Clinical and Hemodynamic Results After Conversion from Single to Biventricular Circulation After Fetal Aortic Stenosis Intervention.

At our institution a multidisciplinary team has performed fetal aortic valvuloplasty (FAV) for severe aortic stenosis with evolving hypoplastic left heart syndrome with high technical success rates. Measurement of postnatal success has been biventricular circulation (BC). Postnatal survival for patients after FAV who achieved a BC appears encouraging. However, there are limited late clinical and hemodynamic outcomes in this cohort and there is concern for diastolic dysfunction. We reviewed all patients with FAV at our institution who initially underwent single ventricle palliation and subsequently BC, as this is likely the subset at high-risk for poor outcomes. Clinical, imaging, and surgical data were collected. Two of 7 patients (29%) died within 16 months of BC, and 1 patient has been listed for transplant. Diastolic dysfunction was common and progressive with median left ventricular end diastolic pressure of 12 mm Hg before BC, and increasing to 22 mm Hg for survivors at last follow-up. Left ventricular size was adequate with all patients reaching a left ventricular end diastolic volume (LVEDV) z score in the normal or elevated range. Presence and severity of residual valve lesions decreased over time secondary to a median of 6 interventions (range 3 to 10), either surgical or cath-based, performed for these 7 patients during the study period. In conclusion, clinical outcomes are concerning for this high-risk group. Diastolic dysfunction is persistent and progressive despite anatomic interventions and adequate left ventricular growth. The main contributing factor to poor outcomes may be intrinsic myocardial dysfunction and primordial pathology. Achievement of a BC after FAV may not be an appropriate measure of success.

Transcatheter Intervention of Coronary Obstructions in Infants, Children, and Young Adults.

This study assesses the characteristics of coronary obstructions that underwent transcatheter intervention in a pediatric catheterization laboratory, the procedural details, and patient outcomes. Acute cardiac failure due to coronary obstructions in children is rare. The role of catheter based intervention is largely unreported. Single center retrospective review between January 2000 and December 2016. Thirty-three patients (median age 2y/o [0-38], weighing 9.6 kg [2.2-91]) underwent 39 transcatheter interventions on 39 lesions, mainly left main coronary (16/39; 39%) and right coronary (9/39; 23%) arteries. Most patients had congenital heart disease (29/33; 88%). Cath indications included ventricular dysfunction (17), cardiac arrest (7), failure to wean from cardiopulmonary bypass (5), and other (4). Almost half (18/39; 46%) were performed on ECMO support. Obstructions were post-surgical (16; 4 with coronary manipulation), thrombotic (13; 5 < 30 days from cardiac surgery), and miscellaneous lesions (10). Interventions included 25 bare metal stents implanted in 22 lesions in 17 patients (mainly post-surgical lesions; 3 at Damus-Kaye-Stansel anastomosis), nine balloon angioplasty only, four lytic therapy ± mechanical disruption of thrombus, and four technical failures. There were no procedure-related deaths. Most patients survived to discharge or transplant (24/33; 73%). Six patients who received stents had follow-up catheterization (median 15.5 months [1-106]); all were without restenosis. Most coronary obstructions intervened upon in a pediatric cath lab were on young, critically ill patients with congenital heart disease secondary to surgical manipulation/injury or thrombosis. Transcatheter intervention should be considered a potential treatment strategy in this population.

Targeted Increase in Pulmonary Blood Flow in a Bidirectional Glenn Circulation.

In patients with a Glenn shunt and unilateral pulmonary vascular abnormalities, supplemental pulmonary blood flow may improve antegrade flow in the target lung and may permit eventual Fontan completion, while mitigating the risks of uncontrolled additional flow to the contralateral lung. We attempted this by inserting a small aortopulmonary shunt into the affected pulmonary artery and banding the central pulmonary artery. We performed a retrospective review of all patients who underwent this procedure from 2000 to 2015. Comparisons of nonparametric variables were performed with the Wilcoxon signed rank test. Twenty patients were followed for a median of 36 months. Vascular abnormalities included recalcitrant unilateral pulmonary arterial (n = 8) or venous (n = 5) obstruction or hypoplasia, combined disease (n = 4), or abundant aortopulmonary collaterals (n = 3). Nine had retrograde flow from the affected lung. The most frequent complications were pleural effusions (n = 4) and shunt thrombosis (n = 4). Postoperatively, all patients demonstrated antegrade flow to the target lung at the earliest postoperative catheterization. Glenn pathway pressures and saturations were unchanged, whereas the shunted pulmonary arterial oxygen saturation and pressure increased by 4% (P = 0.04) and 6 mm Hg (P = 0.04), respectively. Three patients died; 9 achieved definitive palliation, 4 were deemed to have no improvement, and 4 continue to have a contralaterally shunted Glenn at this time. Targeted additional pulmonary blood flow may be useful for the palliation of single ventricle patients with abnormal pulmonary vasculature. However, morbidity and mortality are common in this high-risk population.

