

Reoperations or interventions
One patient was reoperated on for restenosis at the distal end of the aortic patch, and several procedures were performed for recurrent or residual pulmonary artery stenosis. After patch enlargement of the right pulmonary artery, early restenosis developed in 1 patient at the site of the pericardial patch, and the patch was replaced 1 year after the initial operation. The patient who underwent replacement of the right ventricular outflow tract by a homograft had obstruction of the homograft with a gradient of 50 mm Hg after 6.5 years. Attempted balloon dilation of the stenotic homograft failed, and the stenosis was relieved by insertion of a generously sized preclotted Dacron patch. In 6 patients, one or more balloon dilations of pulmonary artery stenoses were performed during the follow-up period, in 1 case including placement of an intravascular stent. Overall freedom from reoperation or intervention estimated by the Kaplan-Meier method was 75% (70% CI, 66-84%) at 5 years, 59% (70% CI, 46-71%) at 10 years, and 49% (70% CI, 35-62%) at 20 years(Fig 3, B). Multivariable analysis revealed that patients with a preoperative RV/AoDT pressure ratio of 1.0 or greater were at higher risk for reoperation or intervention(Fig 4, A). Six of the 9 patients who required reoperation had an RV/AoDT pressure ratio of 1.0 or greater, and 20 of the 23 patients not requiring reoperation had a pressure ratio of less than 1.0 (adjusted hazard ratio, 7.4; 70% CI, 3.6-14.9; P = .01). Cox regression also revealed that patients with pulmonary artery stenoses necessitating surgical or interventional treatment at the time of operation for SVAS were more likely to undergo reoperation or intervention during follow-up (adjusted hazard ratio, 4.0; 70% CI, 1.5-10.8; P = .03). Operation after 1987 also proved an independent risk factor for reoperation or intervention (hazard ratio, 1.3; 70% CI, 1.1-1.6; P = .02), which may be influenced by the fact that interventional treatment options for patients with severe pulmonary artery stenosis were not available before.

View larger version (9K): [in this window] [in a new window]   Fig. 3. Kaplan-Meier estimated 20-year overall survival (A) and freedom from reoperation or intervention (B). Error bars indicate the lower 70% CI. Number of patients at risk are shown in parentheses.

View larger version (13K): [in this window] [in a new window]   Fig. 4. Kaplan-Meier estimated 20-year freedom from reoperation or intervention (A) and survival (B) for patients with elastin arteriopathy and suprasystemic right ventricular pressure (RV/AoDT pressure ratio > 1) and patients with an RV/AoDT pressure ratio of less than 1. P values shown on the plots were calculated by the log-rank test. Error bars indicate the lower 70% CI. Numbers of patients at risk are shown in parentheses; the group with an RV/AoDT pressure ratio of less than 1 is shown in italics, and the group with an RV/AoDT pressure ratio of greater than 1 is shown in boldface.

View larger version (24K): [in this window] [in a new window]   Fig. 5. RV/AoDT pressure ratio preoperatively and at follow-up. PAS not treated, Patients who underwent operations for SVAS only; PAS treated, patients who underwent operations for both SVAS and pulmonary artery stenosis. The P values displayed on the plots were determined by the paired Student t test. Follow-up measurements were obtained 4.7 ± 2.9 years postoperatively (median 3.4 years). Horizontal bars indicate median.