Tissue expander-stimulated lengthening of arteries for the treatment of midaortic syndrome in children.

BACKGROUND: Midaortic syndrome (MAS) is a rare condition characterized by stenosis of the abdominal aorta. Patients with disease refractory to medical management will usually require either endovascular therapy or surgery with use of prosthetic graft material for bypass or patch angioplasty. We report our early experience with a novel approach using a tissue expander (TE) to lengthen the normal native arteries in children with MAS, allowing primary aortic repair without the need for prosthetic graft material. METHODS: We conducted a retrospective review of patients with MAS undergoing the TE-stimulated lengthening of arteries (TESLA) procedure at our institution from 2010 to 2014. Data are presented as mean (range). RESULTS: Five patients aged 4.8 years (3-8 years) underwent the TESLA procedure. Stages of this procedure include the following: stage I, insertion of retroaortic TE; stage II, serial TE injections; and stage III, final repair with excision of aortic stenosis and primary end-to-end aortic anastomosis. Stage II was completed in 4 months (1-9 months) with 12 (7-20) TE injections. Goal lengthening was achieved in all patients. Stage III could not be completed in one patient because of extreme aortic inflammation, which precluded safe excision of the aortic stenosis and required use of a prosthetic bypass graft. The other four patients completed stage III with two (one to three) additional vessels also requiring reconstruction (renal or mesenteric arteries). At 3.2 years (1-6 years) of follow-up, all patients are doing well. CONCLUSIONS: The TESLA procedure allows surgical correction of MAS without the need for prosthetic grafts in young children who are still growing.

Impact of standardized clinical assessment and management plans on resource utilization and costs in children after the arterial switch operation.

BACKGROUND: Standardized Clinical Assessment and Management Plans (SCAMPs) are a quality improvement initiative designed to reduce unnecessary utilization, decrease practice variation, and improve patient outcomes. We created a novel methodology, the SCAMP managed episode of care (SMEOC), which encompasses multiple encounters to assess the impact of the arterial switch operation (ASO) SCAMP on total costs. METHODS: All ASO SCAMP patients (dates March 2009 to July 2015) were compared to a control group of ASO patients (January 2001 to February 2009). Patients were divided into "younger" (<2 years) and "older" (2-18 years) subgroups. Utilization included all cardiology visits, tests, and procedures. Standardized costs were applied to each unit of utilization. RESULTS: There were 100 historical and 63 SCAMP patients in the younger subgroup, and 163 historical and 165 SCAMP patients in the older subgroup. In the younger subgroup, the SCAMP had a 28% reduction in outpatient clinic visits (P < .001), a 52% reduction in chest radiographs (P < .001), a 21% reduction in electrocardiograms (P < .001), and a 30% total reduction in costs. In the older subgroup, the SCAMP had a 21% reduction in outpatient clinic visits (P < .001), a 20% reduction in chest radiographs (P = .05), a 10% reduction in echocardiograms (P = .05), a 25% reduction in exercise stress tests (P = .01), and a 14% total reduction in costs. The total cost savings of the ASO SCAMP was $216 649 in the first 6 years of the SCAMP. There was no difference in clinical outcomes between the historical and SCAMP cohorts. CONCLUSION: SCAMPs can improve resource utilization and reduce costs after the ASO operation while maintaining quality of care.

Mechanism of valve failure and efficacy of reintervention through catheterization in patients with bioprosthetic valves in the pulmonary position.

BACKGROUND: Surgical and transcatheter bioprosthetic valves (BPVs) in the pulmonary position in patients with congenital heart disease may ultimately fail and undergo transcatheter reintervention. Angiographic assessment of the mechanism of BPV failure has not been previously described. AIMS: The aim of this study was to determine the mode of BPV failure (stenosis/regurgitation) requiring transcatheter reintervention and to describe the angiographic characteristics of the failed BPVs and report the types and efficacy of reinterventions. MATERIALS AND METHODS: This is a retrospective single-center review of consecutive patients who previously underwent pulmonary BPV placement (surgical or transcatheter) and subsequently underwent percutaneous reintervention from 2005 to 2014. RESULTS: Fifty-five patients with surgical (41) and transcutaneous pulmonary valve (TPV) (14) implantation of BPVs underwent 66 catheter reinterventions. The surgically implanted valves underwent fifty reinterventions for indications including 16 for stenosis, seven for regurgitation, and 27 for both, predominantly associated with leaflet immobility, calcification, and thickening. Among TPVs, pulmonary stenosis (PS) was the exclusive failure mode, mainly due to loss of stent integrity (10) and endocarditis (4). Following reintervention, there was a reduction of right ventricular outflow tract gradient from 43 ± 16 mmHg to 16 ± 10 mmHg (P < 0.001) and RVp/AO ratio from 0.8 ± 0.2 to 0.5 ± 0.2 (P < 0.001). Reintervention with TPV placement was performed in 45 (82%) patients (34 surgical, 11 transcatheter) with no significant postintervention regurgitation or paravalvular leak. CONCLUSION: Failing surgically implanted BPVs demonstrate leaflet calcification, thickness, and immobility leading to PS and/or regurgitation while the mechanism of TPV failure in the short- to mid-term is stenosis, mainly from loss of stent integrity. This can be effectively treated with a catheter-based approach, predominantly with the valve-in-valve technique.

Transcatheter Pulmonary Valve Replacement and Acute Increase in Diastolic Pressure are Associated with Increases in Both Systolic and Diastolic Pulmonary Artery Dimensions.

Stable positioning of a transcatheter pulmonary valve (TPV) in native outflow tracts depends on a clear understanding of underlying anatomy and outflow tract dimensions. We hypothesized that restoration of pulmonary competence may acutely alter these dimensions. A retrospective single-center review of consecutive patients after TPV placement from 2007 to 2014 was performed. Patients with less than moderate pulmonary regurgitation were excluded. We reviewed acute catheterization data on 46 patients, most with tetralogy of Fallot (70%). Baseline and post-implant (7.5 ± 3 min post-deployment) measurements of central pulmonary arteries (PAs) were determined angiographically. The right PA diameter increased (20 ± 4-24 ± 6 mm systole*, 16 ± 4-21 ± 6 mm diastole*), as did the left PA (20 ± 6-24 ± 8 mm systole*, 16 ± 5-21 ± 7 mm diastole*). PA pressures increased from averages of 29.3/10.6 (17) to 29.8/15.1 (21) mmHg. We noted that pre-implant systolic PA diameter correlated with diastolic PA diameter post-implant (r = 0.9). On follow-up catheterization in seven patients [median 3 years; (1-8)], combined central PA diameter decreased an average of 20% (systole: 20% ± 12, diastole: 18% ± 11) as compared to post-implant measurements. Acute pulmonary valve competence in patients with at least moderate pulmonary regurgitation results in an immediate increase in PA diameter (20% systole and 30% diastole). The cause of this diameter change is unclear. This acute change may have implications for device and patient selection (*p < 0.001).

Concept of an expandable cardiac valve for surgical implantation in infants and children.

BACKGROUND: Options for cardiac valve replacement in children are limited to fixed-diameter prostheses that do not accommodate for somatic growth. An externally stented bovine jugular vein graft has been modified for surgical valve replacement in pediatric patients, with the intention of subsequent valve expansion in the catheterization laboratory as the child grows. METHODS: Pediatric patients at a single institution who underwent surgical implantation of an expandable bovine jugular vein valve between 2010 and 2014 were reviewed retrospectively. Forty-two patients underwent implantation at median age of 10 months (range, 3 weeks to 5.8 years) in aortic, mitral, pulmonary, or tricuspid positions. Numerous techniques for valve modification and implantation were used. RESULTS: The valve was competent with low gradient acutely postoperatively in all patients. Eight patients experienced central or paravalvular deterioration, and 7 required reoperation for valve-related adverse outcomes. Twenty patients underwent at least one previous valve repair or replacement. Twenty patients underwent 32 episodes of catheter-based balloon expansion of the valve, exhibiting a significant decrease in median gradient from 12 mm Hg to 8 mm Hg (P < .001) with no significant increase in grade of regurgitation. At 12 months after implantation, Kaplan-Meier analysis indicated that 88% would be expected to be free from reoperation (95% confidence interval, 78%-98%). A total of 6 deaths occurred, 3 before discharge and 3 late. CONCLUSIONS: A surgically implanted externally reinforced bovine jugular vein demonstrates acceptable short-term function and is amenable to catheter-based enlargement as the child grows. Modification of valve design and implantation techniques are necessary to reduce perivalvular complications.