	Discussion

Top Abstract Introduction Methods Results Discussion Conclusion References

The opposite end of the spectrum is represented by patients with severe, generalized, obstructive arteriopathy, for whom the anatomic term macaroni arteriopathy was coined. They usually have severe biventricular pressure overload, are at exceedingly high risk of myocardial ischemia, and are often deemed untreatable. A large proportion of the patients who underwent treatment of right-sided stenoses are very close to this end of the spectrum. In addition to significant SVAS requiring surgical reconstruction, the majority of these patients had multiple pulmonary artery stenoses or complex right ventricular outflow tract obstruction, resulting in suprasystemic right ventricular pressure(Fig 6). They were referred for surgical treatment at a significantly younger age than patients with milder stenoses. Our selective approach combining preoperative balloon dilation of peripheral pulmonary artery stenoses and surgical relief of central stenoses at the time of operation for SVAS resulted in a 20-year survival of 79%(Fig 4, B), which is similar to the previously reported overall survival of patients with SVAS. ¹¹ We consider it important to reduce right ventricular pressure overload before or at the time of operation for SVAS because the ischemic injury imposed on such severely hypertrophied hearts during the repair can have deleterious effects in the presence of excessively high afterload. The hypertrophied myocardium is more susceptible to ischemia, ^22,23 and in addition to our own experience, the literature shows several reports of patients with elastin arteriopathy who had right ventricular failure after the operation for SVAS. ^11,17 Eight patients had previously undergone balloon dilations of pulmonary arteries, ^24-27 so that in combination with surgical enlargement of more proximal stenoses, right ventricular pressure load was reduced before or at the time the heart was subjected to global ischemia for repair of SVAS.

View larger version (54K): [in this window] [in a new window]   Fig. 6. A, Pulmonary angiogram (right pulmonary artery) of a patient with diffuse pulmonary artery stenosis (age 3.7 years) at the time of diagnosis (RV/AoDT pressure ratio, 1.2; Z-scores: right pulmonary artery, –3.9; left pulmonary artery, –2.1). The patient underwent preoperative balloon dilation of several lobar pulmonary arteries followed by an operation for SVAS and insertion of a pericardial patch in the central right and left pulmonary arteries. B, Pulmonary angiogram of the same patient 10.2 years postoperatively. The central pulmonary arteries are of good size (Z-scores: right pulmonary artery, –0.6; left pulmonary artery, –0.2) but peripheral pulmonary artery stenosis persists. Multiple balloon dilations of peripheral pulmonary arteries were subsequently performed with angiographic and hemodynamic improvement (RV/AoDT pressure ratio, 0.5).

Several reports have suggested that the severity of pulmonary artery stenoses in Williams syndrome decreases over time. ^10,13,16-18 However, it is notable that very few of the patients included in these reports initially had suprasystemic right ventricular pressure. A possible explanation may be that these patients rarely reach the age for a follow-up examination without undergoing treatment or dying. We observed improvement of right ventricular pressure overload without treatment in 5 patients. Because serial hemodynamic assessments are frequently not available, in some reports the correlation between patient age or body surface area and severity of pulmonary artery stenoses has been used to support the concept of improvement of pulmonary artery stenosis over time. ^13,17 We also found a correlation between age and severity of pulmonary artery stenosis (assessed by RV/AoDT pressure ratio). However, as opposed to waiting for spontaneous improvement of pulmonary artery stenoses, we advocate an early relief of right-sided obstructions to minimize the risk of an operation when relief for SVAS is indicated.

Limitations of the study
As a retrospective study based on a small number of patients with complete functional follow-up but incomplete hemodynamic and morphometric data, the statistical power of this analysis is certainly limited. The patient selection was based on clinical criteria (undergoing an operation for SVAS while having significant pulmonary artery stenosis) that are likely to influence the clinical course of the patients. However, as we and others have pointed out previously, the underlying disease is probably identical in all patients with congenital SVAS. Furthermore, we did not include patients with the same etiology who underwent interventional treatment of right-sided obstructions only.

	Conclusion

Top Abstract Introduction Methods Results Discussion Conclusion References

 
In summary, we conclude that an individualized, combined, cardiac surgical and interventional approach to children with the severe forms of elastin arteriopathy, biventricular pressure overload, and suprasystemic right ventricular pressure results in favorable long-term survival. However, generalized arteriopathy with severe bilateral outflow tract obstruction and suprasystemic right ventricular pressures remains a surgical challenge. Surgical treatment is palliative and requires careful follow-up examinations and frequently additional pulmonary balloon angioplasty to ensure successful long-term outcome.

	References

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Christof Stamm Emile Bacha John E. Mayer Richard A. Jonas Pedro J. del Nido Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Stamm, C. Articles by del Nido, P. J. Search for Related Content PubMed PubMed Citation Articles by Stamm, C. Articles by del Nido, P. J.