A Pediatric Cardiology Fellowship Boot Camp improves trainee confidence.

Introduction New paediatric cardiology trainees are required to rapidly assimilate knowledge and gain clinical skills to which they have limited or no exposure during residency. The Pediatric Cardiology Fellowship Boot Camp (PCBC) at Boston Children's Hospital was designed to provide incoming fellows with an intensive exposure to congenital cardiac pathology and a broad overview of major areas of paediatric cardiology practice. METHODS: The PCBC curriculum was designed by core faculty in cardiac pathology, echocardiography, electrophysiology, interventional cardiology, exercise physiology, and cardiac intensive care. Individual faculty contributed learning objectives, which were refined by fellowship directors and used to build a programme of didactics, hands-on/simulation-based activities, and self-guided learning opportunities. RESULTS: A total of 16 incoming fellows participated in the 4-week boot camp, with no concurrent clinical responsibilities, over 2 years. On the basis of pre- and post-PCBC surveys, 80% of trainees strongly agreed that they felt more prepared for clinical responsibilities, and a similar percentage felt that PCBC should be offered to future incoming fellows. Fellows showed significant increase in their confidence in all specific knowledge and skills related to the learning objectives. Fellows rated hands-on learning experiences and simulation-based exercises most highly. CONCLUSIONS: We describe a novel 4-week-long boot camp designed to expose incoming paediatric cardiology fellows to the broad spectrum of knowledge and skills required for the practice of paediatric cardiology. The experience increased trainee confidence and sense of preparedness to begin fellowship-related responsibilities. Given that highly interactive activities were rated most highly, boot camps in paediatric cardiology should strongly emphasise these elements.

Systemic rapamycin to prevent in-stent stenosis in peripheral pulmonary arterial disease: early clinical experience.

OBJECTIVES: We have taken a novel approach using oral rapamycin - sirolimus - as a medical adjunct to percutaneous therapy in patients with in-stent stenosis and high risk of right ventricular failure. BACKGROUND: Peripheral pulmonary artery stenosis can result in right ventricular hypertension, dysfunction, and death. Percutaneous pulmonary artery angioplasty and stent placement acutely relieve obstructions, but patients frequently require re-interventions due to re-stenosis. In patients with tetralogy of Fallot or arteriopathy, the problem of in-stent stenosis contributes to the rapidly recurrent disease. METHODS: Rapamycin was administered to 10 patients (1.5-18 years) with peripheral pulmonary stenosis and in-stent stenosis and either right ventricular hypertension, pulmonary blood flow maldistribution, or segmental pulmonary hypertension. Treatment was initiated around the time of catheterisation and continued for 1-3 months. Potential side-effects were monitored by clinical review and blood tests. RESULTS: Target serum rapamycin level (6-10 ng/ml) was accomplished in all patients; eight of the nine patients who returned for clinically indicated catheterisations demonstrated reduction in in-stent stenosis, and eight of the 10 patients experienced no significant side-effects. Among all, one patient developed diarrhoea requiring drug discontinuation, and one patient experienced gastrointestinal bleeding while on therapy that was likely due to an indwelling feeding tube and this patient tolerated rapamycin well following tube removal. CONCLUSIONS: Our initial clinical experience supports that patients with peripheral pulmonary artery stenosis can be safely treated with rapamycin. Systemic rapamycin may provide a novel medical approach to reduce in-stent stenosis.

Occult progressive pulmonary arterial occlusion associated with right ventricular hypertension in patients with systemic arteriopathy.

OBJECTIVES: Peripheral pulmonary artery stenosis (PPS) is a heterogeneous disease associated with numerous clinical or syndromic disorders including Williams syndrome. Previous studies focusing on patients with Williams syndrome have documented spontaneous improvement in branch pulmonary artery (PA) stenosis and right ventricular pressure. The goal of this study is to identify angiographic evidence of spontaneous occlusion or loss of segmental PAs in patients with PPS. METHODS: Patients undergoing serial catheterization for PPS at Boston Children's Hospital between 1999 and 2014 were selected. Patients with structural heart disease such as tetralogy of Fallot, truncus arteriosus, transposition of the great arteries, or single ventricle were excluded. Hemodynamic data were extracted from catheterization reports, all available angiograms were reviewed, and evidence of segmental PA loss was documented based on defined angiographic criteria. RESULTS: Forty-two patients were included in the study. Each patient underwent an average of 5 catheterizations over the 15-year study period. The average RV pressure at initial catheterization was near systemic levels. Evidence of segmental PA loss was present in 40% of patients. Almost 30% of patients with vessel loss demonstrated loss at their initial catheterization, and 65% of patients experienced loss of multiple vessels over time. Patients with vessel loss tended to be older at initial catheterization and have higher average RV pressures at their most recent catheterization than those without vessel loss. CONCLUSIONS: Progressive segmental PA loss in patients with systemic arteriopathy and PPS has not been well described previously. In this cohort, segmental PA loss occurred in 40% of patients, resulting in persistently elevated PA pressures relative to patients who did not develop vessel loss. These findings highlight the importance of surveillance in this population of patients with systemic arteriopathy and severe PPS.

Gathering and learning from relevant clinical data: a new framework.

Given the rising costs of health care in today's economic environment, the need for effective, value-driven care has never been more pressing. While the U.S. health care system strives continually to improve patient outcomes, it struggles with the inadequacies due to variation in care and the inefficiencies of unnecessary resource utilization. The tools traditionally used to study care, from retrospective studies to randomized controlled trials, may be inadequate to address the complicated, interdependent questions related to defining effective care. To overcome the deficiencies of these traditional tools and better optimize our health care system, a new kind of methodology is required--one that integrates the functionality of previously existing tools in a novel way. Standardized Clinical Assessment and Management Plans (SCAMPs) were designed to accomplish this goal. A SCAMP is a care pathway, designed by clinicians, to guide medical decision making around a particular disorder. SCAMPs are unique in that they invite knowledge-based diversions from their recommendations and are accompanied by data collection and continuous improvement processes. Through these mechanisms, SCAMPs successfully reduce practice variation, optimize resource use, and create an integrated medical learning system which overcomes many of the inadequacies of traditional research tools. As such, the SCAMP paradigm may represent an important breakthrough in the effort to define and implement effective health care.

Percutaneous left atrial decompression in patients supported with extracorporeal membrane oxygenation for cardiac disease.

OBJECTIVES: Left atrial decompression using cardiac catheterization techniques has been described at centers with extracorporeal membrane oxygenation programs. Left atrial decompression can decrease cardiogenic edema, minimize ventricular distension, and allow myocardial recovery. We describe Boston Children's Hospital's experience with percutaneous left atrial decompression techniques, acute outcomes, and clinical impact of left atrial decompression in extracorporeal membrane oxygenation patients. SUBJECTS: Patients supported with extracorporeal membrane oxygenation undergoing percutaneous left atrial decompression were identified and assigned to two groups 1) myocarditis/suspected myocarditis or 2) nonmyocarditis cardiac disease. INTERVENTIONS: Three techniques including vent placement, static balloon dilation, and stent implantation were used. MEASUREMENTS AND MAIN RESULTS: Change in left atrial pressure and severity of pulmonary edema on chest radiography pre and post procedure, impact of timing and technique of left atrial decompression on resolution of left atrial hypertension, and extracorporeal membrane oxygenation survival were evaluated. Furthermore, we evaluated the presence of residual atrial septal defect during follow-up. Percutaneous left atrial decompression was performed in 44 of 419 extracorporeal membrane oxygenation cases (10.5%) and was frequently used for myocarditis (22 of 44 patients; 50%). Techniques included 25 vents, 17 static balloon dilations, and two stents. All techniques were equally successful and significantly reduced left atrial pressure and pulmonary edema. Survival to hospital discharge was not associated with extracorporeal membrane oxygenation duration prior to left atrial decompression, change in left atrial pressure, or technique used. Persistent atrial septal defect was noted in five surviving patients (excluding transplant recipients and deceased), two required closure. CONCLUSIONS: Left atrial decompression can be performed effectively in children on extracorporeal membrane oxygenation using various percutaneous techniques. Reduction in pulmonary venous congestion is usually evident by chest radiography within 48 hours of intervention. Persistent atrial septal defect may require closure at the time of extracorporeal membrane oxygenation decannulation or during long-term follow-up.

Fetal aortic valvuloplasty for evolving hypoplastic left heart syndrome: postnatal outcomes of the first 100 patients.

BACKGROUND: Fetal aortic valvuloplasty can be performed for severe midgestation aortic stenosis in an attempt to prevent progression to hypoplastic left heart syndrome (HLHS). A subset of patients has achieved a biventricular (BV) circulation after fetal aortic valvuloplasty. The postnatal outcomes and survival of the BV patients, in comparison with those managed as HLHS, have not been reported. METHODS AND RESULTS: We included 100 patients who underwent fetal aortic valvuloplasty for severe midgestation aortic stenosis with evolving HLHS from March 2000 to January 2013. Patients were categorized based on postnatal management as BV or HLHS. Clinical records were reviewed. Eighty-eight fetuses were live-born, and 38 had a BV circulation (31 from birth, 7 converted after initial univentricular palliation). Left-sided structures, namely aortic and mitral valve sizes and left ventricular volume, were significantly larger in the BV group at the time of birth (P<0.01). After a median follow-up of 5.4 years, freedom from cardiac death among all BV patients was 96±4% at 5 years and 84±12% at 10 years, which was better than HLHS patients (log-rank P=0.04). There was no cardiac mortality in patients with a BV circulation from birth. All but 1 of the BV patients required postnatal intervention; 42% underwent aortic or mitral valve replacement. On the most recent echocardiogram, the median left ventricular end-diastolic volume z score was +1.7 (range, -1.3 to +8.2), and 80% had normal ejection fraction. CONCLUSIONS: Short- and intermediate-term survival among patients who underwent fetal aortic valvuloplasty and achieved a BV circulation postnatally is encouraging. However, morbidity still exists, and ongoing assessment is warranted.

Mixed aortic valve disease in the young: initial observations.

The short-term surgical results for mixed aortic valve disease (MAVD) and the long-term effects on the left ventricle (LV) are unknown. Retrospective review identified patients with at least both moderate aortic stenosis (AS) and aortic regurgitation (AR) before surgical intervention. A one-to-one comparison cohort of patients with MAVD not referred for surgical intervention was identified. The 45 patients in this study underwent surgical management for MAVD. A control group of 45 medically managed patients with MAVD also was identified. Both groups had elevated LV end-diastolic volume (EDV), elevated LV mass, a normal LV mass:volume ratio (MVR), and a normal ejection fraction. Both groups had diastolic dysfunction shown by early diastolic pulsed-Doppler mitral inflow/early diastolic tissue Doppler velocity z-score. The LV end-diastolic pressure (EDP) was correlated with age (R = 0.4; p = 0.03) and LV MVR (R = 0.4; p = 0.03) but not with AS, AR, or the score combining gradient and LV size. As shown by 6- to 12-month postoperative echocardiograms, aortic valve gradients and AR significantly improved (gradient 65 ± 17 to 28 ± 18 mmHg, p = 0.01; median regurgitation grade moderate to mild; p < 0.01), LV EDV normalized, and LV mass significantly improved (p < 0.01). Diastolic dysfunction was unchanged. Symptoms did not correlate with any measured parameter, but the preoperative symptoms resolved. In conclusion, despite diastolic dysfunction, systolic function is invariably preserved, and symptoms are not correlated with aortic valve function or LV EDP. Current surgical practice preserves LV mechanics and results in short-term improvement in valve function and symptoms.

Frequency and risk of in-stent stenosis following pulmonary artery stenting.

Peripheral and central pulmonary artery (PA) stenoses can result in right ventricular hypertension, dysfunction, and death. Percutaneous PA angioplasty and stent placement relieve obstruction acutely, but patients frequently require reintervention. Within a heterogeneous patient population with PA stents referred for catheterization because of noninvasive signs of PA obstruction, we have observed that in-stent stenosis (ISS) occurs commonly in some groups, challenging previous reports that this phenomenon occurs infrequently. We set out to evaluate the incidence and demographics of patients with previous PA stent placement who develop ISS. Consecutive patients with previously placed stents presenting for catheterization and undergoing PA angiography were reviewed (104 patients, 124 cases). We defined ISS angiographically, as a 25% narrowing of the contrast-filled lumen relative to the fluoroscopically apparent stent diameter at any site along the length of the stent. For inclusion, we required that the stenotic segment be narrower or equal in size to the distal vessel. ISS was diagnosed in 24% of patients, with the highest incidence among patients with tetralogy of Fallot and multiple aortopulmonary collaterals, Williams syndrome, or Alagille syndrome. In conclusion, ISS after PA stent placement is a more frequent problem than previously reported, and patients with inherently abnormal PAs are disproportionately affected. Increased clinical surveillance after stent placement and investigation of innovative preventive strategies may be indicated.